The cumulative use of compost teas and rhizobia against Megalurothrips jostetti for yield improvement in field grown cowpea at Ngaoundere (Cameroon)

Abstract

Cowpea (Vigna unguiculata) is a food crop legume, considered as one of the cheapest sources of protein. However, its culture is subject to attack by many pests that drastically reduce yield. An alternative for better pest control and increased yield is the simultaneous use of biopesticides and biofertilizers. The objective of this study was to control the pests, while optimizing yields of this legume in a sustainable manner. To achieve this, compost teas and rhizobia were first produced and characterized. Then a pot experiment was set up in a triplicated randomized block design comprising 11 treatments, in order to determine the ability of compost teas and rhizobia to control insect pests and optimize the yield of this Fabaceae. The characterization of the compost teas revealed that the pH varied around the neutrality with an abundance of alkaloids and terpenoids and the absence of tannins. The three isolates obtained were all Gram negative bacteria and did not absorb the dye Congo red. Compost teas reduced and stabilized thrips (Megalurothrips jostetti) population development. Non-aerated compost teas from Tithonia diversifolia (PNA) alone, and its association with rhizobia (Rh + TNA) resulted in a reduction of the number of flower buds attacks. Their effects appeared to be limited outside the pods as they did not positively affect the number of seeds attacked. Both PNA and Rh+TNA treatments increased pod number, and seed biomass. Rhizobia and rhizobia + non-aerated compost tea from Tithonia diversifolia (Rh+TNA) significantly increased the yield of this plant species.