Fall armyworm, Spodoptera frugiperda (Figure 1), is known to feed on over 80 host plants. In Kansas, it can damage several important crops, pasture, turf, and home landscaping. This insect does not overwinter in Kansas. Rather, it is native to the tropical regions of the western hemisphere and is active year-round along the Gulf Coast and southern Florida, migrating in from these locations each year. Two full generations are possible in Kansas, with defoliation and grain damage being the biggest concerns.
Figure 1. Full-grown Fall Armyworm caterpillar. Photo from Department of Entomology, Kansas State University.
Start scouting now
Fall armyworm trap counts from pheromone traps steadily increased through August, particularly in central and eastern Kansas. Reports of egg masses in residential and agricultural settings have recently been reported (Figure 2). At-risk crops should be scouted regularly for the remainder of the growing season. Caterpillars increase in size exponentially, and most of the feeding occurs during the later stages of development. It is critical to scout thoroughly and treat if needed before the caterpillars are over ½ inch long. Larger caterpillars are harder to control and do the most damage. Recommended thresholds and products labeled for control of fall armyworm caterpillars (Table 1) can be found below.
Figure 2. Fall armyworm egg mass. Photo courtesy of K-State Department of Entomology.
Fall armyworm thresholds
Alfalfa: 1-2 caterpillars per square foot can destroy seedling alfalfa. 10-15 per square foot can destroy 12” tall plants.
Corn: damage to whorl stage in early summer; treatment may be needed if 75% of plants are damaged. Bt corn may prevent ear damage.
Sorghum: damage to whorl stage in early summer; treatment may be needed if 75% of plants are damaged. During flowering to soft dough, 1-2 larvae/head reduces yield 5-10%.
Wheat: Larval “window-paning” (Figure 3) in early planted wheat can be a concern. If 25-30% of plants show damage, examine the field frequently. Treat at 2-3 active larvae/ft.
Table 1. Registered products for the control of fall armyworm in Kansas crops. Always refer to the actual label on the product for more specific information relative to any insecticide.
|
Chemical Name |
Trade Name |
Mode of Action Class |
Alfalfa |
Corn |
Sorghum |
Wheat |
|
alpha-cypermethrin |
Fastac CS |
3A |
yes |
yes |
yes |
yes |
|
beta-cyfluthrin |
Baythroid XL |
3A |
yes |
yes |
yes |
yes |
|
bifenthrin |
numerous products |
3A |
yes |
|||
|
biological insecticide |
Fawligen |
- |
yes |
|||
|
carbaryl |
Sevin |
1A |
yes |
|||
|
chlorantraniliprole |
Vantacore |
28 |
yes |
yes |
yes |
|
|
cyfluthrin |
Tombstone |
3A |
yes |
yes |
||
|
deltamethrin |
Delta Gold |
3A |
yes |
yes |
||
|
gamma-cyhalothrin |
Proaxis |
3A |
yes |
yes |
yes |
yes |
|
indoxacarb |
Steward EC |
22A |
yes |
|||
|
lambda-cyhalothrin+chlorantraniliprole |
Besiege |
3A+28 |
yes |
yes |
||
|
lambda-cyhalothrin |
numerous products |
3A |
yes |
yes |
yes |
yes |
|
methomyl |
Lannate |
1A |
yes |
yes |
yes |
|
|
methoxyfenozide |
Intrepid 2F |
18 |
yes |
|||
|
permethrin |
numerous products |
3A |
yes |
|||
|
spinosad |
Blackhawk |
5 |
yes |
yes |
yes |
|
|
zeta-cypermethrin |
Mustang MAXX |
3A |
yes |
yes |
yes |
yes |
|
zeta-cypermethrin+bifenthrin |
Hero |
3A |
yes |
Figure 3. Window-paning from young caterpillar feeding. Photo from Department of Entomology, Kansas State University.
Anthony Zukoff, Extension Entomology, Southwest Research and Extension Center
azukoff@ksu.edu
Tags: insects pastures alfalfa fall armyworms