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Extension Entomology

Tag: itch

Green June Beetles: Out-and-About

— by Dr. Raymond Cloyd

Green June beetle (Cotinis nitida) adults are actively flying around and “bumping” into people and objects. Adults are 3/4 to 1.0 inches in length, and velvety-green, tinged with yellow-brown coloration (Figure 1).

IMG_6145
Fig 1: Close-up of adult green June beetle.

Green stripes with yellow-orange margins extend lengthwise on the front wings. The underside of the body is distinctly shiny and metallic green or gold. Adults fly like “dive bombers” over turfgrass for several weeks in mid-summer. The green June beetle has a one-year life cycle, and overwinters as a mature larva (grub). Adults emerge in late-June and are active during the day, resting at night on plants or in thatch. The adults produce a sound that resembles that of bumble bees.  Adults will feed on ripening fruits (Figure 2) and may occasionally feed on plant leaves.

Fig 2: Adult green June beetle feeding on fruit.
Fig 2: Adult green June beetle feeding on fruit.

The male beetles swarm in the morning, “dive bombing” to-and-fro above the turfgrass searching for females that are located in the turfgrass (they are desperately seeking a mate. Females emit a pheromone that attracts males. Eventually, clusters of beetles will be present on the surface of the soil or turfgrass with several males attempting to mate with a single female (I think this qualifies as an “insect orgy.” Mated females that have survived the experience lay a cluster of 10 to 30 eggs into moist soil that contains an abundance of organic matter. Eggs hatch in about 2 weeks in early August and the young larvae feed near the soil surface. The larvae feed primarily on organic matter including thatch and grass-clippings; preferring soils that are excessive moist. Larvae are 3/8 (early instars) to 1.5 (later instars) inches in length, and exhibit a strange behavioral trait—they crawl on their back (Figure 3) because that they have a constant itch.

Fig 3: Larva (grub) of green June beetle crawling on its back.
Fig 3: Larva (grub) of green June beetle crawling on its back.

 

Oak Vein Pocket gall: Back with a Vengeance!

–by Dr. Raymond Cloyd

We have received numerous inquiries (in fact…LOTS) regarding gall-like growth on the underside of pin oak (Quercus palustris) leaves. In some cases, many pin oak trees have extensive galling on nearly all the leaves, with the leaves twisted or distorted. In fact, one tree on the Kansas State University (Manhattan, KS) campus, located behind Umberger Hall, is nearly 100 percent infested with this gall. I really think the gall makes the tree more attractive J. The culprit is the oak vein pocket gall, which is caused by the gall-midge, Macrodiplosis quercusoroca. Galls are elongated, pocket-like swellings on the lateral veins and mid-rib of pin oak leaves (Figures 1 through 3). The gall-making organism is a small fly called a midge (Family: Cecidomyiidae). Adults are 3.0 mm long and resemble small mosquitoes (but they are not mosquitoes so do not worry). Female midges attack newly developed leaves that are unfolding – just before they are flattened. After the eggs hatch, small larvae or maggots migrate to the lateral and mid-veins, and subsequently begin feeding. After several days, tissue forms and surrounds each larva. Full-grown larvae are white and approximately 2.0 mm in length. Development is completed by mid-spring to early summer. The larvae eventually emerge from the gall, fall to the ground, and overwinter or enter diapause (a physiological state of arrested development) until the next spring. There is one generation per year. There are no control measures for this gall. Remember, this is not the gall-former that the oak leaf itch mite feeds on…that is the marginal oak leaf fold galler (Figure 4).

Figure 1. Oak Vein Pocket Gall
Figure 1: Oak Vein Pocket Gall

Figure 2. Oak Vein Pocket Gall
Figure 2: Oak Vein Pocket Gall

Figure 3. Oak Vein Pocket Gall
Figure 3: Oak Vein Pocket Gall

Figure 4. Leaf Marginal Fold Gall
Figure 4: Leaf Marginal Fold Gall

I want to acknowledge Matthew McKernan; Horticulture Agent (Sedgwick County; Wichita, KS) for keeping me abreast of the situation (and sending images) regarding the oak vein pocket gall in south-western Kansas.

Not so mysterious “Itching” (Oak Leaf Itch Mite)

–by Dr. Bob Bauernfeind

Whereas scratching an itch sometimes provides satisfying (almost pleasurable) relief, at other times scratching an itch can be painful and distressing.  The latter situation is attributable to the mite, Pyemotes herfsi (Oudeman).

Unlike chiggers which have been long-recognized for producing annoying but fleeting bouts of itchiness, mysterious “bites” causing raised quarter-sized reddened areas each with a centralized pinhead-size blister were of widespread occurrence in 2004 in various Midwestern states.

#2

 

Through investigative studies, the aforementioned Pyemotes herfsi mites were identified as being responsible for the mysterious bites.  Although the existence of these mites had been well known for multiple decades, the correlation between them and reported widespread occurrences of human discomfort was unknown.  The severity of the 2004 outbreaks resulted in cooperative efforts between K-State and the University of Nebraska entomologists, the resultant being the identification of Pyemotes herfsi as responsible for the stressful skin disorders.

Pyemotes herfsi were recovered from marginal fold galls on (primarily) pin oak leaves.  Marginal galls are associated with the larvae/maggots of tiny midges.  That is, Pyemotes herfsi prey upon the midge larvae.  The following side-by-side close-up images show an intact marginal gall, and a dissected gall revealing female Pyemotes herfsi.  Despite their small size, they become readily visible due to their bulbous abdomens which can contain up to 200 offspring.

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Due to their minuscule size compared to that of midge larvae, Pyemotes herfsi possess a potent neurotoxin used to paralyze their maggot hosts.  This toxin is that which is responsible for initiating the skin irritations which cause discomfort in individuals upon which Pyemotes herfsi happen to come in contact with.  Because Pyemotes herfsi are associated with the midge larvae responsible for marginal galls on oak leaves, Pyemotes herfsi have been given the common name, Oak Leaf Itch Mite.  It is believed that oak leaf itch mites also prey upon the larvae of another closely related midge species responsible for the formation of vein pocket galls on the undersides of oak leaves.  A full description of the oak leaf itch mite life cycle is available online by accessing Kansas State University Extension Publication MF2806.

The good news is that oak leaf itch mite populations may be extremely low or absent for years-on-end —— people can enjoy the outdoors without having to contend with oak leaf itch mite encounters.  The bad news is that the reappearance/resurgence of oak leaf itch mite populations is unpredictable. There are various unknown factors as to the whys-and-where their populations are and when they will surge.  Undoubtedly there are ever-present reservoir populations of oak leaf itch mites, but, where are they?  Possibly a major factor for population explosions is contingent on fluctuating populations of the appropriate gall midges responsible for the formation of  marginal galls and/or vein pocket galls.  An intriguing question then would be, “How do the tiny mites detect and move to the galls up in tree canopies?”  

More bad news:  Each female oak leaf itch mite produces many progeny.  And the developmental cycle is reported to be just 7 days.  The resultant is the production of uncountable numbers of oak leaf itch mites which ultimately leave the confines of leaf galls. Passive dispersal via air currents is the bane to people, especially those in neighborhoods where pin oaks constitute the main trees species.

The bad news continues: There is a wide time frame during which encounters with oak leaf itch mite might occur.  It is not only the initial late summer encounters, but the presence of oak leaf itch mites extending well into the fall when people are raking leaves and kids having fun playing in leaf piles.

And if this is not enough negativity regarding oak leaf itch mites, there is little to be done (well, actually nothing to be done) in treating and reducing/eliminating their populations.  THEY WILL HAVE THEIR WAY!

 The people who are most likely to encounter oak leaf itch mites will be those in living in areas/neighborhoods where oaks (again, especially pin oaks) are the dominant tree species.  When oak leaf itch mite populations are excessive, restricting outdoor activities is one method of reducing the risk of exposure.  While the use of repellents may work against annoying insect species which actively seek a host, repellents have little effect against oak leaf itch mites which are passively dispersed, and lack the ability to alter their course/direction.  It has been suggested that susceptible individuals (yes, some people do not have negative reactions to oak leaf itch mite bites) spend as little outdoor time as possible.  And showers immediately upon returning indoors might eliminate/wash off mites before they bite and cause reactions.

Individuals experiencing oak leaf itch mite encounters might utilize medications and lotions so designed to provide relief from itching discomfort as well as secondary infections of excoriated areas.  Seek advice and recommendations from appropriate personnel.

 

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