Efficacy of some insecticides and their combination in chemical control of alfalfa weevil, Hypera postica in field condition
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عنوان دوره: سومین کنگره بین المللی حشره شناسی ایران
نویسندگان
1Department of Plant Protection, Faculty of Agriculture, University of Tabriz, Tabriz, Iran,
2Tabriz Agriculture-Jahad Management, Eastern-Azarbaijan Agriculture-Jahad Organization, Tabriz, Iran
3Department of Plant Protection, Faculty of Agriculture, University of Tabriz, Tabriz, Iran
چکیده
Alfalfa Medicago sativa L. is a perennial plant which is planted as an important forage crop in many countries. Alfalfa weevil Hypera postica Gyllenhall (Col.: Curculionidae) is the most important pest of alfalfa in Iran. Intense early season defoliation by pest causes serious yield loss. Both adults and larvae feed on alfalfa, but larval damage on foliage, especially new vegetation is considerable. There are many reports which indicate insufficient effects of insecticide applications on alfalfa weevil. In this study the effect of some insecticides and their combination were evaluated on larval stage of H. postica. Treatments including fenvalerate (0.12 mg ai / L), malathion (1.03 mg ai / L), chlorpyrifos (0.61 mg ai / L), cypermethrin (0.42 mg ai / L), acetamiprid (0.1 mg ai / L), lambda-cyhalothrin (0.21 mg ai / L), gitavate (2.5 ai / L), malathion + cypermethrin, fenvalerate + dursban, acetamiprid + malathion, malathion + gitavate, cypermethrin + gitavate, lambda-cyhalothrin + cypermethrin and distilled water as control were used in a completely randomized design with 3 replications in an infested alfalfa field (2500 m2) located in the Khalat-Poushan, Agricultural Research Station of University of Tabriz. Each plot was 50 m2 with a 1 meter margin around it. The number of larvae was counted in 10 plants per each plot 24 h before treatment and repeated 24, 72 h and one week after spraying. The number of larvae was compared by Tukey’s HSD test (P ≤ 0.05). Results showed no significant difference among treatments in 24 h (F = 1.43, df=11, 24, P= 0.22). In subsequent bioassays all insecticides killed more weevil larvae than the control (F= 16.46, df=11, 24, P< 0.0001 in 72 h and F = 15.62, df=11, 24, P< 0.0001 in 1w bioassays, respectively). Furthermore, in the second bioassay (72h), malathion + cypermethrin, dursban, acetamiprid and lambda-cyhalothrin + cypermethrin had stronger effect compared to malathion + gitavate that may suggest more accelerate effect of these treatments. The results also showed a 41% increase in H. postica numbers in control, compared to 15.7-88.7% decrease in insecticide treatments. It may imply an advantage of 7.46 times less survival rate of the pest in lambda-cyhalothrin + cypermethrin compared to that in fenvalerate which were the most and the least effective insecticides treatments, respectively.
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