Seasonal Distribution of Mites on Texas Grapefruit1

Abstract

The important species of mites on grapefruit in Texas were found to f1uctuate considerably during the year. Eutetranychus banksi (McG) was found to have its greatest increase in population during May-July. Increases were associated with periods of very little mill fall, lower relative humidity and 8 to 10 hours per day of average temperatures above 80. Rainfall appeared to be a regulatory factor. Populations of the citrus rust mite, Phyllocoptruta oleivora (Ashm.), increased particularly during periods of high relative humidity while periods of low relative humidity and very windy weather seemed unfavorable. Rust mites increased generally following periods of greater precipitation, and increases in winter occurred each year. Typhlodromus spp. increased during .May and numbers were greater during the summer and fall months. Tydeid and Brevipalpus mites were more numerous during the latter half of the year.