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

Abstract

Avermectin B[sub1], 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[sub1] 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[sub1] 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[sub1] 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[sub1] 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[sub1] 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). Key words: avermectin, chemical control, fenamiphos, Hoplolaimus galeatus, isazofos, nematode, Poa annua, turfgrass, Tylenchorhynchus dubius.