Insecticidal activity of aqueous indigenous plant extracts against insect pests associated with cucumber (Cucumis sativus L.) in Southern Guinea Savannah Zone of Nigeria

Abstract

Insect pests of cucumber are mainly controlled using synthetic insecticides. However, considering the various ecological dangers caused by their usage, it becomes imperative to provide alternatives to them. The insecticidal activities of aqueous extract of five selected plants, Lantana camara Linneaus, Zingiber officinale Roscoe, Tithonia diversifolia Hemsl, Azadirachta indica A. Juss and Piper guineense Schum and Thonn. extracts against insect pests (Phyllotreta cruciferae Fabricius, Diabrotical undecimpunctata Howardi Barber, Epilachna vigintiopunctata Fabricius and Monolepta spp Coquillett) of cucumber were evaluated. The extract of each plant was prepared by pounding 1000 g which was then soaked in 2000 ml of water for 24 hours to form stock solution. The mixture was serially diluted into two concentrations (10 and 15%v/v) and applied to cucumber (Cucumis sativus L.) Data collection commenced at 2 weeks after planting on weekly basis for six weeks. Severity of insect damage on leaves, fruits, and yield were assessed. A. indica (10%v/v) and Z. officinale (15%v/v) demonstrated significantly (p < 0.05) highest efficacy with least insect population of 1.46 and 1.52, respectively. At 5–6 weeks after treatment, A. indica and Z. officinale plant extracts had the same efficacy with Karate 25EC®. At 10% concentration, P. guineense, T. diversifolia and L. camara performed better than the control. Plant treated with 10% Z. officinale extract had the highest fruit yield (2.58 t/ha) compared with karate (0.84 t/ha). In conclusion, all the plant extracts applied were as effective as Karate 25EC® in controlling insect pests of cucumber. It is therefore recommended that A. indica, Z. officinale and P. guineense extracts could be used to effectively control insect pests of cucumber.