The feeding performance of Psyllobora vigintiduopunctata (L.) (Coleoptera: Coccinellidae) on cucurbit powdery mildew, Erysiphe cichoracearum (DC.) (Helotiales: Erysiphaceae)

The feeding capacity of Psyllobora vigintiduopunctata on Erysiphe cichoracearum was investigated under laboratory (25 ± 2 °C, 70 ± 5% RH, 12:12 h photoperiod) and semi-field conditions. Under laboratory conditions, the total powdery mildew-infected area consumed approximately 19 cm² over the entire larval period. Over their lifetime, adult males consumed an average of 195.86 ± 5.48 cm² of infected area, whereas females consumed 225.14 ± 5.48 cm². The semi-field experiments were performed to determine the efficacy of P. vigintiduopunctata against powdery mildew by releasing 10, 15, and 20 adults onto squash plants at the initial stage of infection. Only distilled water was used as the control treatment. A commercial fungicide containing 200 g/L azoxystrobin and 125 g/L difenoconazole (Quadris® Maxx), 80 ml/100 L water) was applied to infected plants as the positive control treatment. The infected leaf area on squash plants was measured at five-day intervals, and the trials were terminated on day 20. In the control group, the plants were infected with 100% powdery mildew by day 20. The mean disease severity in plants where 10, 15, and 20 adult P. vigintiduopunctata were released was determined 16.99–17.07%, 12.88–13.42%, and 8.55–8.79%, respectively by 20. day. The mean suppression effects were determined as 82.93–83.01%, 86.58–87.12%, and 91.21-91.45%, respectively. In squash plants that received the fungicide treatment, the severity of powdery mildew increased from day 15 onwards, reaching approximately 11% and 89% effectiveness by day 20. These results were in agreement with laboratory-based feeding capacity data and revealed that releasing 20 adult P. vigintiduopunctata per plant at the initial stage of infection can provide highly effective suppression of E. cichoracearum, representing a strong alternative to chemical control strategies.