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Extension Entomology

Category: Wheat

Beneficial’s

–by Dr. Jeff Whitworth — Field Crops

Beneficial’s continue to be very active throughout all crop fields in the eastern half of Kansas (please see fig 4–pink spotted lady beetle depositing eggs, 15 July). Thus, the practice of just adding an insecticide into any tank mix with fungicides and /or herbicides “just in case” is NOT recommended. Please ensure any targeted pest meets, or is close to, a treatment threshold before utilizing an insecticide application.

Figure 4. Pink Spotted Lady Beetle depositing eggs (pic by Kaysie Morris)

Click Beetles

–by Dr. Jeff Whitworth — Field Crops

Click beetles (fig 1) are becoming very active and this activity will continue for at least the next month. There are several species of click beetle in Kansas that can be a pest of crops. The larvae of these species are generally called wireworms and may feed on roots, root hairs, germinating seedlings, etc. In other words, just about any plant parts found underground including seeds can be damaged by click beetle larvae. The adults, of all species, are often attracted to lights at night or may be found under plant residue in fields. Insecticide seed treatments do really well at protecting seeds and seedlings, from planting up to about 28 days post-planting, from wireworm attack.

Figure 1.  Click beetle   (picture by Cody Wyckoff)

 

Wheat Aphids

–by Jeff Whitworth — Field Crops

 

Wheat aphids, primarily bird cherry oat but with a few greenbugs mixed in, have been migrating into Kansas, especially the southern parts, over the last couple of weeks. Sampling a couple dozen fields throughout the central part of the state, however, over the last week (from I-35 to Hwy 77 west to east and from Hwy 24 north to Hwy 56 on the south) yielded very few aphids but also very few beneficials-which makes sense. However, in one field we did find one aphid — just as the only lady beetle we found in that field also found it and promptly gobbled it up (see fig 3). Most wheat was at least at the jointing stage. If aphid migrations increase significantly in the next couple of weeks, coupled with the lack of beneficials, these aphid populations could explode and thus cause some stress to the developing wheat. Thus, monitoring should continue — but please remember it takes approximately 20+ aphids/tiller throughout the field, with very few beneficials, to actually cause a negative effect on yield. Also, please remember adding an insecticide to an application of a fungicide to kill any insect pests, “just in case” is never a good idea.

 

Army Cutworms

–by Dr. Jeff Whitworth, Professor, Field Crops

Army cutworms are again relatively common this year, however, thus far, not nearly as destructive as last year (2020). This could be because infestations are much reduced compared to 2020 – or that growing conditions have been much better than last year for both alfalfa and wheat. However, birds (and/or skunks) feeding in alfalfa or wheat fields are still the easiest way to detect army cutworm larvae.

Volunteer Wheat

–by Dr. Jeff Whitworth

 

Much wheat has been planted but much is still to be planted. Please remember that volunteer wheat (see fig 4) needs to be dead at least 3 weeks prior to planted wheat germinating. This really helps mitigate wheat pests that may be utilizing this volunteer wheat as a “green bridge”– just waiting to move from these plants to infest the germinating new plants.

Figure 4 Volunteer Wheat (Cayden Wyckoff)

 

VOLUNTEER WHEAT

–by Dr. Jeff Whitworth

Frequent rains over the last few weeks throughout the eastern half of Kansas have really started germination of volunteer wheat (figures 4 and 5). This is the “green bridge” that most wheat pests rely upon for their existence, from the time last fall’s planted crop matured until this fall’s planted crop germinates. Thus, destroying volunteer wheat can really help mitigate most wheat pests.

Figure 4-5 “Green Bridge” of volunteer wheat (Cody Wyckoff)

Wheat Update – armyworms, grasshoppers

–by Dr. Jeff Whitworth

Some fields have already established good stands of wheat this fall. However, there are also some pretty well established fields of volunteer wheat (see pic provided courtesy of Jay Wisby). There have been reports of armyworms and grasshoppers causing concern in some wheat fields that are struggling because of lack of moisture, but the recent cold weather should control both armyworm and grasshopper feeding.

 

 

Wheat

–by Dr. Jeff Whitworth

 

Some reports are being received mainly from south eastern/south central Kansas relative to “worms” feeding on early-planted wheat. First, it is usually better to plant wheat as late as possible to help avoid all wheat pests, whether pathogens or insects. The “worms” reported so far, have been either armyworms or fall armyworms, both of which will do about the same type of damage. They feed on leaf tissue and consume more, as they get larger, thus it is best to monitor wheat fields early to detect any larvae while they are still small. They usually do not reduce wheat stands, just remove the leaf tissue, but under stressful growing conditions plant stands may be impacted. Under good growing conditions, plants should be only temporarily affected. However, if there are 8-10 worms per sq. ft. and the worms are small, i.e., less than ½”, treatment may be justified. Remember also, if the leaf feeding continues into the winter it might be caused by army cutworms, which will feed all winter anytime temperatures are over 45 F, and into the spring. However, armyworms and fall armyworms will only feed until the 1st hard freeze, but not through the winter.

 

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.

 

 

Wheat Aphids and Mites

–by Dr. Jeff Whitworth and Dr. Holly Davis

 

Most wheat fields we sampled around north central Kansas between 2-6 May had populations of bird cherry-oat aphids which were relatively easy to find.  They were in 100% of the sampled areas, however, not on 100% of the plants within those areas.  They are relatively easy to see, because of their dark color, if you examine the lower portion of the plants.  There are no symptoms or signs of their feeding nor would we expect there to be any because of the good growing conditions so far.  The populations are not yet at the density to warrant any concern.

Some winter grain mites were also noted but are nothing to worry about.  Winter grain mites are usually in their summer aestivation, or dormancy, period by now as they prefer cool, cloudy weather.  Thus, they will not be a problem moving forward into this growing season but the fact that there are still a few around is indicative of the cloudy, cool conditions we have experienced thus far this spring.

 

 

It is still NOT recommended to add an insecticide to a fungicide application just to save application costs and to kill the few aphids that are present.  This will do much more harm than good in the long run.  For more information relative to wheat pest and their management, please see the Wheat Insect Management Guide available here: https://www.bookstore.ksre.ksu.edu/pubs/mf745.pdf