The following points highlight the three main types of bio-pesticides. The types are: 1. Bio-Insecticides 2. Bio-Nematicides 3. Bio-Herbicides.
Bio-Pesticide: Type # 1. Bio-Insecticides:
Microorganisms like bacteria, fungi and viruses show greatest commercial importance as bio-control agents than the commercial synthetic pesticides. With the more progress of scientific achievement the bio-insecticide becomes popular in different countries.
Several bacterial pathogens of different insects are being used as insecticides. These are Bacillus, Clostridium, Pseudomonas, Enterobacter, Proteus, Serratia etc. Out of these, Bacillus thuringiensis has been used extensively. The bacterium has been shown to be successful against a wide range of more than 1 50 insects.
It shows insecticidal activity against larvae of Lepidoptera. B. thuringiensis var. israelensis (BTI) is highly active against larvae of mosquito vectors of malaria. Unlike DDT, the pathogen is environmentally safe in use and mosquito does not show any resistance against the bacterium. It also shows excellent result to control black fly — the carrier of widespread river blindness in Africa.
Four different toxins are produced by the B. thuringiensis and about 16 formulations have been prepared based on the above toxins. These are used in different countries like USA, Russia, France, Germany etc. Some of the registered products like Sporcine, Condor, Cutlass, Thuricide, Foil etc., are commonly used.
In India, it has been found that 0.4% thuricide is more effective than malathione, endrine and DDT to control insect pests of crucifer, lac and sugarcane. In USA, different registered formulations prepared from B. thuringiensis are used to control pests of different crops like Alfalfa caterpillar (Alfalfa), Bollworm (Cotton), Cabbage worm (Cabbage and Cauliflower). Orange dog (Orange), Crape leaf folder (Grapes) etc.
With the help of recombinant DNA technology, the gene having insecticidal properties of Bacillus thuringiensis has been transferred to the crops plans like tomato in 1987, with the help of bacterium, Agrobacterium tumifaciens. Later, similar success has been achieved in different crop plants like tobacco, cotton etc., by using the similar technique. Now-a-days, Bt cotton is very popular among the farmers.
Different entomogenous fungi have been used to protect different crops from insect damage. Species of the different genera like Aschersonia, Beauveria, Coelomomyces, Entomophthora, Hirsutella etc., are in common use. Some registered products are also produced and used by different countries like Australia, Brazil, China, France, Japan, USA, UK etc.
List of some of the products, producing fungi in parenthesis and insects on which it acts are:
i. Aseronija (Aschersonia aleyrodis) — Whitefly of many crops.
ii. Boverin and Boverol (Beauveria brassiana) — Pine caterpillar, Green leaf hipper, Colorado potato beetle etc.
iii. Mycotal and Vertalec (Verticillium lecanii) — Whitefly and Aphids of glasshouse crop.
Viruses are also very much effectively used as bioinsecticide. There are three major groups of viruses that can infect different insects.
(a) Nuclear polyhedrosis viruses (NPV),
(b) Granulosis viruses (GV) of Baculoviridae, and
(c) Cytoplasmic polyhedrosis viruses (CPV) of Reoviridae.
The NPVs are effective against moths and butterflies, while CPVs are effective mainly on caterpillars. These are used in different countries like USA, UK, Canada, lapan, Germany etc.
List if some viruses, registered trade names in parenthesis and target insects are given below:
i. NPV (ELCAR) — Tobacco budworm and Cotton bollworm.
ii. NPV (GYPCHEK) — Gypsy moth.
iii. NPV (VfROX) — European sawfly.
iv. CPV (MATSUKEMIN) — Pine caterpillar.
v. GV (MATEX) — Insects of different food crops like Codling moths.
Bio-Pesticide: Type # 2. Bio-Nematicides:
Different fungi are known to act as nematicide. Fungi of different genera like Arthrobotrys, Dactylella, Dactylaria and Monacrosporium are used to control different members of genera like Heterodera, Meloidogyne and Rotylenchulus, cause diseases of different crop plants.
The fungi damage nematode in four different ways:
i) By haustoria:
Fungi penetrate haustoria in the body of the nematode, digest the cell contents and draw the nutrients.
ii) Catching by loop:
The fungal mycelium forms loops at intervals. As a nematode passes through the loop, it constricts and thus the nematode is trapped.
iii) Production of adhesive hyphae:
The fungal mycelium produces some adhesive branch which may stick with the body of nematode on accidental contact.
iv) Formation of hyphal mesh:
The mycelium forms mesh-like cobweb and is able to catch nematodes.
The other groups of fungi are commonly present in the soil and can act as nematicides. These are Verticillium chlamydosporium, Paecilomyces lilacinus and Dactylella oviparasitica — they often attack nematodes as well as their eggs.
Bio-Pesticide: Type # 3. Bio-Herbicides:
Fungi are found to be much more suitable as herbicide than bacteria and viruses. Fungus like Phragmidium violacerum is used to control European blackberry in Chile and Puccinia chondrillina to control rush skeleton weed in Australia. Others, like Phytophthora palmivora, has been developed as herbicide at commercial level.
The name of the registered product, producing fungi in parenthesis and the target weeds are:
i. DE VINE (Phytophthora palmivora) — Milk-weed vine in USA,
ii. LUBOA (Colletotrichum gloeosporiodes f. sp. cuscutae) — Dodders in China,
iii. BIOMAL (Colletotrichum gloeosporioides f. sp. malvae) — Round-leaved mallow in Canada and USA.