Evaluation of different larval instars and predator-prey release ratio of indigenous generalist predator, common green lacewing, Chrysoperla carnea, for the management of two-spotted spider mite, Tetranychus urticae, on cucumber, Cucumis sativus crop

The present research aimed to study the efficiency of the indigenous generalist predator, Chrysoperla carnea, for the management of the two-spotted spider mite, Tetranychus urticae, infesting cucumber, Cucumis sativus plants in greenhouses. The most effective predator stage was determined by placing egg cards and releasing different larval instars (1<sup>st</sup>, 2<sup>nd</sup>, and 3<sup>rd</sup>) with a release ratio of 1:20 for T. urticae management. The population reduction percentage of T. urticae was 5%, 41%, and 47% after four, eight, and 12 days of 1<sup>st</sup> larval instar release as compared to egg cards. Among the three larval instars, the 2<sup>nd</sup> and 3<sup>rd</sup> instars significantly reduced the T. urticae population after eight days, with 75% and 79% population reduction percentages, respectively. Furthermore, less visual damage and webbing density per plant of T. urticae were observed where 2<sup>nd</sup> instar larvae were released. The 2<sup>nd</sup> instar larva was further evaluated with three predator-prey release ratios to manage T. urticae population on C. sativus plants in the greenhouse. The T. urticae population reduction percentages were 66%, 61%, and 24% at the release ratio of 1:30, 1:60, and 1:90, respectively, after 12 days of predator release. Moreover, less visual damage and localized webbing on leaf per plant was observed for the release ratio of 1:30. The outcomes of the present study showed that the 2<sup>nd</sup> instar larvae of the indigenous predator, C. carnea, could potentially manage the T. urticae infestation on greenhouse crops.