Effect of temperature on life table parameters and the efficacy of Feltiella acarisuga releases against Tetranychus urticae on cucumber crop in greenhouses

This study evaluated the developmental biology, predatory performance, and field control efficacy of Feltiella acarisuga (Vallot) (Diptera: Cecidomyiidae) as a biocontrol agent against Tetranychus urticae Koch (Tetranychidae) at different constant temperatures. Laboratory study results indicated that the duration of egg-to-egg development decreased significantly with an increase of temperature, ranging from 29.3 days at 15°C to 10.7 days at 30°C for both females and males. Female reproductive performance was the highest at 25 °C with fecundity reaching 36.2 eggs per female and a balance between development and reproduction was observed. Life table parameters supported the optimum temperature of 25°C for the highest net reproductive rate and population growth potential. Strong temperature-dependent developmental rates were found through linear regression analysis (R² = 0.93 – 0.99), with growth developmental thresholds below 7.2–8.4°C. Predation by T. urticae larvae increased significantly with increasing temperature with third-instars larvae consuming a maximum total prey count of 159.8 at 30°C. In field experiments, the release of F. acarisuga larvae significantly reduced mite infestations on cucumber plants with the highest control efficacy (98.3% reduction) associated with a release rate of 30 larvae/plant. These results suggest that the cucumber predator, F. acarisuga may be a promising option for biological mite control especially in warm season, and make sex pheromone-based mass rearing and field control techniques more practical in cucumber mite, T. urticae control programs, including integrated pest management (IPM).