Efficiency of three indigenous species of coccinellid predators for controlling aphids and whiteflies on cucumbers in greenhouses

Cucumber plants can be infested with many insect pests such as aphids, whiteflies, and thrips, especially in greenhouses, resulting in significant damage to the crops. This study investigated the efficacy of three species of coccinellids (Coccinella undecimpunctata, Coccinella septempunctata, and Hippodamia variegata), indigenous to the Taif region of Saudi Arabia, to control Bemisia tabaci whiteflies and Aphis gossypii aphids on cucumbers in greenhouses. The study was conducted with a release rate of five second-instar larvae of each coccinellid species per plant. One week after the first release of coccinellids, there were no significant differences among the treatment groups in terms of infestation rate, but all three groups differed significantly from the control group. After the first week, the B. tabaci and A. gossypii infestation rates decreased significantly in the H. variegata group compared with the other two coccinellid species, a trend that continued until the end of the experiment. These results suggested that H. variegata was the most effective of the three species at decreasing the B. tabaci population. After the second release of each coccinellid species, the reduction rates were >90% in all three groups, being significantly higher in the H. variegata group. Thus, these results suggest that second-instar larvae of all three coccinellid species would be effective predators of B. tabaci and A. gossypii on cucumbers in greenhouses, with those of H. variegata showing the greatest efficacy. Future research should focus on the effects of these predators on outdoor cucumber fields and on other crops grown in the Taif region.