–by Eva Zurek
Insect Diagnostic Laboratory Report
http://entomology.k-state.edu/extension/diagnostician/recent-samples.html
Month: April 2017
Clover Mite
–Dr. Raymond Cloyd
We have received inquiries regarding homes being invaded by populations of the clover mite, Bryobia praetiosa. This is the time of year when clover mites can be found entering homes, apartments, and commercial buildings, with large numbers crawling around and causing people to “freak out.” In general, clover mites enter buildings from the sunny-side or southwest exposure. They can aggregate in large numbers in the corners of buildings (Figures 1 and 2). Clover mites are primarily considered a nuisance pest because they do not bite humans. However, clover mites will leave a red stain when purposely or accidently crushed.
Figure 1. Cluster Of Clover Mites In Corner Of Building
Populations of clover mites only consist of females since males have never been found (we may need to look harder). Adult clover mites are slightly larger than a pinhead (1/30-inch long), red in color, with extremely long, pink front legs that may be used to distinguish clover mites from other mite pests. Clover mites overwinter as eggs in protected locations and there is usually one generation per year. Adults feed on over 200 plant types including: clover, grasses, ivy, honeysuckle, apple, and elm. Clover mite populations can be extensive in well-fertilized turfgrass near foundations, and their feeding will cause turfgrass to appear silvery or frosty.
Figure 2. Extensive Population Of Clover Mites Entering Building
The management of clover mites involves the following: 1) remove turfgrass near building foundations; 2) place an 18 to 36-inch wide band of an inorganic mulch around the foundation; 3) mow and trim turfgrass as short as possible; 4) avoid over-fertilizing turfgrass, especially with water-soluble nitrogen-based fertilizers; 5) remove weeds growing around the foundation; 6) remove or limit the growth of ivy or other host plants growing around the foundation or walls; 7) use plants near the foundation that are not typically attractive to clover mites, including: marigold, petunia, geranium, arborvitae, and/or yew; and 8) caulk or seal cracks or openings in the foundation or around window seals. Clover mites inside a home or building can be vacuumed up, however, be sure to avoid crushing them. Applications of insecticidal soap (potassium salts of fatty acids) will kill clover mites on contact. You can trap/capture clover mites on saran wrap (Figure 3) or a hardened surface coated with a sticky substance and position by openings such as window seals. If necessary, consult with a pest management professional for recommendations regarding perimeter treatments of pesticides (miticides) to keep clover mites from entering homes or buildings.
Figure 3. Clover Mites Captured On Saran With Sticky Substance
European Pine Sawfly
–Dr. Raymond Cloyd
Yesterday (April 17, 2017) European pine sawfly, Neodiprion sertifer larvae were detected feeding on my “indicator pine” in Manhattan, KS (I was totally excited!). Young caterpillar-looking larvae are 1/4 inch in length and olive-green in color with a black head (Figures 1). Mature larvae are >1.0 inch long with green stripes. The larvae are gregarious or feed in groups on needles of a variety of pines, especially Scotch, red, and mugo pine. When disturbed, each individual larva will arch their head and abdomen (last segment of an insect body) back, forming a “C-shape” (Figure 2), which is a defensive posture to ward-off predators.
Figure 1. Young European Pine Sawfly Larvae
Eventually, larvae will strip the needles of mature foliage, leaving only the central core, which is white and then turns brown (Figure 3). In general, larvae complete feeding by the time needles emerge from the candelabra. Therefore, those really is only a minor threat of branch or tree death resulting from sawfly larval feeding. However, the loss of second- and third-year needles will be noticeable in landscape trees; thus ruining their aesthetic appearance. In late spring, larvae drop to the ground and pupate in brown, leathery cocoons located at the base of trees. Adults, which are wasp-like, emerge in fall and lay eggs in needles prior to the onset of winter. There is one generation per year in Kansas.
Figure 2. European Sawfly Larvae In A Defensive Posture (Arching Head And Abdomen Back)
Sawfly larvae look-like caterpillars; but, they are not caterpillars (Order: Lepidoptera). Sawflies are related to ants, bees, and wasps (Order: Hymenoptera). The primary way to distinguish a sawfly larva from a caterpillar is by the following: 1) sawfly larva have prolegs (fleshy abdominal legs) on every abdominal segment whereas caterpillars are missing prolegs on the abdomen and 2) caterpillar larva have hairs or crochets on their feet whereas sawfly larva do not have hairs or crochets on their feet.
Figure 3. Feeding Damage To Pine Caused By European Pine Sawfly Larvae
Sawfly larvae are not caterpillars, therefore, the bacterial insecticide, Bacillus thuringiensis subsp. kurstaki (sold as Dipel) will not directly kill sawfly larvae. Dealing with sawfly larvae involves hand-picking (you can wear gloves if you wish) or dislodging larvae from plants by means of a forceful water spray. If necessary, there are a number of insecticides that may be applied to suppress European pine sawfly populations including: acephate (Orthene), azadirachtin, carbaryl (Sevin), spinosad (Captain Jack’s DeadBug Brew and Conserve), and any pyrethroid insecticide (e.g., bifenthrin, cyfluthrin, and lambda-cyhalothrin). Be sure to read the insecticide label to make sure that sawflies are listed. For more information regarding European pine sawfly management contact your county or state extension specialist.
Wheat Update – Aphids
–by Dr. Jeff Whitworth and Dr. Holly Schwarting
Wheat aphids have really started showing up in wheat fields throughout north central Kansas. English grain and bird cherry-oat aphids are the two most commonly observed so far.
These aphids usually do not build up in sufficient populations to stress wheat or impact yield, especially when growing conditions are good, which they have been for the last couple of weeks. These aphids can vector barley yellow dwarf virus, however at this time of year this should not impact yield. These aphids are providing a plentiful food source for lady beetles, and all wheat fields sampled in the last seven days contained significant numbers of lady beetles.
Therefore, it is prudent not to spray for these wheat aphids unless there are 20+/tiller on a field-wide basis. Especially do not include an insecticide in a mixture with a fungicide “just in case”.
Alfalfa Update
–by Dr. Jeff Whitworth and Dr. Holly Schwarting
Alfalfa weevil feeding activity has slowed significantly in north central Kansas, at least south of I-70. North of I-70, larvae are still developing and thus feeding, but even in the northern counties this feeding and resultant damage should be significantly reduced by the end of the next week. There are still some small larvae but the majority of populations are pupating or have pupated. Adult weevils are still hanging out in alfalfa fields and probably will until that 1st cutting, or temperatures get into the mid-80’s or warmer.