کارایی کفشدوزک شکارگر Hippodamia variegata (Goeze) و زنبور پارازیتوئیدLysiphlebus fabarum (Marshall) در کنترل شته‌ جالیز Aphis gossypii (Glover) ، روی گیاه خیار در شرایط آزمایشگاهی

Intra- and inter -species interactions between organisms usually have important positive or negative consequences, when they utilize a common food source. Evaluating the controlling effects of different combinations of natural enemies before using them in the biological control programs, can be important successfully to control of a pest. In this study, the effects of separate and combined release of the second-instar larvae of the ladybird Hippodamia variegata (Col., Coccinellidae) and the parasitoid wasp Lysiphlebus fabarum (Hym., Braconidae) on the predation and parasitism rates of these two natural enemies, were investigated against the melon aphid, Aphis gossypii (Hem., Aphididae) in laboratory-caged conditions on single cucumber plants (greenhouse Negeen cultivar) infected with immature growth stages of aphids (150 aphids per plant). Experiments were performed at five treatments (n = 8) including separate and combined releases of two biocontrol agents (consecutively at an interval of 3 days) and in different densities of natural enemies including primary density (one individual of second instar larva of ladybird and 30 females of the parasitoid wasp), double density (two individuals of second instar larvae and 30 female wasps), and control treatment in large cages (60 × 60 × 120 cm). Monitoring and data collection were performed every 5 days to determine the density of remaining aphids on cucumber plants. At the end of the experiment, the total number of remaining aphids on treated plants had a significant difference compared to control treatment. The treatment including two second instar larva of ladybird had the most reduction effect on the aphid population, so that the remaining aphids at the end of experiment was 139.62 ± 15.09 on average. The combined application of these biocontrol agents in double density showed the greatest effect in limiting growth of the aphid population, with the average number of remaining aphids of 230 ± 13.96. The lowest efficiency was related to the combined release of two agents at half density (1 and 30) with an average of 355.62 ± 16.83 the number of remaining aphids at the end of the experiment. Regarding the parasitism activity of L. fabarum, the most favorable performance was observed in the combination release treatment with a double ratio, so that the largest number of mummies was significantly obtained in this treatment (281.50 ± 10.66 the number of mumies). In the other words, the parasitism rate was increased at the presence of second instar larvae in double density. The findings of this study can be used in integrated pest management programs for separate or simultaneous usage of these natural enemies against A. gossypii.