Kansas State University

search

Extension Entomology

Month: May 2019

Grasshoppers

— by Dr. Jeff Whitworth and Dr. Holly Davis

Grasshopper nymphs, both longhorned (typically not a pest), and shorthorned are common and they will probably just keep increasing in density for another month or more. Another reminder that the best time to manage them is while they are still small and thus, less mobile.  An application of an insecticide labeled for grasshopper control is most effective, cheaper, and less environmentally disruptive if applied in a timely manner relative to grasshopper development.

Potato Leafhoppers

— by Dr. Jeff Whitworth and Dr. Holly Davis

These small, lime-green, wedge-shaped, herky-jerky moving insects have already migrated into the state.  Some fields are at or exceeding treatment thresholds.  However, swathing should cure this problem, at least temporarily.  Historically, potato leafhoppers migrate into Kansas a little later in the season, i.e. between the 2nd and 3rd cutting. Some “hopperburn” is already becoming evident.

Pea Aphids

— by Dr. Jeff Whitworth and Dr. Holly Davis

Pea aphids are also abundant at the present time.  Alfalfa weevil insecticide applications decimated most beneficials which usually help control these aphids.  However, lady beetle populations appear to be increasing which should help control these aphids, as should warmer summer weather.

 

Alfalfa Weevils

–by Dr. Jeff Whitworth and Dr.Holly Davis

Seems like alfalfa weevils have caused concern for considerably longer this spring than usual as they have been active since early April, at least in north central Kansas.  While there are very few larvae or pupae left, there are adults remaining in fields which is unusual for this late in the year, but not unique.  Adult alfalfa weevils typically remain in the alfalfa canopy until the 1st cutting.  After swathing, the adults migrate to other areas that provide more shade where they spend the summer.  However, in years when there is a relatively cool spring accompanied by cloudy, rainy weather that delays getting into the fields to harvest, the canopy provides more shelter than when it is swathed in a timely manner.  This results in adult weevils hanging around in the alfalfa fields later into the spring than usual because of the cooler conditions within this canopy.  Adult alfalfa weevils are not the voracious leaf defoliators that the larvae are.  However, they will feed a little on leaf tissue, but more frequently around the exterior of stems.  This is called “barking” and normally does not stress plants under good growing conditions.

 

One problem with swathing while adults are still active in fields is that when the alfalfa is swathed and then windrowed, it does not kill the weevils, but does concentrate them into smaller areas.  They seem content to remain in the shade provided by these windrows where they may feed on the freshly cut stems, retarding their regrowth.  Often, this adds to the characteristic “striping” in these fields, especially if the windrows cannot be picked up as soon as usual.  There is no management remedy for this situation, other than drier weather.

Ticks

— by Dr. Jeff Whitworth and Dr. Holly Davis

 

Ticks are becoming more active this spring, especially wood ticks, also called American dog ticks, Dermacentor variabilis.  These are probably the most common tick encountered in Kansas and they are more common in grasses around field borders and areas with more trees.  They can transmit several diseases and thus should be carefully and safely removed, head intact, before feeding occurs for more than a few minutes, if possible.  For more information on the species of ticks found in Kansas, please see Household Pests of Kansas (pg. 97): https://www.bookstore.ksre.ksu.edu/pubs/MF3291.pdf

 

Armyworms|

— by Dr. Jeff Whitworth and Dr. Holly Davis

Armyworm larvae are apparently getting large enough now to cause noticeable feeding damage in a few places in southeast and north central Kansas.  Armyworms prefer grasses; thus they are now feeding on brome.  They should not be a problem while these good growing conditions are allowing the plants to outgrow the armyworm feeding.  However, this is the 1st generation of this common pest and we usually have 2-3 per year.

If conditions remain good for plant growth, armyworms should not be a problem.  However, they sometimes feed in wheat and when the leaves start to senesce, they move to the beards to feed and /or clip the heads, which can be problematic if there are large numbers.  After wheat and other grasses senesce, the armyworms often move to corn and sorghum where they may cause some alarm by feeding on the leaf tissue between the leaf veins or feeding in the whorl which may contribute to the ragged-looking leaves as they grow out of the whorl.

 

 

Grasshoppers

— by Dr. Jeff Whitworth and Dr. Holly Davis

Just started finding very small, recently hatched grasshopper nymphs.  If, or when, these nymphs start to increase in numbers in the next few weeks, remember the best time to manage them is while they are still small and thus, less mobile.  An application of an insecticide labeled for grasshopper control is most effective, cheaper, and less environmentally disruptive if applied early so it can be better targeted in a smaller area at the most susceptible time to control these pests.

Alfalfa Update – Alfalfa Weevils, Pea Aphids, Etc.

— by Dr. Jeff Whitworth and Dr. Holly Davis

Alfalfa weevil activity has slowed considerably but has not stopped yet.  Fields that have not been treated at all this season still have relatively large populations of larvae, of all sizes, and increasing numbers of adults.

 

Small larvae along with later, more mature instars, plus pupae and newly emerging adults are still developing because of the recent cooler weather which has slowed down weevil development.  The field shown here withstood a weevil infestation feeding on the leaf tissue since early April but is starting to come back with some regrowth as the larval population matures into pupae, then adults. However, the 1st cutting, at least, has been donated to the alfalfa weevil.  In contrast, fields treated in a timely manner are now being, or are ready to be, swathed as soon as possible.

 

Pea aphid populations are starting to increase in fields treated earlier for alfalfa weevils.  However, this is also allowing beneficials to build up which should be helpful for controlling other aphid populations in other crops throughout the growing season.

 

Another example of alfalfa being a great “sink” for other insects – it is the main habitat for adult bean leaf beetles where they hang out until soybeans start germinating.  They will then migrate from alfalfa to feed on seedling soybeans and begin ovipositing around the base of these seedlings.

Bean leaf beetles are often confused with southern corn rootworms which can also be very common in soybeans but do not have the potential to negatively impact yield.  For more information on alfalfa pest management and/or soybean pest management, please refer to the KSU Insect Management Guides.

KSU Alfalfa Insect Management Guide: https://www.bookstore.ksre.ksu.edu/pubs/MF809.pdf

KSU Soybean Insect Management Guide: https://www.bookstore.ksre.ksu.edu/pubs/MF743.pdf

Termites

— by Dr. Jeff Whitworth and Dr. Holly Davis

The last few days of warm, sunny conditions after the preceding few days of cooler, wet weather have apparently initiated considerable termite swarming activity.

Again, make sure to positively identify the insects swarming, as ants are also actively swarming.  There is a huge difference in damage potential between termites and ants, even carpenter ants.  So, please refer to these KSU extension publications to properly identify and manage ants and termites:

 

Termites, MF722: https://www.bookstore.ksre.ksu.edu/pubs/MF722.pdf

Ants, MF2887: https://www.bookstore.ksre.ksu.edu/pubs/MF2887.pdf

Biting Gnats

–by Dr. Jeff Whitworth and Dr. Holly Davis

We have received a few calls about “biting gnats”.  These are most likely small black flies, commonly called black flies or buffalo gnats.  These appear every year, usually near moving water, and they can be very persistent at getting a blood meal, which the females require in order to produce viable eggs.  While they can be aggressive biters for 7-10 days, they do not transmit pathogens.  Management is difficult because the females deposit their eggs in slow moving creeks and streams.  Larval populations typically decline considerably once water temperatures reach 75-80°F.

 

For more information, please refer to Household Pests of Kansas (page 65): https://www.bookstore.ksre.ksu.edu/pubs/MF3291.pdf

 

Subscribe By Email

Get every new post delivered right to your inbox.

This form is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.