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Extension Entomology

Tag: garden webworm

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

Soybean Update

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

(thistle caterpillars, painted lady/thistle caterpillar chrysalis, garden webworm, bean leaf beetle, false chinch bug)

Soybeans seem to be the crop getting the most attention throughout north central Kansas.  Thistle caterpillars have been pupating in their unique little chrysalis that can be lime green to brownish in color and is often found hanging on the underside of leaves within the soybean canopy.

 

Some fields, especially in areas north of I-70 Highway, have many thousands of these painted lady butterflies flying around, often focused around the borders of soybean fields.  These fields are where the thistle caterpillars have been feeding and pupating.  The orange, black, and white spotted butterflies will be depositing eggs in soybeans, sunflowers, and many different weed species and the small spiny larvae will then begin feeding.  So, sampling in soybeans and sunflowers should continue for about the next three weeks.

 

 

 

Webworm larvae are feeding on soybean leaves and bean leaf beetle adults are starting to emerge and both are adding to overall defoliation in soybeans.  For management decisions regarding soybean defoliators, please refer to the KSU Soybean Insect Management Guide: https://www.bookstore.ksre.ksu.edu/pubs/MF743.pdf

 

 

 

 

False Chinch bugs have also been reported from soybeans.  These bugs are often mistaken for chinch bugs, hence the name, but unlike chinch bugs, they will sometimes feed on soybeans after their natural weed hosts are killed.  However, this feeding is usually of little consequence.  Although these bugs often congregate by the hundreds and thousands, they usually disperse within a few days with no tell-tell signs that these huge numbers were ever there.

 

 

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