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Encarsia formosa - Parasitic wasp
Enforce is a tiny parasitic wasp that specializes in parasitizing whitefly, specifically greenhouse whitefly (Trialeurodes vaporariorum), although it will attack other whitefly species.
It is very useful in greenhouse crops as part of an Integrated Pest Management programme, and has been used successfully in crops such as tomato, cucumber, eggplant and ornamental plants.
The Enforce wasp is 0.6 mm long and is recognizable by its black head and thorax and a yellow abdomen.
A female wasp inserts her eggs into 3rd and 4th instar nymphs of greenhouse whitefly. The egg hatches and the wasp's larva develop inside greenhouse whitefly nymph eventually killing it.
After about 10 days, the greenhouse whitefly nymph will begin to turn black, and about 10 days later an adult wasp will emerge.
Once the Enforce wasp has hatched, it will seek out more whitefly nymphs to parasitize, leaving the black case behind.
Enforce is not considered harmful to humans and animals, and no environmental impacts are expected.
The pest: whitefly (left) & the solution: Encarsia (right)
Normal whitefly pupa (white) and parasitized pupa (black). An adult Encarsia will emerge from the black scale(right)
Greenhouse whitefly adults are small, white, fly-like insects that are generally found in the head of plants and the undersides of the leaves, and cause damage by sucking sap from the plant.
Greenhouse whitefly lay their eggs on the underside of leaves, where they mature through four nymph or 'scale' stages before emerging as adults. All nymph and adult stages cause damage to the plants, and in severe infestations they may kill plants.
Signs and symptoms of a greenhouse whitefly infestation may include:
Adult greenhouse whitefly present on the plant, generally near the top on new growth
Greenhouse whitefly eggs and pupae may be present on the plant (a hand lens may be required to see some nymph stages)
Plants may appear weak, and growing poorly
Honeydew and black sooty mould may be visible on stems and leaves
Enforce lays its eggs within the whitefly larvae developing on the leaves. Enforce can eat whitefly eggs and young larvae, the preference is to lay eggs in the third and fourth larvae instars.
A wasp life cycle will take between 10 and 30 days, depending on temperature.
Enforce works best at temperatures of 20-28 C, below 18 C the wasp's activity decreases, and temperatures above 38 C are lethal. Temperature is required to be above 10.3C for the Enforce larvae to develop.
Enforce is supplied as black parasitized greenhouse whitefly nymphs or black 'scale' on cardboard tags, and the adult wasp emerges from this 'scale'.
Two tag sizes are available:
Wasps per metre squared:
Enforce should ideally be introduced to the crop when greenhouse whitefly populations are low as a preventative.
It is recommended that Enforce is introduced regularly when whiteflies are present, initially at a minimum of every 2 weeks over at least an 8 week period.
Enforce™ will not attack adult whiteflies, if you have large numbers of whiteflies present on the plants, it is recommended that a soap spray or other spray with low residual activity (such as neem), is used prior to the first introduction of Enforce™. These sprays will kill adult Enforce™ wasps, so it is not recommended to use these after having introduced the Enforce™ unless presented with no other option.
Enforce™ tags need the following handling and treatment:
Do not touch the black 'scale' on the tags
Do not expose the tags to direct sunlight
Hang the tags immediately within the crop,
If the tags must be stored, store them in darkness at 10-15 ° C.
DO NOT REFRIGERATE
Do not store the tags for more than 2 days
Tags come in strips of 10 tags and should be separated and hung individually
Hang tags one metre below heads of crop, so the wasps work upwards
Hang tags in shade
Ensure tags are hung in different places each week
Tags should be distributed evenly through the crop
Leave tags in crop for at least 14 days
Enforce™ adults will begin to emerge from the black 'scale' on the tags within 2-6 days at 20 ° C. The black case will stay attached to the tags. A small hole should be visible with a hand lens once the adult has emerged.
After three weeks it is safe to assume all Enforce wasps have hatched, so the tags may be removed if desired.
Within four weeks of release, black 'scale' should be present within your crop, on the lower leaves of your plants. Adult wasps should emerge within 2-3 weeks.
Before introducing Enforce™ into your crop, please check residual chemical effects and ensure you know chemical compatibilities and products that may be applied.
Lists of compatible pesticides and persistence periods can be found in the publication "The Good Bug Book", Second edition (2002), editor Richard Llewellyn. Excerpts of the book can be obtained from the Encarsia page of the Australasian Biological Control Association website.