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Extension Entomology

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.

Ash/Lilac Borer: Don’t Get “Bored-Down” By This Caterpillar Borer

–by Dr. Raymond Cloyd

 

        The time of year has come to be thinking about dealing with the ash/lilac borer (Podosesia syringae). First, you need to understand that this is not the same insect pest as the Emerald ash borer (Agrilius planipennis), which was recently discovered (March 31, 2017) in Doniphan County (Kansas now has 7 counties under quarantine). Emerald ash borer is a wood-boring beetle whereas the ash/lilac borer is a wood-boring caterpillar. Ash/lilac borer adults are generally active from mid-April through early-May. Adults are brown, clearwing moths that resemble paper wasps (Figure 1). Peak moth activity commonly occurs from May through June; however, this depends on temperature. Adult females lay tan-colored, oval-shaped eggs in cracks and crevices, or wounds at the base of plant stems. A single female may live approximately one week and lay up to 400 eggs. Below are the major life history parameters and management strategies affiliated with the ash/lilac borer:

Figure 1. Ash Lilac Borer Adults Mating

 

* Larvae cause plant damage by creating tunnels and feeding within the bark (cambium). Moreover, larvae may bore further into the wood and feed within the sapwood and heartwood.

 

* Feeding by the larvae restricts the flow of water and nutrients causing shoot or branch dieback. Ash/lilac borer primarily feed near the base of plant stems creating swollen areas or cracks at the base of plants, and where major branches attach to the trunk.

 

* Evidence of larval feeding includes the presence of light-colored sawdust that accumulates at the base of infected trees or shrubs.

 

* Ash/lilac borer overwinters as a late-instar larva located in feeding tunnels or galleries.

* To determine if trees or shrubs are or have been infested with ash/lilac borers check for the presence of brown papery pupal cases that protrude from the bark (Figure 2). These are the pupal cases where adults emerged from.

 

* In Kansas, there is generally one generation per year.

Figure 2. Pupal Cases of Ash Lilac Borer Protruding From Tree Trunk

 

* The way to avoid problems with ash/lilac borer is to minimize “plant stress” by properly implementing cultural practices, such as; irrigation (watering), fertility, pruning, and mulching. Stressed plants are more susceptible to attack than so called “healthy plants.” A two to three foot wide mulched area around the base of trees and shrubs prevents injury from lawn mowers and weed-trimmers. In addition, avoid pruning plants in late spring through early summer (under usual weather conditions), because this is when adults are typically present and the volatiles emitted from pruning cuts may attract adult females.

* Insecticides containing the active ingredients, permethrin or bifenthrin can be applied to the bark, at least up to six feet from the base, in order to prevent ash/lilac borer larvae from entering plants after eggs hatch. Clear-wing borer larvae crawl on the bark searching for entry points, which exposes them to insecticide residues.

 

* Pheromone traps are commercially available for capturing adult males (Figure 3), which helps to determine when females will be laying eggs. Pheromone traps help in timing insecticide applications. Insecticide spray applications should begin seven to10 days after capturing the first adults. Be sure to also check pheromone traps two to three times per week and record the number of newly captured adult males.

 

Figure 3. Pheromone Trap Used To Capture Ash Lilac Borer Adult Males

 

* For more information regarding ash/lilac borer management contact your county or state extension specialist.

Alfalfa Update

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

 

Alfalfa weevil populations in north central Kansas seem to be developing as expected.  Fields sampled this week that had not yet been treated had greatly reduced foliage and were showing obvious signs of significant larval feeding, especially compared to fields that had been treated.

 

 

The good news is that the treated fields seem to be doing well and the untreated fields will probably only continue to be seriously impacted for about another week.  Weevil populations are predominately pupae, pre-pupae, or mature larvae which should cease feeding in the next few days.

 

 

This should give the alfalfa a chance to recover.  However, in untreated fields, and even fields that were treated later, after a majority of the larvae pupated, may have some adult feeding, as they may remain in fields until the 1st cutting or until temperatures start getting into the higher 80’s °F.  Adults feed a little on foliage and/or may cause ‘barking’ on stems, but this usually doesn’t stress plants too much unless there are significant numbers of adults.

 

Very few aphids were detected, but there were a few so periodical sampling should continue to ensure that these aphid populations remain at insignificant levels.

 

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