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Extension Entomology

Category: Wheat

Armyworms in Brome

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Armyworms have been feeding in brome throughout north central Kansas for about the last three weeks.  However, they have just, in the past week, gotten large enough to start being noticed.  They are first being detected because the infested patches of brome do not have any leaves, due to armyworm feeding, and/or no heads where the seeds develop.  These infested areas will have delayed development due to this feeding but the stand should recover.  These armyworms are already “making the ground come alive” as they reach maturity and crawl down the plants, usually many at about the same time, to seek pupation sites in the soil.  This is noticeable even on dirt roads or lanes near these infested fields.

 

 

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”.

Wheat

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Some winter grain mite infestations have been noted in the last 7-10 days.  These seem to become evident every fall, especially under dry conditions, but don’t warrant a pesticide application.  Moisture and/or colder weather will alleviate these infestations, at least until warmer spring weather returns.  For more information on winter grain mites, please visit: http://entomology.k-state.edu/extension/insect-information/crop-pests/wheat/winter-grain-mite.html

winter-grain-mite-1

winter-grain-mite-2

Alfalfa and Wheat “Worms”

–by Dr Jeff Whitworth and Dr Holly Schwarting

Wheat and alfalfa fields throughout south central and north central Kansas should be monitored for signs of defoliation.  Many pests can defoliate either crop this time of year, i.e. grasshoppers and flea beetles (usually around borders), and “worms”.  These larvae are most commonly armyworms, fall armyworms, and/or army cutworms.  Identification is important for these “worms” because armyworms and fall armyworms will feed until the temperatures cool into the mid-20’s or they pupate, whichever comes first.

armyworm

fall-armyworm

 

Army cutworms, however, are and have been hatching from eggs deposited by moths as they return from over-summering, probably in Colorado.

army-cutworm

These army cutworm larvae will feed a little this fall, overwinter, then start feeding again in early spring.  So, if the “worms” causing the defoliation now are relatively large, ½ inch or more, they are probably armyworms and/or fall armyworms.

 

We have been hearing about and seeing a mixture of both armyworms and fall armyworms (see pics below).  These small worms start by causing small “windowpanes” in wheat or alfalfa.  No army cutworm infestations have been verified yet.

small-worm-1

small-worm-2

windowpane-feeding_wheat

Flocks of birds in wheat or alfalfa fields in fall or early spring are often indicative of a “worm” infestation as the birds are feeding on the larvae.  Fields with 25-30% of the plants showing “windowpane” feeding need to be monitored frequently as these larvae consume more as they get larger.  Treatment should be applied before stands become threatened.  For more information on treatment thresholds and management options please see the Wheat Insect Management Guide: http://www.bookstore.ksre.ksu.edu/pubs/mf745.pdf

Volunteer Wheat

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Frequent rain over the last few weeks has played havoc with volunteer wheat control.  Each rain seems to bring another flush of volunteer.

volunteer-wheat

 

This is an ideal situation for most wheat pests, i.e. Hessian flies, winter grain mites, wheat curl mite, and the wheat aphids (mainly greenbugs, bird cherry oat and English grain) as well as the pathogens they may vector.  Thus, please remember to destroy all volunteer at least 2 weeks prior to planting to help manage these pests.

Volunteer Wheat

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Wheat harvest is completed, or at least real close, across the State. So, it is time to start thinking volunteer wheat control. As wheat producers know, volunteer wheat is very persistent. Every time it rains or the fields are irrigated, another flush or crop of volunteer wheat germinates. Thus, control needs to be just as persistent. Volunteer wheat can be a harborage for most wheat pests, especially bird cherry-oat aphids, Brown wheat mites, English grain aphids, greenbugs, Hessian flies, wheat curl mites, and many of the more common pathogens. Season-long control is always best, but rarely practical. So, volunteer wheat eradication at least 2 weeks prior to planting is the next best management practice.

 

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