Effect of biological activity of Carapa procera DC. (Meliaceae) seed oil on the tomato leaf miner, Tuta absoluta Meyrick 1917 (Lepidoptera: Gelechiidae)

Abstract

Abstract Tuta absoluta poses a serious threat to tomato production worldwide as it can cause more than 80% yield losses. Its control is currently mainly based on the use of synthetic chemical insecticides, which unfortunately selects resistant populations and entails public health risks. The aim of this study was to evaluate the insecticidal, repellent and sublethal effects of Carapa procera seed oil on all stages of T. absoluta. Larvicidal (by contact and by ingestion), ovicidal and anti-feeding effects were evaluated by testing 1.5%, 3%, 4.5%, 6% and 7.5% concentrations of oil. Larvicidal and ovicidal effects were tested by direct application of Carapa solutions on larvae and eggs but also by feeding the larvae leaves dipped in solutions. The adult repellent effect was investigated by identifying the preferred area on filter paper partly non-treated vs fully treated using LC10, LC50 et LC90 of larvae after ingestion. LC50 was also used on 2-day-old larvae to evaluate the sublethal effects on larval and pupal duration, longevity and adult morphology. Results showed that, regardless of the mode of application, all concentrations had larvicidal effects with a higher dose-response effect and a higher mortality rate via ingestion than via topical application. The ovicidal effect varied with the concentrations tested, the highest mortality rate was obtained at a concentration of 7.5%. At the same dose, Carapa oil reduced large feeding galleries from 92.22 ± 5.02% in controls to 3.33 ± 3.65% at the highest dose and had a repellent effect on 80% of adults. Carapa oil increased larval and pupal duration by 2.14 and 1.35 days, respectively, and reduced adult female longevity by 2.2 days and male longevity by 1.1 days. A deformation rate of 28.33% was observed in newly emerged adults. This study demonstrated insecticidal and insect repellent effects of Carapa oil on different stages of T. absoluta. This botanical oil is a very promising biopesticide to control this major new pest of Solanaceous crops. Its use in an agroecological pest management strategy is discussed.