Kansas State University

— 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.

— 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 2^nd and 3^rd cutting. Some “hopperburn” is already becoming evident.

— 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.

–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 1^st 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.