The Effect of Infestation by the Spider Mite Septanychus tumidus on Growth and Yield of Cotton1

Abstract

In a small field plot test at Baton Rouge, La., during 1950, injury to cotton resulting from infestation by the spider mite caused a 45% reduction in the amount of seed cotton produced, reduced vegetative growth, number of leaves per plant, and size of leaves. On that portion of the crop represented by bolls developed at the first node of the 7th fruiting branch there were reductions in the avg. number of seeds per boll and in the weight, viability, and the oil content of the seeds. There was little effect on lint percentage as a result of mite infestation, but when the lint index was used as a criterion of lint production there was a sharp decrease. A reduction in length and maturity of fibers was also attributable to spider mite injury.