Effect of Rainstorms upon the Cotton Jassid in the Sudan Gezira

Abstract

Empoasca lybica de Berg., a pest of cotton in the Sudan Gezira Scheme, invades the seedling crop early in September, the infestation normally reaching its maximum intensity in the last half of November. Hanna¹ records that peak populations of this insect are affected by rainstorms of 10 mm. and more in July and August as well as by dust storms in September. Field observations by Cowland and Hanna² suggest that populations upon cotton are also affected by rainstorms in September. Rainstorms, probably because of the mud which splashes on to the lower leaves, reduce the number of jassids infesting the cotton. Those findings which concerned the direct effect of rainstorms upon jassids at nine sites in the northern part of the Sudan Gezira were not reported by Hanna¹ in his published paper on rainfall and jassid numbers.