Whitefly is a perennial problem in greenhouses everywhere, but biological control is an increasingly popular tool for greenhouse growers to manage these pests.
Here are some of the most commonly used beneficials for this pest, as well as handling, application and management suggestions to help you maximize the effectiveness of each.
■ Encarsia formosa
Pests Attacked: Whiteflies. Encarsia formosa is most effective against greenhouse whitefly. It attacks whitefly nymphs, not adults nor eggs. E. formosa is the best beneficial to use against the greenhouse whitefly.
Identification: This is a tiny wasp (they grow up inside a whitefly nymph) It has a black head and thorax and yellow abdomen. Parasitized whitefly pupae turn from white to black.
Biology: E. formosa has similar parasitoid biology to A. colemani, except Encarsia does not attack aphids.
How to check for shipment viability: Encarsia is shipped as parasitized whitefly pupae glued to small cards. Place a few cards individually into clear jars and hold them in the shade at room temperature until many tiny wasps are seen walking around inside the jar. A sticky trap can be placed inside the jar and inspected for wasps.
How to release into crop: Hang the Encarsia cards within the foliage, shaded, to allow wasps to emerge from the cards and fly in the plant canopy to search for whitefly nymphs.
■ Eretmocerus eremicus
Pests attacked: Whiteflies. It will attack nymphs of both greenhouse whitefly and sweetpotato whitefly. E. eremicus is more effective against sweet potato whitefly than is E. formosa.
Identification: Female E. eremicus are yellow and the males are
Biology: E. eremicus is somewhat similar to E. formosa. E. eremicus remains effective at warmer temperatures (above 86°F) than E. formosa.
Checking for shipment viability and release methods: These are the same as for E. formosa. Some companies sell a mixture of E. formosa and E. eremicus.
■ Delphastus catalinae
Pests Attacked: Delphastus is a tiny ladybeetle that attacks whitefly eggs and nymphs.
Identification: The beetles are shiny black and females have a reddish-brown head. Larvae are greyish with a somewhat fuzzy appearance.
Biology: Both larvae and adults are voracious predators of whitefly eggs and nymphs. Females lay eggs in whitefly patches; the hatching larvae begin eating. Females cannot produce eggs unless they can consume at least 200 whitefly eggs per day. Thus, Delphastus works best in whitefly hotspots. The beetles will avoid eating whitefly nymphs that are parasitized by older-stage Encarsia or Eretmocerus.
How to check for shipment viability: Delphastus is shipped in bottles or vials containing adult beetles mixed in buckwheat hulls or other carrier. Active beetles will be obvious in a viable shipment.
How to release into crop: Delphastus should be used in combination with Encarsia or Eretmocerus, and the beetles should be released into whitefly hotspots.
■ Fungal Pathogens
(BotaniGard, Preferal, Met52)
Pests Attacked: These fungal pathogens may be effective against whiteflies.
How to release into crop: They are applied as a foliar spray and good coverage of the undersurfaces of leaves is important because the immobile nymphal stages of the whiteflies is the target. Several applications will be needed for good control. Humidity should be above 80 percent for germination of the fungal spores that will then penetrate the whitefly skin and cause infections and death. Do not use fungicides for several days before or after an application. See product labels for more information.