Populations Dynamics of Soybean Insect Pests vs. Soil Nutrient Levels
- J. E. Funderburk,
- I. D. Teare and
- F. M. Rhoads
The use of fertilizers can influence crop injury from arthropod pests through alterations in crop growth or nutritional levels of plants parts. The objective of this field study was to determine the effect of soil nutrient levels on population dynamics (population density and cycles) of larval velvetbean caterpillars (VBC), Anticarsia gemmatalis (Hübner), and nymphal and adult southern green stink bugs (SGSB), Nezara viridula (L.), in relation to physiological development (V4 to R6) and yield of soybean, Glycine max (L.) Merr. ‘Braxton’ soybean was grown on a Norfolk loamy sand (fine, loamy, siliceous, thermic Typic Kandindult) during 1986 and 1987. Soil nutrient variables were four levels of P and three levels of K and Mg. Insecticides were not applied at any time during the experiment. Orthogonal comparisons were used to separate the effects of P, K, and Mg levels. The higher soil levels of P and K increased seed yields of each year. Yield results were not affected by Mg levels. Population densities of larval VBC at the higher levels of P were greater than at the lower levels of P. Population densities of VBC were increased by K in 1987, but not in 1986. Magnesium levels did not affect VBC either year. Adult populations of SGSB invaded and began reproducing at R4, but data are not shown due to poor precision of sample estimates resulting from a typical clumped dispersion pattern. Population density estimates of nymphal SGSB were greater at the higher P levels in 1986 when populations were very great, but not in 1987 when populations remained low. Population density estimates of nymphal SGSB were not affected by K or Mg. These findings should aid in implementation of cultural control strategies for these major pests of soybean in the southeastern USA.
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