BIOLOGICAL CONTROL AGENTS FOR WHITEFLIES

The two whitefly parasitoids that we offer (Encarsia formosa and Eretmocerus erimucus) both kill whitefly in two ways: through parasitism and through 'host-feeding'. In the latter case, the whitefly is pierced by the wasp's ovipositor (egg-laying apparatus) and the wasp feeds on the fluids released from the wound; although no eggs are laid in these hosts, they are nevertheless killed by the host-feeding process. 

In choosing between Encarsia formosa and Eretmocerus erimicus, keep in mind the target whitefly species and the prevailing environmental conditions. In many situations, the two species can be complementary, as detailed below.

Encarsia formosa

Adult females of this parasitic wasp (pictured above) are about 0.6 mm long, with a dark brown head and thorax and a yellow abdomen. Males are rare in commercial strains. This species will attack both the greenhouse whitefly (Trialeurodes vaporariorum) and the sweet potato whitefly (B. tabaci). The former is generally considered the better host for this species, but E. formosa can also be a useful complement to Eretmocerus erimicus (below) for managing B. tabaci.

E. formosa will use all life stages (except eggs) of both greenhouse whitefly and sweet potato whitefly for host-feeding, but prefers older nymphs (3rd, 4th and pre-pupal stages) for parasitism. Parasitized greenhouse whiteflies eventually turn black and die as the wasp larvae develop within; sweet potato whitefly parasitized by E. formosa typically turn a paler amber-brown. 

Encarsia formosa is most effective in sunny/well-lit conditions and at temperatures between 20 to 28 °C (68-82 °F). Activity is much reduced at daytime temperatures below 18 °C (64 °F) and by reduced light intensities. 

At temperatures of 21-22 °C (70-72 °F), the life-cycle (egg to adult) is completed in approximately 25 days. When conditions are favorable, E. formosa is extremely active and efficient at searching for whitefly larvae, making it a good choice for release at low whitefly densities. Like most parasitoids, E. formosa can detect and avoid whitefly nymphs that are already parasitized and avoid depositing another egg into such hosts. 

Encarsia formosa is available as pupae (at or near the point of adult emergence) on hanging cards (50 or 100 pupae per card), in pack sizes ranging from 5000 to 15000 in total.

Eretmocerus eremicus 

Adult females of this species are approximately 0.7 mm long, with a lemon-yellow head and body; males are slightly smaller and somewhat darker in color. Both sexes are normally present in approximately equal proportions, and both have green compound eyes and three red simple eyes (ocelli) at the top of the head. 

Like Encarsia formosa, this species will also attack both the greenhouse whitefly (T. vaporariorum) and the sweet potato whitefly (B. tabaci), but in this case the latter is generally considered to be the better host. 

Eretmocerus eremicus will use all immature whitefly stages (except eggs) for host-feeding, but prefers the 2nd and 3rd instars for egg-laying. Rather than inserting its eggs inside the host, this species lays its eggs between the whitefly nymph and the leaf surface. On hatching, the wasp larva chews through the underside of the host and begins to feed, completing its development inside the pupal stage of the host. 

The 'mummified' body of the dead whitefly host is yellowish-beige in color, somewhat darker than healthy (unparasitized) host stages. When the adult wasp is fully formed and ready to emerge, it chews an exit hole through the mummy and crawls out. 

Daytime temperatures for E. eremicus should be at least 21 °C (70 °F), with the optimal range being approx. 25–30 °C (77-86 °F). Eretmocerus eremicus can maintain active host searching at temperatures slightly higher than 30 °C, and generally tolerates higher temperatures than can E. formosa. At 21 °C (70 °F), the life-cycle is completed in approximately 23 days.

Eretmocerus eremicus  is available as pupae (at or near the point of adult emergence) on hanging cards or in blister packs in pack sizes ranging from 5000 to 15000 in total.

We currently offer two predators for whitefly management: one ladybeetle and one predatory mite.

Delphastus catalinae

Adult D. catalinae are small, shiny dark brown/black beetles (less than 2 mm in length) with a rounded body and a tan or black head. This species is a specialized whitefly predator and both adults and larvae will feed on the two main species of whitefly found in greenhouses (sweet potato whitefly (Bemisia tabaci) and greenhouse whitefly (Trialeurodes vaporariorum)). 

Adult D. catalinae require high numbers of whitefly eggs (approx.100-150 per day) for reproduction. For this reason, D. catalinae is especially useful for addressing whitefly 'hotspots'. In such cases, Delphastus can serve as a 'back-up' for the parasitic wasps discussed above, since it tends to avoid consuming whiteflies containing older wasp larvae or pupae. (Note, however, that recently parasitized hosts (which will contain wasp eggs or very young larvae) may still be at risk of predation).

The eggs of D. catalinae are laid in whitefly colonies on the undersides of leaves, and at 28 °C the life-cycle (egg to adult) is completed in approximately 21 days. Depending on temperature, you can expect to see the first larvae within a few weeks of introducing adults. 

For this species, the optimal temperatures for population growth are between 25 to 28°C (77-82°F). The lower limit for development is estimated to be approx. 10 °C (50 °F), but development and activity would be very slow at this temperature.

When monitoring for Delphastus pay particular attention to the underside of leaves in areas of high prey density. Keep in mind that the mature larvae tend to move further down the plant to pupate.

Delphastus catalinae is available in units of 100 or 1000 adults.

Amblyseius swirskii 

Amblyseius swirskii is a small, pear-shaped predatory mite. Adults are about 0.4 mm in length, with the males being slightly smaller than females. Like other mites, A swirskii has five life stages: egg, larva, protonymph, deutonmyph and adult. The larval stage is very pale in color and has three pairs of legs, whereas the protonymph, deutonymph and adult stages all have 4 pairs of legs. The older stages are generally darker than the larvae, but color can vary with diet: when feeding on whiteflies, they are typically yellowish to pale tan. 

A. swirskii is a generalist predator which will feed on a wide variety of prey, including various stages and species of thrips and mites, as well as the eggs and young nymphs of both greenhouse whitefly (T. vaporariorum) and sweet potato whitefly (B. tabaci). When prey is scarce, these mites can also survive and reproduce on pollen from various plants (including eggplant and bell pepper).

Amblyseius swirskii is typically found on the underside of leaves where it can prey on its hosts and lay its eggs. The latter are often found at the intersection of the main vein and lateral veins, or in similar protected areas of the leaf. 

A. swirskii can complete its development at temperatures between 18 to 35 °C (64-95 °F), but performs best at temperatures above 25 °C (77 °F). At the latter temperature, it will complete its life-cycle in approximately 5 days. It is important to note, however, that humidity plays an important role in its population growth: relative humidity should be maintained at or above 65% for egg development and hatching. This mite is not known to enter diapause, and can be used for much of the growing season provided that daytime temperatures are consistently 22 °C (72 °F) or higher.

Amblyseius swirskii is available in a variety of product types, ranging from sachets to shaker tubes and bulk bags. Depending on formulation, numbers per unit (mixed life-stages) range from 25,000 to 250,000. Please contact us for further details.