Control whiteflies with beneficial insects
What are Whiteflies?
The whiteflies are tiny insects with yellowish bodies, white colored wings and they look like small moths. Life cycle of whiteflies consists of egg, nymph (four nymphal/larval stages), pupa and adult stages. Both the adults and nymphs of whiteflies have piercing and sucking types of mouth parts that they use for sucking cell sap (juice) from the several different plant species including vegetables, ornamental plants and fruits and field crops. Whiteflies can cause a serious damage to plants by directly feeding on the leaves and by transmitting plant viruses. During feeding, both adults and nymphs suck cell sap (juice) from underside of the leaves (Fig. 1) that generally turn yellow, then dry and fall off the plants prematurely. Also, the plants heavily infested with whiteflies can die prematurely. Also, honeydews secreted by whiteflies stimulates the growth of black sooty mold on the surface of leaves. This black sooty mold affects the photosynthesis (a process used by plants to convert light energy from sun to chemical energy for the synthesis of their own food including carbohydrates and proteins), and reduces the quality of the produce as well as aesthetic value of many ornamental plants. In addition, whiteflies are known to transmit different types of plant viruses that may be responsible for tremendous economic loss to the agricultural, horticultural and greenhouse industries (Jones, 2003).
Biological control of whiteflies
Since chemical pesticides are not allowed to use in organic productions due to their detrimental effects on humans, animals and environment, the following five beneficial insects have a potential to use as biological control agents to control whiteflies.
1. Green lacewings, Chrysoperla rufilabris
Green lacewings, Chrysoperla rufilabrisare considered as one of the most aggressive nocturnal (active during night–time) predators of immature stages of whiteflies. Green lacewings are predator meaning . Adult lacewings are tiny about 0.5 inch long, green in color with two pairs of transparent wings (longer than their body length), big eyes and very long and thin antennae. Green lacewing adults generally feed on nectar, pollen and honeydews but their larvae are predatory in nature. Mature larvae of green lacewing are brown in color and look like small alligators. All the larval stages of green lacewing can voraciously feed on nymphs (larvae) of whiteflies. Green lacewings are commercially sold in three developmental stages including eggs, larvae and adults but only larval stages are predatory in nature. Eggs of green lacewings can be placed directly in your garden and it would be beneficial if their hatching is coincided with the outbreak of whiteflies.
2. Predatory mite, Amblyseius swirskii
Predatory Mite, Amblyseius swirskii is an excellent biological control agent that has been frequently used in controlling whiteflies that cause a serious damage to many economically important crops grown both in the greenhouses and fields. Amblyseius swirskii are warm adapted predatory mites and therefore they perform better against whiteflies when the temperature is between 20°C (68°F) and 29°C (84.2°F). Because of their warm temperature adaptability, these predatory mites are considered as the ideal biological control agents for controlling whiteflies such as a greenhouse whitefly, Trialeurodes vaporariorum in the US greenhouses where temperatures often exceeds 25°C (77°F) during summer. Predatory , Amblyseius swirskii can be used to target whiteflies infesting indoor plants late in the fall or in the winter as they do not undergo diapause due to short day-lengths or low temperatures. Each adult mite can easily consume daily 15 larvae or 10 eggs of whiteflies.
3. Predatory beetle, Delphastus cataliniae
Whitefly predatory, Delphastus cataliniae beetles are tiny brown colored and hemispherical shaped ladybird beetles. Both the larvae and adults of these beetles are well known predators of several species of whiteflies including banded-winged whitefly, Trialeurodes spp., California giant whitefly, Aleurodicus dugesii, cloudywinged citrus whitefly, Dialeurodes spp., greenhouse whitefly, Trialeurodes vaporariorum, silverleaf whitefly, Bemisia argentifolii, sweet potato whitefly, Bemisia tabaci and tobacco whitefly, Bemisia tabaci. Adult female beetles generally lay eggs among whitefly eggs. These predatory beetle eggs hatch into small pale-yellow to cream colored larvae which are very aggressive predators that can consume a large number of eggs (over 9000-10,000 eggs) and immature stages of whiteflies during their lifetime. These predatory bugs perform better against whiteflies when temperature between 60 and 90°F (16 and 35°C) and a relative humidity above 75%.
4. Parasitic wasp, Encarsia formosa
Encarsia formosa are very small (about 0.5 to 1 mm long), blackish colored wasps that are endoparasites of both the larvae and pupae of whiteflies including greenhouse whitefly, Trialeurods vaporarium, silverleaf whitefly, Bemicia argentifolii and sweet potato whitefly, Bemicia tabaci. These wasps are called endoparasites because all of their stages (eggs, larvae and pupae) except adults complete their development inside the bodies of nymph or pupae of whiteflies. Female wasps generally lay eggs inside the bodies of whitefly nymph or pupae. These eggs hatch into tiny larvae that immediately starts feeding on the body content of whitefly nymph or pupae and develop through three larval stages and eventually kills the whitefly nymphs or pupae. Depending upon the species of whiteflies, the parasitized dead nymphs or pupae can turn light brown to dark brown or black in color within 7 to 10 days after parasitization.
5. Parasitic wasp, Eretmocerus eremicus
Eretmocerus eremicus are tiny parasitic wasps that mainly parasitizes several species of whiteflies including the banded winged whitefly, Trialeurodes abuttnea, greenhouse whitefly, Trialeurods vaporarium, silverleaf whitefly, Bemicia argentifolii and sweet potato whitefly, Bemicia tabaci. Female wasps are yellowish in color with clubbed antennae whereas males are yellowish brown in color with elbowed antennae. Females of this wasp lay eggs the leaf surface underneath the immature stages (nymphs) of whiteflies. After hatching from eggs, young wasp larvae generally attach to the underside the whitefly nymph’s body using a hook-like mouth parts. The wasp larvae then enter into whitefly nymph’s body by chewing a small hole and become an internal parasite. Once inside the whitefly nymph, wasp larvae become and remain dormant until whitefly nymphs forms pupae. Once pupae are formed, wasp larvae becomes active and begin releasing digestive enzymes that helps to liquefy body content of whitefly pupa.The wasp larvae then starts feeding on the liquefied body content and eventually kill the pupae of whiteflies. Eretmocerus eremicus wasps are warm adapted species and work better against whiteflies when temperature is between 25°C (77°F) and 30°C (86°F). Eretmocerus eremicus wasps are generally sold as parasitized pupae that can be easily released in the field for the control of whiteflies. Eretmocerus eremicus wasps are commercially available as parasitized whitefly pupae. It is recommended to release three Eretmocerus eremicus parasitized whitefly pupae per plant infested with whiteflies every week for 4 weeks.
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