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Extension Entomology

Tag: north central Kansas

Sorghum Update

Posted on by Sharon Schroll

–by Jeff Whitworth and Holly Schwarting

Double cropped sorghum in north central KS seems to have a significant infestation of “ragworms”.  The larvae are a combination of fall armyworms and corn earworms and are of various sizes.

corn earworm_ragworm

windowpane ragwormfall armyworm_ragworm

 

Leaf feeding in the whorl by either species is highly visible but should not have a significant effect on the plants or yield.

windowpane ragworm

ragworm feeding

Also, most fields in north central KS are infested with aphids.  Corn leaf aphids can produce a great deal of honeydew but mostly in the whorls.  This honeydew may retard head extension but usually does not affect many plants over a large area.

corn leaf aphids

greenbugs

Yellow sugarcane aphids

Also found greenbugs and yellow sugarcane aphids.  None of the invasive sugarcane aphids were detected in north central Kansas.  However, many beneficials are, and will continue to be, present in sorghum fields as evidenced by the numerous green lacewing eggs and lady beetle eggs.

lacewing eggs

Sorghum Update

Posted on by Sharon Schroll

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Chinch bugs are really common in sorghum fields throughout north central Kansas.  Their feeding will weaken stalks if dry conditions are prevalent.

Green lacewing eggs were present, indicating the presence of future beneficials to help with control of potential future aphid populations.

lacewing egg

chinch bug nymps2

Alfalfa Update

Posted on by Sharon Schroll

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Swathing seems to have interrupted the potato leafhopper increases that were seen prior to cutting.  All the fields sampled prior to swathing in north central Kansas exceeded the treatment thresholds.  Conversely, all the fields sampled post-swathing had potato leafhopper population well below economic injury levels, i.e. 20 potato leafhoppers per 20 sweeps pre-swathing vs. two per 20 sweeps post-swathing.  Continued monitoring would be prudent as these pests may stray around until October and continue to produce offspring.

 

Spotted alfalfa aphids are still present in alfalfa fields but at relatively insignificant infestation levels.  These aphids seem to do very well in mid-summer’s hot, dry conditions but usually don’t reach densities heavy enough to cause yield-reducing stress.

spotted alfalfa aphid

Corn Pests

Posted on by Sharon Schroll

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Most corn pests have come and gone throughout north central and south central Kansas, with a few exceptions.  Japanese beetle adults have been causing concern in north eastern KS, from about Topeka to the Nebraska border and east to the Missouri border.

Japanese Beetle

Green june beetle

 

These beetles are attracted to green silks and can feed so voraciously that they eat into the husks and damage some of the kernels on the tip.  These populations usually do not occur in such numbers to affect pollination over a large area of many fields.  However, in small areas they can cause concern but are relatively well controlled if a foliar insecticide is justified.  Some adult green June beetles are also feeding on corn silks and/or ‘naked ears’ and have been mistaken for Japanese beetles.  Japanese beetles usually migrate to soybean fields to feed on pollen when fields start pollinating but probably not to the extent that they affect yield.

 

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

–Dr. Jeff Whitworth and Dr. Holly Schwarting

Potato leafhopper populations are very active throughout north central Kansas.  There are small nymphs, many adults, and the adults seem to still be migrating into the fields.

PLH adult2

Leafhopper nymph (2)

PLH burn

Could not find significant populations in fields swathed within the last 7-10 days but as regrowth occurs and immigration continues, these fields need to be monitored.  Fields not yet cut are already showing signs of “hopper burn” and should be swathed ASAP or an insecticide application may be justified.  Potato leafhoppers have few, if any, natural enemies.  Thus, these populations probably will not diminish without management, i.e. either swathing (my preference) or insecticide application.  For more information on potato leafhopper management, please visit the Alfalfa Insect Management Guide: http://www.bookstore.ksre.ksu.edu/pubs/mf809.pdf

 

Corn Update

Posted on by Sharon Schroll

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Lady beetles are unusually common in corn fields right now.  Most corn plants in north central Kanas are from V2-V6.  Checking corn rootworm plots revealed western corn rootworm larvae of various sizes and thus they are starting to feed enough to cause a little root damage.

CRW larvae

CRW larvae_sizes

CRW larva on root

CRW root damage

Seems like, despite the recent cooler, wetter conditions, the rootworm development is about where it usually is at this time.  Most western corn rootworms have completed the larval stage by the 1st of July, thus root damage will be completed later this month as the larvae begin to pupate in south central and north central Kansas.

 

Alfalfa Update

Posted on by Sharon Schroll

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Potato leafhoppers continue to inhabit every alfalfa field sampled in north central Kansas.  Populations are still mostly composed of adults but a few nymphs are emerging.  These potato leafhoppers have few natural enemies and thus populations will just continue to increase.  There are still relatively plentiful numbers of lady beetles and green lacewings in most alfalfa fields, and while they probably won’t help with potato leafhoppers, they should continue to help control any developing aphid populations.

Alfalfa Update

Posted on by Sharon Schroll

–Dr. Jeff Whitworth and Dr. Holly Schwarting

Much of the alfalfa in northcentral Kansas that could be swathed has been in the last week.  The cool damp weather has kept the adult alfalfa weevils in the fields.  They are congregated under windrows in the cut fields where they do a little feeding on the stems, resulting in characteristic spots of epidermis removal, called ‘barking’.  As these windrows are picked up there will be the characteristic striping across the fields where the windrows held back the regrowth underneath, plus provided the weevils with a protected site to continue feeding.  Fields not yet swathed also have significant populations of adults but this should not impact the foliage prior to cutting.

AW adult and barking

Windrows

Pea aphids are also present in both cut and uncut fields, but lady beetles and green lacewings are also, so would not expect pea aphid populations to have a negative impact on alfalfa.

Pea aphids adult and nymph

greenlacewing

pinkspotted lady beetle

Sevenspotted lady beetle

Potato leafhopper adults are already present in all alfalfa fields we checked over the past week.  This is earlier than usual for these pests as they typically don’t migrate into the state for another month, between the 2nd and 3rd cutting.  Some of these populations already exceed the treatment threshold with just adults, so hatching nymphs will just increase the populations further.  These potato leafhopper populations need to be monitored throughout the rest of the growing season.

PLH adult and nymph