Release Strategies of the Mirid Macrolophus caliginosus in Protected Tomato Crops | Strategie d'introduction du predateur Macrolophus caliginosus en culture de tomate sous abri

Macrolophus caliginosus is an important beneficial in protected tomato crops, but it often establishes too slowly in early crops in the Swiss conditions. Four preventive release methods were compared based on the time needed by the predator population to reach an «operational threshold», in the absence of suitable prey. The threshold was empirically fixed at 15% of occupied tomato leaves. Costs of each method were also estimated. A) The «Standard release» dose of 1.0 predator per m2, evenly distributed was not efficient: more than 5 months were required for establishment. B) When 0.8 predators per m2 of planted crop were released at several points, the average time for establishment was 4 months. The predators were nourished around the release points with eggs of Ephestia kuehniella. C) The use of banker-plants (9 units/1000 m2) permitted over-wintering of M. caliginosus and its reestablishment the next year into the tomato crops without the necessity of repurchasing predators. The banker-plants used were tobacco (Nicotiana tabacum) and tamarillo (Cyphomandra betacea). Predators were fed during over-wintering in a small heated glasshouse compartment. With this method, the operational threshold was reached after 3 months, assuring compatibility with the usual phenology of pest-targets. D) Finally, the shortest time of establishment (8 weeks) was reached by inoculating tomato plants under net in the nursery. Predators were fed and introduced at the dose of 0.7 per m2 of planted crop. Costs for introduction per 1000 m2 of crop were: A) CHF 230.- for the standard introduction, B) CHF 191.- for the multiple-points release, C) CHF 267.- for the banker-plants method and D) CHF 343.- for nursery inoculation. The cost/efficacy ratio supports the latter two methods, which deserve further development.