BYGL Weekly News for July 8, 2019
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
Assassins are Roaming Around, but Don’t Panic
Authors Joe Boggs
Published on July 6, 2019
Insects belonging to the Hemipteran family Reduviidae are collectively known as “Assassin Bugs.” The family includes over 190 species in North America and they are all are meat eaters. The common name for the family clearly describes how these stealthy hunters make a living.
Family members sport potent predatory equipment including strong raptorial front legs for seizing and holding prey and powerful piercing-sucking mouthparts to suck the life out of their victims. Assassins are highly effective stealthy hunters able to sneak up on some of the most powerful and well-armed insects. I once watched an assassin bug grab and dispatch a bald-faced hornet which is no easy meal.
Some assassin bugs like those in the genus Zelus have additional assistance with their grabbing power in the form of a sticky goo covering their front legs. The gluey material is produced by glands on their front legs making them function like sticky fly paper. You may find the Pale Green Assassin Bug (Z. luridus) hanging out on flowers waiting to grab a quick meal with their sticky legs.
Once the assassins seize their prey, they use their piercing-sucking mouthparts, called a “beak,” to inject paralyzing and pre-digestive enzymes. In their final insecticidal act, the assassins suck out the essence-of-insect from their hapless victim.
Assassin bugs pass through three developmental stages: eggs, nymphs, and adults. This is known as “incomplete metamorphosis.” However, unlike other incomplete metamorphic insects such as grasshoppers with the nymphs resembling miniature adults, the nymphs of some assassin bugs may look nothing like the adults.
In fact, the nymphs of our native Wheel Bug (Arilus cristatus) are often mistaken for spiders. The nymphs have long, spindly spider-like legs and they parade around with their abdomens held upright. Of course, insects have six legs and spiders have eight legs.
Wheel bugs are one of the largest and most common assassin bugs found in Ohio. Their name refers to a peculiar morphological feature that rises from the top of the adult bug’s thorax. The structure looks like half of a cogwheel, with the gear teeth clearly visible. Wheel bugs are big, measuring almost 1 1/2″ long, and their color varies from light gray to bluish-gray to grayish-brown.
Caterpillars and sawfly larvae are favored table fare of these voracious predators; however, they will not turn their beaks up at other arthropod meat morsels. Indeed, they will even nail the probing fingers of uninformed gardeners!
While these are beneficial insects, they should not be handled. All members of the family are capable of delivering a painful bite to people. The pain of a bug bite has been described as being equal to or more powerful than a hornet sting, and the wound may take over a week to heal. It is best to appreciate these beneficial insects from afar.
A Bug-Induced Panic
Wheel bugs were at the center of a bug hysteria that swept through Ohio as well as several other states in 2015. The panic was induced through a series of unfortunate events starting with wheel bugs being misidentified as kissing bugs (Triatoma spp., family Reduviidae).
The name “kissing bug” may sound non-threatening until you learn why they were given that name. Several species of bugs belonging to the genus Triatoma are collectively known as “kissing bugs” because they tend to bite near a person’s mouth. These “triatomine bugs” get away with their cheeky behavior by biting people while they sleep.
The bites are usually painless but may lead to a serious disease if the bugs are harboring the protozoan Trypanosoma cruzi in their gut. The bugs don’t inject the protozoan when they bite; they release it from their other end when they defecate. Infection occurs if the protozoan is accidentally rubbed into the bug’s feeding wounds or onto mucous membranes such as nasal passages. The resulting Chagas disease is nothing to sneeze at; it can be deadly.
Thankfully, the kissing bug / Chagas disease connection only occurs in Central and South America with some rare occurrences in Texas. Conditions don’t support the same relationship here in Ohio.
Even though wheel bugs and kissing bugs belong to the same family, their lifestyles are completely different. Wheel bugs suck insect juice; kissing bugs suck animal blood.
However, with their long spindly legs, large bodies, narrow heads with beady eyes, wheel bugs do share family features with their kissing cousins. Consequently, pictures of wheel bugs started showing up on the Web identified as kissing bugs. That spawned an alarm that rippled through several media outlets.
The second round of bug-induced panic occurred back in April. This time, it was based on the reality that there is a kissing bug called the Bloodsucking Conenose (Triatoma sanguisuga) that may be found in the northern U.S. including Ohio. Although it has a scary sounding common name, the conenose is very rare in Ohio and it doesn’t acquire and spread the protozoan responsible for Chagas disease. You can read about this second panic in a BYGL Alert that I posted on April 25 titled, “Kissing Bug Hysteria Rises Again,” by clicking on this hotlink: https://bygl.osu.edu/index.php/node/1243
Dog-Day Cicadas and Cicada Killers
Authors Joe Boggs
Published on July 5, 2019
Annual Dog-Day Cicadas (Tibicen spp.; family Cicadidae) are starting to sing in southern Ohio. This means their nemesis, Cicada Killer Wasps (Sphecius speciosus), will soon be seen cruising woodlands and landscapes in search of their exclusive prey.
The annual cicadas share several behavioral traits with periodical cicadas (Magicicada spp.; family Cicadidae). The nymphs of both types of cicadas develop underground sustained by juices sucked from tree roots and it takes multiple years for them to complete their development from eggs to new adults.
Periodical cicadas are so-named because it takes 17 or 13 years for new adults to emerge en masse in spring. It takes 2-3 years for dog-day cicada nymphs to complete their development; however, some adults emerge every year due to overlapping generations. The adults appear sporadically throughout the “dog days” of summer usually beginning in July.
Like their periodical familial cousins, dog-day cicada males also “sing” to attract females. However, they do not “chorus” with large numbers synchronizing their song. An occasional dog-day cicada buzzing to entice a female doesn’t compare to the cacophony created by a multitude of periodical cicadas. It’s like comparing a barbershop quartet to a million man chorus!
As with periodical cicadas, dog-day cicada females use their long, spade-like ovipositors to insert eggs through the bark of twigs and into the white wood. The resulting damage splits the bark and white wood leaving deep longitudinal furrows of ruptured tissue. The injury often causes the twig to die, the leaves to turn brown (“flag”), and the twig to detach and drop. However, owing to the smaller numbers of dog-day cicadas, their egg-laying damage usually goes unnoticed.
Dog-Day Cicada Nemesis
Cicada killer wasps feed exclusively on annual dog-day cicadas; they do not prey upon periodical cicadas. That’s why the wasps appear on the scene long after a periodical cicada brood emergence has left the scene. The synchrony with annual cicadas makes sense if you consider that the wasps would starve to death waiting 13 or 17 years for a cicada meal.
The wasps measure 1 1/8 to 1 5/8″ in length and are one of the largest wasps found in Ohio. As with all Hymenoptera (wasps, bees, etc.), only the females possess stingers (ovipositors); however, they are not aggressive. The males are aggressive, but they lack stingers.
The females spend their time digging and provisioning burrows with paralyzed cicada-prey. They prefer to dig their brood burrows in bare, well-drained soil that is exposed to full sunlight. Although the wasps are considered solitary, all of the females have the same nesting requirements. So it is not unusual for there to be numerous burrows, and wasps, in relatively small areas.
The males spend their time establishing and defending territories that encompass multiple females. They are notoriously defensive and will aggressively buzz any transgressor who dares to enter their territory including other males as well as picnickers, golfers, volleyball enthusiasts, and gardeners. Fortunately, it’s all a rouse since they lack the necessary equipment to deliver a sting.
Cicada killers are considered beneficial insects. However, their large size coupled with low-level flights over sand volleyball courts, sparse lawns, and bare areas in landscapes can be disconcerting generating demands for control options.
Insecticide applications to kill the killers is not recommended. First, they are beneficial insects. Second, the females are not aggressive; stinging encounters are very rare. Finally, the best way to manage cicada killers is to modify their habitat. Renovating lawns late this summer to thicken the turfgrass will keep the killers out of lawns. Applying mulch to cover bare soil or raking mulch to disturb and redistribute possible burrowing sites will convince females to nest elsewhere. The same is true for golf course sand traps and sand volleyball courts: periodical raking will prevent the wasps from becoming established.
A Word about Big Wasps
The annual appearance of our native cicada killer wasps invariably triggers e-mails and phone calls to Extensioneers in Ohio and elsewhere about Asian Giant Hornets (Vespa mandarinia) or the subspecies, Japanese Giant Hornets (V. m. japonica). To be clear: these non-native hornets have never been confirmed in Ohio or elsewhere in North America.
Unfortunately, some online postings of Asian hornets “found” in the U.S. show images of European Hornets (V. crabro), which are rare but can be found in the U.S. including Ohio, or cicada killer wasps. This is not to say the Asian giants won’t appear in the U.S., but please get a confirmation from an official agency (e.g. ODA, USDA APHIS, etc.) before adding to the web confusion.
Authors Joe Boggs
Published on July 5, 2019
Flatid planthoppers (family Flatidae, order Hemiptera) are relatively small insects with the adults measuring no more than around 1/4″ in length. The adults and immatures (nymphs) look nothing alike which can lead to identification issues with connecting one to the other.
The adults of many species have broadly triangular shaped front wings that they hold tent-like over their abdomens. The adults are commonly found resting on plant stems and are often mistaken for moths.
A good example is provided by the Citrus Flatid Planthopper (Metcalfa pruinosa). Despite its common name, this planthopper is commonly found in Ohio. It ranges throughout the eastern U.S. from Maine to Florida where true to its common name, it’s often found on citrus.
Early instar nymphs are often obscured by a dense cloak of tangled waxy, white, cotton-like “fluff.” They congregate in groups, or “colonies,” and their profusion of flocculent material on plant stems may cause them to be mistaken for woolly aphids or mealybugs. Late instar nymphs look like some form of Star Wars troop vehicle with tufts of white filaments streaming behind.
Clusters planthopper nymphs are appearing on plants in southwest Ohio. They are most commonly found in woodlands, but will occasionally creep up the stems of plants in landscapes as well as vegetable gardens. They are most often found near the ground; however, I was surprised to find fluffy clusters at around eye-level on the stems and leaves of several woody ornamentals.
Like their aphid, mealybug, and soft-scale cousins, flatid planthopper adults and nymphs use their piercing-sucking mouthparts into phloem vessels to tap plant sap. They discharge the excess sugar-rich liquid from their anus in the form of a sticky, sugar fluid called “honeydew” which can become colonized by black sooty molds.
Fortunately, flatid planthoppers seldom rise above the status of nuisance pests. However, their resemblance to other sucking insects that cloak themselves in white, cotton-like material can lead to misidentifications.
Nymphs can be washed from plant stems using a coarse stream of water from a garden hose which will also wash away the white “fluff.” Insecticide applications are seldom warranted, but if needed, insecticidal soap applications are highly effective and will preserve the hopper’s natural enemies.
Authors Amy Stone
Published on July 2, 2019
Here is your link to the weekly video update (recorded on 06.28.2019) from the OSU Turfgrass Team. Updates are from Dr. David Shetlar, aka The Bug Doc; Dr. David Gardner; Dr. Ed Nangle; Dr. Pamela Sherratt (virtual); Joe Rimelspach; and Michael O’Keeffe this week.
Sumac Gall Aphid: An International Story
Authors Joe Boggs
Published on July 2, 2019
The bladder-like galls produced the Sumac Gall Aphid (Melaphis rhois) are becoming evident on the leaflet midveins of its namesake host in southwest Ohio. They currently measure between around 1/4″ to 1/2″ in diameter and their size coupled with their light green color can make them difficult to detect.
This will change as the season progresses. The galls will eventually become variegated with areas that are greenish-white bounded by areas that are mottled reddish-pink. The starkly contrasting colors will make the galls very evident.
The online literature indicates smooth sumac (Rhus glabra) and staghorn sumac (R. typhina) are the aphid’s primary hosts, if not the only sumac hosts. I’ve never found them on any other sumac.
As with the vast majority of insects that produce plant galls, the sumac gall aphid appears to cause little injury to the overall health of their host plants. Although heavy galling may cause early coloring and shedding of some sumac leaflets, the overall impact appears to be inconsequential relative to plant health.
The aphid has a complex life cycle with summer generations producing galls on sumac and winter generations living on mosses beneath or near the sumac. Females released from the summer galls drop onto moss where they reproduce asexually and the subsequent generations survive the winter.
Males and females arise from the moss colonies in the spring with winged, mated females flying to sumac where each female lays a single egg. The egg hatches into a “stem mother” which initiates gall formation and gives rise to a series of parthenogenetic (without males) generations that proliferate inside the gall. The galls eventually split open in the fall to release winged females that drop onto moss starting the alternating moss-sumac host cycle over again.
A Deep Time International Story
In 2015, Zhumei Ren (School of Life Science, Shanxi University, Taiyuan, China) visited Greater Cincinnati on a collection trip hosted by Sue Lutz (Botanist, Smithsonian National Museum of Natural History) and funded by the Museum’s Global Genome Initiative. Ren was doing research on prehistoric connections between gall-making aphids on sumac that are found in Asia and North America.
Research had clearly shown that our native sumac gall aphid, Melaphis rhois, and the Chinese sumac aphid, Schlechtendalia chinensis, are “biogeographically disjunct” Asian and North American species meaning they are related, but separated geographically. Indeed, Ren’s research showed our native aphid’s mitochondrial genome (mitogenome) is identical to that of the Chinese aphid which begs the question: just how “native” is our native sumac gall aphid?
Based on aphids Ren gathered in Ohio and elsewhere in 2015, a phylogenetic study she published in 2017 showed the North American gall aphid genus, Melaphis, diverged from its Asian relatives around 64.6 million years ago during the early Paleogene Period in the Paleocene Epoch
Alert readers will recognize that the timing is very close to the mass extinction that marked the end of the Cretaceous period as well as the non-avian dinosaurs (the so-called K-T Boundary). While the exact chain of events causing the demise of T-Rex remains hotly debated, there is no doubt a meteor impact played a key role.
The meteor muddled-up more than just reptiles. Owing to continental drift, Earth’s land masses were aligned differently 65 million years ago. North America was strongly attached to Asia by more than just a land bridge across the Bering Sea. There is no doubt many insect-plant relationships were shared between the two continents. However, the mass extinction radically changed things [see “2002: Impact …” in “More Information” below].
The meteor impact appears to have scrambled the phylogenetic record in such way that science may not be able to untangle the exact historical relationship between our sumac gall aphids and those found in Asia. At least, that’s a conclusion Ren and her co-authors presented in their 2017 paper. Of course, if Ren’s research thus far teaches us anything, it’s that science does not stand still. And, the lessons taught by the sumac aphid is more than just gall deep; they are deep time deep.
More Information
2002: Impact of the terminal Cretaceous event on plant–insect associations
http://www.pnas.org/content/99/4/2061
Ailanthus Webworm: Hope Springs Eternal
Authors Joe Boggs
Published on July 1, 2019
Ailanthus Webworm (Atteva aurea) caterpillars feed exclusively on the non-native, highly invasive, misleadingly named Tree-of-Heaven (Ailanthus altissima, family Simaroubaceae). The webworms are the larval (caterpillar) stage of a beautiful ermine moth (Family Yponomeutidae). In my opinion, this is one of the most beautiful moths found in Ohio.
Multiple overlapping generations occur each season so it is common to find both moths and caterpillars active at the same time. Both are active throughout the season with the moths appearing on both early and late-blooming plants.
The webworms produce communal nests by pulling leaflets into a network of loose webbing. Several caterpillars live within the nests consuming the leaflets enveloped in their webbing.
The webworms can grow up to 1 – 1 1/2″ long and they have a wide, light greenish‑brown stripe down their backs and several thin, alternating white and olive green stripes along their sides. The caterpillars are sparsely covered with short, erect hairs, which help to suspend them within the webbing. When disturbed, the caterpillars move backward out of the nest and drop towards the ground on strands of silk.
Ailanthus webworms are native to tropical regions in Central and South America where the caterpillars feed on native trees in the genus Simarouba (family Simaroubaceae). The moth was originally assigned the scientific name, Atteva punctella, and it was observed that this moth had expanded its palate to take advantage of the non-native tree-of-heaven that was flourishing in Central and South America.
It was once assumed the moths exploited the ever-expanding range of tree-of-heaven to move north into the U.S. and Canada. However, research involving DNA bar-coding, moth morphology, and food plant records eventually revealed that while A. punctella and A. aurea co-inhabit tropical regions of the New World, the moth in the U.S. and Canada is, in fact, A. aurea.
The caterpillars are capable of defoliating their odoriferous namesake host and they may feed on stem tissue once all leaves are devoured. Unfortunately, such extreme damage is rare on large trees. Although feeding by this webworm has yet to halt the spread of tree-of-heaven, hope springs eternal since this is one of only a few insects known to infest this encroaching interloper.
Authors Joe Boggs
Published on July 1, 2019
I post a BYGL Alert each year about Dogbane Beetles (Chrysochus auratus) because the beetle’s light-blending artistry makes it one of the most beautiful beetles found in Ohio. Enjoying these shimmering living gems on their namesake host is the entomology equivalent to “stop and smell the roses.”
The beetle’s scientific name, Chrysochus auratus, loosely translates to “made of gold.” In fact, gold is only one of a medley of colors displayed by these gorgeous native beetles. As you change your viewing angle, the beetles glisten with mixed shades of green, copper, blue, red, and of course gold.
The secret to the myriad display of colors is found just below the surface of the beetle’s exoskeleton. Beneath an outer translucent layer rests stacks of tiny slanting plates that cover color pigments. Light rays striking the surface of the plates are reflected as a shimmering sheen, while light rays that bounce off the pigments produce various colors. The result is a lustrous mix of ever-changing hews; a kaleidoscope of colors that are almost unmatched in the insect world.
Of course, the beetle’s colorful display isn’t meant to elicit “oohs and ahhs” from humans; it’s meant to signal, “don’t mess with me” to predators. Using bright colors to send a warning message to enemies is known as “aposematic coloration.”
Dogbane (Apocynum spp.) is the representative species for the dogbane family, Apocynaceae, which includes milkweeds and other plants that ooze sticky white sap ladened with poisonous alkaloids (cardiac glycosides). Indeed, the genus name Apocynum translates to “poisonous to dogs,” or “dog killer.” Sap from dogbane is reported to have been used at one time against ravenous feral dogs.
Dogbane beetles feed on the three dogbanes found in North America: common or hemp dogbane (A. cannabinum), fly-trap or spreading dogbane (A. androsaemifolium), and intermediate dogbane (Apocynum × floribundum). Although there are reports in the literature that the beetle feeds on various milkweeds (Asclepias spp.), I’ve scoured milkweeds in Ohio without finding this beetle. I’ve wondered if perhaps the reports are actually referring to the Cobalt or Blue Milkweed Beetle (C. cobaltinus) that does feed on western milkweeds. However, this beetle has not been reported in Ohio.
Dogbane beetles ingest the poisonous cardiac glycosides in dogbane sap, store the chemicals in specialized glands, and then they secrete the noxious chemical brew when threatened by predators. Their bright coloration advertises their nasty chemical defense strategy.
So, get out and look for dogbane beetles while enjoying the heat! If you find them, experience the kaleidoscope of colors by viewing the same beetle at different angles to the sun. They are eye candy … but don’t eat them.
Authors Jim Chatfield Erik Draper
Published on July 1, 2019
We all know how oppressive the mid-June rains were for many of us in Ohio, but how do you think the sweet cherries felt? It turns out that excessive moisture is a significant problem for this stone fruit. Fruit cracking from moisture can occur from several causes, from prolonged exposure to too much water in the root zone, but perhaps most likely from continued rainwater on the developing fruits.
In areas of northeast Ohio rain and relatively cool temperatures prevailed seemingly every day for weeks recently, including six inches or more in two days. This resulted in continuous water on those fruits with their thin cuticles as the fruit started the early period of ripening. Microcracks in the fruit at this point can expand from water absorption. Periods of rainfall in excess of 1.5 inches are known to enhance such cracking.
What can prevent this? In high production areas, intensive management is usually the only way to limit this problem if heavy rains keep coming. This includes drying the fruits in an orchard with airblast sprayers or even helicopters, the use of retractable orchard covers, and use of spraying hydrophobic coatings or osmotic salts multiple times. So, nothing for the faint of heart or pocketbook. To some extent, this has resulted in increasing sweet cherry production in drier climes. Otherwise, no-rain dances, though this has proved ineffective this year.
There are of course other hazards of horticulture for cherry production. Birds can strip the fruit. And Monilinia brown rot may follow cracking, moisture accumulation, and bird damage. The common brown rot disease, caused by the Monilinia fructicola fungus, occurs on stone fruits such as cherry, peach, apricot, plum, and almond (elsewhere) in the genus Prunus¸ with blossom and twig infections leading to fruit rots that result in un-harvestable fruit mummies. Moisture and injury to plant tissue favors disease development. Fungicides and sanitation (rogueing out affected fruit) are control practices.
Here are two excellent references for cherry fruit cracking that were used in compiling this bygl-alert:
https://www.growingproduce.com/fruits/stone-fruit-avoiding-cherry-fruit-cracking-is-a-balancing-act/
https://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/em9227.pdf