Contact and ingestion toxicities of plant extracts to Thaumetopoea solitaria Frey. (Lepidoptera: Thaumetopoeidae)

Thaumetopoea solitaria is a serious pest of pistachio throughout the Mediterranean and the surrounding region. In this study, contact and ingestion toxicities of Bifora radians, Fumaria officinalis, Humulus lupulus and Rhododendron ponticum extracts against T. solitaria larvae were examined under laboratory conditions. Dimethoate was used as a positive control. In the contact toxicity bioassays B. radians extract was the most toxic, causing 32% mortality. In the ingestion toxicity bioassays H. lupulus extract was the most active, causing 83% mortality after 48 h. This shows that H. lupulus is acting as a stomach poison. The LC₅₀ and LC₉₀ values for H. lupulus ingestion toxicity bioassays were 1.7 and 8.7%, respectively. The LT₅₀ value was 29.3 h. Since H. lupulus extract caused >50% mortality even 6 days after application, its long lasting residual effect promises fewer applications. These results imply that H. lupulus has potential for use as a crop protectant against T. solitaria.