Potential side-effects of fungicides on natural enemies and pollinators used in greenhouse vegetable production

Project Code : MUR06-080

Project Lead

Les Shipp - Agriculture and Agri-Food Canada

Objective

To determine the compatibility of the new reduced-risk fungicides Pristine, Switch and Milstop, with the biological control agents used in greenhouse production for insect control and for pollination

Summary of Results

Background

Greenhouse vegetable growers in Canada deal with a variety of insect and disease pressures. To manage pests growers often implement integrated pest management (IPM), an approach that combines monitoring, biological and cultural controls and sometimes pesticides. Biological control utilizes natural enemies such as predatory mites and parasitic wasps to reduce pest populations, and greenhouse growers are particularly high users of this technology, with more than 90% of growers reporting their use in certain crops for certain pests. Greenhouse vegetable growers also make use of insects such as bumble bees as pollinators in their operations to increase the marketable value of their crop. Pesticides, while often a necessary component of IPM, can have negative impacts on these beneficial insects and mites, therefore making the identification of bio-compatible, reduced-risk insecticides and fungicides a priority for Canadian growers.

While this project initially was to focus on the potential side effects of three fungicides, the scope expanded to include bio-compatibility testing of insecticides with additional funding from the Agriculture Adaption Council through a Canada Ontario Research and Development IV grant provided to Ontario Greenhouse Vegetable Growers. Key collaborators in this project included: AAFC research Centres at Harrow and London, University of Guelph, OMAFRA (Harrow), Biobest Canada Ltd. and Koppert Canada Ltd.

Approaches

The side effects on 4 commonly used beneficial arthropods were studied in this project: Orius insidiosisßitalicize (a predatory bug often used to control Western flower thrips); Eretmocerus eremicus (a parasitic wasp often used for the control of greenhouse whitefly); Amblyseius swirskii (a predatory mite often used for the control of greenhouse whitefly); and the beneficial arthropod Bombus impatiens, a bumble bee used for pollination. A literature review was completed on the non-target effects of pesticides against these beneficial arthropods. The pesticides selected were either used or had promise for use in Canadian greenhouse vegetable production at the time of this study. Those tested included four different insecticides (imidacloprid, abamectin, metaflumizone, and chlorantraniliprole) and three different fungicides (myclobutanil, potassium bicarbonate, and cyprodinil + fludioxonil)

Laboratory bioassays to assess direct contact toxicity were conducted with all beneficial test species using foliar spray technology. Greenhouse residual toxicity trials were then conducted to simulate commercial production conditions. With the bumble bees, the sub-lethal effects of the pesticides were evaluated using a new micro-colony technique to feed the bees pollen contaminated with the pesticides being tested.

Results

Under the conditions of this study the insecticides imidacloprid and abamectin were found to be moderately harmful to harmful to bumble bees following direct contact (i.e., foliar spray). When provided with imidacloprid-contaminated and abamenctin-contaminated pollen worker bees were found to have have a significantly shorter life span and consume less pollen. Micro-colonies provided with imidacloprid-contaminated pollen did not initiate oviposition and therefore did not produce any larvae. Worker bees given abamectin-contaminated pollen initiated oviposition significantly later than worker bees provided with untreated pollen. Metaflumizone was found to be moderately harmful in this study at high concentrations following direct contact, but did not cause sub-lethal effects as a residue in pollen. Chlorantraniliprole was shown to be harmless through direct contact and oral exposure. Similarly, the fungicides myclobutanil, potassium bicarbonate, and cyprodinil + fludioxonil showed no evidence of harm to bumble bees under the testing conditions of this study.

Orius insidiosus and A. swirskii tolerated all insecticides and fungicides tested in the laboratory bioassay and, in the case of abamectin, metaflumizone, myclobutanil, and potassium bicarbonate, also in greenhouse bioassays. Most insecticides and all fungicides tested were harmless to E. eremicus under the protocols of this study. Metaflumizone, however, was slightly harmful in leaf dip bioassays and under certain conditions of the greenhouse bioassay.

Next Steps

The queen-less micro colonies method developed for this study was shown to be a good protocol for the evaluation of sub-lethal impacts of pesticides on pollinators and would be useful as a standardized protocol, although more work remains to determine if the technique is appropriate for other bumble bee species.

This study’s results on direct and indirect toxicity with pesticides on beneficials provides useful knowledge for growers in making pesticide application decisions. However, little information is known about the sub-lethal impact of pesticides on biological control agents (life span, oviposition rate, predation/parasitism levels, etc.). A useful extension of this work would be to determine if the sub-lethal effects are an important consideration when evaluating the impact of pesticides on biological control agents.

The results of this research were transferred to growers, greenhouse industry, extension specialists and researchers through 2 scientific papers, 2 technology transfer articles, 3 posters and 1 oral presentation at scientific meetings, OMAFRA Greenhouse Vegetable course and grower open houses. The researchers will continue to share the results of this work with growers, helping them to make informed, economical and reduced risk pest management decisions.

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