The effect of Volk oil on the ladybirds Cryptolaemus montrouzieri and Chilocorus bipustulatus (Col.: Coccinellidae)

Predator ladybird, Cryptolaemus montrouzieri and the armored-scale ladybeetle, Chilocorus bipustulatus (L.) are important predators of Diaspididae and Eriococcidae families in Iran. Application of mineral oils are among chemical methods to control mealybugs which are more compatible with the environment and relatively quickly are destroyed in the environment and the risk of secondary pest resistance in regards with these compounds is very low. In this study, the effect of Volk oil® on adult and different larval stages of C. montrouzieri and C. bipustulatus was evaluated on citrus leaves in orchard conditions. Ladybeetles were released and then sprayed with Volk oil at the concentrations of 0.5, 1, 1.5 percent and water (control) was carried out and after 24 hours the number of dead and alive insects were determined.. The results showed that there were significant differences between the effects of different concentrations on life stages of both ladybirds at 5% level. The concentration 1.5% had the highest mortality rate, as 92.16±1.11and 96.83±1.24 percent on the 1st larval stage of C. montrouzieri and C. bipustulatus ladybirds, respectively. Based on the results and compared with the evaluation criteria of the International Organization for Biological Control (IOBC), mortality rate caused by 1 and 0.5% concentrations of Volk oil in most age stages for both predators were placed in the second group of side effect ranking (Moderately Harmful).