Evaluation of the Predation Capacity of Podisus maculiventris (Hemiptera: Pentatomidae) on Microtheca ochroloma (Coleoptera: Chrysomelidae) in Field Cages

The predation capacity of the spined soldier bug, Podisus maculiventris (Say) (Hemiptera: Pentatomidae), was evaluated at three release rates in field cages containing larvae of the yellowmargined leaf beetle, Microtheca ochroloma Stål (Coleoptera: Chrysomelidae), a pest of organic crucifer (Brassicaceae) crops in the United States. The experiment was conducted twice, in February—March 2009 and in February—March 2010. On the same day as the introduction of 132 first instars of M. ochroloma into the cages, four (= low), 10 (=medium), or 16 (=high) first instars of P.maculiventris were released evenly among six turnip (Brassica rapa L.) plants in cages. Control treatment cages received no predators. In 2009, the mean number of M. ochroloma larvae declined progressively during the first four sampling dates. On the final (seventh) sampling date, the mean numbers of total M. ochroloma in the two higher release-rate treatments were significantly lower than in the low release-rate and control treatments. Overall survivorship of P. maculiventris was 39.1% in the high release-rate treatment. In 2010, the mean number of M. ochroloma larvae declined progressively during the first four sampling dates. On the fourth sampling date and the final (ninth) sampling date, there were no significant differences among treatments involving predator releases. The lowest overall survivorship of P.maculiventris (3.1%) was in the high release-rate treatment. Two tentative recommendations for growers emerged from this study: 1) release 10 first instars of P.maculiventris per six plants if the plants are expected to have ≥7 leaves per plant; or 2) release four first instars of P.maculiventris per six plants if the plants are expected to have ≤6 leaves per plant.