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 > or = 7 leaves per plant; or 2) release four first instars of P. maculiventris per six plants if the plants are expected to have < or = 6 leaves per plant.

Development time and predation rate of Podisus maculiventris (Hemiptera: Pentatomidae) feeding on Microtheca ochroloma (Coleoptera: Chrysomelidae).

Microtheca ochroloma Stål is a beetle native to South America and was introduced to the United States in 1945. Since then, M. ochroloma has become a serious pest in crucifer crops because of the lack of natural enemies. The objective of this study was to measure the predation rate and development time of the commercially available predator Podisus maculiventris (Say) feeding on M. ochroloma at four constant temperatures in the laboratory as a first step to evaluating the predator's capability as a biological control agent of the pest. Nymphal development of P. maculiventris increased from 23 d at 25°C to 99 d at 15°C. There was no development of first instar or egg hatch at 10°C. Number of fourth-instar M. ochroloma killed during nymphal development varied significantly from 65 at 15°C to 53 at 20°C because of length of the nymphal period. A mean total of 741 eggs of M. ochroloma were consumed during nymphal development at 25°C. Adult P. maculiventris preyed on nine and 12 times more fourth-instar M. ochroloma during 10 d at 20° and 25°C, respectively, than at 15°C. We conclude that P. maculiventris can develop successfully on a diet of eggs or fourth-instar M. ochroloma, but its predation and development rates will be significantly curtailed during the cool months from November to March when M. ochroloma is a key pest of organically grown crucifers in Florida.