Integrating insecticides and Trichogramma ostriniae to control European corn borer in sweet corn: Economic analysis

We compared the economics of controlling European corn borer (Ostrinia nubilalis) in sweet corn by using the egg parasitoid, Trichogramma ostriniae, alone and integrated with insecticidal sprays. An initial experiment in 2003 compared T. ostriniae alone against insecticide alone and a second set of experiments conducted over 3years (2006–2008) compared (1) insecticide alone [Insecticide]; (2) no insecticide, no T. ostriniae [Untreated Check]; (3) T. ostriniae alone [T. ostriniae 1X]; and (4) T. ostriniae+insecticide [Integrated]. In 2007 and 2008, a fifth treatment was added consisting of three approximately weekly releases of T. ostriniae [T. ostriniae 3X]. Parasitism of O. nubilalis eggs was higher in plots receiving T. ostriniae; O. nubilalis eclosion was lower with T. ostriniae; there was no interaction of T. ostriniae and insecticide on parasitism, O. nubilalis eclosion, or total O. nubilalis larvae at harvest time. Partial crop budgets were conducted for each treatment. In three of the 4years, Untreated Checks had the highest sweet corn ear damage. Ear damage after a single release of T. ostriniae was statistically no different than using insecticides. In two of the three years, the Integrated treatment (T. ostriniae 1X+insecticide) generated the largest increase in profitability. The insecticide only treatment generated the second best increase in profitability. When comparing a single release of T. ostriniae to the insecticide only, the latter provided a better combination of efficacy and profitability. The breakeven costs of the T. ostriniae justified their use relative to the Untreated Check treatment, but not when compared to the Insecticide treatment. The breakeven costs for T. ostriniae in the Integrated treatment exceeded the actual cost in two out of three years, suggesting again that conventional growers could benefit from integrating T. ostriniae with insecticidal treatments. Projected profitability based on ear packout obtained by combining data among years suggests that in general, for low prices and yields, the increase in profit is quite modest. In the lowest price-yield combination, the change in profit is T. ostriniae 3X>Integrated>Insecticide>T. ostriniae 1X⩾Untreated Check. At high prices and high yields, the differences between the management options when compared to Untreated Check are considerable. In the highest price-yield combination, the change in profit is T. ostriniae 3X>Integrated≫Insecticide>T. ostriniae 1X≫Untreated Check.