The Survey Effects of Garlic Extract Sirinol® and Chemical Acaricide Spirodiclofen Envidor® on Two-Spotted Spider Mite Tetranychus urticae Koch (Acari: Tetranychidae) under Laboratory and Field Conditions

The two-spotted spider mite is a cosmopolitan species that exist in wide areas of the world and fed from different varieties of plants. The control of this pest was done by chemical pesticides and acaricides. Due to the high cost of chemical compound and problems such as durability and environmental pollution, alternative control means are necessary. Plants may provide potential alternatives to currently used insect control agents. Plant materials have several advantages over traditional pest control agents; such as specificity, biodegradability and low mammalian toxicity. Sirinol is a natural compound based on garlic extract. Spirodiclofen with a trade name of Envidor® is a broad spectrum acaricide acting via lipid biosynthesis inhibition (LBI) with no cross-resistance to currently available acaricides and with additional insecticidal properties. Envidor is positive IPM listed but in the frame of resistance, management limited to one application per season. In pear growing Envidor constitutes an important tool in pear sucker control in a tandem strategy with abamectin. In this research, the effect of this compound was investigated on the egg and adult of T. uricae under laboratory and field condition.
Materials and Methods Rearing of T. urticae: An initial mite colony was collected from infected fields in Sari and was transferred to the laboratory in Sari Agricultural Science and Natural Resource University, plant protection department. The adult mites were released on the bean leaves (3 weeks after leaves germination) and removed 24 h after treatment. Infected plants to mite eggs were placed in a growth incubator at 25±2˚C, 65±5% RH and 16:8 photoperiods. 12 days after treatment and emerging of adults, they were used for the bioassay.
Bioassay: First of all, primary experiments were performed to determine the minimum and maximum concentrations. Then, seven concentrations and also control were considered. The concentrations used for sirinol were 250, 381, 593, 922, 1434, 2230 and 3500 ppm and for spirodiclofen were100, 134, 180, 242, 326, 438 and 600 ppm. The original bean leaf discs (30 mm diameter) were cut and 15 adults of T. urticae were released on each leaf. Then, 500 microliters of each concentration was sprayed on the leaves using spray potter tower and the leaves were put on the petri plates containing moist cotton. The treatments were placed in a growth incubator at 25±2˚C, 65±5% RH and 16:8 photoperiods. The number of dead mites was counted at 24, 48 and 72 hours post-treatment. To evaluate the effect of three concentrations 1000, 2000 and 4000 ppm of sirinol and 300, 600 and 1200 ppm of spirodiclofen an experiment with seven treatment and four replications was conducted in a randomized complete design under field condition. The numbers of T. urticae and P. persimilis (egg and adult) on leaf samples were counted one day before treatment and 3, 7, 14 and 21 days after treatment.
Statistical analyses: The mortality results were analyzed statistically using SPSS data processing software. Significant differences among the groups were determined using the unpaired Duncan-test. A value of P