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Extension Entomology

Category: Corn

Fall Armyworms

Posted on by Sharon Schroll

–by Jeff Whitworth – Field Crop Entomologist

Adult fall armyworms are moths (fig. 1) and have been reported from southern Kansas for about the last 2 weeks and probably will be in the rest of the state soon-if not already. A quick refresher relative to this pest: they normally do not overwinter in Kansas, but in the lower portions of southern states, and down into Mexico and Central America. The moths usually arrive in Kansas anywhere from mid-June to mid-July as they fly/are blown here on southern winds. Fall armyworms have a wide host range but in Kansas are most often a cause for concern in corn and/or sorghum and later sometimes in wheat depending on planting date and weather. Also, in Kansas, especially the last 2 years, brome has been seriously defoliated (in combination with armyworms) in many areas around the state. Armyworm larvae may be part of the “ragworm” complex of larvae feeding in the whorl of corn and/or sorghum and then later the next generation become part of the complex of “headworms” or larvae feeding in the sorghum head directly on the developing grain. So the moths are here, ovipositing and thus the larvae are, or soon will, be feeding on whatever host the eggs were deposited on. Fall armyworms were quite common (in combination with other species) in 2020 and 2021 and thus monitoring should be initiated in any potentially susceptible crops. For management considerations please refer to the 2022 KSU Insect Management Guide for the crop of interest.

(Photo of fall armyworm moths taken of a Riker mount provided by revered KSU Extension entomologist, now retired, Dr. Bob Bauernfeind).

 

Figure 1: Fall armyworm moths

 

 

Corn Earworms

Posted on by Sharon Schroll

–by Jeff Whitworth –Field Crops Entomologist

 

Most corn has recently tasseled, just is, or will be soon. 100% of all the ears we examined in the last 2 weeks, both sweet and field corn, were infested with at least one “earworm”. This is not unusual. All “earworms” were only one half to three fourths grown (see fig 1)

Figure 1: Corn ear worm

as of 18 July. Thus, these worms should cease feeding in the next 7-14 days, pupate in the soil for 4-7 days, and then emerge as adult moths. These moths will then mate and fly to a suitable host plant to start depositing eggs. Whether sorghum or soybeans depends upon the crop’s stage of growth when these moths are actively depositing eggs. Double cropped soybeans may be attractive to moths for another 1-3 months as the plants continue to set pods, and thus there could be another 1- 3 generations of larvae feeding on the bean within the pod. Sorghum, however, should only attract moths from flowering to soft dough–a much smaller oviposition window, but very critical because generally one larva causes 5% loss in grain.

 

 

WORMS, WORMS, and MORE WORMS (army cutworms, fall armyworms)

Posted on by Sharon Schroll

–by Jeff Whitworth — Field Crops

 

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)

Picture 3: Fall Armyworms (pic by Jay Wisbey)

 

 

Japanese Beetles

Posted on by Sharon Schroll

–by Jeff Whitworth — Field Crops

 

Japanese beetles have been very active throughout Kansas for the last 2 months. However, they seem to have been more widespread north of Interstate 70 from the Missouri border west to about Smith Center. There were a few “hotspots” south of I-70 but not as widespread. Japanese beetles can be a concern in field crops because they can feed on green silks in corn or on leaf tissue in soybeans. They do have a wide host range but those are the two vulnerable crops and it is just a matter of timing as to which are attacked. If any corn in the vicinity of where the adult beetles emerge is silking, it seems that is highly attractive to the hungry beetles. However, if corn silks are starting to turn brown when the adults are foraging they seem to be attracted to new succulent soybean leaves (see pic 3). Japanese beetles seem to be slowly increasing in numbers and range. The larvae are white grubs and most commonly feed on roots in some area of undisturbed plants, i.e. turf, pastures vineyards, etc. After the larvae pupate, the adults emerge and fly to any nearby food source. This usually starts towards the end of June or in early July. They then feed voraciously for a few days before disbursing to start depositing eggs back in the “nursery” area. They continue this feeding-disbursing, etc. usually for about a month or so. Adults then die, eggs hatch, and the cycle starts all over again.

Picture 3: Japanese Beetle damage (pic provided by Jeff Hammer)

Grasshoppers

Posted on by Sharon Schroll

–by Jeff Whitworth — Field Crops

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)

 

 

Grasshoppers

Posted on by Sharon Schroll

–by Jeff Whitworth — Field Crops

 

“Worms” are not the only pests feeding on crops right now! Grasshoppers (see fig 5) are especially numerous this year and will also continue to feed into the fall and continue to deposit eggs in the soil mainly in undisturbed areas adjacent to crop fields.  (All pictures by Cody Wyckoff)

Figure 5: Grasshopper feeding in corn

Beneficial’s

Posted on by Sharon Schroll

–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)

Corn Rootworms

Posted on by Sharon Schroll

–by Dr. Jeff Whitworth — Field Crops

 

 

Western corn rootworm adults have been emerging throughout north central Kansas since at least 6 July. One relatively easy and quick method of detecting corn rootworm adults if they emerge prior to tasseling/silking is to look for characteristic signs that the adults have/are emerging and feeding on leaves (see fig. 1) This type of leaf feeding, where the beetles just feed on the top side of the leaf, is very characteristic of adult western corn rootworms– this type of leaf injury can be from other causes, but is very symptomatic of adult western corn rootworms. They will move up to feed on the silks, however, when they start emerging (see fig. 2, from 14 July). Please remember, if there is a 50%+ adult infestation (5 adults/10 plants, etc.) this year in any continuous corn fields, those fields should be considered for a corn rootworm control  method (adult spray this year-crop rotation, etc.)  if destined for corn next year.

Figure 1.  CRW leaf feeding

Figure 2.  Corn rootworms  (note the gravid female at the top)

 

Click Beetles

Posted on by Sharon Schroll

–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)

 

Corn Rootworms

Posted on by Sharon Schroll

–by Dr. Jeff Whitworth — Field Crops

 

Fields planted to corn rootworm susceptible varieties for 3+ years should probably be monitored for corn rootworm larval feeding. Several fields were sampled this week (13-16 June) that have been planted for at least 3 consecutive years without regard for corn rootworms, i.e. not varieties that had a Bt event to help control rootworms. All varieties, however, had commercially applied fungicide+insecticide seed treatments. All fields were planted this year from 15 Apr-3 May, but regardless, were all in the 8-10 leaf stage of development. Insecticide seed treatments seem to always work well but the toxins are only active for up to 21-28 days from the day of planting. Even though rootworm larvae were found in each field, no obvious signs of lodging or goosenecking were evident in any of the fields, which could be indicators of root pruning by rootworm larvae. However, northcentral Kansas has not had a great deal of wind over the last couple of weeks and the majority of the root feeding will probably occur over the next 10-14 days as the rootworm larvae get larger (see fig. 1). If there is not much wind or wind events over the next couple of weeks, the plants may compensate for the root damage and the lodging may be inconsequential. Most larval development in northcentral Kansas, thus seems to be on track to be completed prior to 4 July,–as it has been every year for at least the last 25 years.

Figure 1. Corn rootworm larvae (14 Jun 2021)  (pic by Cody Wyckoff)