Soybean Cultural Practices: Effects on Populations of Green Cloverworm, Velvetbean Caterpillar, Loopers and Heliothis Complex 12

Abstract

Insects were monitored in soybean of early-, medium-, and late-maturity groups planted April through July in several row spacings at four locations in Mississippi for 1 to 3 years. Nondamaging populations of the green c1overworm, Plathypena scabra (F.), were present from June through September, and damaging populations were observed at one location after a drought. Green cloverworm populations were generally higher in late plantings, in late-maturing cultivars, and in narrow-row plantings. Damaging populations of the velvetbean caterpillar, Anticarsia gemmatalis Hubner, occurred in August or September. In 1976 and 1978 only the June and July plantings were seriously defoliated, but in 1977 all but the early-maturing April and May plantings were seriously defoliated. Velvetbean caterpillar populations were highest in late plantings, late-maturing cultivars, and in narrow-row plantings. Populations of loopers, Pseudoplusia includens (Walker) and Trichoplusia ni (Hubner), were generally less than 1/m2, but populations up to 3.2/m2 occurred at one location after insecticide treatment. Effects of planting date, cultivar, and row spacing were not consistent. Populations of the Heliothis complex larvae were generally less than 0.05/m2, but populations as high as 3.74/m2 were observed in blooming soybean. Populations of the Heliothis larvae were about equal in narrow- and wide-row plantings. In wide-row plantings, populations of Heliothis larvae averaged 0.98/m2 in closed canopy and 0.24/m2 in open canopy soybean.