Kansas State University

search

Extension Entomology

Category: Wheat

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

 

Wheat Aphids

–by Jeff Whitworth and Holly Davis

We are getting calls relative to wheat aphids in many fields throughout south central and north central Kansas.  So far they are mainly bird cherry-oat aphids but a few greenbugs as well.  This is normal for this time of year.  These aphids migrate in, or are blown in, all spring on southern winds.  However, at this time of year/ this stage of wheat development, there is little to worry about relative to aphid feeding.  Also, the weather has been conducive to wheat growth so any aphid population buildup should not significantly impact the wheat.  Any viruses aphids may vector should not impact the wheat at this developmental stage enough to significantly reduce yields.  Aphid populations now will provide a food source and thus help many beneficial insect populations establish for later season aphid invasions.

It is not a good practice to mix a little insecticide in with a fungicide treatment “just in case”, as this is deadly to beneficial insects, i.e. lady beetles, lacewings, etc.  that will provide help later in the growing season on other crops.  Yes, it does save on the cost of an insecticide application but will probably do much more harm than good at this time of year.  For more information on wheat insect management, please refer to the KSU Wheat Insect Management Guide: https://www.bookstore.ksre.ksu.edu/pubs/mf745.pdf

Volunteer Wheat

–By Dr. Jeff Whitworth and Dr. Holly Schwarting

Again, please remember every moisture event prompts the growth of volunteer wheat.  This volunteer wheat needs to be controlled at least 2 weeks prior to planting to help mitigate all wheat pests;  pathogens, mites, and insects.

 

Volunteer Wheat

–by Dr. Jeff Whitworth and Dr. Holly Davis

 

It is once again time to control volunteer wheat!  This needs to be done at least 2 weeks prior to wheat planting and will help mitigate problems with Hessian flies, wheat curl mites, wheat aphids (Russian, bird cherry-oat, greenbug, etc.) and diseases.

Metopolophium festucae cerealium (Stroyan), a new aphid in Kansas wheat

— by Dr. J.P. Michaud — Hays, KS

In 1982, Stroyan distinguished a subspecies of Metopolophium festucae, sensu stricto, as M. f. cerealium based on morphological characters.  Whereas the former subspecies infests various wild grasses and is only incidental on grain crops, the latter is a potentially significant pest of cereals, especially wheat.  Although this aphid complex has been present in North America since the 1970s, it was not until 2011 that significant M. f. cerealium infestations of wheat (as well as barley and oats) were discovered in the Pacific Northwest.  The winged adults are pale yellowish with dark markings on the dorsal surface (Fig. 1), whereas apterae are pale yellow, similar in color to sugarcane aphids, but with a more elongate body shape (Fig. 2).

Fig. 1

Fig 2

On the morning of May 17, 2018, we collected a number of winged M. f. cerealium using a sweep net in wheat plots on the Agricultural Research Center-Hays.  Other aphids present included Sitobion avenae and Rhopalosiphum padi, but all three species were present in low numbers, and were attended by the usual complex of aphid predators.  It should also be noted that apterous M. f. cerealium were not found, so the winged forms are most likely very recent migrants.  It is quite possible that existing biological controls will maintain this new aphid below economic levels along with all the other species present in wheat, but farmers should be vigilant for possible outbreaks in particular fields, especially later-maturing varieties that will give the aphids more time to feed and increase their numbers.  It is also possible for these aphids to move to spring oats and barley after winter wheat matures.

Insect Management Guides, 2018

–by Jeff Whitworth and Holly Davis

 

 

 

Ms. Donna Sheffield, Communications Department, recently sent the links to the 2018 Insect Management Guides which can be found as follows:

Alfalfa, MF809: https://www.bookstore.ksre.k-state.edu/Item.aspx?catId=42&pubId=1492

Corn, MF810: https://www.bookstore.ksre.ksu.edu/Item.aspx?catId=221&pubId=20262

Cotton, MF2674: https://www.bookstore.ksre.k-state.edu/Item.aspx?catId=1081&pubId=20259

Sorghum, MF742: https://www.bookstore.ksre.k-state.edu/Item.aspx?catId=281&pubId=20260

Soybean, MF743: https://www.bookstore.ksre.k-state.edu/Item.aspx?catId=281&pubId=20261

Wheat, MF745, https://www.bookstore.ksre.ksu.edu/Item.aspx?catId=299&pubId=1463