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Managing cabbage pests and protecting the "good guys"

Two years of effort funded by IPM grants have added greatly to our knowledge of beneficial insects and spiders in cabbage fields. Spiders, hover flies, and lady bird beetles have been found to be the most numerous, but the question "Which is the most efficient predator of the imported cabbageworm?" is still to be answered.

Once we know which beneficials are present and which best manage this major cabbage pest, it makes sense to look at how standard chemicals affect these beneficials. Selection of pesticides that are effective against the pests without harming natural enemies is one way growers can enhance naturally occurring biological control.

Three pesticides were tested in 1996. All three were effective against the imported cabbageworm, but two were also highly toxic to natural enemies. The third left lady bird beetles and "harvestmen," another beneficial species, unharmed.

Results of this project were summarized in a "selectivity index" calculated for each pesticide. This index will be incorporated into future IPM recommendations for cabbage, enabling growers to choose pesticides with foreknowledge of their effects on natural enemies.