A voluntary phase-out of the manufacture of dicofol, the principal miticide used for chemical control of pecan leaf scorch mite, Eotetranychus hicoriae McGregor (Acari: Tetranychidae), and the recent discovery and evaluation of western predatory mite, Galendromus occidentalis (Nesbitt), as a biological control of pecan leaf scorch mite have led to the registration of the selective miticide, bifenazate, as a possible replacement for dicofol for control of pecan leaf scorch mites in pecan orchards in the US. The impact of bifenazate on the pecan leaf scorch mite and phytoseiid predatory mites was studied in field trials conducted from 2003–2006. Bifenazate was an effective miticide and had the additional benefit over dicofol of conserving phytoseiid mites. The lowest effective concentration as a foliar spray application was 0.3 g actual bifenazate/l water. The effective residual activity of bifenazate at 0.3 g active ingredient/I applied at 1400 l/ha was 2–6 wks depending on the year and location. Bifenazate conserves a portion of the phytoseiid mite population as phytoseiid abundances were similar in the nontreated and bifenazate-treated trees for up to 4 wks after treatment. Treatment of pecan trees with bifenazate plus the release of phytoseiid mites was a more effective method for pecan leaf scorch mite control than the application of bifenazate alone. Among 8 chemical control treatment alternatives to dicofol, pecan trees treated with bifenazate had similar predatory mite abundance to the non-treated control.
Author notes
3Cooperative Extension Service, Department of Agricultural and Applied Economics, University of Georgia, Rural Development Center, Tifton, GA 31793-1209.
4Cooperative Extension Service, Department of Entomology, University of Georgia, Horticulture Building, Tifton, GA 31793-0748.
