Alfalfa weevils continue to cause concern around the state, but that shouldn’t last much longer. After checking many fields in north central Kansas, from 20-23 May, it is obvious that alfalfa weevil infestations have been very problematic–but has run its course, for the most part. All fields sampled had alfalfa weevil larvae (see fig. 1), whether previously treated or not. All fields, including 2 untreated, had less than a 2% infestation of larvae and adults. There were still a few adults (see fig. 2) hanging around in these unswathed fields which is common as the uncut alfalfa canopy does provide shade for these adults until it is swathed. After swathing these adults usually emigrate from the alfalfa fields and not return until early fall. Adult alfalfa weevils do feed- but at a much reduced rate compared to larvae.
Alfalfa caterpillars (see Fig. 1) are also becoming more common in alfalfa fields throughout the state. These develop into the common white or yellow butterflies, again usually very common around both alfalfa fields and, later on, soybean fields. However, these larvae do not usually cause enough damage to be of any consequence.
Figure 1: Alfalfa weevil larvae (smaller larvae with dark heads) and Alfalfa caterpillar (larva on the left)
Termites have been “swarming” around the state for about the past 2 weeks. Apparently weather conditions this year have been conducive to this behavior which has caused considerable concern–especially since it has been a couple of years since we have seen, or had any reports of, this swarming activity (actually, since 2019). Termites have usually swarmed about 10 days after the 1st warm spring rains, which have generally occurred in April. But we have seen termites swarm in late February to early June, depending upon the weather. Since termite swarms are more common this year a little refresher is apparently needed to help answer some questions. Adult termites (see figs 1 & 2), the “swarmer’s”, are relatively easy to distinguish from ant “swarmer’s”. Termite adults have 4 wings of equal size–ants have hind wings smaller than their front wings; adult termites are dark brown/black with a more cigar shaped body–ant swarmer’s have a distinct “waist”; termite swarmer’s have straight antennae–ants have bent or elbowed antennae. Also, often at the site where the termite swarmer’s are issuing there may be a few white termite workers and/or soldiers (see figs 3 & 4) whereas ants do not have these white soft bodied individuals present. For more information, please see “Household Pests of Kansas: MF 3291. All pictures courtesy of David Hallauer.
Japanese beetles (see fig 1-adults) were 1st recorded in Kansas in 1992. However, they have been in the U.S. since about 1916, and have been a serious pest of ornamental and agricultural crops in several states east of Kansas for many years. They seem to be slowly spreading across Kansas from east to west, and there have been reports of small but dense populations of Japanese beetles extending west past Interstate I-35 (see fig 2-soybean plants defoliated by adult Japanese beetles in Republic Co. in 2021-photo by J. Hammer). Japanese beetle larvae, commonly called white grubs, can now be found in some no-till areas of fields that were infested with the adults in 2021 (see fig 3 by J. Hammer). This is becoming more common because the adults feed for a short time then fly to nearby undisturbed areas to oviposit. Depending upon when these adults emerge they may feed on young corn leaves, silks, and/or young soybean leaves, as far as agricultural crops are concerned.
Figure 1 Adult Japanese beetles
Figure 2 Soybean defoliation by Japanese Beetles in 2021, Republic Co., KS
Figure 3 Japanese beetle larvae, 2022, from field in Fig. 2.
Wheat (and alfalfa) continue to develop slowly throughout north central Kansas. Wheat mites, mostly winter grain and brown wheat mites, are still active throughout the central part of the state, but both species are slowly transitioning into their summer, non-feeding, stage (i.e., mite count in several fields averaged 50-60 winter grain mites per plant on 10 April, but only 7-10 per plant on 20 April). They have been feeding and thus competing with the plants for the little moisture that is present, thus we are often seeing the kind of feeding damage as in figure 1. Hopefully, adequate moisture plus the transition to the mite’s non-feeding stage will help these areas recover.
Figure 1 Mite damage on the Dickinson Co. line (picture by Jay Wisbey)
–by Anthony Zukoff — Entomology, Southwest Research and Extension Center
Reports of brown wheat mite outbreaks have come in from southwest and northwest Kansas in the last two weeks and the climate outlook for the region is likely to favor continued issues with this pest.
Brown wheat mite (Figure 1)
Figure 1. Brown wheat mite
is a sporadic pest of wheat in western Kansas but can also become problematic in eastern Kansas during dry years. Typically, continuous wheat faces a higher risk of damage from this pest and injury can be confused with drought stress. Mites damage individual cells in the leaf causing stippling while concentrated feeding at leaf tips causes plant tissue to dry out and die. Plants take on a scorched appearance and eventually wither (Figures 2 and 3).
Figure 2. Appearance of a field infested with brown wheat mites
Figure 3. Stippling caused by brown wheat mite feeding.
Brown wheat mites present in fields right now are from eggs that hatched last fall. They can easily survive cold temperatures and can produce multiple generations during the winter and an additional two to three generations in the spring. These mites are active during the day and peak activity is during the afternoon on warm days. They do not produce webbing like spider mites and can easily be observed moving rapidly on leaf surfaces when scouting a field. Their rapid movement and tendency to drop to the ground when disturbed can make assessing the level of infestation difficult.
The economic threshold is estimated to be several hundred mites per foot of row in early spring; stressed plants are most likely to succumb to damage. A solid rainfall is typically all that is needed to knock brown wheat mite populations below damaging levels, but that does not look to be in the forecast any time soon. Fields with noticeable populations of mites should be scouted for their eggs. Brown wheat mites lay two different types of eggs on soil clods and debris; red “winter” eggs and white “summer” eggs (Figure 4).
Figure 4. Brown wheat mite eggs. Left: winter eggs that will be hatching now, Right: summer eggs that will be hatching in the fall.
The white eggs will remain dormant through the rest of the growing season and hatch in the fall. Red eggs will continue to hatch this spring and add to the current population. By late April, adults begin to lay the white, diapausing eggs. Once there are more white eggs in the field than red eggs, the population is naturally declining and treatment is not likely warranted.
For fields that require treatment, options for control of brown wheat mite are limited as there are no miticides registered for use in wheat and a popular option for control, chlorpyrifos, is no longer available. Dimethoate continues to provide good control of this mite, but there are some options for suppression of brown wheat mite populations when treatment is warranted and dimethoate is not an option (Table 1). As always, be sure to follow all directions on the labels for proper use of any chemical.
Table 1. Products registered in Kansas for control or suppression of brown wheat mite. For more specific information relative to any insecticide, always refer to the actual label on the product.
Alfalfa weevils (see fig 1) have been hatching from eggs over about the last two weeks. However, they have not been developing very quickly, nor has the alfalfa, at least throughout north central Kansas. There will be more larvae. This is always a problem for producers, to treat early or not, especially with less foliage to accept the insecticide. If your treatment threshold is reached, irregardless of time it’s probably prudent to make an insecticide application as soon as possible. Less foliage may mean better coverage and therefore kill. But, it also probably means less foliage to accept the spray and thus there may be a little less residual control. But this is always part of alfalfa weevil management.
Figure 1 Alfalfa weevil larvae and leaf damage
We also see conspicuous aphid populations all around the state—both pea (see fig 2) and cowpea (see fig 3). These aphids are causing concern, especially in areas where moisture is lacking. However, these aphids usually do not buildup to the density to actually reduce yield but more often provide a food source for many beneficials if left untreated.
–by Anthony Zukoff — Southwest Research and Extension Center
The recent freeze and a lack of flowering sorghum has ended adult sorghum midge activity in the area. Adult midges were observed on station grounds in Garden City starting the first week of July and were still present on late flowering panicles into the first week of September. As sorghum reaches maturity, it is easy to find evidence of midge activity even if you did not see adults when the fields were blooming. Simply look for flattened, blank zones on the heads. These seeds never developed because the maggots consumed them from the inside. A general recommendation for avoiding losses due to midge is to make sure the field blooms uniformly and before mid to late August. For comparison, in the Texas panhandle, growers are encouraged to have fields blooming no later than the first of August to avoid issues with sorghum midge. Beginning the last week of July, sorghum on the station this year bloomed over a long period of time, which allowed some general observations to be made regarding blooming time and midge damage once heads reached maturity. Plants that began blooming on July 25 were free of noticeable midge damage. Those that began blooming around August 5 experienced damage to the upper 1/5th of the panicles. A final location that bloomed very unevenly starting August 11 experienced significant losses with most panicles being almost completely blank (Figure 1). While midge damage is very easy to spot on varieties with red panicles, it might be more challenging to see on varieties with white panicles; however, damage will show up the same regardless of color (Figure 2). In addition to midge damage, headworm and bird damage were prevalent in the later blooming field but are easy to differentiate (Figure 3). If you have observed midge damage this season anywhere in the state, consider sending me a report including an estimate of acreage impacted and panicle damage. For additional information and control options, please refer to the Sorghum Insect Management Guide. https://bookstore.ksre.ksu.edu/pubs/MF742.PDF
Figure 1. From left to right: example of undamaged panicle from plants that began blooming July 25, slightly damaged panicles from plants that began blooming August 5 and severely damaged panicle from plants that began blooming August 11.
Figure 2. White panicle variety: undamaged head on the left severely damaged head on the right from a plant blooming the first week of September.
Figure 3. Various types of damage to sorghum heads. Left to right: undamaged head, severe sorghum midge damaged head, a head with heavy bird damage and on the right, a head exhibiting headworm damage.
Sugarcane aphids are still quite active throughout the eastern 2/3rd’s of Kansas in fields that still have some green leaves. These aphids are continuing to migrate in and almost as soon as they land on green leaf tissue, they start producing the tiny nymphs (see fig 1-just produced nymphs with winged female that produced them). These aphids are still infesting sorghum but, so far, have not caused any problems throughout northcentral Kansas. It is getting late enough in the growing season that they should not have enough time to increase to the point where they will be a problem.
Figure 1: SCA nymphs and mother (photo by Cody Wyckoff)
Figure 2 shows an area outlined by a marker, on the underside of a sorghum leaf that was infested by a substantial (200+) colony of sugarcane aphids in early September but was subsequently eliminated by natural causes-no insecticides. This has been typical for the last 3 years, i.e. sugarcane aphids migrate into Kansas, starting in about mid-July and continue until late October, and establish small isolated colonies but with very few areas actually developing significant populations that require treatment.
Figure 2: Underside of leaf previously infested by SCA colony (photo by Cody Wyckoff)
“Worms” (larvae of armyworms, fall armyworms, etc.) are still causing considerable concern, at least throughout the eastern 2/3rd’s of Kansas. They have slowed a little over the last couple of weeks, as many have been pupating, mating, egg laying, etc. Therefore, if you have experienced significant “worm” activity in the last month or two, it will be a great time to start monitoring those vulnerable areas, i.e. seeding wheat, brome, alfalfa, etc. to detect any new “worm” infestations while the worms are small before they can do much feeding. The picture on the left is a brome field in Saline County that had a significant infestation of armyworms and was sprayed approximately 2 weeks prior to this picture and there was no rain between spraying and the date of this picture. The picture on the right is a patch of that same pasture that could not be sprayed.
(Pictures provided by a rancher in Saline Co.)
Also, we have conducted 2 separate insecticide efficacy trials against armyworms, one in brome and one in volunteer wheat. The raw data from the trial in brome are presented here. Analyzed results of both trials will be available on the KSU Entomology website, hopefully, in the near future.
