Damage of stem borer species to Zea mays L., Sorghum bicolor L. and three refugia graminae

Abstract

This study aimed at determining the magnitude of damage inflicted by stem borer species to Zea mays L. and Sorghum bicolor L. and refugia graminae. It involved two growing gramineous crops: maize Z.mays L. and S.bicolor L. and three gramineous forages: Napier grass, Sudan grass and giant Setaria grass. These were planted both in pure and mixed stands and exposed to natural infestation in the field.Sampling for the borer infestation was done throughout the phenology of crops .Field and laboratory bioassays were conducted to determine biophysical efficacies of the control strategy from stem borer fecunditie.The type of the gramineous refugia had a significant (p < 0.05) effect to the magnitude of damage caused by the stem borers. The B. fusca was the most devastating species with a mean of 4.8800, 3.8800, 2.2400 and 1.4000 borers while S. calamistis was the devastating with a mean of 1.0600, 0.9200, 0.4600 and 0.6100 borers in maize, sorghum, Napier and Sudan grass. However C. partellus was the most devastating species in giant Setaria grass with a mean of 3.300 and B.fusca being the least devastating with a mean of 0.6800 borer. Maize was the most damaged host indicating that it provided the best geographical requisites and nutritional attributes. These were more attractive to B. fusca.This implies that it has desirable traits attractive to the stem borers especially the great devastating B. fusca as chemical and biophysical morphology and stem diameter. B.fusca was the most devastating both in the laboratory bioassays and field. Maize was the most damaged host and Napier grass was the most preferred forage refugia. B.fusca was the devastating stem borer species and it preferred hosts with larger stems..However, more research should be conducted to understand the moths better:their biology,seasonality dynamics and generations in different locations and natural enemies surviving on maize and sorghum for their biocontrol. Keywords: Stem borer species, Sorghum bicolor L and refugia graminae.