INTRODUCTION
Biological control may be defined as, the use of natural enemies (parasitoids, predators and pathogen)) to control pests. (Biological sense) Biological control is a part of natural control. Biological control is always only one component of any Integrated Pest Management program.
Now a days whitefly has become the most serious pest in the many region of the world. These insects feed on the underside of leaves. They can reduce plant vigor and cause a number of plant disorders and viruses. They reproduce quickly and spread at a rapid rate.
Whiteflies have an extremely wide range of hosts such as citrus, guava, allamanda, banana shrub, tomato, okra, sweet potato, boston ivy, cape jasmine, chinaberry, coffee, English ivy, jasmine, pear, Portugal cherry, pomegranate wateroak, persimmon, and devilwood or wide olive etc.
White fly is well distributed in Florida, , South Carolina, North Carolina, eastern Virginia, Mississippi, Louisiana (New Orleans), Texas (Rio Grande Valley), and California; Mexico (Veracruz area); Guatemala; Bermuda; Chile; Peru; Argentina; Brazil; France (Alpes-Maritimes); Sri Lanka; China; Taiwan; India; Bangladesh; Vietname; Japan;; Pakistan; Sikkim.
The most common whiteflies on greenhouse crops are the greenhouse whitefly (Trialeurodes vaporariorum), sweetpotato whitefly (Bemisia tabaci) and the silverleaf whitefly (Bemisia argentifolii), (Lane Greer-2000)
Whitefly predators eat from 150 up to 600 whitefly eggs per day and It takes about 30 seconds to eat a single Whitefly egg.
Above all discussion it is that the biological control of white fly is very much significant.
MATERIALS AND METHOD
This paper mainly depends on the secondary data. Different published reports of different journals mainly supported in providing data for this paper. It has been prepared by comprehensive studies of various articles published in different journals, books and proceedings available in the libraries of Sher-e-Bangla Agricultural University, Bangabandhu Shiekh Mujibur Rahman Agricultural University,Bangladesh Agricultural University, Bangladesh Agricultural Research Institute, Bangladesh Rice Research Institute. Variable information has been collected through contact with respective persons and with the help of computer CD room search and Internet facilities.
The objectives of this study
1. To take idea about the biological controlling agents of white fly in the world.
2. To know the possible technique which is eco-friendly.
3. To give emphasis on the practices which are not harmful to us.
DISCUSSION
Whitefly Bemisia tabaci belonging to the family Aleyrodidae and under the order homoptera it has sueking type mouthparts by which it occurs the sucking function easily. It is white in color and very small in size. It causes serious damage on crop plant mainly tomato, okra, sweet potato etc. It also act as a vector of several virus disease in plants such leaf curl virus, yellow leaf curl virus, yellow top virus etc. It secretes honey dew and developed shooty mould fungus and finally reduce photosynthesis
PREDATORS:
The organisms those are usually larger than prey, always kills host, more than one prey is required to complete its development is called predator.
Bemisia tabaci is attacked by predatory species representing eight arthropod orders, including members of the families Phytoseiidae (Acari), Coccinellidae (Coleoptera), Syrphidae (Diptera), Anthocoridae, Nabidae, and Miridae (all Hemiptera), Chrysopidae and Coniopterygidae (both Neuroptera). At least four species of predators that are commercially available have been evaluated for their ability to control B. tabaci strain B on greenhouse grown crops; Delphastus pusillus LeConte, Macrolophus caliginosus Wagner, Chrysopa carnea, and Chrysoperla rufilabris (Burmeister). (Mark S. Hoddle, 1999).
Delphastus pusillus (Coleoptera: Coceinellidae): sometimes called the whitefly destroyer, is a very small, black lady bird beetle that attacks all stages of whiteflies, but prefers eggs and nymphs. The females lay their eggs within clusters of whitefly eggs. Adults can consume 160 eggs or 12 large nymphs every day. A larva consumes 1000 whitefly eggs during its development. These beetles perform best at temperatures between 65 and 90°F, with relative humidity above 70% . These predators can be used in combination with Encarsia species (Cloyd, et.al. 1999).
Delphastus pusillus, Delphastus pusillus is often associated with high density populations of whiteflies and feeds readily on B. tabaci. Adults and immature beetles feed by piercing the whitefly integument and extracting the contents resulting in a flattened, empty whitefly cuticle. Adults and all larval stages will feed on whitefly eggs, nymphs, and adults. (Mark S. Hoddle, 1999).
Chrysoperla spp. (Neuroptera: Chrysopidae): Ten species of lacewings have been reported to feed on whitefly nymphs, including the commercially available species C .carnea and C .rufilabris The three larval stages of C. carnea will feed on B. tabaci and T. vaporariorum eggs, nymphs and pupae, C. rufilabris larvae will feed, on all immature stages of B. tabaci Mark S. Hoddle, 1999.
The predators that feed on various white flies.
Organism Pests Controlled
Chrysopa carnea Whiteflies
Chrysoperla rufilabris Whiteflies
Coleomegilla imaculata Whiteflies
Deraeocoris brevis Whiteflies
Delphastus pusillus Greenhouse whitefly, sweetpotato whitefly
Harmonia axyridis (Asian lady beetle) Whiteflies
Hippodamia convergens (lady beetle) Whiteflies
Cycloneda sanguinea L. Cytrus whiteflies
Chrysoperi spp. Whiteflies
Macrolophus caliginosus Whiteflies
Praying Mantid Tenodera aridifolia sinensis Whiteflies
Scymmus punctatus Cytrus whiteflies
Delphastus catalinae Whiteflies
Nephapsis oculatus Whiteflies
Source: Cloyd, et.al.1999
PARASITOIDS:
The organisms those are often same size as host, always kills host, only one host is required to completed its development is called parasitoid. Peculiar characteristics have present for successful biological control in parasitoids. They are as follows:
1. Presence of specialized ovipositor for drilling to pierce the host to lay eggs.
2. To inject paralyzing venom into the host.
3. Tip of ovipositor sometimes having very sensitive sense organ to predict the suitability of the host.
The most common parasitoids attacking Bemisia in Florida are in two genera, Encarsia and Eretrnocerus, Encarsia pergandiella and Encarsia transvena are common throughout the state, while Encarsia nigricephala is common in north central Florida. Several species of Eretmocerus are also common throughout the state. Eretmocerus species cause mortality to whiteflies by host-feeding, in addition to parasitism. (Heather J. et.al. 2000).
Whitefly parasitoids belong to just three hymenopterous families Platygasteridae (e.g. Amitus spp.), Aphelinidae (e.g., Eretmocerus and Encarsia spp.), and the Eulophidae (e.g., Euderomphale spp.). The best studied of these whitefly parasitoids are E. formosa and Eretmocerus eremicus Mark S. Hoddle, 1999.
Eretmocerus eremicus (Hymenoptera: Aphelinidae) Females oviposit under suitable hosts, and parasitoid larvae, after hatching, penetrate the ventral surface of the host and develop as endoparasitoids inside the host. Eretmocerus eremicus host feeds by inserting its ovipositor in the vasiform orifice of the host. Weekly releases (three female wasps per plant per week) of E. eremicus have proven to be more effective than the same release rate of E. formosa for controlling B. tabaci (Mark S. Hoddle, 1999).
Much mortality is caused by minute parasite wasps (parasitoids) is the aphelinid family, Female parasitoids lay their eggs inside the whitefly nymph or between the whitefly and the leaf surface, depending on the genus of wasp. The immature parasitoids develop within the whitefly host, eventually consuming the entire host, except the integument (Heather J. et.al. 2000).
The parasitic wasp Encarsia formosa preys on immature whiteflies and is commonly used for greenhouse whitefly. Encarsia wasps kill whitefly nymplus in one of two ways; they either lay an egg inside the nymph, providing food for their young, or they kill the nymph right away and feed on the fluids inside of it (Gill, Stanton, 2000).
Two other wasp parasites, Encarsia luteola and Eretmocerus californicus are commercially available for control of these species (Anon. 1995).
Mark has also compared the effectiveness of Encarsia formosa and Eretmocerus californicus on silver leaf whitefly. In a 1996 study, both parasitoids controlled whiteflies at a 99% control rate (Grossman, Joel,1996).
Parasitoids that feed on various whitefly.
Organism Pests Controlled
Encarsia formosa (parasitic wasp) Greenhouse whitefly, sweet potato whitefly, silver leaf whitefly
Encarsia luteola E. deserti Whiteflies
Eretmocerus californicus or E. eremicus (parasitic wasp) Greenhouse whitefly, silver leaf whitefly, sweet potato whitefly
Eretmocerus eremicus Whiteflies
Encarsiella noyesi Hayat Greenhouse whitefly
Encarsia lahorensis Howard Greenhouse whitefly
Source: (Mark S. Hoddle, 1999).
PATHOGENS
Some microorganisms also control whiteflies. For instance, the fungus Beauveria bassiana (trade names Naturalist and Botany Gard )is effective against eggs, immature and adult whiteflies. Thorough coverage of leaf undersides and correct timing of applications result in best control.
Another fungus, Paecilomyces fumosoroseus (trade name PFR-97TM) is now commercially available. It controls whiteflies, aphids, and spider mites. Both B. bassiana and P. fumosoroseus need high humidity for best results. (Williams, et.al. 1995).
Beauveria bassiana and Verticillium lecanii, two fungal pathogens with efficacy against Bemisia and other insects, have been commercialized and are available for field and greenhouse application against Bemisia, (Heather J. et.al. 2000).
Beauveria bassiana- Beauveria bassiana is a naturally occurring fungus disease that affects a very wide range of insects – including aphids, whiteflies, psyllids, billbugs and caterpillars. Newly infected insects often are somewhat light brown; when the fungus sporulates it covers the insect with white spores. Available formulations are sold as Mycotrol and Naturalis.
The most commonly observed fungal pathogens of whiteflies are Paecilomyces fumosoroseus, Aschersonia aleyrodis, Verticillium Lecanii, and Beauveria bassiana Vuillenin. Of these, V. lecanii. B. bassiana and P. fumosoroseus are commercially available. (Mark S. Hoddle, 1999).
Pathogens that feed on various whiteflies
Organism Pests Controlled
Verticillium lecanii Whiteflies
Beauveria bassiana Whiteflies
Paecilomyces fumosoroseus Whiteflies
Aschersonia aleyrodis Whiteflies
Source: (Mark S. Hoddle, 1999).
CONCLUSION
The various whitefly species and biotypes look very much alike, but they have subtle physiological differences. These differences can cause them to respond differently to control strategies. Because control measures must be selected according to the type of whitefly present, accurate identification is critical to successful control. Above all discussion the biological controlling agents related to various species of white flies are whitefly predator, Green Lacewings, Pirate Bugs, Greenhouse whitefly Parasite, Sweet potato Whitefly Parasite, Beauveria bassiana.
Economics of Whitefly Biological control and Future Prospects is very much important. Incorporation of E. eremicus in to an IPM program would diversify whitefly control options, reduce reliance on insecticides, enhance cost effectiveness of biological control, and provide a more sustainable whitefly control program.
