Potassium and nitrogen impacts on survival and development of fall armyworm (Lepidoptera: Noctuidae).
This study determined the effects of nitrogen (N) and potassium (K) plant fertilizers on the survival and development of fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), on 'TifEagle' bermudagrass [Cynodon dactylon (L) Pers. x C. transvaalensis Burtt-Davy]. The treatments were various ratios of N:K: (1) 0:0, (2) 1:0, (3) 2:1, (4) 1:1, (5) 0:1, and (6) 1:2, where 1 = 113.4 g N or K per 92.3 m2. Treatments were applied from May to October in 2018 and 2019 at biweekly intervals via foliar spraying. Neonates of S. frugiperda were introduced to treated plants under laboratory conditions. In 2018, survival was significantly lower in the 0:1, 1:2, 1:0, and 0:0 treatments than in the 2:1 and 1:1 treatments at 10 d and 24 d postintroduction; whereas, in 2019, survival was significantly lower in the 0:0 treatment than in the other treatments at 10 d and 24 d postintroduction. Development of S. frugiperda larvae was significantly faster in the 2:1 treatment than in the 1:1 treatment in both years. Our data indicate that N favors and K discourages the growth and development of S. frugiperda larvae on bermudagrass.