Inf1uence of Citrus Leaf Nutrition on Survivorship, Sex Ratio, and Reproduction of Euseius tularensis (Acari: Phytoseiidae)

Abstract

Citrus trees, Citrus sinensis (L.) Osbeck, grown in pots were fertilized weekly for 3 mo after grafting with 1, 1/10, 1/100, or 1/1,000× concentrations of a fertilizer solution. Eggs of the predaceous mite, Euseius tularensis (Congdon), were placed with ice plant, Malephora crocea (Jacquin) pollen on excised leaves, and no differences in survivorship or sex ratio were found during the 1st or 2nd generations of rearing. During the 2nd generation, however, egg production by E. tularensis reared on leaves from the 1× fertilized trees was higher both on the 1st d of oviposition and throughout most of the lifespan of the females compared with the other treatments. As fertilizer concentration decreased, fewer total eggs were deposited by E. tularensis females. Leaf analyses revealed significant, decreasing linear responses in concentrations of N, K, Mn, and Zn in the leaves as fertilizer concentration was decreased. Decreasing concentrations of N and Mn were significantly correlated with decreasing reproduction in the predaceous mite. These data suggest that E. tularensis feeds on leaf sap and its reproductive tential is influenced by the nutritional status of the citrus tree.