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

1. Predators 

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.

2. Parasitoids 

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.

3. Pathogen 

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.

4. Competitors 

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.

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