Singular and Joint Usage of Third Larval Instars of <i>Hippodamia Variegata</i> (Goeze) and <i>Chrysoperla carnea </i>(Steph.) in Biological Control of <i>Aphis gossypii</i> Glover in Greenhouse

The efficiency of singular and joint usage of third larval instars of ladybeetle, Hippodamia variegata</em> (Goeze) and green lacewing, Chrysoperla carnea</em> (Steph.) was studied against cotton aphid, Aphis gossypii</em> Glover on cucumber plants in greenhouse. The predator-prey ratio of 1:30 reduced the population of pest significantly. Singular and joint usage of predators, however, was not significantly different. The predator-prey ratio of 1:90 reduced the population of host significantly but the treatment with larvae of both predators and the treatment with only ladybeetle larvae were not significantly different. However, only the treatment with lacewing larvae was significantly different from the two above-mentioned treatments.