Comparison of Two Methods of Releasing Chrysoperla carnea (Steph.)

Green lacewing, Chrysoperla carnea (Steph.), is one of the important natural enemies of cotton aphid, Aphis gossypii Glover. In this study, two experiments were conducted on cucumber plant in netted cages (70*70*40 cm) in a greenhouse. In the first experiment, Chryso-bags (special net bags with 360 holes per 2.5 cm2 and 8 cm in width and 12 cm in length) were used. Seven treatments of release ratios included 1:1, 1:5, 1:10, 1:15 and 1:20 (predator: prey) and two control treatments with and without empty bags were compared. The experiment was conducted once in spring and once in autumn. In the second experiment, better release ratios were compared with two methods, Chryso-bag and sawdust as a carrier of eggs. Release ratios were 1:1 and 1:5 (predator: prey). Control treatments included only empty bag and sawdust, respectively. Results of the first experiment showed that the ratios of 1:1 and 1:5 were significantly different in spring, whereas they were not in autumn. The difference was probably due to the difference in temperature. Interaction between treatments and seasons showed that the ratios of 1:1 and 1:5 were not significantly different. In the second experiment, the release ratios of 1:1 and 1:5 in sawdust with each other and with 1:1 in Chryso-bags were not significantly different, while the ratio of 1:5 in Chryso-bag compared with 1:1 in both methods were significantly different. However, leaf necrosis was observed in the sawdust treatment.