Entomopathogenic nematodes as a component of citrus root weevil IPM.

Abstract

The entomopathogenic nematode, Steinernema riobrave, is routinely used by many citrus growers in Florida as a component of IPM programs to control a root weevil, Diaprepes abbreviatus. because: J) D. obbreviatus is currently the major biological threat to citriculture in the state; 2) until 1998, no effective chemieal pesticides were registered for control of weevil larvae in soil; 3) the short-term effieacy of S. riobrove has been consistently documented; and 4) use of nematodes is relatively inexpensive. Although unexp loired, natural control ofroot weevils byundescribed species ofind igcnous nematodes in Florida appears to be high. However, major questions remain regarding optimum use of S riobrave and other entomopathogenic nematodes. Constraints on sampling methodologies have impeded the derivation of economic thresholds and of models of weevil population dynamics that could be used to estimate optimum timing and frequency of nematode treatments. The recommended nemarode application rate appears to be adequate far treatment of yoling trees. but may be too low to provide cousistem results in larger mature trees. Research is also needed to estimate: I) the long-term efficacy of uernatodes against weevils;:2)the relative efficacy of'uematodes compared to insecticides in an IPM program, and 3) the profitability of D. abbreviatus IPM.