Nursery, Greenhouse, and Landscape News

Compatability of Delphastus pusillus and Wasp Parasitoids of Sweetpotato Whitefly

Delphastus pusillus, a small lady beetle predator, is available from many biological control supply houses for controlling whiteflies in the greenhouse. It has a voracious appetite, consuming approximately 700 4th instar nymphs, or 10,000 eggs in a lifetime, and has the ability to feed on all immature stages of whiteflyso these beetles have the potential to decimate large populations of whiteflies in the greenhouse. However, adult female beetles must feed on over 200 eggs per day in order to reproduce.

Because these beetles are unlikely to persist when whitefly numbers are low, it would be ideal to use them in conjunction with other biological control agents that can maintain themselves in greenhouses when whitefly numbers are low, if the beetles don't interefere with the other natural enemies.

Studies with sweetpotato whitefly parasitized by the aphelinid wasps Encarsia transvena or Eretmocerus sp. nr. californicus show that D. pusillus doesn't eradicate other natural enemy populations. Adult and larval beetles avoid feeding on parasitized whiteflies when wasps are in later stages of development. D. pusillus feeds by penetrating its prey, and alternately sucking and regurgitating fluids to digest and consume it. Whiteflies containing later stages of wasps, especially those containing hardened pupae, may be more difficult to digest because of air spaces beneath the outer skin of the parasitized prey. Similar patterns have also been observed with other predators and other whitefly species.


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