Efficacy and profitability of insecticides and crop management practices in the integrated management of Leucinodes orbonalis Guenée (Lepidoptera: Crambidae) on garden eggs

Abstract

Leucinodes orbonalis is a key insect pest of garden eggs (Solanum aethiopicum) in Ghana. Generally, L. orbonalis is managed by the use of harmful pesticides, necessitating the development of strategies which are more environmentally benign. This study compared the effectiveness and profitability of using black plastic mulch (PM) to manage L. orbonalis incidence with chlorpyrifos-ethyl (C-ethyl) and emamectin benzoate (EB). The PM was laid before transplanting whilst C-ethyl and EB were applied fortnightly up to the fruiting stage. The incidence of L. orbonalis on shoots and fruits, the percentage of infested fruits, yield and gross margins of the treatments were determined. The incidence of plants with newly infested shoots between treatments across all treatment dates were not significant (p > 0.05). Between 30.41% (PM+EB) and 94.49% (PM+C-ethyl) of fruits harvested showed signs of L. orbonalis infestation. Significant differences in the percentage of infested fruits between treatments were respectively observed at 12 (p = 0.021) and 16 (p = 0.035) weeks after transplanting. Plants from plots with EB as mixture (PM+EB) or sole (EB) treatment produced the highest yield advantage over the Control of 33.6% and 30.3%, respectively. Gross margin analysis indicated that the treatment of plants with EB was most profitable at peak price. At the least price obtainable, the use of all treatments particularly, PM was not profitable. Due to the possibility that movement of larvae between fields reduced the ability of PM to effectively suppress L. orbonalis populations, future work should evaluate the effect of PM using whole fields.