Abstract
The effects of diflubenzuron on planktonic, nektonic, and benthic invertebrates in a residential-recreational lake were studied during the period of April to Oct 1977. A 25% WP formulation was applied at 156 g a.i./ha (0.012 ppm) to the entire lake surface, once on April 26, and again on August 24. The April treatment severely affected populations of the cladocerans Daphnia laevis, Ceriodaphnia sp, Bosmina longirostris and the copepods Cyclops spp and Diaptomus sp, completely eliminating them within one week. Daphnia and Ceriodaphnia did not recover even after 6 months of treatment but B. longirostris reappeared 11 weeks posttreatment. Diaptomus was depleted for four months, while Cyclops recovered within 6 to 7 wk after treatment. The amphipod Hyalella azteca was completely eliminated within four weeks remaining absent for more than 6 months after the treatment. The prolonged absence of these nontarget organisms is probably due to the seasonal cycle of the species involved and the inability of some to rapidly recolonize the treated habitat. Larvae of Caenis sp (Ephem., Caenidae) were reduced 99%, recovering in 6 weeks. The IGR had no adverse effects on oligochaetes (Naididae and Tubificidae), Hydrachnellid mites, the gastropod Physa sp, and the ostracod Cypridopsis sp. The second application eliminated Cyclops and B. longirostris within one to two weeks, the former recovering in 4 weeks and the latter in 8 to 9 weeks. Caenis , also was adversely affected, recovering in 4 to 5 weeks. No significant reduction in Cypridopsid, Hydrachnellid, Physid, or oligochaete populations was noted.