Testing Low-Tech Trap To Detect Egg Masses Of Fall Armyworm In Corn & Forage Fields
DR. RAUL T. VILLANUEVA
LEXINGTON, KENTUCKY
Recent correspondence with county Extension agents, growers, and Extension colleagues in forages indicated a surge of fall armyworms (FAW) (Spodoptera frugiperda, Noctuidae) in forages. These reports originate from various regions of Kentucky, beginning in August and continuing until the first week of September. Counties reporting the presence and damages in pastures included Carlisle, Russell, Todd, and Wayne counties
Biology, Identification, and Description of the Fall Armyworm
This insect usually reaches Kentucky by the end of June to the beginning of July as they migrate to northern regions; however, they can eventually develop into large populations during the fall. Female FAW lay 50 to 200 eggs per cluster, which are covered with scales. Egg clusters have been observed on leaves, wood poles, screens, and plastic field flags (Figure 1). A single female can produce up to 2,000 eggs during its life span. Larvae from this egg cluster hatch at the same time and then can move to the ground or ballooning hanging from a strain of silk. The FAW has six larval instars that can be completed in 14 to 30 days, depending on the temperature. Fall armyworm resembles corn earworm and armyworm; however, fall armyworm has a white “Y” mark on the head capsule between the eyes (Figure 2). Pupation occurs in the ground, and adults can live up to 20 days.
Trap to Detect FAW Egg Masses
Two traps were installed at the Research and Education Center in Princeton. One trap was located in a conventional corn (non-GMo) plot and the other in an alfalfa plot, a distant of 3 miles from each. This trap was built using a black woven polypropylene Weed Barrier Landscape fabric. The design was based on a study of asparagus in Peru, where FAW is a pest of this crop. The trap is used in asparagus fields in Peru to detect oviposition and the presence of FAW in these fields. The trap had two wood stakes (49.2 inches.) placed in the ground at a distance of 19.6 inches. The area between the two stakes has the weed barrier fabric with pledges (19.6 wide by 39.3 in height), as shown in Figure 3. So far, two sets of data have been collected from these traps. From August30 to September6 and September 6 to September 13. In the corn field, egg masses were not found; in the alfalfa field, there were 12 and 15 egg masses during each collection date. In addition, pheromone-basde traps used to capture adults in Princeton had an increase in male adults from 4 to 62 during the last two weeks reported above.
Discussion & Management
Based on the results from the black woven fabric traps shown above, it seems that the FAW strain that is abundant in Kentucky this period might be the rice strain that had preference for rice, pastures, and forages. Also, the pheromone-based traps showed an increase in the male adult moths flying or migrating northward. Additionally, there was no report on failures of pyrethroid applications to control FAW in forage fields this year. Thus, this strain might be susceptible to pyrethroids, which are effective against this pest. However, it is known that insecticide efficacy decreases for late larval instars. Then, early detection of infestations will allow for more effective control of FAW if larvae are smaller than 1/2 inch in length. If sprays are necessary, consult with your county Extension agent. ∆
DR. RAUL T. VILLANUEVA: University of Kentucky