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Extension Entomology

Tag: leaf tissue

Soybean Update – Green Cloverworms, Thistle Caterpillars, Stink Bugs, Soybean Aphids, and Beneficials.

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

 

Insect activity is still increasing around north central Kansas.  One positive, bean leaf beetles seem to be at really low densities in most fields, at least so far.  Green cloverworm larvae are at various developmental stages but there are still many early instars.  This means there probably is considerable defoliation to come because, as the larvae get larger, they simply eat more leaf tissue.  However, as green cloverworm populations increase, they are often infected with an entomophagous fungus which decimates their populations.

 

There also are many areas with significant infestations of thistle caterpillars and garden webworms.  Both species web leaf tissue around and over themselves, creating a relatively secure area from which they feed on leaves.  Many thistle caterpillars are really small right now and may not be noticed yet.  So, continued monitoring is important, especially with soybeans just entering the reproductive stages of development.

 

Green stink bugs are relatively common in both conventionally planted and double-cropped soybeans.  There are eggs, nymphs, adults, and mating adults all present at this time so sampling needs to be conducted periodically as these bugs can feed on the beans while they are developing inside the pods.

Soybean aphids were detected in double-cropped soybeans in Dickinson Co. on 24 August. Many soybean fields have significant populations of green lacewings and lady beetles, both of which may help control soybean aphids if and when they migrate into these fields.  So, as always, please take these into consideration if insecticide applications are contemplated.

 

For more information of thresholds and management options for these pests, please refer to the KSU Soybean Insect Management Guide: https://www.bookstore.ksre.ksu.edu/pubs/MF743.pdf

Western Corn Rootworms

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Most of the corn in north central and south central Kansas is at, or just passed, the whorl stage and there seem to be very few whorl-feeding larvae.  However, the Western corn rootworm adults are just starting to emerge from the soil.

WCR adult 1

WCR adult 2

These adults were 1st detected on 23 June in Dickinson County.  These beetles are feeding on the leaf tissue as the plants are not yet tasseling or producing silk/pollen.  There is quite a disparity of rootworm life stages in this same field.  There are many adults in the northwest corner but still mostly larvae, even relatively small ones, in the southeast corner of this same field.  Some of the feeding damage caused by the rootworm larvae can be seen in the last photo.

WCR larvae

WCR larval feeding damage

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