I have received a few calls within the last 10 days about “Miller moths” flying around lights at night and flying/running into the house when an outside door is opened the 1st thing in the morning. Those, at least from my experience and the specimens I have seen, are adult army cutworms (see pictures by Cayden Wyckoff). Like most adult cutworms, the army cutworm is a relatively thick bodied but otherwise nondescript moth. These moths are even more nondescript after losing wing scales while flying and/or hiding under objects during the day. They are a relatively agile, quick moving moth, and in Kansas always seem to be present just before and/or during Memorial weekend. As far as crops go, the army cutworm feeds on wheat or alfalfa since those were the crops growing last fall when the female moth was depositing eggs. Thus, since last fall the larvae have fed all winter and spring, pupated, emerged as adults, and are/or have headed for over- summering sites, usually somewhere in the Rocky Mountains. These same moths then, at least the ones that survive the summer, will be heading back this way in late summer or early fall and depositing eggs in wheat and alfalfa fields along the way. After depositing their eggs, these adult moths expire, but have started the next generation.
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.
“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.
Grasshoppers continue to be quite numerous in some alfalfa fields, and late-planted soybeans (see pic. 2). As these crops senesce or dry down, these grasshoppers sometimes move into wheat fields when the newly planted wheat starts to germinate where they can be a real hindrance to establishing a good stand.
Adult Grasshopper (there are many different kinds currently in the fields – this is a Differential Grasshopper) (pic by Cayden Wyckoff)
–by J.P. Michaud — Entomologist, Agricultural Research Center, Hays, KS
There have been some heavy infestations of fall armyworms in early-planted wheat in Ellis County, with some plantings completely destroyed, and the larvae trying to finish up on the pigweeds. This is a very asynchronous, late generation of fall armyworm, with most larvae now almost mature, but some still quite small. Treatment will not be justified at this point. The best recommendation is to just wait until worms have finished feeding, recalling that larvae can “march” across to new fields after killing plants. If larvae are still active in adjacent fields, it will be best to wait until later in the planting window (up to 2nd week of October for Ellis County). The emerging moths should migrate south without laying any more eggs.
There have been many reports across the Midwest of large fall armyworm populations damaging crops, lawns and turf, so they are having a good year. There were some reports of true armyworms also. The color of these caterpillars is highly variable; the dark color depends on melanin deposition, which can increase at low temperatures, and the intensity of bright colors depends on plant pigments obtained in the diet. To help distinguish between these two worms, refer to the features identified in photos shown below.
Figure 1. Fall armyworm showing key identifying features. Photo by J. Obermeyer.
Figure 2. True armyworm with key identifying features. Photo by M. Spellman.
2021 might be called the “year of the worm”. Starting in late winter/early spring, 2021, there was considerable activity by army cutworms. Most of the problem was caused by the larvae decimating thin strands of wheat and/or alfalfa. Then, since late spring/early summer, a combination of armyworms and fall armyworms have been causing serious concern and damage in lawns, pastures, and alfalfa fields throughout about the eastern 2/3rd’s of the state. Army cutworms spend the summer in the Rocky Mountains but start to migrate back into Kansas in early fall every year. The larvae may feed on just about any plants but mostly affect wheat and alfalfa, as these are usually the only plants actively growing this time of year. Armyworms, probably more so than fall armyworms, may continue to cycle through another generation or even two as they overwinter in Kansas, and thus it will probably take a “hard” frost or freeze to stop them. Fall armyworms, since they don’t usually overwinter in Kansas, may migrate south after this generation become adults-but there could be another, or at least partial generation. Armyworms infest primarily grasses, i.e. sorghum, corn, brome pastures, lawns, and often this time of year, wheat, but occasionally alfalfa, etc. Thus, if armyworms are the problem they could be around through another generation or maybe even two depending upon the weather. So, if armyworms are relatively small (see pic 1) they will probably feed for another 10-14 days then pupate (stop feeding). If they are relatively large (see pic 2) however, they will probably pupate in the next 3-7 days. There will probably be at least one more generation of armyworms. Fall armyworms (see pic 3) have a little wider host range, which includes alfalfa, soybeans, corn, sorghum, wheat, etc., but don’t usually overwinter in Kansas, thus, hopefully, will be heading south after these larvae finish feeding and become moths. Also, in the next 30-60 days army cutworm moths should have returned from their summer Rocky Mountain retreats to deposit eggs throughout at least the western 2/3rd’s of the state and thus, these tiny worms will start feeding on wheat and/or alfalfa all winter.
Picture 1: Small Armyworm (pic by Cayden Wyckoff)
Picture 2: Larger Armyworm (pic by Cayden Wyckoff)
As noted before, grasshoppers seem to be really numerous this year throughout northcentral Kansas. We have seen, or heard about, more grasshopper-riddled fields (see pic 1) then we have maybe in the last 15-20 years. The species responsible for most of the crop damage is the common, relatively large, yellow, differential grasshopper (see pic 2). These grasshoppers are still feeding a little, but are also moving to grassy/weedy/undisturbed areas where they are depositing eggs in the soil. These eggs will then hatch next spring and the young nymphs can start feeding on any nearby crops.
Picture 1: Grasshopper riddled field (pic by Cayden Wyckoff)
Picture 2: Differential grasshopper (pic by Cayden Wyckoff)
“Worms” have been voraciously feeding throughout at least the eastern 2/3’s of Kansas for about the last 3 weeks. However, they have only recently gotten large enough to cause considerable damage and thus concern. The main problem in alfalfa, so far, seems to be a combination of fall armyworms (see fig 1), armyworms (see fig 2), and somewhat surprising, alfalfa caterpillars (see fig 3).
Figure 1: Fall armyworm
Figure 2: Armyworm
Figure 3: Alfalfa caterpillar
Alfalfa caterpillars are usually quite common in alfalfa and soybeans, however, not at the densities detected this year. Alfalfa caterpillars pupate then emerge as the common yellow (see fig 4) or white butterflies usually seen flying around alfalfa and soybean fields.
Figure 4: Adult alfalfa caterpillar
Regardless of which larval species, it is apparent that the majority of the larvae are relatively mature and thus will be/or are pupating soon. Pupation will probably take 4-5 days. Then the adults will emerge, mate and start depositing eggs. These eggs will hatch, and then in 4-7 days the new, but very small, larvae will start the feeding process all over again. Armyworms (fig 2) will attack mainly grasses, i.e. brome, late-planted sorghum, wheat, etc. Alfalfa caterpillars (fig 3) will mostly stay in alfalfa or soybeans, before they get too mature, and fall armyworms (see fig 1) may feed on just about any crop. However, sorghum should only be susceptible to “headworms” from flowering until soft dough. All three species may have at least one more generation, if not more, until a hard freeze puts a stop to them.
–by Anthony Zukoff — Southwest Research and Extension Center
Weather patterns can have a significant impact on grasshopper populations year to year. Hot, dry summers increase survival of nymphs and adult grasshoppers, leading to increased egg production during the growing season. Cool, wet weather promotes fungal pathogens that can reduce egg and nymph survival, but if the following spring is warm and wet, egg hatching will increase and more nymphs survive. So, several years of hot, dry summers followed by warm, wet springs can eventually lead to large populations of grasshoppers in some regions.
As the weather in western Kansas continues to be hot and dry this summer and areas of drought increase, larger populations of grasshoppers going into the fall season could be possible. This year’s USDA Rangeland Grasshopper Hazard map (Figure 1) may explain the recently observed buildup of grasshoppers along field edges and in grassy areas. As non-crop sources of food are exhausted, grasshoppers will shift their grazing over to anything still growing in the landscape. In areas with greater grasshopper pressure seedling alfalfa and wheat could be at risk.
Before planting alfalfa, treatment should be considered if there are 15 or more grasshoppers per square yard around the planting area. Once planted and growing, consider treatment if 3-5 grasshoppers per square yard are found in the seedling alfalfa stand.
Vegetated borders around areas where wheat will be planted should be scouted 10 days before planting. Consider treating those borders if there are 7 to 12 grasshoppers per square yard. Once growing, 3 or more grasshoppers per square yard within the field can destroy seedling wheat stands. If grasshopper populations are low to moderate, seed treatments can protect emerging wheat plants for several weeks if products are applied at the highest registered rate. Seed treatments will be less effective under severe grasshopper pressure. Avoid planting too early as this will help reduce the time that wheat will need to be protected.
In either crop, depending on the products used and severity of the season’s grasshopper buildup, multiple applications might be necessary. Please refer to the most recent Alfalfa and Wheat Insect Management Guides for specific control information.
