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Pyrethroids may not be best choice for controlling Colorado potato beetle

Colorado potato beetle

PACIFIC NORTHWEST: Growers who haven’t treated for Colorado potato beetle (CPB) at planting may begin finding adults, eggs or larvae in their fields. Rising potato production costs have growers searching for economical solutions to control CPB. While cost is always a valid concern, failure to observe sound control  strategies may compound problems as the season progresses.

When timing your first foliar application to control CPB, apply as soon as you see very small larvae begin to emerge from the eggs (bright yellow eggs turn dark right before the larvae emerge) as small larvae are the most venerable to insecticides. Waiting till larvae are large (picture above) will require using higher recommended rates and might result in reduced control. Use sufficient water to obtain the best plant coverage. Because potato plants are growing rapidly, additional foliar applications might be necessary to provide effective control.

Colorado potato beetle

If you’re considering pyrethroids, know that they are best used at the end of the season. As broad-spectrum insecticides, they can be devastating to beneficial insect populations. In other words, a pyrethroid application eliminates natural predators roaming potato fields, which can result in higher populations of mites, aphids and potato psyllid.

Wait to use a pyrethroid until the end of the season, when potatoes are senescing and beneficial insects play a lesser role. A pyrethroid with a short pre-harvest interval (PHI) fits well in the program at that time.

All photos are the property of Syngenta unless otherwise noted.

Reporting from Magic Valley, ID

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