Pest of the Month: Colorado Potato Beetle

{Sponsored} A pest that can quickly get out of control and decimate a potato field, the Colorado Potato Beetle (CPB) is more common in the Eastern U.S. than in Washington state. In 2020, Eastern and Midwestern growers saw typical, predictable pressure from CPB — but surprisingly, Washington growers also contended with an abnormal number of the pests.

Colorado-potato-beetle-Leptinotarsa-decemlineata-Illustration-4In the Tri-Cities and southern and central regions of Washington, the trend of higher CPB pressure in 2020 threw growers for a loop. With the higher survival rates last winter, CPB put pressure on crops immediately. Beetles emerged starting in May in the South Basin and the North Basin saw them in early June. With larval hatch occurring about three weeks after adult emergence, growers needed to be prepared to start knocking down the beetle populations very early in the season.

How to prevent and control CPB

Going into the 2021 growing season, it is imperative that growers apply at planting. Infestations often start with adult CPB overwintering in soil. Some growers have attributed this issue in 2020 to the lack of a deep freeze in the winter of 2019-2020.

Applying a seed treatment chemistry such as Cruiser® from Syngenta will help protect young plants in development for up to 60 days after planting. Another option is a soil-application of a neonicotinoid.

Due to the fast reproductive rate of CPB, growers need to be prepared to target foliar applications properly, and with the correct variance in chemistries, to knock down the pests and avoid resistance management issues.

When foliar applications are required to fight CPB populations, Agri-Mek® SC (FRAC Group 6) from Syngenta is a foliar insecticide that fights both mites and CPB in potatoes. “Agri-Mek’s active ingredient is Abamectin. It has a good alternative mode of action. It is really effective on CPB, has a lot of use across a lot of acres and is a popular product. It’s good to incorporate into a foliar program, especially in mid-to-late June, when you don’t want to apply any of the foliar products like Warrior II with Zeon Technology® or neonics,” said Dan Maxfield, agronomic service representative at Syngenta.

Growers can also use Besiege® insecticide, a premix of Chlorantraniliprole and Lambda-cyhalothrin — FRAC Groups 28 and 3 — which has “strong activity on CPB and other pests,” said Meade McDonald, product lead for insecticides at Syngenta. One of the newest tools in the fight against CPB is Minecto® Pro insecticide from Syngenta, which launched in 2017-2018.

“Getting out and scouting, looking for egg masses, is the first indication of pressure in that field. The first spray for Minecto Pro should be targeted after 50% of egg masses have hatched and early larvae are present,” McDonald said.

Resistance management

Resistance to various insecticide classes is present in some populations of CPB, and Syngenta encourages growers to employ resistance management practices to preserve effective tools.

“CPB is known to be highly resilient in potatoes, and in many cases, there are resistant populations to neonics, pyrethroids and organophosphates,” McDonald said.

2021 Outlook

For growers who had CPB infestations in 2020, it is imperative to plan a strong program for prevention and control of the beetles for 2021. This is a pest that can wreak havoc in potato fields as heavy infestations can cause defoliation, which negatively impacts yields.

“For growers in high-pressure fields, the first CPB application should be made when populations are low. When CPB populations are high, use the highest labeled rate,” McDonald said. “Also, thorough coverage is essential for the best results. Minecto Pro has exceeded grower expectations for performance on CPB in 2020 and is an excellent choice in a program approach as part of a CPB strategy in 2021.”

To learn more about Agri-Mek SC, visit

More details about Besiege are available at

For more information about Minecto Pro, visit minecto-pro.

Product performance assumes pest presence.

Agri-Mek SC, Besiege, Minecto Pro and Warrior II with Zeon Technology are Restricted Use Pesticides.

© 2020 Syngenta

75 Applewood Dr. Ste. A
P.O. Box 128
Sparta, MI 49345


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