Not Only The Fall Armyworm Is Present In Fields Of Kentucky, But Other Spodoptera Species During The 2024-Fall

DR. RAUL T. VILLANUEVA, JOSE BRAVO AND FELIPE C. BATISTA

LEXINGTON, KENTUCKY

In the University of Kentucky’s Research and Education Center at Princeton, we planted some conventional (non-GMo) and GMo corn in August 2024 to have a large population of pests and conduct some studies.

In this field, we identified a beet armyworm (Spodoptera exigua) caterpillar. This caterpillar was feeding on corn foliage planted as indicated above. The larva of this species has a light-green coloration with a smooth cuticle, four pairs of abdominal prolegs, and many fine white wavy lines along its dorsum and a broader stripe along each side (Figure 1). The beet armyworm has a wide host range, injuring vegetables, field, flower crops, field crops, alfalfa, hay, and other crops.

 Theyellowstriped armyworm (YSAW) (Spodoptera ornithogalli) is common in the eastern United States. Coloration is variable, but larvae bear a broad brownish band dorsally, with a faint white line at the center. Also, it has black triangular markings along each side, with a distinct yellow or white line below (Figure 2a). Its hosts include greens, tomatoes, peppers, beans, cucurbits, and cole crops, but it also feeds on tobacco, soybeans, corn, and alfalfa. While it is primarily a foliage feeder and can seriously injure young plants in the early season. This species is more common in hay and field crops from May to July. However, in 2024 we observed its presence throughout the entire growing season, and during the last week of September we have been finding egg masses in black traps.

 The most common species present in the fall is the fall armyworm (FAW) (Spodoptera frugiperda). This species 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. Both female FAW and YSAW can lay 50 to 200 eggs per cluster, which are covered with scales. Egg clusters have been observed on leaves, wood poles, screens, or plastic field flags.

 All these species have six larval instars that can be completed in 14 to 30 days, depending on the temperature. Fall armyworm resembles corn earworm and armyworm; however, FAW has a white“Y” inverted markon the head capsule between the eyes. Although the YSAW also has a pattern resembling an inverted “V” mark (Figure 2b).

 Although all these species can be managed with entomopathogens (Bacillus thuringiensisor virus), pyrethroids, or other insecticides, there are occasions that populations can reach large numbers, and from one day to the next, farmers notice that their fields are being affected. Recently, we have received reports during mid-September on the presence of egg masses in Wayne County and this week from Virginia on the application of insecticides on 40 acres of hay. It is important to scout these fields, but in addition, try to identify the species affecting them, as they may be changing their phenological pattern.  ∆

DR. RAUL T. VILLANUEVA, JOSE BRAVO AND FELIPE C. BATISTA: University of Kentucky