Biological Methods of IPM (Integrated Pest Management) with advantages and disadvantages
Biological control is a method of controlling pests such as insects, mites, weeds and plant diseases using other organisms. It relies on predation, parasitism, herbivory or other natural mechanisms but typically also involves an active human management role. It can be an important component of integrated pest management (IPM) programs. Biological control can be accomplished as the follows
Organisms which feed on other insects having body size greater or equal to the insect is called predators. Predators catch and eat their prey. Some common predatory arthropods include lady bird beetles, carabid (ground) beetles, staphylinid (rove) beetles, syrphid (hover) flies, lacewings, minute pirate bugs, nabid bugs, bigeyed bugs, and spiders. e.g. Lady bird beetle feeds on aphids, Chrysoperia carnea insect feed on all soft bodied insects like aphids, jassids, white flies, mealy bug, etc. Cryptolaemus montrouzieri insect feeds on mealy bugs on grapes.
Those insects whose larvae feed internally or externally on the body of other insect is called parasites. Most insect parasitoids are wasps or flies. Parasitoids (sometimes called parasites) do not usually eat their hosts directly. Adult parasitoids lay their eggs in, on or near their host insect. When the eggs hatch, the immature parasitoids use the host as food. Many parasitoids are very small wasps and are not easily noticed. Encarsia formosa is a small predatory chalcid wasp which is a parasitoid of whitefly. Gonatocerus ashmeadi (Hymenoptera: Mymaridae) has been introduced to control the glassy winged sharp shooter. Parasitoids often require a source of food in addition to their host insect, such as nectar or pollen. This also includes,
i) Egg parasite: Trichogramma chilonis parasites egg of Helicoverpa armigera.
ii) Larval parasite: Bracon hibitor parasites larvae of H. armigera.
iii) Pupal parasite: Goniopthalmus halli parasites pupae of H. armigera.
iv) Adult parasite: Epiricania melanoleuca parasites adults of sugarcane pyrilla.
v) Egg larval parasite: Copidosoma kohleri parasities egg of potato tuber moth and comes out at larval stage by killing the pest.
Biological control using pathogens is often called microbial control.
Bacteria: One very wellknown microbial control agent that is available commercially is the bacterium Bacillus thuringiensis (Bt). B. papillae develops disease in coleopterous pests. The bacterium Paenibacillus popilliae causes milky spore disease has been found useful in the control of Japanese beetle, killing the larvae. It is very specific to its host species and is harmless to vertebrates and other invertebrates.
Fungi: Several insectpathogenic fungi are used as microbial control agents including Beauveria, Metarhizium and Paecilomyces. These are most often used against foliar insect pests in greenhouses or other locations where humidity is relatively high. Beauveria bassiana is used for control of lepidopterous pests. Lecanicillium spp. are deployed against white flies, thrips and aphids. Metarhizium spp. are used against pests including beetles, locusts and other grasshoppers, Hemiptera and spider mites. Paecilomyces fumosoroseus is effective against white flies, thrips and aphids; Purpureocillium lilacinus is used against rootknot nematodes and 89 Trichoderma species against certain plant pathogens. Trichoderma viride has been used against Dutch elm disease and has shown some effect in suppressing silver leaf.
Virus: Nuclear polyhedrosis viruses (NPV) and granulosis viruses (GV) are available to control some caterpillar pests. For example, the Lymantria dispar multicapsid nuclear polyhedrosis virus has been used to spray where larvae of the gypsy moth are causing serious defoliation. The moth larvae are killed by the virus they have eaten and die, the disintegrating cadavers leaving virus particles on the foliage to infect other larvae.
Algae: Lagenidium giganteum is a waterborne mould that parasitizes the larval stage of mosquitoes. As with all biological control agents, it is especially important to match the correct microbial control agent with the correct pest in order for them to be effective.
Protozoa: Nosema bombysis develops pebrine disease of silkworm. N. apis develops decentary in honey bee.
Nematodes: Among different groups of nematodes Mermithids causes disease in insect, this includes Neoplectana carpocapsae is commonly known as DD136. This carries bacteria called Acromobactor nematophilus which develops disease in insect.
The legume vine Mucuna pruriens is used to control for problematic Imperata cylindrica grass. The vine is extremely vigorous and suppresses neighbouring plants by outcompeting them for space and light.
5. Combined use of parasitoids and pathogens
In cases of massive and severe infection of invasive pests, techniques of pest control are often used in combination. An example is the emerald ash borer, Agrilus planipennis, an invasive beetle from China, which has destroyed tens of millions of ash trees in its introduced range in North America.
Advantages of Biological Methods of IPM (Integrated Pest Management)
1. Highly specific to one pest.
2. A long term solution if equilibrium is established.
3. Inexpensive over the long term.
4. No environmental contamination.
5. Can be used in a glasshouse.
Disadvantages of Biological Methods of IPM (Integrated Pest Management)
1. Only a few working examples ( Agents not known for most pests).
2. Expensive to research and a high level of skills and initial set up costs.
3. Agent may become a pest itself.
4. Frequent input needed to maintain population balance.
5. Needs to be large scale.