Avermectin B1, Isazofos, and Fenamiphos for Control of Hoplolaimus galeatus and Tylenchorhynchus dubius Infesting Poa annua.

Avermectin B, isazofos, and fenamiphos were evaluated in greenhouse experiments for efficacy against two common turfgrass parasites, Hoplolaimus galeatus and Tylenchorhynchus dubius. Treatments in all experiments were arranged in a completely randomized design and replicated four times. In the first experiment, avermectin B at rates of 0.2 and 0.4 kg a.i./ha and isazofos at rates of 2.3 and 23 kg a.i./ha significantly reduced populations of both species of parasitic nematodes compared to controls at 14 and 28 days after treatment (P </= 0.01). In the second experiment, the greatest reductions in both nematode populations occurred at 28 and 56 days after treatment, where 23 kg a.i./ha of isazofos was applied (P </= 0.01). These reductions, however, were not different from reductions of H. galeatus at 28 and 56 days after treatment (P </= 0.01) or T. dubius at 56 days after treatment (P </= 0.01), where 0.2- and 0.4-kg a.i./ha rates of avermectin B were mixed throughout the soil. In the third experiment, the greatest population reduction of H. galeatus was observed with a 0.4-kg a.i./ha treatment of avermectin B at 56 days after treatment (P </= 0.05). T. dubius populations were reduced by the 0.4-kg a.i./ha rate of avermectin B at 28 (P </= 0.01), 56 (P </= 0.05), and 70 (P </= 0.01) days after treatment. In the fourth and fifth experiments, avermectin B at rates of 7.5 and 15.2 kg a.i./ha consistently reduced nematode populations compared to controls and performed as well or better than fenamiphos (P </= 0.01).