The Colorado potato beetle (CPB) is a notorious pest that causes significant damage to potato crops worldwide. Known for its voracious appetite, rapid reproduction, and ability to develop resistance to insecticides, CPB poses a persistent challenge to potato farmers.
Fortunately for growers, the research community and industry work tirelessly to develop new options and control methods. During a recent webinar, hosted by Potatoes in Canada and presented by BASF, Christine Noronha, research scientist (entomology IPM) at the Agriculture and Agri-Food Canada (AAFC) Charlottetown Research and Development Centre, joined Anne McRae, senior technical service specialist for horticulture at BASF, to discuss CPB control and management.
Big history, big impact
First described in 1824 in the Rocky Mountain area, CPB primarily fed on nightshade, a relative of potatoes. However, it wasn’t until 1859, when it was discovered damaging potato crops in Nebraska, that its threat to agriculture became evident, Noronha says. Since then, CPB has rapidly spread across North America, Europe, and parts of Asia, establishing itself as a challenging potato pest.
“It’s considered one of the most important pests of potatoes as it defoliates the plant, usually either by flight or by walking in the spring,” Noronha explains, noting the beetles can fly 1.5 kilometres. “A single female beetle can lay about 500 eggs over a four-week timespan. You can imagine how fast the population would grow if each female lays 500 eggs.”
Both adult and larvae feed on both leaves and stems, and in severe infestations, even attack potato tubers, causing significant economic losses for farmers.
The pest’s lifecycle involves overwintering in hedgerows before emerging in spring to infest potato fields. Adult beetles lay eggs on the underside of potato leaves, which hatch into larvae that undergo several developmental stages. Eventually, mature larvae pupate in the soil before emerging as adult beetles, completing the cycle.
“These are known as the summer adults and will start feeding again quite voraciously because they’re preparing for overwintering . . . and they can do quite a bit of damage in that time,” she explains. Once the insect has collected enough fat reserves, it will either walk or fly to the overwintering site.
“An uncontrolled population can cause 40- to 80-per-cent yield reduction. We know that if 75 per cent of the foliage is lost, you could have a total crop loss,” Noronha says, adding that usually intervention occurs before that level of damage happens.
Control measures and challenges
Historically, insecticides have been the primary method for CPB control. However, the insect has shown a remarkable ability to develop resistance to various classes of insecticides, posing challenges for effective pest management.
“At one point, the Colorado potato beetle developed resistance to all the major classes of insecticides. That was in the ’80s and ’90s where resistance development resulted in control failure in many regions. There were no new chemicals on the market at that time, so growers had quite a hard time trying to figure out how to control this insect,” Noronha explains.
Physical control methods like bug vacuums, flamers and plastic-lined trenches, as well as biological control methods, including pathogens and natural predators, were explored and may still be viable additions to an integrated pest management strategy to control CPB. Today, Noronha says a well-rounded strategy is more important than ever.
“Potato beetles are known to develop cross resistance,” Noronha explains, referring to the CPB’s “super bug” nickname. “It’s very important to have a good resistance management program, rotating chemistries and delaying the development of resistance,” she adds, noting that growers should scout and observe fields to know if the chemicals they are using are effective, or if signs of resistance are showing.
New solutions and innovations
For growers looking to expand their insecticide toolbox and preserve some of the current solutions, McRae shares that BASF’s Cimegra insecticide recently received label expansion to include Colorado potato beetles as a foliar application.
Cimegra is the first Group 30 meta-diamide registered in Canada, McRae says. The product, which is also used to control wireworms, works similarly to other neonicotinoids, disrupting the nervous system, leading to paralysis and eventual mortality.
“The difference is the site of action,” McRae explains. “The insect’s nervous system works with inhibitory and excitatory signals, which must be going on and off in order for an insect to walk, eat and act normally. Cimegra blocks those channels so the insect can no longer control its movements.”
McRae notes that Cimegra can be added to rotations to help preserve other chemistries helping to mitigate resistance. It is not a systemic product, meaning it can work in-furrow and as a foliar product, but it should not be tank-mixed with liquid fertilizers, she adds.
“Water volume is important,” she notes. “If you want it to work well, you need excellent coverage of the full plant, because those Colorados can be hiding anywhere on that plant.”
Cimegra is registered in the U.S. and Canada for potatoes (and sweet potatoes) only, so McRae reminds growers to speak to their potato contractor about MRL approvals prior to use. She also stresses the importance of proper storage and insecticide stewardship, reminding growers to be mindful of environmentally sensitive areas, buffer zones and vegetative filter strips. And above all, a diverse toolbox will preserve the efficacy of existing insecticides.
“As a Group 30 product, Cimegra does provide excellent control, and it’s a good new option to add to your toolbox to preserve some of the insecticides you’re currently using, and try out a new one as well,” she says.
Growers, researchers and industry stakeholders can all play a role in addressing the challenges posed by CPB through knowledge-sharing, implementing best practices, and adopting sustainable solutions.
“Insecticides play a big role in IPM,” Noronha concludes, emphasizing that rotating chemistries is the best way to delay the development of resistance. “We should take care of them and make sure they continue to be available.”
Watch a recording of the webinar with more insights from Anne McRae and Christine Noronha, and learn more about Cimegra here.
