By STACY CAMPBELL
Cottonwood Extension District
There has been an increase of insect infestations this growing season around the state.
Two of the more widespread pests have been lepidoptera larvae (worms): the fall armyworm and the armyworm. These pests could become problematic for our fall planted wheat and alfalfa.
Fall armyworm (FAW)
Adults are a light brown/dark brown mottled color and are typical of the noctuid moths, which mainly hide during the day and fly around depositing eggs at night. Adults cause no problems other than depositing the eggs from which the voracious feeding larvae hatch. These larvae feed on just about anything green and have been a problem this year, mainly in brome fields and other grassy areas in eastern Kansas. Larvae can be identified by the four dark spots, in the form of a square, on the top of the eighth abdominal segment.
In our area there are significant populations of FAW feeding in sorghum heads and as wheat planting approaches, fall armyworm problems are possible. However, reportedly, FAWs do not overwinter in Kansas. Thus, we may have one more generation of FAWs, but hopefully, most adults have emerged by the middle of September and migrate to overwintering sites without causing any damage to wheat, says Jeff Whitworth, K-State Extension Entomologist.
Armyworms (ARW)
Adults are mostly light brown with a white spot on each forewing. Larvae are darker with several conspicuous light-colored stripes on both sides of their bodies, and they present a somewhat different problem than the FAW, because they do overwinter in Kansas. Therefore, the larvae may be around when the 2025 planted crop germinates.
Thus, planting as late as possible is important, as is destroying all volunteer wheat well before wheat planting begins. This is also important because it is the female moth that initiates the infestation by where she deposits her eggs, and she won't deposit any eggs unless she detects some greenery for a potential food source for the developing larvae.
From past experience with armyworm infestations, they may continue to feed until temperatures dip into the mid-20s °F for a couple of hours. Armyworms seem to overwinter mostly as mature larvae, but it has been reported that they can also overwinter as pupae and/or adults. Thus, fall armyworms should not be a problem for the fall-planted wheat crop, but armyworms might be, especially in early-planted fields, says Whitworth.
Army cutworms
One other worm to consider is the Army cutworm. These moths migrate back into Kansas in the fall, looking for any greenery on which to deposit their eggs. So, they will not be the same problem as armyworms, as their feeding will be ending this fall, but the army cutworms will just be starting their feeding and culminate in the common "Miller moths" in the spring.
The best ways to help mitigate an infestation in fall-planted wheat from any of these worms are to plant as late as possible and destroy all volunteer wheat well before any wheat is planted in your area.
Information provided by Jeff Whitworth, K-State Extension Entomology Specialist.
Stacy Campbell is a Crop Production Extension agent in the Cottonwood District (which includes Barton and Ellis counties) for K-State Extension. You can contact him by e-mail at [email protected] or by calling 785-628-9430.