Enhancing the efficacy of a natural mustard biopesticide against nematodes, wireworms and microbial pathogens of carrots and potatoes in New Brunswick and Prince Edward Island

Project Code: BPI07-200

Project Lead

Loretta Mikitzel - Province of New Brunswick

Objective

To assess the in vitro activity of CA-1 against fungal pathogens, nematodes and wireworms, establish the effective rate of CA-1 in growth chamber experiments, and conduct field experiments on carrot (PEI) and potato (NB)

Summary of Results

Potato and carrot represent a substantial proportion of vegetables grown in Canada, and both are affected by numerous pests. Currently in Canada, with the exception of soil fumigation, there are no registered synthetic pesticides available to control common scab (Streptomyces scabies) on potato (Solanum tuberosum) or to control parasitic nematodes and wireworms on carrot (Daucus carota). These pests cost the carrot and potato industries substantial dollars each year.

CA-1 is a new biopesticide (trade name BioGreen) manufactured from pelletized mustard (Brassica juncea) meal. Preliminary lab tests have confirmed that CA-1 is active against many organisms that are serious problems for Maritime potato and carrot producers.

Efficacies of CA-1 against wireworms, nematodes and potato scab under field conditions were evaluated in both carrot and potato plots. The CA-1 was incorporated into the soil at a range of rates just prior to planting, or during the growing season. Laboratory studies evaluated the efficacy of various concentrations of the active ingredient of CA-1 against several microbial pathogens.

From the field trials with potato, CA-1 shows potential to control common scab (Streptomyces scabii), especially when applied at the time of planting and at rates higher than 0.025% CA-1/soil (w/w). CA-1 does not appear to be an effective wireworm control option in potato. Results from the carrot field trials suggest CA-1 has the potential to repel wireworms in carrot. CA-1 applied at a rate of 0.05% (w/w) to soil around carrots at the time of foliage trimming restricted wireworm damage to the bottom portion of the carrot; however, injury to the carrot shoulders indicate the product can be damaging to the plant itself. Nematode infestation of the carrot trial sites was severe and no clear nematode controlling effect was noted.

Applying CA-1 immediately before planting inhibited potato and carrot growth, while applying at time of planting significantly reduced potato and carrot yield. As time of application was delayed from planting to second hilling in potato and from prior to planting to foliage trim in carrot, these effects disappeared. Damage to plants from CA-1 was related more to time of CA-1 application rather than to the rate of application. Measurements of potato and carrot fresh and dry matter, and visual observations during the growing season confirmed that rate of CA-1 did not interfere with plant development or maturity. Lab tests showed the CA-1 bioactive inhibited seed germination. These results indicate there should be a delay between CA-1 application and planting to protect potato and carrot from adverse effects.

Soil samples taken shortly after CA-1 application and again three months later indicated that there were no dramatic or long lasting effects of CA-1 on the soil microbiology. The activities of both fungi and bacteria were initially repressed, but these effects were temporary.

The lab results showed the CA-1 bioactive killed all of the tested microbial pathogens of carrot and potato; however, at high concentration, it could also damage plant tissues. Some microbes were much more sensitive than others, and more sensitive than the plant tissue. Of particular interest in this respect was Phytophthora infestans (late blight). The CA-1 bioactives stopped this pathogen's growth at very low concentrations. Preliminary test results suggest that formulated CA-1 bioactive could control P. infestans on both inoculated stored potato tubers and plants. New formulations are being developed with these goals in mind. Research on the potential of products like CA-1 as alternatives to traditional methods such as fumigation is ongoing. As these products become registered they will provide effective and reduced risk solutions for growers' in their ongoing management of crop pests.

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