Encarsia formosa

Encarsia formosa is a small insect. It belongs to the family Aphelinidae, the order Hymenoptera. It is a specialized parasite of the glasshouse whitefly (Trialeurodes vaporariorum). The species has been introduced from Canada. The female of Encarsia formosa is 0.6 mm in length. It has a black head and a thorax, a yellow abdomen. The male occurs seldom and it has a dark coloration.

Encarsia is a parthenogenetic organism. The female lays eggs in larva bodies and puparia of the whitefly by means of an ovipositor. A female infests on an average 50 individuals of the whitefly and lays about 10–15 eggs per day. During 10–15 days the hatched larvae of Encarsia feed on the contents of pest larvae and puparia, which are blackened and mummified gradually. Encarsia pupates inside a mummy and emerges from it through a hole, which is gnawed out by an imago. The whole cycle of entomophage development lasts 21 days at a temperature of 23°C and varies from 15 days at 26°C to 32 days at 18°C. The imago lives 20–35 days in the optimal conditions consuming the hemolymph excreted from the bodies of whiteflies through the punctures of the ovipositor. Encarsia formosa prefers to lay eggs in the third and the forth larva ages, and in the nymph stage of Trialeurodes vaporariorum ontogenesis.

Application

Encarsia formosa is applied on many vegetables and ornamental crops in glass-covered ground for the control of glasshouse whiteflies. The start of entomophage invasion in the conditions of glass-covered ground is coordinated with the appearance of the whitefly. In this period cards with the puparia of the whitefly mummified by Encarsia (each card contains about 50 puparia) are equally allocated on the whole area of a greenhouse. Invasions are made twice with an interval of 1.5–2 weeks. In prophylactic invasions the rate of application is 5–10 individuals per 1 m². The emergence of adults occurs at a temperature of 22–30°C in 3–5 days. In case of the considerable development of pest population the density of invasion is 15–30 individuals per 1 m²  with an interval of 1–2 weeks until the balance between the pest and the parasite is achieved. The cards with Encarsia are allocated inside the vegetative mass of a crop. Practice demonstrates that systematic prophylactic invasions have the best effectiveness.

The optimal conditions for development of Encarsia are: a temperature of 25–30°C, an air humidity of 50–70%, an illumination of 7–8 thousands luxes and a period of daylight time of 14–17 hours. The adult wasps are able to move for the search of food source at 10–15 m. Under 18°C the ability to move and to search food is limited. The life span is quickly reduced under high temperatures (more than 30°C). The sugary excretions of pests prevent from the motility (mobility) and the effective operation of the parasite even under intensive activity of its development.

Remark:
Some synthetic pesticides (pyrethroids) may influence negatively on Encarsia.
But it is possible the application of correcting treatments with chemicals which are loyal to the parasite.

Advantages

• application for the most of crops cultivated in glass-covered ground;
• effective search ability and motility;
• the discovering of the nymphs affected by the parasite is not difficult (easy to diagnose entomophage effectiveness).

Transportation and storage

• don't expose to direct sunlight;
• transport and store at 5–10°C;
• apply immediately or within 18 hours since the moment of reception.