Efficacy Comparison of Methoxyfenozide with Some Insecticides against Grape Berry Moth, Lobesia botrana L. (Lepidoptera: Tortricidae) Under Field Conditions

Grape, Vitis vinifera L. is one the most important economic and major global crop. Grape production is aimed at various markets, namely, table grapes for fresh consumption and processed grapes that are dried into raisins or pressed for grape juice. The European grapevine moth, Lobesia botrana Denis and Schiffermuller, (Lepidoptera: Tortricidae) is one of the major pest of grape in Iran and worldwide. Larvae of the first generation feed on bud clusters and flowers, whereas larvae of the subsequent generations feed exclusively on ripening and ripe berries and causes considerable yield losses. One L. botrana larva is capable of damaging between 2 and 10 berries, depending on the cultivar and the grape phenology. L. botrana is a multivoltine species with three to four generations per year. The focus of the control methods against this pest in our country is the use of insecticides. In Iran, three insecticides azinphos-methyl, diazinon and phosalone (all registered in 1968) were previously registered to control this pest. However, azinphos-methyl and diazinon have been now phased out from the list of authorized pesticides. Therefore, registration of the new active ingredient of insecticides with novel mode of action is very important. Methoxyfenozide is one of the most effective of the non-steroidal ecdysteroid agonist insecticides that has been commercialized and used against Lepidoptera species globally. Its mode of action is based on their capacity to induce a premature and incomplete moulting and susceptible insects die from desiccation and starvation. In addition, methoxyfenozide have a high safety profile against natural enemies of pests. Accordingly, methoxyfenozide is compatible in integrated pest management (IPM) programs. In directions to register new pesticides and diversify the pesticide basket in our country, the current research was done to evaluate the field efficacy of methoxyfenozide (SC24%), in comparison with spinosad (SC24%), Bacillus thuringiensis (Bt) and Lufox® (Lufenuron+Fenoxycarb, EC10.5%).

 The project was performed against the second and third generations, based on a completely randomized design with three replicates in Dizaj Dol (Urmia West Azarbaijan), Khalil Abad (Kashmar, Khorasan Razavi) and Dehnok (Takestan, Qazvin). The efficacy of the treatments was done based on the damaged bunches. To do this, at 3, 7, 14 and 21 days after treatment, the total bunches of each treatments firstly were counted and then the rate of damaged bunches were evaluated. The experimental treatments were: 1) methoxyfenozide (0.5 ml/L); 2) methoxyfenozide (0.75 ml/L); 3) spinosad 4) Lufox; 5) Bt and 6) control. The control treatment was sprayed by water only. Applications were made according to pheromone trap captures of males. In each treatment, 50-90 randomly selected bunches (from five treated plant) were collected and carefully examined for damage caused by L. botrana. Statistical analysis was performed using the SAS software (ver. 9.1). One row was considered as the distance between the experimental units.

The combine analysis of variance showed that interaction of treatment×location was significant, meaning that the experimental treatments had different responds in different locations. Accordingly, the data were statistically analyzed based on this. Moreover, the results of the factorial statistical analysis indicated that the effect of generation and the interaction between generation and location were not significant. Thus, in this article only the results of the second generation are provided. The results showed that in all cases, methoxyfenozide has acceptable efficacy at 14 and 21 days of post treatment. Therefore, no notable expectation of methoxyfenozide, in term of efficacy, should be expected until one week after spraying. The observed delayed toxicity of methoxyfenozide is consistence with previous reports and it is due to unique mode of action being moulting hormone agonist which induce premature moulting leading to death. It is necessary to note that there was no statistically significant difference in the efficacy of methoxyfenozide with Spinozad and Lufox during the mentioned period. For example, in Urmia methoxyfenozide (0.75 ml/L) exhibited 78.72% efficacy (at 14 days of post treatment, which was not statistically significant with spinosad (80.63%) and Lufox (81.04%). In conclusion, our results showed that methoxyfenozide exhibited acceptable efficacy against Lobesia botrana, required for registration in Iran. However, since the both methoxyfenozide concentrations (0.75 and 0.5 ml/L) had the same efficiency and considering the low-input of pesticides to the environment, it is recommended to use the application rate of 0.5 ml/L against this pest.