The following articles were compiled during the last 7 days by members of the Extension, Nursery, Landscape, Turf (ENLT) team to benefit those who are managing a commercial nursery, garden center, or landscape business or someone who just wants to keep their yard looking good all summer. Access the BYGL website for additional information on other seasonal topics at: http://bygl.osu.edu
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Authors Joe Boggs
Published on August 3, 2019
I’ve long had a fascination with Turkey Vultures (Cathartes aura) starting when I was a kid in West Virginia. I liked to lay on the ground observing these avian gliders catching thermal updrafts to stay aloft for hours without flapping their wings. This stopped when one of my uncles observed that I looked dead.
Of course, I wouldn’t have sprung to my feet so quickly had I known then what I know now about turkey vultures. While it’s true that turkey vultures are carrion feeders, they rely on more than just their excellent eyesight to locate an expired meal. They also have an exceptional sense of smell.
During a recent drive in southern Ohio, I came across another type of vulture: the Black Vulture (Coragyps atratus). These vultures are not as large as turkey vultures; however, they are still big birds. Their name comes from their black, featherless heads. Only the juveniles have feathers on their heads. Turkey vultures have featherless red heads which makes them resemble turkeys.
Black vultures have excellent eyesight but lack the olfactory capabilities of turkey vultures. In fact, freeloading black vultures often stay close to turkey vultures letting their carrion-seeking kin locate smelly, dead meals.
Turkey vultures have silver-gray flight feathers beneath their wings. Although I don’t have a picture of a black vulture in flight, the feathers beneath their wings are entirely black except for the base of the flight feathers at the tips of the wings which are silvery-white.
Turkey vultures live year-round throughout South America north into the middle part of North America. Their range extends into southern Canada during the summer. Historically, black vultures shared a large portion of this range, but they did not migrate out of the southern U.S. states. However, that has gradually changed. Over the past several decades, black vultures have found their way into our state as well as Kentucky and Illinois.
My uncle’s tongue-in-cheek warning may have carried more weight had turkey vultures shared the West Virginia skies with black vultures. That’s because black vultures will kill things. While they are primarily scavengers, black vultures are known to kill newborn calves, lambs, and small pets. However, their handiwork may be blamed on other predators, particularly where they have just moved into a new area. Prevention is not straight forward because both turkey and black vultures are protected by the Migratory Bird Treaty Act of 1918 and can only be killed under a Migratory Bird Depredation Permit through the U.S. Fish and Wildlife Service. It is legal to harass the birds. Perhaps laying in wait on the ground has some value after all …
What’s in a Name?
I grew up calling turkey vultures “buzzards.” However, in preparing this Alert, I came across numerous esteemed ornithological resources that failed to provide information on buzzards. Just try typing “buzzard” into the website search engines for the Cornell Lab of Ornithology or the Audubon Guide to North American Birds.
I eventually discovered that bird people reserve the “buzzard” name for several species of birds of prey that belong to the genus Buteoand are found in Europe and Asia. What?
Although the taxonomy is still being sorted, in general, vultures are divided into two types grouped in the order Accipitriformes. New World vultures belong to the family Cathartidae and include seven species found in North, Central, and South America. Two of the species are the turkey and black vultures.
Old World vultures belong to the family Accipitridae which includes 16 species. All have “vulture” in their common name and are found in Europe, Asia, and Africa. The family also includes eagles, hawks, and buzzards. The eagles and hawks are found throughout the world and include our own Bald Eagle (Haliaeetus leucocephalus). However, the buzzards are only found in Europe and Asia. Just try telling that to the good people of Hinckley.
Authors Joe Boggs
Published on August 1, 2019
I attended a meeting last Thursday on plant pollinators at the Cincinnati Zoo and Botanical Garden (CZBG). One focus was on managing pests by increasing the abundance and diversity of flowering plants in a landscape.
Many beneficial insects wear two hats by serving as both plant pollinators and enemies of other insects. It’s likely one reason the CZBG rarely needs to deal with significant plant pest problems is because the CZBG’s widely diverse landscape encompasses a smorgasbord of flowering plants including trees and shrubs as well as annuals and herbaceous perennials. They make no insecticide applications because they don’t need to apply this pest management tool; they’re using another one.
After the meeting, Steve Foltz (Horticulture Director) showed me an expanse of sand that was literally buzzing with a perfect example. Small wasps were busily digging burrows. They were female Bicyrtes quadrifasciatus, a species with no approved common name. However, the wasps are generally referred to as the Stink Bug Hunter (SBH) based on their preferred prey. They are arch enemies of stink bugs including the non-native invasive Brown Marmorated Stink Bugs (BMSB) (Halyomorpha halys)
SBH belongs to the family Crabronidae which also includes the Eastern Cicada Killer (Sphecius speciosus). However, they are only about 3/4ths the size of cicada killers. Both wasps have conspicuous cream-colored abdominal markings on a black background. The SBH females have four abdominal stripes which are referenced in their specific epithet, quadrifasciatus, means “four banded.”
As with the cicada killers, SBH is considered a “solitary wasp” even though they typically nest in large numbers over relatively small areas with their collection of burrows often referred to as “colonies.” The colonies evolve because the females of both species have specific nesting requirements. It is also speculated that large numbers of females gathered in one location helps males to find them which increases the chances all of the females will be mated.
SBH digs their burrows almost exclusively in sand which is why they are grouped within the Sand Wasp tribe, Bembicini. They are fast diggers and look like tiny dogs shoveling sand with their front legs backward between their hind legs. A close examination will reveal that their first and second pairs of legs are slightly curved inward to support digging as well as grasping their prey.
SBH females may attack different types of True Bugs (suborder Heteroptera) including leaf-footed bugs (family Coreidae). However, it’s their overarching predilection for stink bugs (family Pentatomidae) that makes them such an important enemy of BMSB.
The females tend to select stink bug nymphs, possibly owing to their smaller size compared to the adults. She grabs and stings the nymph to paralyze it, then she carries her prize back to her burrow and stuffs it inside. After she has provisioned her burrow with several helpless nymphs, she lays a single egg, leaves the burrow and seals the entrance. It’s an ingenious way to get around the lack of refrigeration. The immobilized nymphs remain alive (perhaps horribly aware?) to serve as fresh meat for the soon-to-hatch, grub-like wasp larva.
A survey of native biocontrol agents of BMSB conducted in 2011 by Penn State researchers in fruit orchards and surrounding habitat revealed that 96% of the stink bugs found in SBH burrows were BMSB nymphs. While the survey was conducted during a “peak year” in BMSB numbers in PA and in locations with concentrated bug populations (orchards), the results still point to these sand wasps as being an important bio-ally.
What about the risk of getting stung? Like cicada killers and the vast majority of solitary wasps, sand wasps were not aggressive. In fact, as I strolled through the SBH colony at the CZBG to take pictures, the wasps never displayed any type of threatening behavior despite my close-in photo shoots.
Attracting these wasps to landscapes may be an important method for decreasing BMSB populations as well as a number of other stink bugs. The adults feed on nectar; they are pollinators. Adding “pollinator plants” to landscapes provides significant support for these and other bio-allies that can play a critical role in suppressing pests. “Butterfly Gardens” and “Pollinator Gardens” should be appreciated beyond their support of pollinators; they’re also pest management tools.
Authors Joe Boggs
Published on August 1, 2019
I’ve observed slug-type sawfly larvae skeletonizing leaves on the same American bladdernut (Staphylea trifolia) trees growing in a southwest Ohio landscape in 2015, 2017, and again late last week. I’ve concluded they must cause little harm to the overall health of their bladdernut host because the trees continue to flourish despite providing some great photo ops of the sawfly larvae and their damage over the years!
The odd thing about these sawflies is that they are the spitting image of Scarlet Oak Sawfly (Caliroa quercuscoccineae) which is sometimes called the scarlet oak slug sawfly or just oak slug sawfly. The “slug” in the common names are based on their elongated unsegmented bodies and a covering of mucoid-like slime that presumably helps them stick to the undersides of leaves. You can read more about oak slug sawflies in an Alert posted in early June titled, “Be Alert to Scarlet Oak Sawfly”:
However, I have never found host records that indicate scarlet oak sawfly feeds on anything other than its namesake host as well as a few other oaks. I’ve also never found information on a species of sawfly that feeds on bladdernut. This may be undescribed slug sawfly species that is specific to bladdernut. If so, the common name of “Bladdernut Slug Sawfly” seems appropriate.
Although bladdernut slug sawfly larvae look like the slimy scarlet oak sawfly larvae, their feeding behavior is somewhat different and their ultimate leaf damage is very different. Scarlet oak sawfly larvae skeletonize leaves by munching side-by-side across the lower leaf surface consuming everything except the leaf veins and upper leaf epidermis. This produces a windowpane effect that fans out as larval feeding progresses.
Bladdernut slug sawfly larvae also feed on the lower leaf surface and consume everything except the leaf veins and upper leaf epidermis. However, their feeding behavior is much less organized. Rather than marching side-by-side across the lower leaf surface, bladdernut sawfly larvae crawl about in a more casual fashion to produce random window-like skeletonizing.
Initially, the leaves have a faded, whitish appearance. Ultimately, the window-like epidermis dries and drops from the leaf to produce large holes, or the entire bladdernut leaf simply turns brown and becomes paper-like.
Scarlet oak sawfly has 2 – 3 distinct generations per season in Ohio with the number varying between the northern and southern parts of the state. The generations do not overlap and larval development appears to be relatively synchronized; it’s rare to find larvae that aren’t equal aged.
The opposite is true with bladdernut slug sawfly. It’s common to find a range of instar stages feeding on the same leaf. I’ve photographed what appear to be late-instar larvae feeding on one leaf and obviously first-instar larvae feeding on another nearby leaf. I’m not certain if this represents overlapping generations or if egg hatch commonly occurs over an extended period. However, because I’ve observed larvae feeding from early June to early September, it reasonable to assume that this sawfly has multiple generations per season.
Authors Joe Boggs
Published on August 1, 2019
We teach the importance of identifying a pest in order to develop an effective pest management plan. An accurate ID leads to learning about the pest’s lifestyle including host range and numbers of generations per season. Occasionally, a significant insect pest somehow continues to fly below the radar of insect taxonomists.
Such is the case with the “Sedum Flea Beetle.” I’m using quotes because I’ve never found a reference assigning both a scientific as well as the common name to the beetle. This is my own made-up common name, but it captures the host range that I’ve observed thus far.
Purists will recognize that I’m bending plant taxonomy rules a bit by ignoring the fact that the genus Sedum no longer applies to many stonecrop plants used in landscapes. However, gardeners commonly refer to stonecrops as sedum whether the plants belong to the Sedum or Hylotelephium genera.
I first came across the beetle in mid-October, 2011, after receiving a phone call from a homeowner in eastern Cincinnati who said brightly colored beetles were destroying her “sedum.” I visited and found that a flea beetle was doing so much damage the only way I could identify the defoliated plants was through a plant tag; it was Hylotelephium telephium ‘Autumn Joy’ (family Crassulaceae). There was little joy in the appearance of the landscape planting.
Last year, I received a report in mid-June that the same beetle was damaging ‘Autumn Joy’ and ‘Munstead Red’ in a landscape in Dayton. I visited in mid-June and found both adults as well as larvae. This season I’ve gotten e-mail messages with pictures showing the beetle on unidentified stonecrop plants in a suburb of Dayton and in western Hamilton County.
The reports and observations I’ve made thus far; in mid-June and mid-October, strongly indicates the sedum flea beetle has at least two generations, if not more. This may also explain why the plants I observed in October were so heavily damaged. The population along with the damage escalated with each succeeding generation.
The sedum flea beetle looks very similar to the Passionflower Flea Beetle (Disonycha discoidea, family Chrysomelidae). You can see some good pictures of this beetle posted on BugGuide by clicking on this hotlink:
However, the authors of Host Plants of Leaf Beetle Species Occurring in the United States and Canada (Clark et al. 2004) note that the passionflower flea beetle only feeds on passionflowers (family Passifloraceae) including Passiflora incarnata and P. lutea. Neither Sedum nor Hylotelephium is listed as hosts for any of the 31 flea beetle species in the Disonycha genus.
In fact, the home gardener in western Hamilton County noted she is only finding the beetles on sedum. She has not found them feeding on a passionflower growing in her landscape.
Based on reports I’ve gotten thus far, I’ve concluded this beetle has the potential to cause significant damage to various stonecrop plants. I don’t know if the recent reports were plants belonging to the Sedum or Hylotelephium genera.
I’d like to learn more about this beetle as well as its host range. If you see the sedum flea beetle, please drop me a note with your location and contact information. Also, if possible, include the identity of the host plant (is it Sedum or Hylotelephium). Just click on my name at the top of this Alert and then click on my e-mail address.
Authors Joe Boggs
Published on July 30, 2019
I received a phone call last Friday from a homeowner in Reynoldsburg, OH, who reported that his neighbor had been stung by a horde of aggressive ants. He called because he had seen a BYGL Alert posted last year on Asian Needle Ants (Brachyponera chinensis) in southwest Ohio (see “Non-Native Stinging Ant Confirmed in Southwest Ohio,” January 26, 2018: https://bygl.osu.edu/node/970)
Given the homeowner’s close proximity to our Ohio State University C. Wayne Ellett Plant and Pest Diagnostic Clinic (PPDC) located in the Ohio Department of Agriculture’s complex, I urged that he drop specimens off at the Clinic for a positive identification. Ever since the discovery of needle ants in my neck of the woods, I and others have been interested to learn if this aggressive stinging ant had spread to other areas of the state.
Dave Shetlar (Professor Emeritus, OSU Entomology) made the identification of the ants and here is what he wrote in the Clinic report:
About five workers of the common pavement ant (Hymenoptera: Formicidae: Tetramorium caespitum) were found, still alive. The client was wondering if these were the Asian needle ants because the ants had stung during a recent encounter. Pavement ants are easily recognized by the presence of numerous furrows present on the surface of the exoskeleton of the head and thorax plus they have two nodes. The Asian needle ants have a smooth exoskeleton surface and one prominent node. Pavement ant workers have a small stinger which is capable of penetrating human skin where it is thin. Stings are normally considered to be inconsequential, but like all venoms, individual people may have severe reactions to the foreign proteins present in the venom. Such reactions can result in intense burning, itching and even the formation of a small blister. If these develop, frequent washing and application of anti-itching creams can help avoid scratching and secondary infections.
I’ve long been aware of pavement ants. This non-native species was introduced to the U.S. from Europe over 100 years ago and has risen to become one of the most common ants found in Ohio, particularly in urban areas.
This pugnacious ant is well-known for its bare-tarsal brawls. Battles between competing colonies may occur as a single, massive, swirling clash, or as a serious of smaller pitched skirmishes with constantly shifting battle lines. I’ve frequently had a ringside seat to one of these ant melees.
However, I never knew that pavement ants have stingers!
Authors Joe Boggs
Published on July 30, 2019
I posted an Alert yesterday that stated Elm Yellows (EY) has been confirmed by Ohio State University C. Wayne Ellett Plant and Pest Diagnostic Clinic (PPDC) in a park in Greater Cincinnati. This not correct.
The PPDC only detected a phytoplasma in an elm sample. However, more work is being done by the Clinic involving DNA sequencing to learn the true identity of the phytoplasma; whether or not it’s actually ‘Candidatus Phytoplasma ulmi’ which is the bacterium behind the disease known as EY. I jumped the gun.
A Cautionary Tale
Phytoplasmas are small highly specialized bacteria that appear to only infect plants. However, finding a phytoplasma in a host known to be susceptible to a particular phytoplasma-induced disease does not necessarily mean the detected phytoplasma is causing the disease. In other words, finding a phytoplasma in American elm may not mean it’s the phytoplasma that causes EY.
What if it’s an undescribed phytoplasma? What if it’s producing an undocumented disease? What if it’s the phytoplasma that’s responsible for EY, but it’s presenting uncharacteristic symptoms? These points are very important relative to learning the truth of what’s actually going on; a truth the PPDC is still in the process of pursuing.
In my imprudent BYGL Alert, I noted that the symptoms on the American elms were “atypical.” Instead of the leaves rapidly turning an intense shade of lemon-yellow to yellowish-orange, the symptom that gives EY its name, there was minimal yellowing on the leaves on the tree that tested positive for a phytoplasma. The leaves rapidly wilted throughout the canopy and the entire canopy defoliated over just a few days.
I broke my own golden diagnostic rule: do not make the symptoms fit the diagnosis, make the diagnosis fit the symptoms.
This is why I’m correcting my earlier report. The PPDC is sending material for DNA sequencing. Once the PPDC has established the complete story, we will post an Alert at the appropriate time with more complete details.
You can learn more about these plant pathogenic phloem-limited bacteria including the history of their discovery by reading the following paper titled, “Phytoplasmas and Phytoplasma Diseases: A Severe Threat to Agriculture”:
Elm Yellows Still a Concern
Regardless of the outcome of the PPDC investigation, EY remains a concern on American elms in Ohio and elsewhere. Here are some common indicators that an elm may be infected with the EY phytoplasma:
Rapid Leaf Yellowing and Defoliation: the name “elm yellows” describes the color of the leaves on infected trees. The color-change occurs quickly – often within a few weeks – without the leaves first wilting. The yellowed leaves quickly drop from the trees.
Phloem Discoloration: the old name for the disease was “elm phloem necrosis” which captures the essence of the infection. The phytoplasma targets and destroys the phloem with the inner phloem becoming yellowish-brown to caramel colored and the staining extending to the surface of the xylem. The discoloration is generally confined to the lower portion of the trunk and the lower branches. This is because the phytoplasma first migrates to the roots causing rapid and substantial dieback of the fine feeder roots, then the main roots. In essence, there is a “bottom-up” pattern to the infection.
Carefully slicing away the bark on the lower trunk or lower branches using a sharp pocket knife or a draw-knife will expose the off-colored infected phloem tissue. A cautionary note: elm phloem tissue will naturally become discolored by oxidation when exposed to the air. The oxidation occurs in minutes, and mimics the discoloration caused by EY, so samples showing phloem necrosis that is suspected to be caused by EY must be fresh!
Wintergreen Odor: Methyl salicylate (oil of wintergreen) is produced in the phloem tissue that is colonized by the EY phytoplasma. Cut a section of bark to the white wood near the base of the main stem and place the sample in a sealed jar. While the wintergreen scent is usually very faint at first, it becomes easily detectable after the sample has been held in the jar for about 3 – 4 hrs.
Quick Death of Trees: Trees that appear perfectly healthy with normal twig elongation and leaf expansion early in the growing season are often dead by the end of the season.
CONFIRMATION: Although the symptoms listed above provide strong evidence of EY, the only sure-fire way to know that a tree is infected (and infectious!) is to send samples to a diagnostic clinic capable of performing the appropriate tests. Keep in mind that as illustrated by my mea culpa, it takes time for the confirmation to occur.
Other Elm Problems to Consider
Nutrient Deficiency: The chronology of EY leaf yellowing is different from leaf chlorosis caused by nutrient deficiencies. Typically, nutrient deficiency symptoms appear early in the season with new leaves appearing chlorotic. Early defoliation almost never occurs.
Black Leaf Spot: this fungal disease of elms produces irregular dark brown to black spots that may be slightly raised. Heavy infections may cause leaves to yellow and drop. However, yellowing does not occur prior to the development of the leaf spots.
Environmental Calamities: Everything from poor soil conditions to drought to over and under-watering can cause American elms to collapse. However, leaf wilting is usually a tell-tale pre-collapse symptom.
Vascular Wilt Diseases: These diseases prevent water from reaching the leaves by plugging the vascular system. Thus, vascular wilts produce noticeable and sometimes rapid leaf wilting and browning, particularly in the heat of summer, as leaves are starved for water. Vascular wilts usually produce sectional dieback with a few branches succumbing at a time. However, a complete collapse of the canopy is also possible.
American elms that are considered tolerant of DED have succumbed to DED although this is a rare occurrence. It is speculated that trees suffering from severe stress are made more susceptible. Verticillium wilt has long been the nemesis of American elm trees that are under stress. Resistance to DED does not mean that elms will not suffer from branch dieback from this disease.
Although EY has been affecting elms for at least as long if not longer than DED, the disease has continued to appear as sporadic, highly localized outbreaks. Often, only a few trees die even though other elms are within visual range of their demise. Still, with the widespread reintroduction of American elms into urban landscapes, this old killer has re-emerged to present a serious threat. If you suspect a tree is infected, act quickly by getting a confirmation.
Authors Erik Draper
Published on July 30, 2019
As Oriental lilies are about halfway through their “bloombastic tour”, simply walking near them causes one to be stunned visually and in the olfactories too! After drawing in the noticeable, spicy scent wafting all around and through the air nearby the plants, it gives the feeling that breathing the regular, old normal air seem stale! That was just one of the differences between Asiatic and Oriental lilies, which I alluded to in an earlier BYGL article this year.
In that article, written just about 20 days ago, I tried to give BYGLers a sense of the Oriental lilies blooms, both look and size. I wrote “… The huge flowers are 6-9 inches across…” and just to reinforce that seemingly ridiculous size, I took a picture with a ruler for your visual enjoyment!
The other distinguishing characteristic beyond smell and size of the flower, is the delicate, ruffled edges on the petals of the bloom. It is sometimes subtle, but noticeable nevertheless, if you look closely at the petal edges.
To make this bloom tour complete, I just wish that we had “SMELLOVISION” so that you could have the whole “bloomblastic” experience initiated by Oriental lilies!
Published on July 30, 2019
Question # 12 of our 20 Questions of Plant Problem Diagnostics is: What Is The Environmental History?”. Here are three quick examples of the importance of this question.
Planetree Perserverance. As predicted in bygl node.1305 on June 11, planetrees, especially the more susceptible American planetree (sycamore, Platanus occidentalis) that looked almost leafless due to sycamore anthracnose in May and June throughout much of Ohio, have now largely re-foliated and look fine. Cool, moist conditions during leaf emergence, so key to disease development, are past history and trees recovered nicely.
All Hail Honeylocust. Orange-yellow discoloration on stems, elliptical cracking on those stems. Are these fungal cankers on this backyard thornless honeylocust (Gleditsia triacanthos var. inermis ‘Imperial’) in Denver, Colorado? Not totally sure, but I suspect the smoking gun is the homeowner’s report of the environmental history of major hailstorms this spring and summer – and the “What Exactly Do You See/” question #6 of Plant Problem Diagnostics. What I exactly saw was the damage in question only occurring on – upper stem surfaces.
Aesculus Avoidance. On a Denver street, a reminder of home – Ohio buckeye! Leaf scorch in the hot summer heat, and some insect feeding, but – whither the Guignardia leaf blotch fungal diseases, common on the genus Aesculus (buckeyes and horsechestnuts) and the moderately susceptible Ohio buckeye (Aesculus glabra). No Guignardia. The absence of the environmental component of the disease triangle is the key here: not a lot of wet and humid conditions in spring in Denver.
Diagnostics: Question Everything!
Authors Joe Boggs
Published on July 30, 2019
This is the time of the year when Common Bagworms (Thyridopteryx ephemeraeformis) come into clear focus owing to their size and noticeable damage. Overwintered eggs hatched in southwest Ohio in early June (see “Be Alert to Bagworms!” posted on June 6). However, it’s amazing how well these native moth caterpillars crawl below our radar until their burgeoning appetites finally gives them away.
I’m speaking from personal experience. I looked out our kitchen window this past weekend to see a hungry horde of bagworms chowing down on needles at the top of my prized Canaan fir (Abies balsamea var. phanerolepis). How dare they! The cheeky bagworms are no more; I have a sprayer.
Bagworms are so-named because the caterpillars wrap themselves in silk bags festooned with pieces of their plant host material. The arrangement provides highly effective camouflage.
The bagworms spend the winter as eggs inside dead females that remain in their bags. A single female can produce 500 – 1000 eggs meaning that populations can climb rapidly. Just a few undetected females can spawn damaging numbers of caterpillars next season.
Bagworms also have a habit of seeming to appear out of nowhere. That’s partly because of their cryptic lifestyle but also because 1st instar caterpillars can produce a strand of silk to catch the wind and “balloon” to new locations. This behavior is one of the reasons bagworms often appear on hosts that were not infested last season.
Bagworms can also feed on deciduous trees and shrubs as well as evergreens. It is a common misconception that bagworms only eat evergreens. If fact, they are called “Evergreen Bagworms” in many southern states. However, the caterpillars may be found feeding on over 130 different species of deciduous trees and shrubs.
Bagworms can be controlled through physical removal as long as they are destroyed by squeezing or stepping on them once they are plucked from an infested plant. If simply dropped to the ground, they will crawl back upon a host plant. I would have used this method if the top of my Canaan fir wasn’t so far out of reach. There’s a certain satisfaction with doing the “bagworm dance” to dispatch the troublesome caterpillars.
Early instar bagworms can be killed using products based on the naturally occurring biological insecticide Bacillus thuringiensis var. kurstaki (Btk) (e.g. Dipel, Thuricide, etc.) which preserves bio-allies. The image below shows bagworms collected from the same host over the weekend. The age range is not unusual and occurred because of an extended egg hatch. However, it shows that Btk products will only be effective against a small segment of the population. Btk is most effective on small bagworms and becomes much less effective when bags surpass 3/4″ in length.
The clock is also rapidly ticking down for standard insecticides to remain effective. Late instar bagworms can detect insecticide toxicants causing them to hasten pupation, but they do not die. However, they do stop feeding which leads to the perception they were killed. Early-pupating females produce fewer eggs, but they still produce enough to continue the infestation next season.
It’s important to remember that bagworms may remain attached even if the caterpillars were successfully killed with an insecticide. They look just like bags with live caterpillars. The deception may lead to needless repeat applications, but they can only die once.
Authors Amy Stone
Published on July 30, 2019
Here is your link to the weekly video update (recorded on 07.26.2019) from the OSU Turfgrass Team. Updates are from Dr. David Gardner; Dr. Ed Nangle; Dr. Zane Raudenbush; and Joe Rimelspach this week.
Authors Joe Boggs
Published on July 28, 2019
Boxwood Blight was recently confirmed in a private landscape in Greater Cincinnati by The Ohio State University’s C. Wayne Ellett Plant and Pest Diagnostic Clinic (PPDC). The disease causes a severe and usually rapid decline of susceptible boxwoods. Heavy defoliation and branch dieback can occur in a single season killing small plants. The ornamental value of larger infected boxwoods is reduced and plants may become so stressed they succumb to secondary problems.
The disease is caused by the fungal plant pathogen Calonectria pseudonaviculata which was previously named Cylindrocladium pseudonaviculatum or Cylindrocladium buxicola. The literature reports the pathogen and disease were first identified in the United Kingdom in 1994. The current distribution includes 12 other European countries as well as western Asia and New Zealand.
The fungus may infect several members of the box family (Buxaceae) including Japanese spurge (Pachysandra terminalis); Allegheny spurge (P. procumbens); sweetbox (Sarcococca spp.); and of course, boxwood (Buxus spp.). However, all boxwoods aren’t equal. Some are highly susceptible while others are tolerant.
The pathogen and disease were found in Connecticut in 2011 and is now confirmed in 28 states as well as British Columbia, Ontario, and Quebec, Canada. This is not the first time this fungal disease has been found in landscapes in Ohio. This means that Green Industry professionals throughout Ohio must remain informed and ready to take action including confirming boxwood blight by sending samples to the PPDC. Professionals should never rely on a “field diagnosis” to inform their actions.
A Boxwood Blight Case Study
Ron Rothhaas (Arbor Doctor, LLC, Cincinnati, OH) is an ISA Board Certified Master Arborist and a highly capable field diagnostician. However, rather than speculating on what might be happening in a landscape he was visiting, he confirmed what’s actually happening by sending samples to the PPDC. Ron and I will be holding a boxwood blight mini-workshop at our next Greater Cincinnati BYGLive! Diagnostic Walk-About.
It’s essential to separate boxwood blight from the less damaging but more common Volutella Blight produced by the fungal pathogen, Pseudonectria buxi (formerly Volutella buxi). Plants can recover from Volutella blight; however, highly susceptible boxwoods don’t recover from boxwood blight. Adding to the challenge, some of the samples Ron sent to the PPDC tested positive for Volutella meaning both boxwood diseases are occurring at the same time in the same planting.
Volutella blight is also called Pseudonectria Canker owing to the occurrence of stem cankering infections which do not occur with boxwood blight. The leaves on cankered stems turn yellow to yellowish-brown and remain attached to the stems for an extended period of time. Symptoms often appear in early spring and are commonly mistaken for winter injury. Cankered stems can be removed through pruning which promotes plant recovery.
A signature symptom of boxwood blight is rapid defoliation. Leaf infections may sometimes occur to produce leaf spots; however, this is not a consistent symptom. Sometimes, leaves simply wilt, turn dark bluish-green and drop.
Another symptom common to boxwood blight is black streaking on the stems. The streaks are most evident when they occur on green stem tissue.
It must be stressed that neither rapid defoliation nor blackened stems necessarily mean boxwoods are suffering from boxwood blight. However, the symptoms are strong indicators that samples should be sent to a diagnostic lab such as the PPDC in Ohio.
Helpful Online Resources
A great deal of work has been done by universities in states where boxwood blight has been detected. The following are a sample of some excellent university fact sheets on boxwood blight as well as Volutella blight. They also provide in-depth management Plans:
Virginia Tech (VT) Best Practices
University of Kentucky (UK) – Boxwood Blight
University of Kentucky (UK) – Volutella Blight
How the Fungal Pathogen is Moved from Place-to-Place
The literature notes that the boxwood blight fungus produces heavy, sticky spores that are not carried far by the wind. They are better suited to sticking to the feet of birds, the fur of animals, and to pruners, shears, etc. Thus, the fungus may arrive through animal incursions, both human or otherwise.
This further emphasizes the need to confirm the occurrence of boxwood blight, react quickly to contain the disease, and avoid inadvertently spreading the fungus from one landscape to the next on contaminated tools, clothing, etc. In fact, both the Virginia Tech and the University of Kentucky fact sheets provide a list of measures to prevent the site-to-site spread of the boxwood blight fungal pathogen.
For example, it is strongly recommended that tools used for pruning or shearing boxwoods be sanitized before moving from one group of boxwoods to another within a landscape and certainly before working on boxwoods at another site. The Virginia Tech factsheet recommends using o-Benzyl-p-chlorophenol (e.g. Lysol Concentrate Disinfectant) mixed at a rate of 1.25 oz. / gallon. Sodium hypochlorite (household bleach) is also recommended mixed at 1 part bleach to 9 parts water. However, this sanitizer must be mixed fresh at frequent intervals and should be rinsed from tools to reduce damage.
Planting infected boxwoods is another common way for the pathogen to be spread to new landscapes. Horticultural regulatory agencies such as the Ohio Department of Agriculture are keenly aware of boxwood blight and nursery inspectors are well-trained in detecting tell-tale symptoms. However, the movement of plants outside of the protective regulatory shield, such as digging and moving plants from one landscape to another, presents another route for spreading the pathogen.
Don’t Give Up on Boxwoods
The landscape where Ron found boxwood blight includes hundreds of boxwoods; they are integral to the overall landscape design. Indeed, boxwoods often occupy a unique profile in landscape designs based on their hard-to-match appearance.
Research has shown there is a range of boxwood blight susceptibility within the Buxus genus. Some types are highly tolerant while others are highly susceptible. This further emphasizes the need to develop and use tolerant types of boxwoods to thwart boxwood blight.
Research has also shown that boxwood blight can be prevented through season-long fungicidal applications made at around 14-day intervals. However, no fungicides have been found that offer a curative option; the disease cannot be halted in plants that are infected. This means that while fungicides may be used as part of a boxwood blight management plan, they should not be the only tool in the management toolbox.
Much has changed since boxwood blight was first discovered in the U.S. in 2011. At the time, it was widely believed the disease spelled the end of boxwoods in our landscapes. However, research studies conducted since that time by universities and others are proving this to be a premature prognosis.
Both the VT and UK fact sheets, as well as other university-based resources, provide workable boxwood blight management plans for nurseries and for landscapes where the total removal of boxwoods is not a viable option. They involve confirming boxwood blight through sending samples to plant and pest diagnostic labs, removing and destroying infected boxwoods, replanting using less susceptible types, and making fungicidal applications to protect non-infected plants.
Funding Research to Keep Boxwoods in Our Future
It is important to note that research continues on boxwood blight susceptibility as well as fungicide efficacy. The bottom line is that we should not give up on boxwoods.
You can find out more about past and future boxwood blight research initiatives funded by the AmericanHort Foundation, Horticulture Research Institute by clicking on this hotlink:
You can support this research aimed at thwarting boxwood blight by making a charitable contribution in support of the Boxwood Fund. Please contact the AmericanHort Foundation, Horticulture Research Institute (HRI) at 614-487-1117. Make checks payable to HRI at 2130 Stella Ct; Columbus, OH 43215 and include a memo line: Boxwood Blight.
Authors Carri Jagger
Published on July 24, 2019
This week I received two emails from clients about clusters of little insects all over their trees. After closely examining the pictures and sharing them with my Horticulture co-workers they confirmed that they were in fact Barklice.
Barklice are small fairly inconspicuous insects that hang out on trees eating mold, pollen, fragments of dead insects, algae and lichens. Because of this they are actually considered be beneficial. They do cause any harm to trees as they don’t eat bark or bore into trees.
These insects resemble aphids and are called lice but they are not pests or parasites of either plants or animals. There are two species, one is Cerastipsocus venosus which is found on the bark of trees and moves as a group that resembles a herd of animals. The Cerastipsocus venosus species adult has shiny black wings which are held in tent-like fashion over their abdomens. The nymphs appear dark grey and pale yellow banding between abdominal segments. The adults and nymphs have round heads and conspicuous antennae.
The other species is Archipsocus nomas and they make conspicuous silken webs on the bark of tree trunks and limbs. They are very small (less than 1/8 inch long) and soft bodied insect. They live together under the protective layers of the silken webbing.
There is no need to control Barklice as they are harmless to plants and people.
Authors Joe Boggs
Published on July 20, 2019
This is the time of the year when the menagerie of insects that feed on members of the dogbane family (Apocynaceae), including common milkweed (Asclepias syriaca), seem to arrive en masse to the consternation of monarchists. Some well-meaning gardeners aim to reserve milkweeds exclusively for the pleasure of monarchs. What about other native insects that feed on milkweeds; let them eat cake?
Monarch butterflies (Danaus plexippus) are beautiful insects and their plight remains uncertain. Elevated multi-national concerns over their future have raised awareness of the rewards of gardening beyond aesthetics. Monarchs have served as excellent ambassadors for the environmental benefits of expanding our plant selection palettes to paint more diverse landscapes. Milkweeds are no longer weeds.
However, efforts to save monarchs may sometimes morph into crusades to serve the aristocracy at the expense of the proletariat. Good intentions can be taken too far. Royal sovereignty should not rule the distribution of host plant food!
The Milkweed Banquet
Members of the dogbane family try to ward off herbivores by loading their milky, sticky sap with alkaloid toxins, called cardiac glycosides (cardenolides). However, some specialized herbivores, including monarchs, evolved a capacity to handle these toxins. The downside is that these herbivores are so specialized milkweeds are the only food they eat. This includes a diverse range of native insects beyond monarchs.
Part of their dependency on milkweeds involves mounting a successful defense against predators. Like monarch caterpillars, many of these native insects accumulate alkaloid toxins in their flesh that are acquired from feeding on milkweeds. Presumably, this makes them taste bad, but I’ve never tested this theory.
Most members of the milkweed menagerie advertise their toxic character through bright coloration, usually involving an orange-on-black motif. Employing splashy colors and color patterns to defend against being eaten is called “aposematism” from the Greek for “away” and “sign.” Of course, as illustrated by monarchs, gaudy aposematic coloration can be beautiful.
Liberty, Equality, Fraternity
Notable native insects that depend on milkweeds for their livelihood include beautifully colored Milkweed Tussock Moth caterpillars (Euchaetes egle); Swamp Milkweed Leaf Beetles (Labidomera clivicollis); Red Milkweed Beetles (Tetraopes tetrophthalmus); Large Milkweed Bugs (Oncopeltus fasciatus); and Small Milkweed Bugs (Lygaeus kalmii). These native insects have the same inalienable food rights as monarchs.
The small, yellow-green first instar milkweed tussock moth caterpillars have black head capsules and are covered in wispy white hairs. Later instars sport rows of black and orange hairs punctuated by tufts of long white and black hairs; these colorful hairs are the feature most often associated with these caterpillars and are responsible for the alternate common name of “milkweed tiger moth.”
All instars feed side-by-side in groups sometimes called “colonies” and can consume entire leaves leaving only the veins. In fact, the caterpillars can appear to be serious competitors to monarchs. However, tussock moth caterpillars tend to be found on only a few milkweed plants and they focus their attention on one leaf at a time. Plenty of food remains for monarchs.
The milkweed bugs are seed feeders. They use their piercing-sucking mouthparts to skewer seeds, inject enzymes to dissolve the internal tissue, and suck-up the resulting slurry. The bugs may also feed on developing seed pods but seldom cause enough damage to kill the entire pod. They will reduce the number of viable seeds; however, milkweeds are prolific seed producers. How many seeds are enough to carry milkweeds to next season? There’s plenty of seed to go around.
However, I recently observed what happens when large milkweed bugs arrive before their seed-food matures: they become cannibals. They use their digestive enzymes on one another to suck-up the essence of insect. It’s a jungle out there.
Brightly colored swamp milkweed leaf beetles (Labidomera clivicollis, family Chrysomelidae) are one of my favorites; partly because they are somewhat rare. Despite their common name, both the adults and larvae feed on the leaves of several members of the dogbane family.
Although swamp milkweed leaf beetles use milkweed toxins as a chemical defense, there can be too much of a good thing. The latex in the sticky sap can clog their chewing mouthparts. To avoid this, both the adults and larvae will chew through veins “upstream” from their feeding site to reduce sap flow. Evidence of beetle damage includes deep leaf notching usually towards the leaf tip.
The tubular-shaped red milkweed beetles are a type of longhorned beetle (family Cerambycidae). Although the “longhorned” name of the family refers to long antennae, milkweed beetles have relatively short antennae. However, a close examination of their prominent black antennae will reveal another family trait. Their antennae bisect their compound eyes creating two sets of eyes with one set located above the antennae and one set below. The name of the genus, Tetraopes, and specific epithet, tetrophthalmus, describes this unusual feature; both are derived from the Latin for “four eyes.”
Red milkweed beetles feed on entire plants with the adults feeding on the leaves and the larvae boring into the roots and stems. However, I’ve never seen enough damage to present a serious challenge to monarchs.
I support monarch recovery. However, we should embrace all native insects with equal affection. I mean this figuratively since tussock moth caterpillars have defensive hairs and milkweed bugs can drill fingers with their piercing-sucking mouthparts. Members of our native milkweed menagerie should enjoy the same natural born rights to milkweeds as monarchs. The bottom line: liberty, equality, and fraternity for all insects that you may find sharing milkweeds with monarchs.
Authors Joe Boggs
Published on July 18, 2019
Whenever I hear that the naturally occurring biological insecticide Bacillus thuringiensis var. kurstaki (Btk) is not killing caterpillars, the first thing I try to find out is whether or not the “caterpillars” are actually caterpillars. Btk products (e.g. Dipel, Thuricide, etc.) only kill caterpillars, they do not kill sawfly larvae.
Caterpillars belong to the order Lepidoptera meaning they grow up to become butterflies or moths. Many types of sawfly larvae look like caterpillars and even feed like caterpillars, but they are related to bees, wasps, and ants; they belong to the order Hymenoptera. On the other hand, there are some caterpillars like Zebra Caterpillars (Melanchra picta) that look like sawfly larvae.
There’s an easy way to tell the difference between caterpillars and sawfly larvae using a system taught to me by Dave Shetlar (OSU Entomology, Professor Emeritus). Although others may have happened upon this handy system, I always refer to it as the “Shetlar Method.”
A Little Anatomy
Starting from the head and working towards the backend, the first group of legs you find on both caterpillars and sawfly larvae are three pairs of thoracic legs. These match with the three pairs of legs found on the adults. The next multiple pairs of fleshy legs are called abdominal prolegs and the last pair of fleshy legs located at the backend are appropriately called anal prolegs.
Adult insects use their legs for locomotion, or for just standing around thinking insect thoughts if insects think. Caterpillar and sawfly larvae primarily use their thoracic legs for holding onto things; they crawl around using their prolegs.
Count the Prolegs
Count the number of abdominal prolegs; do not count the anal prolegs. Caterpillars have 5 or fewer pairs of abdominal prolegs. Sawfly larvae have 6 or more pairs of abdominal prolegs.
Here’s a handy way to remember this: Caterpillars have the same number or fewer pairs of abdominal prolegs as the fingers on your hand; sawfly larvae have more pairs of abdominal prolegs than the fingers on your hand.
Authors Joe Boggs
Published on July 18, 2019
The common name of “Dogwood Sawfly” was officially assigned years ago when it was believed there was only one species, Macremphytus tarsatus. However, taxonomists later found there are actually three species of sawflies in the genus Macremphytus that feed on dogwood leaves in the eastern U.S. including Ohio: M. testaceus; M. semicornis; and M. tarsatus.
Regardless, the three species share a number of characteristics: they have one generation per season; they are mid-season pests; they may be found feeding on several species of dogwood, and their final instar larvae often bore into wood to spend the winter. They also change their appearance as they molt from one instar stage to the next.
However, dogwood sawfly (M. testaceus) larvae are the true chameleons. Newly hatched larvae look like small caterpillars; they are amber in color and are somewhat transparent. The larvae emerge from their second molt covered with a white powdery material.
When the larvae are resting, they curl into a knot and look like bird droppings to the casual observer. At their final molt, the larvae are about 1″ in length and they lose their white powdery covering, revealing a yellow body with black patches. This final color phase is shared with the other two species.
The behavior and damage caused by the larvae of this and the other two sawfly species also change as they develop. The newly hatched larvae feed together, skeletonizing the leaves. As the larvae mature, they consume the entire leaf, except the mid-vein. Individual branches or entire plants may be completely defoliated. I’m always amazed at how the snowy-white larvae can remain hidden until they’ve stripped all of the leaves from small dogwoods.
The mature yellow and black larvae crawl from their host trees in search of overwintering sites; they may be found crawling along fence rails, sidewalks, etc. Aside from sometimes appearing in unexpected places which may produce a misidentification, the mature sawfly larvae also practice an unusual overwintering behavior which can misdirect identification.
The mature larvae may bore into softwood, if available, to produce an overwintering chamber. While they usually select decaying wood, the larvae may occasionally bore into redwood siding or outdoor furniture. Thus, they are sometimes mistaken for a true wood-boring insect.
Dogwood sawfly damage is well underway for this season. However, further defoliation can be halted by knocking the larvae onto the ground to stomp them or into a bucket of soapy water to drown them. Insecticides may also be used including biorationals such as azadirachtin and spinosad or conventional insecticides such as pyrethroids (e.g. bifenthrin, permethrin, etc.).
The naturally occurring biological insecticide Bacillus thuringiensis var. kurstaki (Btk) (e.g. Dipel, Thuricide, etc.) does not kill sawfly larvae; it only kills caterpillars. To be able to tell the difference, read my next BYGL Alert.
Authors Amy Stone
Published on July 18, 2019
The caterpillar feeding frenzy has ended for the year and adult activity is being observed in NW Ohio. The male moths have taken flight in their zig-zag pattern in hopes of finding a mate. The female moths are white and a bit larger in size, and typically don’t move far distances from the pupal casing that they emerged from. She gives off a pheromone to alert close by males of her location. After a visit from the male moth, she will begin laying eggs. The mass of eggs laid now, will remain in that stage until the following spring, as there is one generation per year.
It is the same pheromone “fragrance” used in the lure, placed in the traps set and monitored across the buckeye state by the Ohio Department of Agriculture (ODA) (see photo below). The data collected from those traps will help as a guide for the state program, that is part of a larger national program coordinated by the USDA Forest Service. Traps monitor the progression, or maybe even regression, of the leading edge and also alert regulators to “hot-spots” that could be building in a particular area.
Adult activity, and more importantly number and size of the egg masses, are tools to help determine what is on the horizon and can aid in predictions of how populations number look for the 2020 season.
For additional information about the gypsy moth and state coordinated suppression treatments, check out the ODA website at: https://agri.ohio.gov/wps/portal/gov/oda/divisions/plant-health/gypsy-moth-program/gypsy-moth-program
Published on July 17, 2019
Reviewed and Additions Provided by:
Dr. Pierluigi (Enrico) Bonello
Dr. Francesca Peduto Hand
The Ohio State University, Department of Plant Pathology
The Ohio Department of Agriculture (ODA) has announced in an official press release a confirmed interception of the plant disease-causing pathogen Phytophthora ramorum in Ohio. You can access the press release by clicking on the hotlink at the end of this Alert.
- ramorumis a water mold organism that causes ramorum blight on over 100 host plants, including rhododendron and lilac, and sudden oak death (SOD) in coastal areas of California and Oregon. SOD has proven to be deadly in California and the Pacific Northwest on oaks (Quercus) and tanoaks (Notholithocarpus). On other hosts, this pathogen causes leaf spots and branch dieback.
A shipment of infected plants, including numerous rhododendron types and lilac, from a nursery in the Pacific Northwest, was sent to a nursery in Oklahoma and subsequently shipped to Walmart and Rural King locations in a number of eastern U.S. states, including Ohio. Though this pathogen was found on rhododendrons and lilacs intercepted here, there was no shipment of oaks with SOD.
For context, it is important to remember the Plant Disease Triangle: a susceptible host, a virulent pathogen, and an environment conducive to disease are all necessary for a particular disease to occur. Over the almost 25 years in which SOD and ramorum blight have been regulated disease issues, we do not know of any cases of this disease becoming established in the U.S. other than those coastal areas of California and the Pacific Northwest.
Although it is impossible to completely know for certain the potential risk of this pathogen becoming established here, Ohio is not considered to be a particularly likely candidate for establishment of SOD. P. ramorum has never been detected before in Ohio nurseries, landscapes, or forests. That said, the vigilance of ODA and our plant regulatory system should be lauded relative to this interception.
Let us proceed with caution. If your customers have rhododendrons or lilacs purchased at Walmart or Rural King between March and May of this year and you suspect they may be infected, drawing from the ODA Press Release, “Plants can be destroyed by burning, deep burial or double-bagging the plant, including the root ball, in heavy duty trash bags for disposal into a sanitary landfill (where allowable). Consumers should not compost or dispose of the plant material in municipal yard waste.”
In addition, it is important to keep in mind there are many different diseases, insects, and physiological problems that may occur on rhododendrons, lilacs, and oak. To sharpen your plant problem diagnostic skills, we will make a point of reviewing some of these at diagnostic training events yet to come this summer and fall. These include a workshop that will be held on the OSU-Mansfield Campus on August 2 and the Ohio Plant Diagnostic Workshop on the OSU-Wooster Campus on September 6 as well as the Greater Cincinnati Diagnostic Walk-Abouts on August 5, September 9, and October 14.
You can access the ODA Press Release by clicking this hotlink:
Authors Joe Boggs
Published on July 17, 2019
While taking pictures of Walnut Caterpillars (Datana ministra), I noticed that the sometimes caterpillar-like Walnut Petiole Galls produced by the eriophyid mite, Aceria caulis (family Eriophyidae), are reaching their maximum size and becoming very evident on their namesake host. The galls are specific to black walnut (Juglans nigra) and may occur on the petiole, rachis, and petiolules of the compound leaf.
The galls are covered in densely compacted hairs that resemble the erineum patches produced by other eriophyid mites. As the galls “mature,” they change color from pinkish-white to pink to deep red and finally to dark brown. They may be very obvious causing tree owners to fear for the health of their trees
Although the galls may cause the compound leaves to become twisted and malformed, they do not disrupt the vascular flow. The affected food-producing leaflets remain functional even though they may be pointed in an array of directions. Thus, the eriophyid galls do not appear to cause significant harm to the overall health of their walnut hosts.
There are online recommendations to remove and destroy the galls on small trees to reduce the mite population. However, this could mean removing a considerable number of food-contributing leaves making the treatment more damaging than the condition. Besides, as with many plant gall-makers, populations of this eriophyid appear to rise and fall dramatically from year-to-year. I seldom see heavy galling two years in a row on the same walnut tree.
Authors Amy Stone
Published on July 17, 2019
The small pinkish flowers caught my eye the other day as I was walking through the garden. While not overly showy, and maybe not even noticed by many, the fruit to follow with be breath taking. The flowers remind of the “beauty” of the berries, just around the corner.
Purple beautyberry (Callicarpa dichotoma), is described by Michael Dirr as the most graceful and refined of the species. Some cultivars include: ‘Early Amethyst’, ‘Issai’, and ‘Duet’.
The oppositely arranged leaves act as a staging area for the purple fruits to come. The berries line the arching stems and are interesting, beginning late summer through fall.
Purple beautyberry can be planted in full sun to part-shade. I have observed it planted in masses, in a mixed garden, and as a hedge row – with my favorite being a serpentine hedge as the summer and fall “bones” of a perennial garden. It can be a little late to get going in the spring. In fact, we can see some branch dieback after a cold winter when temperatures bottom out. If this is the case, cutting the shrub down to the base is recommended and new growth will begin.
Missouri Botanical Garden, Plant Finder
Authors Joe Boggs
Published on July 17, 2019
First-generation Walnut Caterpillars (Datana ministra) are producing noticeable defoliation in southwest Ohio. The moth caterpillars feed in groups, or “colonies,” of 10-30 individuals throughout their development which is why their defoliation is often focused on a single branch or a group of adjoining branches.
As their common name implies, walnut caterpillars are most often found on walnut trees, but they will also feed on hickory and pecan trees and will occasionally infest apple, birch, honeylocust, oak, and willow. Large established trees can typically handle the defoliation with little long-term impact on overall tree health; even when infested by multiple colonies. However, multiple colonies on small trees can cause significant harm.
Walnut caterpillars practice an interesting defense behavior. When disturbed, the caterpillars will rear their front and tail ends, often in unison, presumably to confuse predators. Thus, these caterpillars have great entertainment value!
They also practice an unusual molting behavior. When molting, they group together on trunks, branches, or twigs and all of the caterpillars molt at the same time leaving behind a mass of hairy exoskeletons that looks like a patch of fur. Finding these furry patches on or near denuded walnut leaves is a good way to identify the culprit behind the defoliation.
It’s Just a Phase
The caterpillars pass through distinct “color phases” during their development meaning they change their colors and markings as they mature. There is some debate about whether or not it’s 3 or 4 color phases. Regardless, the changes in colors, markings, and furriness may present a challenge with their identification.
There are at least two generations per year in southern Ohio with some indications there may be only one generation in the northern part of the state. It appears we are nearing the end of the first generation in Greater Cincinnati.
Walnut caterpillars have a wide array of natural enemies from birds to insect predators to insect parasitoids and insect pathogens. These natural controls can keep populations in check; however, there may be occasionally caterpillar outbreaks as is common for native insects.
Early instar walnut caterpillars can be effectively controlled using the naturally occurring biological insecticide Bacillus thuringiensis var. kurstaki (Btk) (e.g. Dipel, Thuricide, etc.). Fortunately, Btk does not kill bio-allies that help provide natural control of the caterpillar populations.
Unfortunately, Btk is most effective on small caterpillars and becomes much less effective when caterpillars reach the middle instar stages. Btk is a stomach poison which means it must be consumed to kill the caterpillars and it has relatively short residual activity. Thus, two applications may be required.
The large caterpillars can be easily managed on small landscape trees using a two-step control method. Step one involves knocking the caterpillars to the ground. Step two consists of performing the “caterpillar stomp.” Thus far, no walnut caterpillars have become resistant to this control method.
Authors Joe Boggs
Published on July 16, 2019
Green June Beetles (Cotinis nitida, family Scarabaeidae) are practicing their annual terrorizing of backyard gardeners, golfers, sunbathers, small pets, etc., as they buzz golf courses and lawns. Despite the “June” in their common name, these beetles appear on the scene in July in Ohio.
The large, metallic green beetles tend to emerge en masse. Their large size, coupled with an audible “buzzing” sound and low-level flight plan; cruising at about 2 – 3′ above the ground, may induce mild panic in the uninitiated. In fact, as I discovered in my (misspent) youth, the attractive beetles have great entertainment value. Tying a string to a hind leg of one of these powerful flyers turned the beetle into a drone before there were drones.
Adults feed on tree leaves as skeletonizers, or they may be found on ripening fruit. They rarely cause significant leaf injury; however, they may seriously damage fruits.
The beetles seek turfgrass with high levels of organic matter (e.g. thatch) in which to lay eggs. It has been speculated that this attraction to decomposing organic matter explains why large numbers of adults will cruise above certain lawns while ignoring neighboring lawns.
Unlike other Scarab beetle larvae found in turfgrass, green June beetle grubs burrow 10 – 12″ vertically into the soil and they remain closely associated with these burrows. The grubs exit their burrows at night to feed on thatch and other organic matter.
This is one of the largest and strangest white grubs you’ll ever see in Ohio. First, the mature grubs are huge measuring well over 1″ in length. They look like white grubs on steroids.
Second, the grubs practice an unusual mode of locomotion: they crawl along on their backs in an undulating motion. Their rolling motion causes them to superficially resemble caterpillars. Their legs are smaller than those of other white grubs in relation to the size of their bodies. Some have speculated their leg-size is an adaptation to life in a burrow while their unusual style of crawling reconciles having small legs. Regardless, the upside-down grubs are surprisingly fast.
Despite their large size, green June beetle larvae seldom cause injury to turf equal to that caused by Japanese beetles or masked chafers. They are mostly considered a nuisance pest. Control efforts should focus on reducing organic matter, particularly thatch, beneath infested lawns. For example, thatch reduction using core aeration to enhance aerobic decomposition will eventually make infested lawns less attractive to these buzz-bombing beetles.
Authors Joe Boggs
Published on July 16, 2019
If you’re in Greater Cincinnati and have the chance visit the beautiful Glenwood Gardens [Great Parks of Hamilton County], grab a map at the main office and ask how to hike to the “Lotus Pond.” It’s a bit of a hike, but do what I did and wait until the afternoon temperature climbs above 90 F. and the humidity allows you to wear the air. Who needs a sauna?
Your intrepid perseverance may be rewarded by a display of American lotus (Nelumbo lutea). It’s one of my favorite native wildflowers and is also known as water-chinquapin and yellow lotus. In my opinion, there is nothing else that rises from our waters to rival the allure of this aquatic beauty.
Fragrant yellowish-white flowers (lutea means yellow) opening up to 10″ wide. Deep green exotic-looking leaves stretching almost 3′ in diameter. What’s not to like? Even the showerhead seed pods draw interest. Of course, there are those who may not share my enthusiasm for this native aquatic plant, but more about that later.
There are only two species of lotus worldwide: the American lotus and the sacred lotus (N. nucifera) which is also called the Indian, Asian, or pink lotus. Both lotus species once belonged to the water-lily family, Nymphaeaceae, in the plant order Nymphaeales.
However, based on DNA sequencing, the lotuses are now placed in their own family, Nelumbonaceae, and moved to a different order, Proteales. This order also includes the plane family, Platanaceae. This means American lotus is more closely related to American sycamore (Platanus occidentalis) than it is to any of the water-lilies.
The apparent similarities between lotus and water-lilies are now considered the result of convergent evolution where natural selection produces comparable features among unrelated or distantly related organisms. A frequently used example are bats, birds, and insects all having wings.
American lotus colonies spread by seeds and submerged rhizomes. The plants are not free-floating; they are firmly rooted in submerged soil. That’s why plants grow around the edges of ponds or in the shallow waters of lake inlets or river backwaters; oxbows are a favored location.
The large lotus leaves are coated in epicuticular waxes. I’ve always appreciated how droplets of rainwater that collect in the leaf centers glisten gem-like in the sun. The leaves and stems have milky sap which has a number of interesting attributes including alkaloids that have been shown to have anti-bacterial properties.
The lotus plants provide a healthy habitat for a wide range of micro and macro-organisms. The large leaves protect immature fish from predators, the seeds are utilized by ducks and other migratory birds, and the rhizomes are eaten by beavers and muskrats.
American lotus can be enjoyed in a number of locations around Ohio beyond Glenwood Gardens. You can find it growing in shallow inlets along Lake Erie as well as Tappan Lake in northeast Ohio and in the shallow upper reaches of Cowan Lake located just southwest of Wilmington, OH. Indeed, there was once a trail in Cowan Lake State Park called “Lotus Cove.” However, while lotus continues to grow in the lake, the cove is choked with silt and the trail is now defunct.
Not everyone views American lotus with the same appreciation. Although native, it can be aggressive in colonizing shallow waters creating a challenge to those who pursue other aquatic beauties such as bass, sunfish, etc., and aquatic activities like boating and water skiing.
Some Lotus May Be Sacred
Don’t confuse American lotus with its non-native cousin; the sacred lotus. Unfortunately, this lotus has found its way into some Ohio waters which is why it is included in the Ohio Field Guide to Aquatic Invasive Species.
The color of the flowers provides a helpful way to tell the difference between our native lotus and the non-native sacred lotus. American lotus flowers are yellow to yellowish-cream colored. Although there are a few varieties and cultivars of sacred lotus that also produce light yellow flowers, most produce flowers that are pink or tinged with pink which is why it’s sometimes simply called the pink lotus.
You can learn more about identifying invasive aquatics in Ohio including the sacred lotus by clicking on this hotlink:
The American Lotus Borer (Ostrinia penitalis (Lepidoptera: Crambidae)) can be a significant pest of American and sacred lotus in Ohio. The most obvious symptom is the skeletonizing-like leaf damage that’s currently giving a ragged appearance to lotus leaves in Cowan Lake and in the Glenwood Gardens Lotus Pond.
The caterpillar is found throughout North America as well as the Amazon basin of South America; the same range as its American lotus host. The moth has two generations per season in Ohio. The current leaf damage is being caused by the first generation; damage by the second generation is typically more severe. Despite its common name, the borer has also been found feeding on various smartweeds (Polygonum spp.).
On lotus, early instar caterpillars are found on the upper leaf where they use silk to pull together two radiating leaf veins creating a shallow trough-like depression. Individual caterpillars reside within these depressions covered by a dense mat of silk which presumably prevents them from falling into the water and provides camouflage against predators. The ruse is not always effective as there are reports of redwing blackbirds shredding leaves in search of the caterpillars.
The caterpillars feed beneath their webbed abodes and also venture forth, apparently mostly at night, to feed on the surrounding leaf surface. During this time, the caterpillars remain anchored to the leaf with silk; an adaptation to their aquatic environment preventing them from being washed away by waves.
True to their common name, as the larvae mature, they eventually change their feeding habits to become borers. The caterpillars burrow into the leaf petiole where the petiole attaches to the leaf and feed by tunneling down the petiole. Their stem boring activity isn’t just confined to the leaf petioles. The caterpillars also tunnel the flower stems to eventually find their way into the seed heads. In fact, this is where the second generation larvae pupate to spend the winter.
There are records of the borer causing serious damage to all parts of its native and non-native lotus hosts including significantly reducing seed production. Indeed, I observed severe leaf damage to the lotus in Cowan Lake. Other than physically removing the caterpillars from the leaves and stems, there are no other effective controls.
Fortunately, as with any native insect, populations tend to rise and fall dramatically from year to year, so the borer seldom causes significant long-term damage to a colony of American lotus. It appears that established American lotus colonies have the ability to recover from the periodical onslaught by its caterpillar.
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