Biopesticides – Expectations for Control Jeanette Gaultier, Crops Knowledge Centre, Manitoba Agriculture, Food and Rural Initiatives, Carman, MB R0G 0J0 Email: [email protected]

A is a naturally occurring organism or substance that can be used to control pests. The term ‘biopesticide’ can be applied to microorganisms, biochemicals and plant extracts that are used as products. Although not the case in , some countries also consider plants with ‘incorporated protectants’ (i.e. transgenic crops) as .

Interest in biopesticides is increasing because such products are often recognized as ‘reduced’ or ‘low’ risk alternatives to conventional . In Canada, a is considered to be of reduced risk if human health and/or environmental risks are decreased relative to other pesticides registered for the same use. General characteristics of reduced risk pesticides include (PMRA, 2002): • Low toxicity; • Limited effects on non-target organisms; • Good environmental profile; • Low pest resistance potential; • Decreased application rates or applications; and • Compatible with integrated pest management principles. A product doesn’t have to be a biopesticide to be considered reduced risk. Conversely, biopesticides are often, but not always, classified as reduced risk.

Biopesticides currently account for only a small percentage (~1%) of the global pesticide market (Copping and Menn, 2000; Warrior, 2000; Rodgers, 1993). These products have generally found commercial success in niche markets such as horticulture, greenhouse, nursery and ornamental, and organic production. Uptake and use of biopesticides in conventional field crop agriculture remains low.

Why is this the case? What should agricultural producers expect from biopesticides?

Regulatory Expectations All pesticides, including biopesticides, available for use in Canada are regulated by ’s Pest Management Regulatory Agency (PMRA). The PMRA carries out health, environment and value assessments on all pesticides prior to their registration. Data requirements for biopesticide assessment are generally similar to those for conventional pesticides (HC-PMRA, 2007; HC-PMRA, 2002). Reduced risk pesticides aren’t given a break on data requirements but are given an expedited review for registration in Canada (HC-PMRA, 2002).

Efficacy data provided for the value assessment is of interest to agricultural producers. Based on this data, product labels indicate whether producers should expect control or suppression of a pest. The PMRA defines ‘control’ as the consistent reduction of pest infestations or pest damage and ‘suppression’ as the consistent reduction of pest infestations or pest damage that is less than optimal but still of value (HC-PMRA, 2005). Registrants are provided with guidelines for determining control vs. suppression (Table 1). These guidelines are sometimes vague, especially for biopesticides where industry standards may not really exist.

1 Table 1. PMRA guidelines for labeled expected level of control No. of Trials† Control (%) Suppression (%) 10 ≥ 80 ≥ 60 3 Industry standard Industry standard 3 Industry standard Industry standard Biopesticides 3 Industry standard? Industry standard? *Control can be set very high (e.g. > 90 to 95%) for pests that affect crop quality or marketability (PMRA, 2003). †refers to the minimum number of trials required, generally over a 2 year period.

Overall, Canada’s regulatory system is not an impediment to the registration and use of biopesticides in conventional agriculture. If fact, the PMRA readily accepts and processes submissions for biopesticides and offers expedited reviews for reduced risk biopesticides.

Agronomic Expectations Production and agronomic constraints are largely responsible for low uptake of biopesticides in conventional agriculture. Relative to synthetic pesticides, biopesticides can be difficult and expensive to manufacture, store and market (Chutia et al., 2007; Rodgers, 1993). Biopesticides may face additional constraints in the field with respect to selectivity and efficacy (Chutia et al., 2007; Rodgers, 1993).

Commercialization of biopesticides requires the production of viable living organisms and stable biochemicals. Manufacturers may experience difficulties scaling up production and maintaining toxicity or viability while keeping costs low. This can be less of a constraint for biochemical pesticides compared with microbial pesticides (living organisms). Biopesticides often have a relatively short shelf-life that can range from a few weeks to several years depending on storage conditions. In addition, biopesticides are often marketed by small companies that can only provide limited technical support. Warrior (2000) notes that, as unique products, biopesticides often require increased extension and technical support for producers.

Pest selectivity by many biopesticides is regarded as a good thing because of reduced effects on beneficials and other non-target organisms. However, unless a pest is a major issue and/or there are limited control options, producers may opt for products with broader selectivity in order to address multiple pests with a single application. The limited selectivity of biopesticides may necessitate the use of conventional pesticides to control other pests, which can lead to compatibility issues.

Biopesticides are often strongly influenced by environmental conditions (e.g. temperature, humidity, pH, etc.), which can result in variable efficacy. These products also tend to be slow acting, requiring weeks to months to be fully effective. This can be viewed negatively by producers that have become accustomed to the rapid knockdown effect associated with conventional pesticides.

Despite these constraints, certain biopesticides have been successful in conventional agriculture. Agricultural formulations of Bacillus thuringiensis (Bt) subsp. krustaki were first approved for use in Canada in 1972. DiPel is a post-emergent Bt bio- that controls Lepidopteran pests in numerous field and horticultural crops (http://www.valent.ca). B. thuringiensis bacteria produce crystalline proteins that are toxic to certain insects upon ingestion (Copping and Menn, 2000; Schnepf et al., 1998). Because of its selective toxicity to a certain order of insects Bt has limited effects on non-target organisms.

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Manufacturers are able to easily and economically produce Bt products on a commercial scale. Toxicity is not an issue because the bacteria naturally produce an abundance of highly toxic crystal proteins (Schnepf et al., 1998). Compared with conventional pesticides, Bt may be considered slow acting (2-48 hours); however, this is quite fast compared with other biopesticides.

Researchers continue to study B. thuringiensis in the hopes of improving pest control. The genetic modification of crops, such as corn, to produce Bt toxins has been very successful (Copping and Menn, 2000). Other improvements may include Bt products that contain different subspecies to broaden pest selectivity or that contain different isolates of the same subspecies to increase toxicity (Schnepf et al., 1998).

Despite its complex mode of action, pest resistance to DiPel and Bt crops has been documented (Schnepf et al., 1998). As such, Bt products should be used in rotation with other control measures.

Other biopesticides have not fared as well as B. thuringiensis. Agriculture and Agri-Food Canada researchers discovered and characterized Colletotrichum gloeosporioides f. sp. malvae, a fungal pathogen that causes anthracnose in round-leaved mallow (Mortensen, 1988). This work led to the registration of BioMal in 1992, the first bio- registered in Canada.

Field trials indicated that up to 100 percent of round-leaved mallow plants can be controlled with BioMal regardless of weed growth stage (Makowski, 1993; Mortensen, 1988). However, efficacy varied from 30 to 100 percent depending on environmental conditions. Dew periods of greater than 20 hours and temperatures between 10 and 25°C result in the greatest efficacy (Makowski, 1993). BioMal is relatively slow acting and can take 1 to 4+ weeks to be fully effective (Makowski, 1993).

BioMal’s registration expired in 2006. The registrant decided against renewing the registration due to production and economical constraints. Up-scaling production of C. gloeosporioides to commercial levels proved difficult. Increased concentrations of inoculum actually caused a decrease in infection (Makowski, 1993). However, it was competition with conventional herbicides that limited the use of BioMal (Bailey, K., personal communication). Few control options existed for round-leaved mallow at the time BioMal was being developed. But shortly after its registration, new, low cost conventional herbicides with broad spectrum weed control, including round-leaved mallow, entered the market.

Biopesticide Recommendations As indicated, biopesticide use in conventional agriculture faces many constraints but certain biopesticides, such as Bt, may still prove effective for field crops. Products that target a major pest issue or a pest for which few control options exist will likely have the greatest uptake in agriculture. Producers may even be considering the use of the newly registered (2009) biopesticides Contans (Coniothyrium minitans) for control/suppression of Sclerotinia or Nolo Bait (Nosema locustae) for suppression of grasshoppers.

Producers wishing to incorporate biopesticides in their pest management strategy should: • Read the label! - Check to ensure the product has a Pest Control Products (PCP) registration number to avoid use of unregistered and unproven products. - Use for the pests and crops indicated on the label.

3 - Pay attention to storage requirements to ensure maximum shelf-life and stability of the product. - Note application recommendations or restrictions (e.g. environmental conditions, subsequent application of conventional pesticides, etc.). • Use as part of an integrated pest management system. • Use under ‘normal’ conditions. Don’t use biopesticides, unless recommended, for outbreak situations since many are slow acting. • Be your own judge – leave a test strip in your field to monitor the effectiveness of the product.

References Chutia, M., Mahanta, J., Bhattacharyya, N., Bhuyan, M., Boruah, P. and Sarma, T. 2007. Microbial herbicides for weed management: prospects, progress and constraints. Plant Pathology Journal 6:210-218.

Copping, L. and Menn, J. 2000. Biopesticides: a review of their action, applications and efficacy. Pest Management Science 56:651-676.

HC-PMRA (Health Canada Pest Management Regulatory Agency). 2007. Regulatory Proposal PRO2007-02: Guidelines for the registration of low-risk biochemicals and other non- conventional pesticides. 32 pp.

HC-PMRA (Health Canada Pest Management Regulatory Agency). 2003. Regulatory Directive DIR2003-04: Efficacy guidelines for plant protection products. 45 pp.

HC-PMRA (Health Canada Pest Management Regulatory Agency). 2002. Regulatory Directive DIR2002-02: The PMRA initiative for reduced-risk pesticides. 30 pp.

HC-PMRA (Health Canada Pest Management Regulatory Agency). 2001. Regulatory Directive DIR2001-02: Guidelines for the registration of microbial pest control agents and products. 105 pp.

Makowski, R. 1993. Effect of inoculum concentration, temperature, dew period, and plants growth stage on disease of round-leaved mallow and velvetleaf by Colletotrichum gloeosporioides f. sp. malvae. Ecology and Epidemiology 83:1229-1234.

Mortensen, K. 1988. The potential of an endemic fungus, Colletotrichum gloeosporioides, for biological control of round-leaved mallow (Malva pusilla) and velvetleaf (Abutilon theophrasti). Weed Science 36:473-478.

Rodgers, P. 1993. Potential of biopesticides in agriculture. Pesticide Science 39:117-129.

Schnepf, E. Crickmore, N., Van Rie, J., Lereclus, D., Baum, J., Feitelson, J, Zeigler, D. and Dean, D. 1998. Bacillus thuringiensis and its pesticidal crystal proteins. Microbiology and Molecular Biology Reviews 62:775-806.

Warrior, P. 2000. Living systems as natural crop-protection agents. Pest Management Science 56:681-687.

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