Effectiveness and profitability of insecticide formulations used for managing snap bean pests
Snap bean (Phaseolus vulgaris L.) farmers rely mostly on insecticides to manage pests and to satisfy the stringent market requirements for insect and blemish-free pods. However, the cost of these pesticides lowers farm incomes. In addition, heavy and wrong use of pesticides could result in residue accumulation, which reduces market access by the farmers. To identify optimal pest control with lower economic risks to farmers, we investigated the effectiveness and profitability of different insecticides and insecticide formulations against bean fly (Ophiomyia spp.) and bean flower thrips (Megalurothrips sjostedtii). Two separate experiments were conducted during 2009 to 2012. The first experiment targeted bean fly and bean flower thrips, comprising the treatments: seed dressings, soil drenches, foliar sprays and an untreated control. We used randomised complete block design, with four replicates. All the seed dressing and soil drenching insecticides, except Apron, significantly lowered bean fly infestation by two to 60 fold when compared with control. These insecticides, however, did not control flower thrips. Confidor® resulted in a marginal returns of 0.89 and Actara® -0.11 compared to seed dressings, which ranged from 0.47 to 1.82. The second experiment laid in a randomised complete block design involved the foliar application of Roket® under different spray regimes. Application of Roket® reduced infestation of thrips, and resulted in positive MRR in all the seasons.
Keywords: Frankliniella occidentalis, marginal rate of returns, Megalurothrips sjostedtii, Neonicotinoids, Ophiomyia phaseoli