Agistemus exsertus Gonzalez (Acari: Stigmaeidae) as a predator of citrus red mite (Panonychus citri [McGregor])

The potential of using Agistemus exseutus to control Paromychus citri was studied in both laboratory and citrus grove. Functional response studies showed that A. exsertus adult females had the highest instantaneous rate of discovery (a = 1.430) and shortest handling time (Th = 1.67 hr) when provided with P. citri eggs as compared to other prey stages. In comparison with adults of both sexes, A. exsertus deutonymphs had the lowest a (0.102) and longest Th (4.32 hr) when P. citri eggs were provided as prey. A. exsertus females clearly exhibited a prey-stage preference; an average of 75.2% of prey consumption consisted of eggs as compared to 16.6 and 8.2% nymphs and adult males, respectively. The intrinsic rates of natural increase (rm) of A. exseutus were higher at 20 and 25 degrees C, bur, lower at 30 and 35 degrees C than that of P. citri. A. exsertus demonstrated a satisfactory control of P. cirri in the greenhouse release study. Under natural conditions, the population of A. exsertus was very low in the winter and increased steadily from May through October.