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Whitefly Control | | | | | Two Bemesia tabaci whitefly pupae. The one on left is parastized by the Nile strain of Encarsia formosa. The two red spots on the larvae are not eyes but rather symbiotic microorganisms. | Encarsia formosa - Nile Strain | Emergence hole of parasitoid from whitefly pupal case. | | The common greenhouse whitefly, Trialeuroides vaporariorum, is easily controlled with Encarsia formosa, a tiny parasitoid wasp that developes within a whitefly pupa. Unfortunately, several new strains of another whitefly species, Bemesia tabaci, are not controlled by the common Encarsia formosa. Although the wasps will feed on the whitefly larvae and pupa, and deposit eggs, they reproduce very poorly at best, and continued parasitoid releases are needed. Several other species of parasitoids from the genus Eretmocerus have been suggested and have apparently been successfully used in some greenhouses. We have not found them to be effective. Unlike Encarsia, they require both males and females to reproduce. Encarsia populations are all female and thus all adults parastize whitefly immatures and populations increase faster. Higher humidities in our region be a factor as the commerically availabale Eretmocerus species originate from desert areas. |  Encarsia are released into greenhouses by hanging cards on which are attached about 50 parasitized whitefly pupa. | Use parasitoids that work on all species of greenhouse whiteflies A strain of Encarsia formosa is now available that will reproduce in Bemisia whiteflies. We have found that the "Nile" strain has been effective in controlling both greenhouse and Bemesia tabaci whiteflies in our trials. Because it is very difficult to distinguish whitefly species captured on sticky cards, it is usuall best to use the Nile strain for control. Another strain of Encarsia formosa, the "Beltsville" strain was highly effect in trials in the late 1990's. This strain was found near Beltsville, MD, and was used in our greenhouses for several years with excellent results. It is no longer available commercially but may be present naturally in much of the mid-Atlantic area. Many predators will consume the soft-bodied larvae and pupae of whitefly, such as minute pirate bug (Orius sp.) or Delphastus, a beetle. Howver, they tend to disperse and leave tomato. Tomato leaves have glandular hairs that contain compounds that appear to irritate insects. | | |
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