Barriers to adoption of biological control agents and biological pesticides

Abstract

Biological (bio)pesticides represent 2.4% of the global pesticide market, but this share is growing quickly and is projected to double by 2010. In contrast, the market for chemical pesticides is flat to declining as transgenic seeds have reduced sprays and governments have restricted or removed products from the market. By combining performance and safety, biopesticides offer value through benefits generally not realized by conventional pesticides. Biopesticides perform efficaciously while providing customers the flexibility of minimum application restrictions, superior residue and resistance management potential, and human and environmental safety benefits. Despite these advantages, there are significant barriers that impede adoption of biopesticides. This review will explore these barriers in depth and offer solutions for increasing adoption. These barriers include a competitive market, risk-averse customers, a complex selling channel, perceived lack of efficacy and lack of awareness.

Specificity and efficacy of purified Bacillus thuringiensis proteins against agronomically important insects

The host range and relative efficacy of three purified Bacillus thuringiensis insect control proteins were determined against 17 different agronomically important insects representing five orders and one species of mite. The three B. thuringiensis proteins were single gene products from B. thuringiensis ssp. kurstaki HD-1 (CryIA(b)) and HD-73 (CryIA(c)), both lepidopteran-specific proteins, and B. thuringiensis ssp. tenebrionis (CryIIIA), a coleopteran-specific protein. Seven insects showed sensitivity to both B. thuringiensis ssp. kurstaki proteins, whereas only 1 of the 18 insects was sensitive to B. thuringiensis ssp. tenebrionis protein. The level of B. thuringiensis ssp. kurstaki protein required for 50% mortality (LC50) varied by 2000-fold for these 7 insects. A larval growth inhibition assay was developed to determine the amount of B. thuringiensis ssp. kurstaki protein required to inhibit larval growth by 50% (EC50). This extremely sensitive assay enabled detection of B. thuringiensis ssp. kurstaki HD-73 levels as low as 1 ng/ml.

Purification and characterization of Bacillus thuringiensis var. tenebrionis insecticidal proteins produced in E. coli

Native and single amino acid variants of the Bacillus thuringiensis var. tenebrionis insecticidal proteins were expressed in Escherichia coli, purified and examined for biological and biochemical properties. A novel, pH dependent, preferential precipitation method was implemented to purify Escherichia coli produced Bacillus thuringiensis var. tenebrionis proteins, which are active against Colorado potato beetle (Leptinotarsa decemlineata) larvae. Cysteine residues of the native Bacillus thuringiensis var. tenebrionis protein were replaced by serine residues by site-directed mutagenesis to investigate the biological and structural importance of the individual cysteine residues. Sulfhydryl determination of the native and amino acid variant Bacillus thuringiensis var. tenebrionis proteins revealed that the native protein contains no disulfide bonds. Modification of the carboxyl terminal cysteine residue (amino acid 540) caused complete inactivation of the protein. Native, truncated and single amino acid variants (other than at amino acid 540) exhibited insecticidal activities comparable to each other and to solubilized crystals from the original strain.