Golf Course Management

JAN 2019

Golf Course Management magazine is dedicated to advancing the golf course superintendent profession and helping GCSAA members achieve career success.

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102 GOLF COURSE MANAGEMENT 01.19 (16 hours light at 70 F [21 C]: 8 hours dark at 57 F [14 C]). For each dose of each active in- gredient, there were two dishes with males and two with females. Mortality was evalu - ated at 24, 48 and 72 hours after treatment. Weevils were considered dead if no movement was observed after probing. No significant differences in insecticide toxicity against ABW males and females were observed, and data were combined for analy - sis. For bifenthrin, lethal doses killing 50% of the test populations (LD 50 ) ranged from 0.002 (HF) to 0.819 micrograms (LI) per insect, re - sulting in resistance ratios (RR 50 s) of up to HF PB GB CN PF RW EW JC LI 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 7 6 5 4 3 2 1 0 µ g a.i./insect µg a.i./insect µg a.i./insect µg a.i./insect µg a.i./insect Bifenthrin λ-cyhalothrin Chlorpyrifos Spinosad Clothianidin NC NC NC NC NC NA 2.2* 2.4* 1.4* 1.5* 343* 136* 95* 76* 65* 52* 31* 324* 174* 117* 123* 64* 77* 18* 15* 3.3* 3.3* 4.0* 3.8* 5.3* 4.1* 7.7* 2.5* 4.6* 4.8* 4.7* 3.4* 4.6* 4.6* 8.0* 6.5* 4.2* 6.7* 9.7* 8.5* Figure 1. Toxicity (LD 50 in micrograms a.i./insect) of five insecticides against nine annual bluegrass weevil popula - tions collected from golf courses in Connecticut, New Jer- sey, New York and Pennsylvania as determined in a topical bioassay at 72 hours after treatment. Numbers above the bars are resistance ratios (RR 50 = LD 50 resistant/LD 50 most susceptible) calculated with HF as the susceptible popula - tion, except for clothianidin, for which the PB population was used. Resistance ratios (RR 50 s) marked with an asterisk differed significantly from those of the susceptible population. NC, not calculated because the population was a baseline population. NA, not applied. Five insecticides vs. nine ABW populations NC 3.1* 3.2* 2.8* 7.5* 2.4* 1.2 HP PB GB CN EW JC LI 14 12 10 8 6 4 2 0 18 16 14 12 10 8 6 4 2 0 Clothianidin Indoxacarb µ g a.i./insect µg a.i./insect ABW populations NC 9.7* 3.5* 7.3* 7.0* 2.8* 1.3 Two insecticides vs. seven ABW populations Figure 2. Toxicity (LC 50 in micrograms a.i./insect) of two insecticides, clothianidin and indoxacarb, against seven annual bluegrass weevil populations collected from golf courses in Connecticut, New Jersey, New York and Pennsylvania as determined in feeding bioassays evaluated 72 hours after treatment. Numbers above the bars are resistance ratios (RR 50 = LC 50 resistant/LC 50 most susceptible) calculated with HP as the susceptible population. Resistance ratios (RR 50 s) marked with an asterisk differed significantly from those of the susceptible population. NC, not calculated because the population was a baseline population.

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