BYGL Weekly News for October 8, 2018
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
For more pictures and information, click on the article titles. To contact the authors, click on their names.
Authors Joe Boggs
Published on October 6, 2018
I came across a green June beetle (Cotinis nitida, family Scarabaeidae) larva (grub) last Thursday slowly slinking across a driveway. 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 a highly unusual mode of movement: they crawl along on their backs in an undulating motion! You can see this bizarre upside-down grub-crawl in a video I posted by clicking on “Grub Crawl” under “More Information” below.
The grubs rolling motion cause them to superficially resemble caterpillars. In fact, when I first saw this grub creeping along, I thought it was a caterpillar. Since green June beetles crawl without the aid of their legs, you’ll notice their legs are smaller than those of other white grubs, particularly in relation to the size of their bodies.
The other unusual thing about these grubs is that unlike other white grubs affecting turfgrass, green June beetle grubs create vertical burrows 10-12″ into the soil, and they normally remain closely associated with these burrows. They primarily feed on decaying organic matter such as thatch and much of their damage to turfgrass is associated with their burrowing and tunneling behavior. However, they have been known to feed on turfgrass producing damage in irregular patches.
The grubs venture out of their burrows in late-evening or during the night to feed or to go on an upside-down crawl-about in search of more food. They may also be driven out by heavy rains to appear in large numbers meandering across driveways and sidewalks or dropping into swimming pools. Although they can damage turfgrass, they’re primarily considered a nuisance pest.
The same is true of the large, metallic green adult beetles. Although they may occasionally feed on tree leaves as skeletonizers, or they may be found on ripening fruit, the beetles are most notorious for emerging en masse to terrorize backyard gardeners, golfers, sunbathers, small pets, etc., as they cruise about 2 – 3 ft. above the ground. Their large size coupled with an audible “buzzing” sound and low-level flight plan may induce mild panic in individuals unfamiliar with this insect. Like their grubs, the beetles have great entertainment value.
There appears to be a strong association between high organic and high populations of this beetle. So, control efforts should focus on reducing organic matter, particularly thatch, beneath infested lawns. For example, thatch reduction using core aeration to hasten decay by infusing oxygen into the organic matter may eventually make infested lawns less attractive as grub development sites by these buzz-bombing beetles.
The grubs are also food for the larvae of the blue-winged wasp (Scolia dubia). This wasp is a common visitor to late-season blooms such as those produced by goldenrod (Solidago spp.). Providing a good late-season nectar source, such as planting late-bloomers in landscapes, can help draw in this parasitoid wasp.
On a final note, I posted a BYGL Alert about this wasp just a few weeks ago (see Blue-Winged Wasps Cruising Lawns, September 17, 2018) and incorrectly stated that it is “a parasitoid of white grubs with a particular affinity for green June beetle (Continus nitida) and Japanese beetle (Popillia japonica) grubs.” This is only half-right. As turfgrass entomologist and (thankfully!) BYGL fact-checker, Dan Potter (Entomology, University of Kentucky) pointed out, there is no scientific evidence this wasp attacks Japanese beetle grubs. However, it’s well established that the wasp is the nemesis of green June beetle grubs.
More Information
Grub Crawl
Authors Joe Boggs
Published on October 6, 2018
Oak bullet galls have reached their maximum size for the season and will soon release their developing female wasps. The galls arise from twigs and are produced under the direction of several species of cynipid wasps (family Cynipidae) belonging to the genus Disholcaspis. So, you may find different types of bullet galls depending on the exact gall-making wasp species that directed their creation.
Most bullet galls are more or less round-shaped and measure about 1/2″ in diameter. Colors vary from light green to reddish-green, to light brown depending on the wasp species and the age of the gall. Some bullet galls are covered in very fine, short hairs, while others are completely smooth. They cause no appreciable harm to their oak hosts because they do not disrupt the vascular flow in the twigs.
Complex Life Cycle
The life cycle of bullet gall-wasps involves two different types of galls produced at different times of the year. The current bullet galls will give rise to female wasps around the end of this month; no males are produced. Wasp emergence is heralded by a small hole in the gall. Once the wasps have emerged, the “spent” galls shrivel, darken in color, and some will detach from the oak stems over the winter.
The self-fertile females crawl to a dormant leaf bud where they lay a single egg per bud. These eggs along with the resulting wasp larvae stimulate the tree to produce small, inconspicuous leaf galls in the spring. Both male and female wasps develop inside these leaf galls and adults emerge in mid-to-late spring.
The mated females fly or crawl to newly elongated twigs where they insert their eggs through the phloem to be in contact with the cambium. Or, depending on the gall-wasp species, they insert an egg in a new leaf bud. This is important because the wasp requires the services of undifferentiated (meristematic) cells to grow their bullet galls.
As with all galls produced by wasps, midge flies, and other insects, the bullet wasp gall-maker uses various chemicals to turn plant genes on and off at just the right time to induce and direct gall formation. Thus far, no researcher has ever duplicated this interaction without the aid of an insect gall-maker.
Paying for Protection
Many bullet galls include extrafloral nectaries (a plant organ) in their gall structure. I find this to be incredible, but it’s not unique to bullet galls. A number of other cynipid wasp galls also exude nectar including the oak bud gall produced by the wasp Neuroterus vesicula.
The nectar exuded from the galls attract a variety of stinging insects including bald-faced hornets (Dolichovespula maculata) and yellowjackets (Vespula spp.) as well as biting insects such as carpenter ants (Camponotus spp.).
Yellowjackets and bald-faced hornets are Jekyll and Hyde wasps. During much of the season, they chow-down on soft-bodied insects such as caterpillars and sawfly larvae. Their predatory lifestyle makes them beneficial insects. However, in the fall, they switch from high-protein diets to high carbohydrate diets. They can be a serious stinging-nuisance as they compete with our own high-carb consumption of soda, donuts, and certain adult beverages.
Bullet gall-makers take advantage of the wasp’s high-carb hankering with the nectar oozing from the extrafloral nectaries on the galls serving as “wasp candy.” Of course, ants will also show-up to the sugar party.
Presumably, the close attention of stinging and biting insects prevents the immature gall-making wasp larvae located within the galls from receiving the unwanted attention of predators and parasitoids. In other words, a little sugar bribe makes the gall-home safe for the gall-makers helpless offspring.
Authors Joe Boggs
Published on October 5, 2018
I came across a beautiful little native fly this week while taking pictures of pollinators on common goldenrod (Solidago canadensis). The fly, Trichopoda pennipes, doesn’t have a common name, but some web-based resources refer to it as the “feather-legged fly.” This is not entirely correct.
It is just one type of feather-legged fly with the common name given to all members of the Trichopoda genus. The name of the genus comes from the Greek tricho meaning “hair;” and poda meaning foot. In fact, some refer to these flies as “hairy-legged flies.” Even with the naked eye, you can clearly see the hair-like structures on the hind tibia that are responsible for the common and scientific names.
I came across an online resource that referred to Trichopoda pennipes as the orange-and-black feather-legged fly. Although this common name hasn’t been approved by the Entomological Society of America, I like it because it’s so descriptive. So, I’ll refer to it in short-hand as the O&B fly.
Other fascinating features that are clearly visible on the O&B fly are their two wings which mean it’s truly a fly belonging to the order Diptera: Di = two; ptera = wings. Flies actually have four wings but the hind wings are modified into two knob-like structures called halteres which are used by flies for balance during flight. It’s one reason flies are such good flyers and are called flies. The saddlebag-shaped halteres on the O&B fly are relatively large compared to many dipterans and they are covered in orange scales making them easy to see.
The O&B fly belongs to the fly family Tachinidae (the parasitoid flies) and is found throughout much of North America. Members of this family are well known for their prowess in tracking their hosts and for their larvae (maggots) ravaging their hosts from the inside out.
The O&B fly focuses its parasitoid scrutiny on the “true bugs” (order Hemiptera, suborder Heteroptera). They can pay particular attention to some significant stink bugs (family Pentatomidae) including the southern green stink bug (Nezara viridula) notable for damaging cotton and other field crops and the brown marmorated stink bug (Halyomorpha halys) notable for damaging a number of different crops then invading homes to brag about it. The fly will also parasitize various leaf-footed bugs (family Coreidae) such as the squash bug (Anasa tristis).
Research has shown that sex pheromones used by the southern green stink bug females to attract mates can be detected and used by the O&B fly to zero in on the bugs. This devious host detection method is not unique to this fly; it’s been reported with other tachinid flies.
Once a bug host is located, the O&B fly females lay single or multiple eggs on the surface of their host. The resulting fly maggots bore into their host; however, only one maggot survives to consume the entire contents of their bug host. Again, this is not unique to this fly, or even to flies. There are some parasitoid wasps that also subject their offspring to a survival of the fittest test.
Some parasitism rates by the O&B fly that are reported outside of scientific publications sound too good to be true, so they probably are. However, various research papers do indicate this fly can have some significant impacts under certain conditions.
For example, there appears to be a connection between nectar sources, successful adult mating, and higher rates of parasitism. Yet another example of the value of providing food for a pollinator adult (e.g. butterfly gardens) so their parasitoid or predator offspring can help reduce the number of nearby plant pests. Where have you heard that before?
ArborEatYumm: OSU’s College of Food…
Authors Jim Chatfield
Published on October 4, 2018
…FOOD Agricultural and Environmental Sciences. Let it never be forgot, the centrality of FOOD. Even in the landscape. So, Come one, come all. Next Tuesday, October 9, at OSU’s Secrest Arboretum, from 5:00 – 8:00 pm, there will be a free Arbor-Eat-Um program. Edible landscaping. Bring your favorite landscape plant products that are edible: blueberry buckle, black chokeberry jam.
Mark Hoenigman and his pawpaw trifle, Cathy Herms and her Autumn olive pate de fruits – controlling invasives one bite at a time. Lois Rose and her Medlar jam. Ramp soup. Honey. Maple syrup. Dolgo crabapple butter – Mike Lee where are you?
Nothing from your landscape? Just bring your appetite. Miller Pavilion. You do not need to register. Be there.
Authors Joe Boggs
Published on October 3, 2018
I enjoy making unexpected discoveries with one revelation leading to the next and then the next like pulling apart one of those Russian nesting dolls. My chain of discoveries started with finding “fresh” puffball mushrooms during a walk in a local park. I was thrilled because I had never taken pictures of the early stages of these peculiar looking mushrooms.
Puffballs are the common name for the fruiting structures of a group of fungi that were once lumped together in the descriptively named but now obsolete taxonomic class, Gasteromycetes (Greek: gaster = stomach; mycetes = fungus). Unlike the mushrooms that we may love on our pizzas with the spores produced and released from external gill-like structures beneath a cap, the spores in puffballs are produced internally inside a hollow cavity called a gasterothecium (= stomach-like).
The puffballs I came across with their white, spongy interiors will eventually undergo a dramatic change to become brown sacs full of powdery spores that puff when squeezed; thus puffballs. I hope to return to capture the next phase in their development unless someone steps on them to release clouds of spores. Puffballs have great entertainment value.
I pulled up one of the puffballs and discovered the bottom was riddled with pits and holes created by pillbugs as they dined on the fungal delicacy. I was thrilled because I had no pictures of these odd looking terrestrial crustaceans (phylum Arthropoda, subphylum Crustacea). It was like lifting off the top of a Russian nesting doll to discover another doll hiding beneath.
Pillbugs are so-named because they roll themselves into a pill-like ball when disturbed. This odd behavior gives rise to other common names such as armadillo bugs based on their roll-up behavior coupled with their obvious body plates.
You see this common name reflected by name of the pillbug family, Armadillidiidae. It also appears in the name of the genus of the two most common pillbug species found in Ohio, Armadillidium vulgare (common pillbug) and A. nasatum. Both are European natives that were introduced to North America so long ago it’s now common to think of them as native species.
Pillbugs live in dark, moist environments and are generally considered to be detritivores feeding on decaying plant debris. However, on rare occasions, they may feed on living plant material and have been known to cause damage to vegetables including root crops like radishes and carrots as well as lettuce leaves and ripe tomatoes. They may also become serious greenhouse pests by consuming seedling roots and young stems in contact with the soilless media. However, pillbugs are mostly just nuisance pests because of their propensity to show up in large numbers where they’re least appreciated such as in cool, wet garages and basements.
Sowbugs (family Oniscidae) are not the same as pillbugs although they both may be found living in the same locations. Sowbugs have two, small, pointed tail-like appendages that stick out of their back ends. Pillbugs do not. However, the big difference is that sowbugs cannot roll their bodies into round balls. They may huff and puff and curl a bit, but they just can’t pull off the rolly-pollie body tuck.
Pillbug management around homes should focus on prevention through closing entry points and environment modifications to promote drying. Door sweeps and door jambs should be inspected and action taken to close gaps that have become too wide. Pillbugs benefit from high moisture, so running dehumidifiers will help keep basements and garages dry. Mulch should be raked away from foundations to produce a “dry barrier.” Also, decaying vegetation should be removed.
Of course, there are things that eat pillbugs which brings me to my third Russian doll discovery. While taking pictures of the pillbugs crawling in and out of the cavities in the puffball, I came across a voracious predacious soldier beetle larva (Chauliognathus spp., family Cantharidae). The soldier beetle larva was thrusting itself into the cavities to enjoy a pillbug meat treat.
Adult soldier beetles are also called “leatherwings” for their soft, flexible front wings. The adults feed on nectar and pollen and are considered important plant pollinators. In fact, goldenrod soldier beetles (C. pennsylvanicus) are currently swarming over the flowers of its namesake native host plant. Another common Ohio species, the margined leatherwing (C. marginatus), made its appearance this past spring and early summer on other flowering plants.
Soldier beetles and their predacious larvae are a good example of the value of providing food for a pollinator adult (e.g. butterfly gardens) so their predaceous larvae can help reduce pestiferous arthropods. Research has shown the same is true for pollinators with parasitoid larvae. It’s like opening a Russian nesting doll to discover unexpected treasure hidden beneath.
Diagnostics of Beech Leaf Disease: The Ultimate Beech Read
Authors Jim Chatfield Joe Boggs
Published on October 2, 2018
Our knowledge of Beech Leaf Disease (BLD), an emergent problem on American beech (Fagus grandifolia) in northeast Ohio and nearby areas is still in the early stages. For example, we do not know what causes BLD. The most promising development in learning causation is that we now have scientists with some grant funding on the case. Carrie Ewing in Enrico Bonello’s lab at Ohio State University is doing her PhD work on BLD.
We also have excellent monitoring and mapping of the disease, including Lake Metro Parks and BLD discoverer John Pojacnik and Cleveland Metro Parks, as well as the Ohio Department of Natural Resources Division of Forestry and Holden Arboretum. But we do not know what causes BLD, if it is a pathogen whether it has a vector, the long-term threat to forest and landscape beeches, and on and on.
We do have some diagnostic aids: what BLD looks like as well as other problems that are often misdiagnosed as BLD. So here is the first in a series of BYGL BLD Diagnostic comparisons. We have discussed BLD in a number of previous BYGL-alerts (https://bygl.osu.edu/node/885), but here is a one on one comparison of look-alikes and diagnostic beech mis-reads.
BLD vs. A Leaf Curling Aphid.
I find this to be the most common BLD mis-read. I wish I could tell you the species of the aphid in this example: I cannot, but it is common in most beech woodlands on a few or many trees. At least I think it is the same aphid; it may very well be that there are a number of aphids that cause this leaf curling on beech. As you can see from the picture, the symptom on beech is the curling of leaf margins, with the sign of the aphid typically being cast skins of the aphids within the curled leaf. Presence of these aphids is not correlated with BLD.
As you can also see, there is a leaf discoloration symptom associated with the leaf curling. This is the key to it being mistaken for Beech Leaf Disease. The yellowing near the infestation is mis-interpreted as the “banding” symptom on BLD. With BLD though, there is clear banding of deep green and lighter greens, not this yellow banding noted from the leaf curling aphid.
This leaf curling aphid causes truly minimal damage to the plant. BLD, on the other hand is a serious problem, causing considerable progressive thinning of the canopy and in some cases tree death. So, check it out when you see beeches in the woods BTW, our landscape European (F. sylvatica) and Asian beeches (F. orientalis and others) have been diagnosed with BLD in nurseries.
Next time, let us remind ourselves of two other aphids that occur on beech: boogie-woogie aphids on American beech and woolly beech aphids on European beech. Also, neither of which is BLD.