Seed Element Uptake, Grain Yield, and Bird Damage of Methiocarb‐Treated Sorghum Hybrids1

Abstract

AbstractBird damage to ripening grain sorghum [Sorghum bicolor (L.) Moench] is a multi‐million dollar problem in the U.S.A. Methiocarb [4‐(methylthio)‐3,5‐xylyl methylcarbamate] (MesurolR) is a chemical insecticide which provides broad spectrum nonlethal avian repellency. This chemical insecticide is not labelled for spray application on ripening grain. This field study, conducted on a Cecil sandy loam soil (Typic Hapludult) during the 1978 and 1979 growing season, sought to investigate uptake of elements into the seed, yield and yield components, height, and bird damage ratings of five sorghum hybrids and to compare results on methiocarbtreated and check plots.Spray treatments, applied in a randomized block split plot design, significantly reduced seed concentrations of N, K, Mn, and Cu, increased P, and did not affect Zn and Fe. The reduction in N resulted in a 5.1% reduction in crude protein. Copper concentration in the seed was reduced by more than 25% after methiocarb treatment. Grain yields were 1,080 kg/ha higher on the treated than on the check plots. Test weight was 2.2 kg/hl higher, 300‐kernel weight was 0.7g higher, plants were 8 cm taller, and bird damage was 39% lower on the treated than on the check plots. Correlation Coefficients were considerably different on the treated versus check plots, especially as related to N content, test weight, and bird damage influences on yield. Methiocarb treatment of ripening grain sorghum provided an effective chemical method for nonlethal bird repellency and more stable yields under bird pressure. However, the significant decrease in N would result in a lower crude protein content. The additional element changes due to methiocarb treatment coupled with reduced crude protein may have a major impact on feed rationing and utilization. The beneficial aspects of this chemical treatment should be weighed against the detrimental aspects when using the material during grain filling.