Entomopathogenic bacteria, viruses, fungi, nematodes, and protozoa have a great potential as a component of integrated pest management. However, they still account for 3% of the total pesticide market, and formulations based on the bacterium, Bacillus thuringiensis (Berliner) account for 80% to 90% of the commercial microbial pesticides. The commercial value of microbial pesticides is estimated at US$100 million per year (Meadows, 1990; Neale, 1997). The major constraint to the use of biopesticides is the need for simultaneous management of three biological systems: the pathogen, the prey, and the crop. Their greatest application is in vegetables, gardens, and orchard crops. Despite several advantages of biological insecticides, many factors have hindered their commercial success and practical effectiveness. Some of the problems associated with the use of microbial pesticides for pest management include:
Quality and effectiveness;• Unstable formulations and delivery systems;• Sensitivity to light, relative humidity, and heat;• Short shelf-life, especially in hot and humid conditions; and• Limited host range and specifi city to a particular stage of the insect.•
Effective use of microbial pesticides often requires a more complex infrastructure than is needed for conventional pesticides. These include control of environmental conditions in the production area, an effi cient system to deliver the product to the farmers, and training the farmers on the effi cient use of biopesticides. With the exception of fungi, microbial insecticides do not kill the target insect on contact, but need to be ingested. The insect must feed on some plant tissue carrying the biopesticide before the agent can cause the
mortality. Insects that bore into the plant tissue or remain hidden inside the plant structures are much less susceptible than insects feeding on foliage. All developmental stages of the insect are not equally susceptible to the microbial agents. As a result, the user must time the application precisely to prevent crop damage from an insect population exceeding the economic threshold. Some aspects of insect behavior also infl uence the performance of biopesticides. If major plant growth occurs after application of the biopesticide, then the unprotected plant surfaces become prone to insect damage. While proper timing of application is important, it may also be necessary to formulate the biological insecticide with feeding attractants such as molasses, which lure the insect to plant surfaces carrying the biocontrol agent. Contact poisons are superior in that an insect traversing a sprayed plant surface enroute to its preferred feeding site will contact the toxic residues regardless of its feeding habits.