RUPERT, Idaho—The best insecticides for controlling the potato psyllids that spread the crop disease zebra chip may lose effectiveness when mixed with common fungicides in potato production, a chemical researcher warns.

Regional potato growers had little need to blend the two products prior to the arrival of zebra chip, which has forced them to increase use of insecticides, often adding them to the same tank as fungicides to minimize aerial application bills.

Complicating matters, Jeff Miller, a partner with Rupert-based Miller Research, said repeated tests show early blight disease is building resistance to Endura and Quadris, fungicides that aren't believed to inhibit insecticide performance. Overuse of the products could exacerbate the resistance problem.

Zebra chip, which first arrived in the Pacific Northwest in the late summer of 2011, blemishes the appearance of potato tubers by raising sugar levels, creating bands that darken when fried. Psyllids are tiny, aphid-like insects.

SOURCE: John O’Connell, Capital Press

http://www.capitalpress.com/newsletter/JO-TankMixTrouble-121412