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Extension Entomology

Tag: armyworms

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

Corn Pest Update

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Checking corn fields between rains indicates some insect activity.  The most visible seems to be corn earworm larvae.  The fields we checked in north central Kansas were in the 8-9 leaf stage and the corn earworm larvae had probably been feeding for about a week.  However, the feeding is only noticed after the leaves unfurl as the larvae are hidden inside the furled leaves.

 

CEW larva

Checking corn fields between rains indicates some insect activity.  The most visible seems to be corn earworm larvae.  The fields we checked in north central Kansas were in the 8-9 leaf stage and the corn earworm larvae had probably been feeding for about a week.  However, the feeding is only noticed after the leaves unfurl as the larvae are hidden inside the furled leaves.

Ragged leaves corn

We also found western corn rootworm (WCRW) larvae feeding on corn roots.  This field was sampled last weekend but no larvae were detected.  However, in this same field, the larvae hatched and have fed on the roots as seen in the picture.  Just in the last 3-4 days, larval feeding has caused some root damage.

CRW larva and damage

CRW larva

Corn and Wheat Pest Update

–Dr. Jeff Whitworth and Dr. Holly Schwarting

Corn

Plants in north central and south central parts of the state are finally starting to grow.  All the cloudy, wet conditions have not been the best for corn development and many fields are a little more chlorotic looking than usual for this time of year.  This stalled development usually allows pests more time to feed and thus cause damage.  Seed treatments only provide protection for 3 to 4 weeks (check label) from planting, so most of that protection has dissipated.  However, we have not seen nor heard about much pest activity yet.  A few thin stands have been noted which can be caused by many different pests, probably most common so far has been wireworms.  Generally, however, most fields are past seedling damage.

wireworm 1

wireworm 2

We have received a few calls about armyworm activity in wheat and sorghum, so when these larvae pupate and then emerge as adults to lay eggs, most corn will be in the whorl stage so there may be some whorl-stage leaf feeding which is always highly visible but causes very little actual impact on yield.

Wheat

We have not seen any “worms” in wheat, but have received several calls about armyworms feeding on leaf tissue.  Armyworms should move to another grass host, i.e. corn, sorghum, brome, etc. as the wheat begins to senesce.  They actually devour leaf tissue and thus are not actually feeding on the grain.

Armyworm

If there are thin, light green or tan worms feeding on the wheat head they are probably wheat head armyworms (see photo).  They can and will actually feed on the grain whereas the armyworm feeds on the foliage around the grain – not the grain itself.

wheat head armyworm

If you decide to treat either pest, please refer to the Wheat Insect Management Guide, 2015: http://www.ksre.ksu.edu/bookstore/pubs/MF745.pdf and make sure to check the label for the preharvest interval (PHI) if spraying wheat this close to harvest.

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