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Roundup-Ready lettuce promising, awaits consumer nod

(Monday, Dec. 16, 2002 -- CropChoice news) --

Western Farm Press: The outlook for glyphosate-tolerant lettuce is promising, but development is on hold, pending consumer acceptance of genetically-modified crops, according to Kai Umeda, University of Arizona Cooperative Extension agent at Phoenix.

Although he had no trials on the practice in 2002, he said his trials in 2000 and 2001 at Yuma showed season-long weed control of Roundup with the Roundup-Ready lettuce cultivar, Raider, was superior to the conventional practice of using the herbicides Kerb and Prefar in pre-emergence soil applications.

Hand hoeing costs, he said, were minimal for the Roundup-Ready plots treated at the two-leaf and four-leaf stages. "Optimum timing was between the two-leaf and six-leaf stages, or about the equivalent of typical thinning time."

Treatments applied at the two- or four-leaf stages required the least amount of hand weeding and yielded the highest fresh weights. Treatment at those times gave nearly total control of major weed pests, common purslane, nettleleaf goosefoot, cheeseweed, and sprangletop. Applications at the six- and eight-leaf stages were less successful on common purslane.

The project, however, is presently on hold because consumers and restaurant operators have not yet accepted the concept of genetically-modified crops. "If this were approved, it would make weed control in a lot of our crops much simpler," he said.

Umeda spoke at Yuma during the recent Desert Crops Workshop sponsored by Western Farm Press, University of Arizona Cooperative Extension, and University of California Cooperative Extension.