Colorado Potato Beetle Control in Tomato
Growing tomatoes for fresh market is a labor intensive and expensive enterprise, involving staking, stringing, harvesting and irrigation. Nonrecyclable black plastic mulch or bare soil culture is typical, but the use of winter annual legume cover crops like hairy vetch is an alternative. Augmentation for control of Colorado potato beetle has been studied in potato and eggplant, but not in tomato. This study in Maryland evaluated the ability of the eulophid egg parasitoid Edovum puttleri and the predatory spined soldier bug, Podisus maculiventris, to successfully search staked tomatoes and find and attack Colorado potato beetle. Also considered was the influence of ground cover - vetch or black plastic - on the efficacy of the releases and the dynamics of the pest.
Multiple releases of the wasp and spined soldier bug resulted in increased parasitism and predation rates of eggs of Colorado potato beetle. There was no consistent effect of the different mulches on potato beetle infestations or the impact of the natural enemies on those populations. No parasitism by E. puttleri occurred in one year of the study, possibly because of insecticide residues (necessary to prevent economic losses in the cooperator's field). Parasitism up to 30.6% was observed in another year when insecticides were not used. The second and third instar spined soldier bug nymphs that were released readily found and attacked potato beetle egg masses. In most cases all the eggs in an attacked mass were destroyed. Despite the ability of both beneficials to search the structurally complex plant and find the pest, neither would have prevented economic loss from Colorado potato beetle because the initial invasion of the field by overwintered adults would have overwhelmed the vulnerable tomato transplants. The cost of maintaining release rates that were high enough to achieve significant control of the pest would be prohibitive.
Probably a better approach would be a trap crop of more attractive potatoes or eggplant adjacent to the tomato field. Such a planting - that occurred unintentionally in one year - would intercept the overwintered adults and could serve as a focal point for mass releases of natural enemies. The beneficials would probably be able to search more efficiently in potatoes than tomatoes (because of their more compact and less structurally complex habit) and could suppress the beetle populations there to prevent major infestation of the tomatoes.
Tipping, P. W., C. A. Holko, A. A. Abdul-Baki and J. R. Aldrich. 1999. Evaluating Edovum puttleri Grissell and Podisus maculiventris (Say) for augmentative biological control of Colorado potato beetle in tomatoes. Biol. Control 16(1):35-42.
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