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Encarsia-System

A small but efficient parasitic wasp

Whitefly is a typical greenhouse pest that effects many crops. With the parasitic wasp Encarsia formosa the greenhouse grower disposes of a practical and economical beneficial insect to control whitefly populations.

Biology: Encarsia formosa

The origin of the parasitic wasp Encarsia is not exactly known, but nowadays it exists in several parts of the world with a mild climate. A population of Encarsia almost exclusively consists of females of about 0.6 mm. Females are black with a yellow abdomen, while the very rare males are completely black.

The female does not need fertilization. She lays her eggs preferably in the third or early fourth instar whitefly flarva. Ten days after parasitation (at 23°C or 73.4°F) the larva pupates. Greenhouse whitefly parasitized pupae turn black. About 11 days later an adult Encarsia leaves the pupa through an exit hole with a jagged edge.

So the total development time takes 21 days at 23°C (73.4°F), but this varies from 15 days at 26°C (78.8°F) to 32 days at 18°C (64.4°F). An Encarsia female deposits daily 10 to 15 eggs and lives under optimal circumstances for two to three weeks. Life span is dramatically reduced at higher temperatures.

Parasitation of the tobacco whitefly is quite similar. Parasitized larvae however do not turn black, but cream or brown. If both species occur, Encarsia prefers the greenhouse whitefly.

Adult Encarsia feed on honeydew and on the body content of punctured whitefly larvae in the first and second larval stage (host feeding). In total, a female Encarsia parasitizes approximately 250 whitefly larvae (maximum 450) and kills another 30 (maximum 70) for host feeding.

Application

Encarsia formosa is applied on a wide range of greenhouse vegetables and ornamentals to control whiteflies. The aim of introducing Encarsia on time is to obtain a balance between whitefly and Encarsia as early as possible. From the first observation of whiteflies on yellow sticky cards (BUG SCAN®) or in the crop, Encarsia is introduced weekly at a curative level until a sufficient parasitation is reached.

If at least 80% of the whitefly pupae are parasitized (black in case of the greenhouse whitefly), one speaks of a good parasitation. Moreover, practical experience has shown that it is also useful to introduce Encarsia preventatively at a lower dose. For a good balance the next points should be taken into account:

	At a temperature below 18°C (64.4°F) the parasitic wasps almost do not fly anymore, and their searching ability is seriously limited. At temperatures above 30°C (86°F) the adult life span is considerably reduced.
	Certain pesticides (e.g. pyrethroids) can have a long residual effect on Encarsia.
	If Encarsia is introduced too late, the excess of honeydew on the leaf hampers the mobility of Encarsia and consequently the parasitation.
	By de-leafing lower leaves too early, parasitized pupae that have not yet emerged, can be removed from the greenhouse.
	Regular dusting of pesticides is harmful for Encarsia.

In certain ornamentals, in which a quasi zero tolerance of pest insects is required, higher introduction quantities are advised. Control will be based almost exclusively on host feeding. Always consult the Biobest side effect list for the effect on Encarsia before applying a pesticide.

Encarsia-System

Encarsia-System is supplied in 2 different packagings. The parasitic wasps are supplied as pupae glued on cards (Encarsia cards) or as loose pupae packed in tubes. Both systems have their own specific use in practice.

Encarsia-System (on cards)

Packed per minimum of 100 pupae of Encarsia formosa glued on cards.

Encarsia-System (loose pupae)

	Packed per 1000 or 5000 pupae in a tube.
	Encarsia formosa can be stored for a short time at 6-10°C (43-50°F), but not at lower temperatures.

User's instructions

Encarsia-System (cards)

The cards have to be distributed equally throughout the greenhouse. Separate the cards along the dotted line of the sheet. Do not touch the pupae with the fingers when loosening and hanging up the cards (to prevent damage). Hang the cards on the plant, at approximately 60-90 cm under the top of the plant.

Encarsia-System (loose pupae)

Material:

	Encarsia-hanger: the loose pupae are sprinkled in a pot (diameter: ca. 55 mm). This pot is hung in the crop by a hanger on for instance a rope. On the bottom of the pot, a filter paper is positioned. If any water drips into the pot, it can float away through the small hole in the bottom (under the filter paper).
	Dispenser: the Encarsia-pupae are dispersed over the pots with a dispenser. A thin black tube (diameter of ca. 3 mm) reaches down through the screw cap to the bottom of the cylinder.

Hanger to disperse Encarsia-pupae in the crop
Dispenser to disperse loose Encarsia-pupae

Application:

Hang up one pot per 100 m² (for 1 ha 100 pots are needed). Do not hang them on the plants but on a rope in the vegetation. At the beginning of the culture the pots are hung between the plants at a height of approximately 30 cm. Later on, the pots are hung at chest height (ca. 120 cm).

	Unscrew the tube containing the loose Encarsia-pupae and screw the top with dispenser on the tube with the pupae. Hold the dispenser horizontally so that the pupae fall on the side of the dispenser tube and not on the bottom. This way they cannot be crushed by the dispenser-cylinder.
	Put the cap firmly on the dispenser tube. The black dispenser should just touch the bottom of the tube.
	Turn the dispenser vertically. Hold the tube between thumb and fingers and shake the bottom quickly 1 or 2 times, or tap it against the palm of your hand. In this way, the pupae will be in the right position on the bottom.
	Sprinkle the pupae carefully on the filter paper in the pot. Keep the cut part of the black dispenser-cylinder up for an equal distribution. Each time 100 pupae are sprinkled in the pot. When 1 pot is hung per 100 m², 1 Encarsia/m² is sprinkled (2 times sprinkling = 2 Encarsia/m², etc.).

Keep the dispenser vertically and shake the bottom quickly 1 or 2 times, or tap it against the palm of your hand.
While sprinkling the pupae, keep the cut part of the black dispenser-cylinder upwards.

Note: Several pesticides have a negative effect on Encarsia formosa. Please be careful when controlling diseases and other pests. Consult Biobest's list of side-effects of pesticides on beneficial organisms.

Benefits

	Applicable in a wide range of crops.
	Efficient searching ability.
	Parasitized pupae are easily recognized.
	Also does host feeding.
	Practical introduction method.
	Reliable result.
	Economical.