Synergism between demethylation inhibitor fungicides or gibberellin inhibitor plant growth regulators and bifenthrin in a pyrethroid-resistant population of Listronotus maculicollis (Coleoptera: Curculionidae).

In 2007-2008, the "annual bluegrass weevil," Listronotus maculicollis Kirby (Coleoptera: Curculionidae), a serious pest of Poa annua L. (Poales: Poaceae) on U.S. golf courses, was shown to be resistant to two pyrethroids, bifenthrin and lambda-cyhalothrin. In 2008, we showed that bifenthrin resistance was principally mediated by oxidase detoxification (cytochrome P450 [P450]). P450s can be inhibited by demethylation inhibitor fungicides and gibberellin inhibitor plant growth regulators, both of which are commonly used on golf courses. We tested these compounds for synergistic activity with bifenthin against a pyrethroid-resistant population of L. maculicollis. The LD50 value for bifenthrin was significantly reduced from 87 ng per insect (without synergists) to 9.6-40 ng per insect after exposure to the fungicides fenarimol, fenpropimorph, prochloraz, propiconazole, and pyrifenox and the plant growth regulators flurprimidol, paclobutrazol, and trinexapac-ethyl. Simulated field exposure with formulated products registered for use on turf revealed enhanced mortality when adult weevils were exposed to bifenthrin (25% mortality, presented alone) combined with field dosages of propiconizole, fenarimol, flurprimidol, or trinexapac-ethyl (range, 49-70% mortality).

Effect of trap size, placement, and age on captures of blueberry maggot flies (Diptera: Tephritidae).

Ammonium acetate and protein hydrolysate baited and unbaited green spheres (3.6, 9.0, and 15.6 cm diameter) were evaluated for effectiveness in capturing blueberry maggot flies, Rhagoletis mendax Curran. Early in the season, baited spheres (9.0 cm diameter) captured significantly more R. mendax flies than spheres of 3.6 and 15.6 cm diameter. As the season progressed, the differences in trap captures became less pronounced among the 3.6-, 9.0-, and 15.6-cm-diameter spheres. In other experiments, the effects of trap positions and age on captures of blueberry maggot flies were assessed. Traps were positioned 15 cm above the bush canopy, 15 cm inside the canopy (from top of the bush), and 45 cm from the ground. Traps placed within the canopy captured 2.5 and 1.5 times as many flies compared with traps placed above the canopy and 45 cm from the ground, respectively. When sticky yellow Pherocon AM boards and green sphere traps were allowed to age in field cages, freshly baited (0 d) yellow sticky boards captured significantly more blueberry maggot flies than boards aged for 11, 28, and 40 d, respectively. No significant differences were observed among boards aged for 11, 28, and 40 d. However, when baited 9-cm sticky spheres were aged in field cages, there were no significant differences between freshly baited spheres and spheres aged for 11 and 28 d, respectively. Spheres aged for 40 d differed significantly from freshly baited ones. The study demonstrated that the baited 9-cm-diameter sphere was more effective in capturing blueberry maggot flies than spheres of 3.6 and 15.6 cm diameter. When this trap is deployed in the center of the bush canopy approximately 15 cm from the top of the bush, it is attractive and accessible to R. mendax flies. The data also indicated that a baited 9-cm sphere has a longer effective life span than Pherocon AM boards when deployed under the same field conditions.

Effect of Carbon Amendment and Soil Moisture on Tylenchorhynchus spp. and Hoplolaimus galeatus.

The effect of amending soil held at 3 different moisture levels with glucose, unsulfured molasses, or nutrient broth (0.3, 0.7, 3.2, 7.1 g carbon/100 g) on Tylenchorhynchus claytoni and T. dubius was investigated. When soil was held under saturated or flooded conditions in the absence of carbon amendments for 7 days, Tylenchorhynchus populations were 19% and 16%, respectively, of the controls. Carbon amendments at all levels tested precipitated a further decline in the nematode population to 1% or less of the unamended controls in 7 days. Two applications of molasses (7.4%, w/w) 3 days apart to nematode-infested soil held in Conetainers under mist for 7 days reduced Tylenchorhynchus spp. and Hoplolaimus galeatus densities to 7% and 3%, respectively, of the controls. Nematode densities in turfgrass field plots also declined following irrigation and repeated drenching with a molasses solution. Based on the observed decline in redox potential and pH in saturated soil, especially following carbon amendment, we propose that the activity of anaerobic fermentative bacteria was responsible for the reduction in nematode densities.

High-pressure Liquid Injection of Isazofos for Management of Hoplolaimus galeatus and Tylenchorhynchus dubius Infesting Turfgrasses.

Three high-pressure liquid injection machines were used to inject isazofos into the root zone of tuff;grass plots to evaluate its potential for control of Hoplolaimus galeatus and Tylenchorhynchus dubius. A Rogers root zone injector delivering isazofos at 2.3 kg a.i./ha through 30 degrees and 60 degrees spray tips at 5,000 psi (3.45 x 10 Pascals) significantly reduced nematode populations at 32 days after a single application and 33 days after a second application. In a second experiment with the Rogers injector at 2.3 kg a.i./ha, H. galeatus populations were significantly lower at 16 days after a single application and at 42 and 61 days after a second application with the 60 degrees spray angle tips. An Envirojet turfgrass injector used to inject isazofos at 1.15 kg a.i./ha and 2.88 kg a.i./ha at 3,000 psi (1.38 x 107 Pascals) significantly reduced nematode populations at 7 days after treatment at the low rate and at 63 days after treatment with both application rates. A Landpride material injector applying isazofos at 6.9 and 13.8 kg a.i./ha at 2,000 psi (1.38 x 10 Pascals) significantly reduced nematode populations at 7, 14, and 63 days after treatment at the high rate and at 63 days after the low-rate application. Although suppression of nematodes with isazofos was found, the degree of suppression is probably not enough to warrant recommendation of high-pressure delivery of isazofos for control of H. galeatus and T. dubius populations infesting turfgrasses.

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