Effects of the mosquito larvicides temephos and methoprene on insect populations in experimental ponds

The nontarget effects of Abate(R) 4E (44.6% temephos) at 0.054 kg of active ingredient (a.i.) per 1 ha and of Altosid(R) Liquid Larvicide (5% methopre ne) at 0.011 kg a.i./ha were investigated in 18 experimental ponds (average area. 202 m(2); maximum depth, 0.7 m) at Patuxent Wildlife Research Center Laurel, Maryland, USA. Ponds were sprayed three times at 3-week intervals. Six ponds were sprayed with Abate, six with Altosid, and six with distille d water. Two insect-emergence traps per pond collected for 7 d and were the n harvested 1 d before each spray and 13 to 14 days afterward. A repeated m easures analysis of variance (ANOVA) revealed significant reductions in Sha nnon diversity, equitability, and numbers of individuals, species, and fami lies in the Abate ponds relative to controls. Significant reductions also o ccurred in Ephemeroptera, Odonata, Diptera, Chironomidae, and Chaoborus sp. Hester-Dendy samplers were installed before spray one and harvested 16 d a fter spray three. Based on one-way ANOVA, Shannon diversity, equitability, and number of Ephemeroptera and Chironomidae were significantly reduced in the Abate ponds. Emergence data indicate only isolated cases with significa nt reductions in the Altosid ponds relative to controls, and the Hester-Den dy data indicate no significant differences between the Altosid and control ponds.