“We’re trying to create what we’d call a push-pull system, where you have something attractive, like the pheromones and potato volatiles, to attract them into a trap,” explained Dr. Rebecca Hallett, University of Guelph School of Environmental Sciences professor and principal investigator. “And you have something repellent that would push them away from the field.”

An effective aggregation pheromone trap and a perimeter or in-row repellency strategy could minimize Colorado Potato Beetle population and yield impacts early on.

According to Hallett, the principal investigator, it’s the first study evaluating different Colorado Potato Beetle pheromone combinations, release rates and effectiveness of pheromone and potato volatile kairomones, which attract pests to host plants, since it was isolated in the early 2000s, particularly within an operational field setting, either at the field edge or in-row.

“It’s an aggregation pheromone. If we can increase the attraction of males and particularly females to these lures,” she said. “There’s quite a high potential to impact potato beetle populations and reduce yield effects, but it’s dependent on getting that really attractive blend of compounds.”

Andy Colton, an entomology Ph.D. student, said that lab studies of the original pheromone showed lower than anticipated attraction rates, requiring significant investment to purify and improve the synthetic pheromone before they could initiate field-level research.

Colton said thousands of beetles responded to pheromone traps in one of the two test sites, which, to his knowledge, was a first with wild beetles.

“One of our strategies is to deploy traps around the perimeter and hope to intercept (the beetles) when they emerge,” he shared, adding Colorado Potato Beetle overwinters in field margins, emerging in May to June to walk into fields.

Ideally, perimeter traps combined with in-row integration will attract emerging pests early on and lure survivors off host plants, diminishing the beetle population.

“(This) is more difficult. There are definitely stages of the season where they’re more primed for the pheromone and host volatiles,” Colton explained. “We’re finding different results at different stages.”

The first in-field trials provided insight into the aggregation pheromone traps, but more work still needs to be done.

“Colorado potato beetle is a global pest, so if it (the new pheromone) works, it may very well be economically feasible (to scale production),” Hallett explained. “But at this point, it’s too early to say. It’s been expensive trying to get this synthesis done properly.”

Colton’s lab research on the efficacy of high volatile plant compounds from hops and cannabis by-products as a repellent is in its infancy.

“Cannabis, in particular, is very high in terpenes, and some research has suggested that the presence of non-host volatiles may deter pest activity,” he explained.

Colorado Potato Beetle females are picky about where they lay eggs, and early lab research indicates cannabis could interrupt feeding and egg-laying patterns, but it has some challenges.

“The regulations are tight (with cannabis), so working with it has been difficult,” he admitted. “I’m excited to get my hands on some hops because it’s an aromatic plant in a similar family, so there could be activity.”

The repellency mulch, sourced from cannabis and craft beer market by-products, could provide a knock-on value for the industry’s waste products.

Hallett anticipates field-level cannabis mulch trials will likely begin in 2025, and trap deployment research to identify the ideal location and Colorado Potato Beetle interception timing as an attractant, rather than luring them off potato plants, will continue.

Growers interested in participating in in-field research are encouraged to contact Colton.

“Colorado potato beetle is a global pest, so if it (the new pheromone) works, it may very well be economically feasible (to scale production),” Hallett explained. “But at this point, it’s too early to say. It’s been expensive trying to get this synthesis done properly.”

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“It’s not a simple problem,” agreed Dr. Ian Tetlow, University of Guelph Department of Molecular and Cellular Biology professor, adding the first documented cold sweetening in low-temperature stored potatoes was in 1882. Research has been looking for a workable solution since then.

Tetlow announced at the Elora Potato Research Open House in August that his interest in starch biosynthesis has evolved into a three-year research project on cold sweetening susceptibility in potato varieties.

Cold sweetening builds up soluble sugars during storage, contributing to browning and potential acrylamide toxin formation during processing.

His research will explore the genome sequence of resistant and susceptible potato varieties, using RNA sequence analysis to decipher the cold sweetening process.

Tetlow already has potential targets, such as phosphorylase, a cold temperature-activated enzyme that breaks down starch.

“That’s an interesting target,” he said. “But it’s a multi-gene phenomenon; it’s not an easy thing to solve by a one-step process.”

The bulk of a potato tuber consists of storage starches, water and soluble starch. However, there are soluble sugars. Cold sweetening is when starch granules convert naturally into simple sugars.

“The potato tuber is a living entity. It’s still respiring (after harvest). The cells in it are alive,” Tetlow explained. “They’re using up carbon, and they’re using some of those reserves at different rates.”

Even at low temperatures, storage must be relatively dry to avoid the development of fungal and bacterial pathogens and reduce sprouting and degradation of the tuber. It doesn’t protect against cold sweetening.

“You would think it would be relatively easy to understand that process,” he said. “Biochemically, we know those processes are a number of enzymes, but likely, it’s not just confined to those small numbers of enzymatic steps.”

Certain varieties show a faster breakdown of starches into sugars at ambient temperature during long storage periods, causing significant issues during processing, such as browning during deep frying.

Processors reject up to 20 per cent of tubers because of cold sweetening’s impact. Tetlow explained that French fries and potato chip processing account for more than 60 per cent of the crop, which can have significant implications.

He said French scientist Louis-Camille Maillard discovered the Maillard Reaction, that says when amino acids react with reducing sugars during heating, it causes browning. Under controlled conditions, this results in a pleasant flavour but, in excess, can produce unwanted compounds.

“If you notice, potato chips which have darkened have this bitter flavour – that’s a result of the Maillard reaction,” he said. “The acrylamide associated with it is a potential neurotoxin and a potential carcinogen.”

Reducing the amount of free sugar in potatoes will lower levels of acrylamide.

While breeders have done an excellent job reducing cold sweetening, Tetlow suggested they may reject varieties with high-yielding and high resistance attributes because of poor cold sweetening results.

“Hopefully, within (our three-year) time frame,” he said. “We’ll have at least an array of target genes that we understand what’s going on in terms of the biochemistry of the potato tuber when it’s subjected to low temperature.”

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In 2023, rain hindered producers’ efforts to spray for late blight, leading to a late blight outbreak. While Ontario struggled to get the fungal disease under control over the last few seasons, droughty conditions and extensive tracking in the western provinces have saved fungicide costs and kept them late blight-free in recent years.

Banks said eastern Canadian producers were ready in 2024 with proactive management plans.

Forgoing spore traps for more accurate field inspections, Dr. Peter Vander Zaag, Sunrise Potato Systems Institute president, said growers opted for preventative treatments using predominately Orondis fungicide with phosphorus acid to mitigate late blight potential this season. Banks said specific and broad-spectrum fungicides help avoid resistance while effectively eradicating late blight lesions in about a week.

“When the late blight came, we used Ridomil Gold wherever it was to kill it,” said Vander Zaag, adding his sample harvest showed healthy tubers and a decent yield.

Good yields will be essential this season to help offset the skyrocketing cost of fungicide applications this year.

“Our irrigation cost is down, but spray is way up. We’re out of pocket,” he said. Stack on the impact of the U.S.-Canadian dollar exchange, high interest rates, and costly equipment, it’s tricky for producers to cultivate a solid financial position.

“What we sell hasn’t gone up the way it should have,” Vander Zaag explained. “Not to complain, everybody has to make ends meet, but we have to make money too.” Banks said producers must remain vigilant about storage issues like fusarium dry rot and soft rot when harvesting too-warm tubers.

“Today, you couldn’t harvest the crop,” Banks said during the Ontario Potato Field Day and Trade show. “It’s too hot, and these other pathogens could penetrate the tubers – then storage would be a nightmare.”

Growers must harvest early in the morning when temperatures are below 16 Celsius to ensure cooler tuber flesh, especially if the skin hasn’t set yet. Vander Zaag is cautiously optimistic but remains vigilant about detecting pathogens, particularly Erwinia bacteria, which could rot late blight-affected potatoes in storage, narrowing the window to get friable stock to market. “Generally (once in storage), the whole process of harvesting is so much shock that the starch turns back to sugar,” he explained. “It takes a while to burn that sugar off, so it will fry.”

Last year, he said warm temperatures led to a failed “sniff test” on late blight potatoes after two weeks in storage, but he managed to sell them in November.

The view from the west

“We never let our guard down. We’ve got a very expansive spore trapping network set up out here in the province (Alberta) to track it,” explained Terence Hochstein, Potato Growers of Alberta executive director. “Any early indication of a spore, we’re all over.” It’s difficult to compare the risk in the two provinces because where Ontario has high humidity, Alberta is semi-arid, with irrigation required in the south and summer nights dipping to 15 to 16 degrees Celsius before rising in the day. 00“We’ve got a massively huge, expensive monitoring program, and it’s paid for itself in spades. That said, next year, we could have a blow-up,” Hochstein said. “We’ve had it in years past when it’s been wet and with different strains, and it’s been devastating.” He said for the last dozen years, Alberta growers have benefited from a Burkard air sampler system to track the fungal disease’s spores, pulling vials daily for testing with excellent results. If spore counts indicate a problem, the producer will disc the affected area immediately to prevent a costly outbreak, explained Hochstein. While some producers pre-emptively spray twice a season, he said that effective spore tracking has saved millions in fungicide costs and prevented 1,000s of kilograms of active ingredients from entering the atmosphere. In addition to tracking late and early blight and other potential diseases, their insect monitoring program scouts for potato psyllids and other pests that could harm their seed industry.

“I know Manitoba fights the Colorado Potato Beetle; we don’t have them here,” Hochstein shared. “I don’t know why, but we don’t.”

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