Kansas State University

search

Extension Entomology

Tag: alfalfa

Soybean Update — Green Cloverworms

Posted on by Sharon Schroll

— by Dr. Jeff Whitworth and Dr. Holly Schwarting

 

Green cloverworm larvae have been very numerous throughout north central and south central Kansas for the past 30-45 days.  However, the larval stage and the leaf defoliation that they’re known for, has pretty much ceased as most larvae have entered, or are entering, pupation.

 

 

A few green cloverworm larvae can still be found in late planted beans and alfalfa, but for the most part, their feeding will soon cease.  The most common question is, with all these green cloverworm adults around, will they be in the same fields next year?  They do not overwinter in Kansas and most soybean fields will be rotated, so the answer is no.  If the same fields are infested next year, it will not be because of the green cloverworms that survived the winter in that field.

 

Soybean Update – Green cloverworms and Stink bugs

Posted on by Sharon Schroll

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Green cloverworm adults are quite numerous and are laying eggs in alfalfa and soybeans.  So, there are, or will soon be, small larvae present.  Feeding by green cloverworms will probably not impact alfalfa or most soybean fields unless there are significant larval populations in really late planted fields.

 

 

Stink bug populations seem to be increasing in north central Kansas but most beans should be far enough along in their development that stink bugs should be of little concern.

 

For management decisions for all soybean pests, please refer to the 2017 Soybean Insect Management Guide: https://www.bookstore.ksre.ksu.edu/pubs/MF743.pdf

Alfalfa Update

Posted on by Sharon Schroll

–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.

 

Soybean Update

Posted on by Sharon Schroll

— by Dr. Jeff Whitworth and Dr. Holly Schwarting

Soybeans seem to be growing well throughout north central Kansas.  Not too many pests have been noted.  However, there seem to be some spider mite populations building throughout the south central and north central parts of the state.  These need to be monitored, especially if adequate moisture is not forthcoming.  Mite populations can expand very quickly and really add stress to plants that are already moisture stressed.

spider mites whole plant

spider mite close

Also, blister beetles are starting to swarm, especially in alfalfa and soybean fields.  This swarming behavior is primarily for mating purposes and may involve anywhere from a few hundred to thousands of individuals.  They may feed a little while swarming and actually cause plant loss, but only in small areas where the swarming occurs.  Thus, treatment is rarely warranted.

Blister beetles

 

Alfalfa Update

Posted on by Sharon Schroll

By — Dr. Jeff Whitworth, Dr. Holly Schwarting

Alfalfa continues to be problematic in NC Kansas.  There seems to be many fields of good alfalfa, apparently treated in an effective manner from both an insecticide and a timing standpoint, and not affected by the freezing temperatures earlier this spring.  Many of these fields have been, or are being, swathed.  However, there are some fields that have had, or are having, a difficult time overcoming the combination of alfalfa weevil larval feeding, early season dry conditions, and the early spring freezing temperatures.  In all fields, the early season warmth sped up alfalfa weevil development and feeding, then the cooler temperatures slowed it back down.  Alfalfa weevil larvae were 1st detected in NC Kansas in early March.  Small, 1st instar larvae are still being detected in some fields.

AW larvae 13

Some larvae pupated and developed into adults as long as three weeks ago, and they are still in the alfalfa fields.  So, NC Kansas still has a significant number of adults.  Treating for adult alfalfa weevils is rarely effective, but swathing within 7-10 days should help manage both larvae and adults without an insecticide application.

AW adult

Adult potato leafhoppers have also been noted in alfalfa fields.  These usually migrate into Kansas between the 2nd and 3rd cuttings, so they are about a month early this year. Leafhopper adult (2)