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Extension Entomology

Tag: summer

Oak Vein Pocket gall: Back with a Vengeance!

Posted on by Jena Ernsting

–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.

Yikes! What’s Biting Now? + Pepper-In-My-Paint = Minute Pirate Bugs (MPB)

Posted on by Sharon Schroll

–Dr. Bob Bauernfeind

Saturday afternoon as I was doing some house painting, I was feeling occasional “little irritations” on my arms and legs.  Looking at the points of discomfort, I recognized my little visitors:  minute pirate bugs – Orius spp.  And, looking in my paint bucket, more were “stuck” on the surface of the paint.

#1

Actually, this was nothing that I hadn’t experienced in the past.  I usually have a spring and summer list of projects.  I seem to put painting (not my chore of choice) off until the heat-of-summer is past, and then gallop to complete the task trying to beat colder weather.  Thus, mid- to late fall is when I am visited by MPB.  What draws them?  It’s not the paint color.  Whether ultra-bright white (for trim), or Coronado Tint Base 410-35 + B20C24F9 (a color for which there is no name) for the body of the house, they show up.  I surmise that the attractant is the paint odor being carried in the air.

Those that land on me take-a-taste.  This is not an unusual.  One way an insect determines whether it has landed on a “choice” food source is to take-a-taste.  While an insect with chewing mouthparts takes-a-bite/chomp, an insect with piercing/sucking mouthparts (such as a MPB) takes a “jab-and-sip”.  They must not get an instant result, because I have watched individuals lingering after their jab caught my attention.  But eventually, because I didn’t qualify as a satisfactory food source, they withdrew.  The fate of those in the paint bucket?  Given their small size, they are painted into and become a part of the coat of paint on my house.

#2

Are MPBs pests or not-a-pest?  While their bite (in my estimation) is but a minor irritation, in their proper place, MPB’s would be considered to be beneficial insects in their role as predators.  Close-up, they are distinctively marked.

#3

Given their small size (1 – 1 ½ mm), their natural prey are correspondingly small —- preferably insect eggs, mites, scale crawlers, thrips, aphids, small stage caterpillars. Using their styet-like mouthparts, they impale their prey and withdraw the body fluids.  They then abandon the spent carcass and search for their next victim.

MPBs mostly go unseen due to their small size.  Yet, they are common and can be found on flowering shrubs and weeds where they subsist on plant juices in the absence of prey.  However, in the presence of arthropod hosts, their true feeding preferences take over.  Both nymphs and adults have been cited to consume 30 or more spider mites per day.  And often times, adult MPBs are drawn to corn silks where they feed on/destroy eggs deposited by corn earworm moths.  MPBs are commercially available and can be useful when released in enclosed facilities such as greenhouses.  But for home gardeners, purchase-and-release tactics are impractical because released MPBs would likely take wing.  Rather, rely on their natural abundance to allow them (on their own) to find their way into home landscapes and gardens.