Solid state fermentation technology of Beauveria Bassiana
- Part 1 -

KC Puzari / Pranab Dutta / LK Hazarika *

The search for an alternative to chemical control for insect pest management resulted in the identification of a mycoinsecticides, an indigenous strain of white muscardine fungus, Beau-veriabassiana. The pathogen has long association with the insect complex of North East India. During the few decades, the fungus has been thoroughly studied in the laboratory of Mycology Research Section and Laboratory of Department of Entomology, Assam Agricultural University, Jorhat with an aim of utilizing it as an efficient biocontrol agent for the management of insect pest under study.

Beauveriabassiana, can infect more than 700 species of insects. It has an extensive host list that includes important pests like cotton whiteflies, Bemisiatabaci; grasshoppers, Heirogly-phusbanian; termites, Odontotermus sp.; Colorado potato beetle, Leptinotars-adecemlineata; Mixican bean beetle, Japanese beetle, Popillia japonica; lygus bugs, chinch bug, Blissus-leucopterus; European corn borer, Ostrinianubilalis, codling moth, Cydiapo-monella and cabbage caterpillar, Pieri-sbrassicae and Dicladispa- armigera (Hazarika et al., 2005).

Unfortunately, natural enemies, such as lady bird beetles, are susceptible too. The much studied and discussed fungi B.bassiana was found to be effective against Helicover-paarmigera, Spodoptoralitura and stored product pest, Sitophilu-soryzae, mole cricket, Gryllotelpaafricana. Scientist of AAU, Jorhat reported that B.bassiana @107 conidia ml-1 infected and killed adults, larvae and eggs of rice hispa, Dicladispaarmigera in field.

B.bassiana was also found to be effective against different rice pests like Scripophagaincertula, Chilosuppresalis etc. The fungus has been found to have virulence of 78-87% with LC50 value of 90.16. During the last few years, methods and technologies have been generated for its mass production (which can yield 39.33 X 107 spore ml-1) and field application. The pathogen has the capacity to spread widely and cause epizootic in a very short period.

MODE OF ACTION

After landing on the host surface the spore germinate, and penetrate through cuticle and then haemocoel. Having proved in the body the conidia begin to circulate in haemolymph. They first attack fat bodies as it act as a source of glucose/sucrose, and then try to attack the food tract of epithelial cell wall. Epithelial cell wall produces some enzyme for self protection.

Therefore, if the epithelial wall gets damaged/infected, their protection ability is reduced and the insect becomes weak. The fungus grows profusely by utilizing the haemolymph and remifies the host cell and cause death. In latter part the fungus burst out from the insect body as spore.

SYMPTOM ON HOST

Infected insects become unrest and mating tendency increases. The affected insect is covered with white crust of fungal growth/wadded coating (conidiophores).

DISPERSAL

As infected insects become unrest and mating tendency increases, the infected insect flies to a long distance and thus the entomopathogen spread from one place to another. The entomopathogen is also spread by wind, rain or contact with other insects can spread infection.

CRITERIA FOR CHOOSING MICROBIAL INSECTICIDES

The groups of criteria that concern pest and ecosystem characteristics are:

* Direct or Indirect Pest: Microbial control generally has a higher success rate against indirect pests i.e. ones that damage parts with no inherent commercial value) than direct pests.
* Extent of Damage: A large potential market is preferable over a small one for a commercial microbial insecticide product.
* Pest Feeding and Behavior: Insects that infest large vegetative areas or that live in soil usually offer more microbial control opportunities than aquatic insects or those with sucking mouthparts.
* Member of a Pest Complex : Even the more generalist pathogens usually are not effective against a wide range of pests and users prefer a control agent that will suppress all pests in a complex.
* Economic Injury Level (EIL): Due to the relatively slow speed or necessity for ingestion of virtually all entomopathogens, crops with a low EIL are less likely to be conducive to microbial control than those with a moderate or high.

CRITERIA FOR SELECTING AN ORGANISM AS ENTOMOPATHOGEN

The following set of criteria address entomopathogen characteristics,

* Host Range: An entomopathogen with a relatively broad effective host range is better for commercial development over one with a narrow host range, however, in rare cases where a beneficial or endangered insect population might be affected.
* Virulence: For the short-term microbial insecticide approach, a high degree of virulence is virtually essential.
* Cost of Production: A major reason for failure in the market has been their cost-competitiveness with other pesticides. Obligate pathogens which must be produced in living insects are more costly to produce than facultative pathogens.
* Suppresses Pest Population Below EIL: For its success, it must possess characteristics that enable it to reliably suppress the pest-population below the EIL.
* Environmental Safety: Environmental safely is a prerequisite.
* Advantage over Competing Controls: The entomopathogen must have a relatively good degree of cost effectiveness compared with other controls.
* Registration: Majority of entomopathogens present no particular difficulty in meeting government guidelines for registration as a pesticide. Although costs are low compared with those for chemicals, they are still prohibitive for a small company developing a microbial insecticide
* Compatible: Another strength of entomopathogens is their compatibility with other insect controlsand with agricultural and resource management practices in general.

PRODUCTION TECHNOLOGY
MATERIALS REQUIRED

(1) Freshly isolated entomopathogen.
(2) PDA media
(3) Substrates (Rich husk, Saw Dust, Rice Bran)
(4) Chitin
(5) Distilled water
(6) Poly propylene bags
(7) Racks
(8) Rubber bands
(9) Laminar flow cabinet
(10) Inoculating needle
(11) Spirit lamp
(12) Cotton (both absorbent and non absorbent)
(13) Methylated spirit
(14) Ethyl alcohol
(15) Petriplates
(16) Cork borer
(17) Measuring cylinder
(18) Muslin cloth
(19) Plastic Bucket and mugs
(20) BOD incubator

To be continued ....