In November, I was fortunate to take a group of PEI potato producers to Belgium for the INTERPOM potato expo, followed by visits to farms, researchers, and equipment manufacturers in the days afterward.
One of the recurrent themes we heard from growers, agronomists, and researchers was that European growers are struggling to deal with a range of pests and diseases, particularly late blight. A major reason for their frustration is the continual loss of effective chemical control options from their “toolbox.” As they’re left with fewer tools, those tools are being over-used, resulting in increasing levels of pesticide resistance. For example, the loss of broad-spectrum fungicides like mancozeb in Europe means producers are reliant on a much smaller list of single-site fungicides. New strains are now evolving that show resistance to some of these chemistries, leaving producers with fewer options in a heavy blight year like 2024.
While some provinces have seen a return of more late blight in the last two years, Canadian producers thankfully aren’t facing the same degree of challenges with late blight as our European friends. Nonetheless, we do face resistance issues with other pests and diseases that warrant our full attention.
A good example for increased vigilance is Colorado potato beetle (CPB), a significant issue for most potato-growing regions of Canada. Resistance surveys conducted by Agriculture and Agri-Food Canada through the last FVGC cluster has shown that CPB resistance to the neonicotinoid class of insecticides is growing.
In some provinces, CPC populations are essentially resistant to neonic products, while in other provinces, the window of control is shrinking. Likewise, there are other foliar insecticides that are also showing reduced levels of effectiveness, depending on the province surveyed.
What does this mean for the individual potato farm? Firstly, connect with agronomy experts in your province to understand what CPB control products are still showing effectiveness where you farm. Then, make an Integrated Pest Management (IPM) plan that includes rotation of chemistries to delay insecticide resistance as long as possible. Don’t use the same pesticide twice in a row; in fact, make sure you don’t use pesticides from the same group (mode of action) twice in a row. Every pesticide label has what FRAC group it belongs to. Switch up those groups to ensure you’re not building resistance in your beetle population.
The same advice goes for early blight and brown spot (Alternaria spp). Fortunately, we have a larger number of available products for control of Alternaria, but there is concern we may be starting to see reduced efficacy of some products. Ensure you’re rotating chemistry groups in your fungicide program, especially when using systemic or trans-laminar products.
We all must do our part to slow down pesticide resistance. The timeframe to register a new chemistry is well over 10 years now, and fewer chemical companies are investing in research into new products with new modes of action because the regulatory environment is so onerous, particularly in the European Union. It’s in our best interest to keep as many tools in the toolbox as possible, be they chemical, cultural, or biological control options. As well, be prepared to lend your voice to surveys and consultations around pesticide re-evaluation. When your provincial potato association or the Canadian Potato Council contacts you to ask for your input on pesticide usage or product re-evaluation, please don’t hesitate to provide your feedback. Producer feedback has been instrumental in preventing product deregistration in the past, especially when growers can provide context on how products are used responsibly under integrated pest management principles.
Have a great “meeting season” this winter, as we prepare to put another season’s promise in the ground.
