Biocontrol Agents

Encarsia formosa

General Information

Encarsia formosa is more effective against GWF (Trialeurodes vaporariorum), but also provides some control against Bemisia.

Encarsia is one of the most widely used natural enemies in greenhouse production. First observed naturally on whiteflies in tomatoes in England in the 1920s, it was produced commercially for a number of years afterwards. Use discontinued with the advent of synthetic pesticides in the 1940s, but as resistance developed in GWF1 production was resumed in the 1970’s.


Adult Encarsia (Figure 1) are about 0.6 mm long, and have a black head and thorax and yellow abdomen.

Parasitized GWF, turn black as the wasp inside it pupates (Figure 2). This change makes establishment of Encarsia very obvious.

Parasitized Bemisia are less obvious, turning a tan to brown colour (Figure 3).


E. formosa is a parasitoid; a parasitic wasp that kills whiteflies by laying eggs into the immature stages (death occurs as the wasp develops inside the whitefly) or by directly feeding on the young whitefly nymphs (host feeding) (Figure 4). Although eggs can be laid in any of the whitefly nymphal stages, the 3rd and 4th stages are preferred. However, the wasp larva can only pupate when the immature whitefly reaches the 4th instar2.

Adult Encarsia can live for a few days (at temperatures above 30oC) to a month or longer (at temperatures below 20oC).

Almost all Encarsia are female and they can lay up to several hundred eggs during their lifetime depending on temperature and food availability2,3.

Developmental time of the immature Encarsia is affected by temperature, whitefly species and the host plant on which the whitefly is feeding. For example, development time can increase by 22% when Bemisia is used as a host, compared to GWF. Likewise, development in GWF on vegetable crops is approximately 15 days, compared to 24.5 days in GWF on poinsettia4.

A parasitized GWF turns black (Figure 5) 10-14 days after being parasitized. On average, another 2 weeks are needed before the adult wasp emerges. When the adult is fully developed, it cuts an opening in the top portion of the black scale leaving a round exit hole in the empty pupal case (Figure 6) – which is still obviously black. Parasitism by Encarsia of Bemisia is not as effective as in GWF. Parasitized Bemisia turn a tan to brown colour (Figure 7) and are not as easily noticeable as parasitized GWF. For biological control of Bemisia, Eretmocerus is a better option.

Whiteflies that have been parasitized are not used for host feeding, and likewise Encarsia will not lay eggs in whiteflies where host feeding has occurred4.

Encarsia searching behaviour appears to involve random searches. Whitefly hosts are located as the wasp walks across a leaf surface. The search can be slowed down by a number of factors including the hairiness of the leaves, leaf veins and large quantities of honeydew4.

Encarsia parasitizes significantly more whitefly during summer conditions than winter5.

Factors Affecting

GH Ornamentals

In ornamental crops, Encarsia is often used on gerbera, where GWF is the most common whitefly pest (at least in Canada). In such situations however, it is often used in combination with other BCA’s such as Eretmocerus and/or Delphastus. In poinsettia, where whitefly is the major pest problem, it is usually Bemisia which is found, so Encarsia has less of a role.

GH Vegetables

In tomatoes, note that deleafing practices can remove parasitized whitefly before the Encarsia has emerged. Many growers will leave removed leaves on the ground to allow the wasps to emerge. However this can encourage build up of Botrytis inoculum in the greenhouse.


1Malais M.H, Ravensberg W.J. 2003. In Knowing and Recognizing: The biology of glasshouse pests and their natural enemies. Koppert BV, Berkel en Rodenrijs, The Netherlands and Reed Business Information, Doetinchem, The Netherlands.

2van Roermund H.J.W., van Lenteren J.C. (1992). The parasite-host relationship between Encarsia formosa (Hymenoptera: Aphelinidae) and Trialeurodes vaporariorum (Homoptera: Aleyrodidae) XXXV, Life history parameters of the greenhouse whitefly parasitoid Encarsia formosa as a function of host stage and temperature. Wageningen Agricultural University Papers, 92-3: 147 pp

3Arakawa R. 1982. Reproductive capacity and amount of host-feeding of Encarsia formosa Gahan (Hymenoptera: Aphelinidae). Z. ang. Ent. 93: 175-182.

4Hoddle M.S., Van Driesche R.G., Sanderson J.P. 1998. Biology and use of the whitefly parasitoid, Encarsia formosa. Annual Review of Entomology, 43: 645-669.

5Zilahi-Balogh G.M.G., Shipp J.L., Cloutier C., Brodeur, J. 2006. Influence of light intensity, photoperiod and temperature on the efficacy of two aphelinid parasitoids of the greenhouse whitefly. Environmental Entomology 35(3): 581-589.

Further Reading

Enkegaard A. 1993. Encarsia formosa parasitizing the poinsettia-strain of the cotton whitefly, Bemisia tabaci on poinsettia: bionomics in relation to temperature. Entomologia Experimentalis et Applicata, 69: 251-261.

Enkegaard A. 1994. Temperature dependent functional response of Encarsia formosa parasitizing the poinsettia-strain of the cotton whitefly, Bemisia tabaci on poinsettia. Entomologia Experimentalis et Applicata. 73: 19-29.

Hoddle M., Van Driesche R., Sanderson J. 1997. Biological control of Bemisia argentifolii (Homoptera: Aleyrodidae) on poinsettia with inundative releases of Encarsia formosa (Hymnoptera: Aphelinidae): Are higher release rates necessarily better? Biological Control, 10: 166-179.

Hoddle M.S., Van Driesche R.G. 1996. Evaluation of Encarsia formosa (Hymenoptera: Aphelinidae) to control Bemisia argentifolii (Homoptera: Aleyrodidae) on poinsettia (Euphorbia pulcherrima): a lifetable analysis. Florida Entomologist, 79(1): 1-12.

Li Zhao Hua, Lammes F., van Lenteren J.C., Huisman P.W.T., van Vianen A., de Ponti O.M.B. 1987. The parasite-host relationship between Encarsia formosa Gahan (Hymenoptera: Aphelinidae) and Trialeurodes vaporariorum (Westwood) (Homoptera: Aleyrodidae), XXV Influence of leaf structure on the searching activity of Encarsia formosa. J. Appl. Ent. 104: 297-304.

Speyer E.R. 1927. An important parasite of the greenhouse white-fly (Trialeurodes vaporariorum Westwood). Bull. Ent. Res. 17: 301-308

Stacey D.L. 1977. ‘Banker plant’ production of Encarsia formosa Gahan and its use in the control of glasshouse whitefly on tomatoes. Plant Pathology, 26: 63-66.

Van Dreische R.G., Hoddle M.S., Roy S., Lyon S., Sanderson J.P. 2001. Effect of parasitoid release pattern on whitefly (Homoptera: Aleyrodidae) control in commercial poinsettia. Florida Entomologist, 84(1): 63-69.

van Lenteren J.C., van Vianen A., Gast H.F., Kortenhoff A. 1987. The parasite-host relationship between Encarsia formosa Gahan (Hymenoptera: Aphelinidae) and Trialeurodes vaporariorum (Westwood) (Homoptera: Aleyrodidae). J. Appl. Ent. 103: 69-84.

van Lenteren J.C., van Roermund H. J. W., Sütterlin S. 1993. Biological control of greenhouse whitefly (Trialeurodes vaporariorum) with the parasitoid Encarsia formosa: How does it work? Biological Control, 6: 1-10.