INFLUENCE OF PLANTING AND INFESTATION DATES ON FALL ARMYWORM DAMAGE TO SOME YEMENI SORGHUM VARIETIES.

The Fall Armyworm is a serious pest of many crops throughout most of the Western Hemisphere particularly those belonging to the family Gramineae. This pest is usually controlled by insecticides which, however, cause many health and environmental problems. Although a rich bank of sorgum germplasm occurs in Yemen, no effort has been made to identify the Yemeni cultivars which might express resistance to armyworm attack. There is very little information to show at what time of the growing season and at what planting stage the sorghum cultivars are most susceptible to armyworms. Therefore, eight Yemeni and two American sorghum cultivars were planted in Tucson, Arizona, during 1983 and 1984. The experimental design was a randomized complete block arranged in split-split plots with four replications. The main plots were the varieties, and subplots were two planting dates and two infestation times. The plants were artificially infested with laboratory reared, first instar larvae. Infestation consisted of five larvae per plant in 1983 and ten in 1984. Results demonstrate the 'IBB' and 'TURBA' received the least leaf damage and 'SGIRL-MR1' and 'ALBAIDA' received the most in 1983. However, during 1984, 'TURBA' and 'HAIDRAN' showed the greatest degree of resistance and 'SGIRL-MR1', 'AMRAN', 'ALMAHWIT', and 'ALBAIDA' the least