Effect of aqueous extracts of Thevetia peruviana K. seeds on the control of late blight and pest insects of Solanum tuberosum L. in Cameroon

In the perspective of effective control of diseases and pests of potatoes (Solanum tuberosum), a study carried out in the Highland West Region of Cameroon permitted to evaluate the effect of aqueous extracts of Thevetiaperuviana seeds (AETPS) on the development of late blight caused byPhytophthora infestans and the population of insect pests. Two potato varieties (local (V1) and one improved variety "Cipira" (V2) were used. Five treatments: AETPS (T1), Bravo 720 fungicide (T3), Decis 5 EC insecticide (T4), mixture of the three substances (T2) and the control (T0) were tested using a double factorial system with completely randomized blocks. The evolution of the disease, insect population and tuber yield were evaluated and compared according to different treatments. The results show that a main disease identified in field and laboratory was mildew. 88 pests were collected and 9 pest families were identified. The Coccinelidae family was most represented (23, 86%). The incidence and severity of late blight in the field were respectively reduced to 22.77 and 76.05 % by the AETPS at 50 g/l, as the synthetic fungicide (T3). The number of insects decreased after treatment but remained relatively stable in control. The insecticidal power was maximum 1 h after application of the decis contrary to the AETPS of with maximum was between 24 and 48 h. The commercial yields obtained in the AETPS treatment were greater than 7.5 t/ha compared to 0 t/ha obtained in the controls (T0). Extracts of T. peruviana can therefore be used as anti-parasite substances in crop protection