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

Abstract

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 Thevetia peruviana seeds (AETPS) on the development of late blight caused by Phytophthora 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.

Inventory of the potato diseases and impact on growth and yield traits in far North Cameroon

“…The incidence of disease observed at both sites was low (<30%). This result is in contrary with that obtained by Lontsi et al (2019) who obtained incidences on the order of 80% for late blight in Cameroon, but in the agro-ecological zone with bimodal rainfall. In addition, Lehtonen et al (2004) obtained very high incidences of around 60% for common scab.…”

“…In the Far North Cameroon Region, particularly in the Mogodé subdivision (Mayo-Tsanaga), the only and main production area, the low yields observed are associated with poor peasant farming practices (Ngoyi et al, 2020), the scarcity or inequality of the rains and especially to diseases and pests. Many diseases have been reported on potatoes in several countries (Masum et al, 2011;Habtamu et al, 2012;Alkher et al, 2015;Son et al, 2018) and in Cameroon (Fontem et al, 2003;Fontem et al, 2005;Lontsi et al, 2019). Late blight (Phytophthora infestans) and Alternaria or early blight (Alternaria spp) appear to be the major fungi diseases threatening production of potato in the world with more 80% of losses (Abuley and Nielsen 2017;Ah-Fong et al, 2017).…”