Effects of Nitrogen Fertilizer Level on Development and Populations of the Pecan Leaf Scorch Mite (Acari: Tetranychidae)1

Abstract

Population development and specific effects of the pecan leaf scorch mite, Eotetranychus hicoriae (McGregor), were studied on pecan seedlings grown under N regimes of 0, 200, or 600 ppm. The largest mite population developed on seedlings with N at 200 ppm (recommended level for good orchard maintenance). The size of this population was attributed to enhanced mite reproduction and not to a shorter life cycle. Generation mortality was 65.3% at 0 ppm, 40.6% at 200 ppm, and 37.8% at 600-ppm N. Compared with that of control seedlings, net photosynthesis (Pn) was less in seedlings with mites at 200-ppm N, but was greater in seedlings with mites at 600-ppm N. Seedlings with mites and provided with 200-ppm N were shorter than seedlings without mites, but in the 600-ppm N test seedlings with mites were taller than seedlings without mites.