Preplant Tillage Effects on Population Dynamics of Soybean Insect Pests
Tillage operations can modify soil and plant characteristics where many insects reside dudag at least part of their life cycle. However, information relating tillage and subsoiling to soybean [Glycine max (L.) Merr.] insect pests is very scarce or inconclusive. The objective of this study was to determine the effect of tillage and subsoiling on population cycles and densities of foliage-inhabiting insect pests in soybean. Soybean was grown on a Norfolk sandy loam soil (fineloamy, siliceous, thermal Typic Kandiudult) and tillage treatments were (i) disk (no subsoil), (ii) disk (subsoil), (iii) conservation (no subsoil), and (iv) conservation tillage (subsoil). Planting curred immediately after disking or in conjunction with conservation tillage. Subsoiling consisted of a chisel plow located on a planter directly under the soybean row. Plots were sampled for insects by beating the soybean plants on both sides of the row onto a ground cloth. Population densities of velvetbean caterpillar (VBC), Anticarsia gemmatalis Hubner, increased at R4 and peaked at soybean Growth Stage R5.5; green cloverworm (GCW), Plathypena scabra (Fabricius) in 1985 and 1986 were greatest at Growth Stage R1 and R2.6, respectively, but remained low in 1987. Preplant tillage treatments usually caused no significant effect on the population dynamics of VBC or GCW. The population densities and cycles of southern green stinkbug (SGSB) nymphs and adults, Nezara viridula (L.), were similar for each preplant tillage treatment in 1985, 1986, and 1987. Since insect pests were not affected by tillage operations at planting, the tillage operation can be selected to promote beneficial insect predators that have shown to be favored by conventional tillage.
Copyright © 1990.