Efficacy on the decline

11/01/2009 01:00:00 AM
Vicky Boyd, Editor

Kevin Seitzinger, the crop protection manager for a large tomato grower/packer/shipper near Immokalee, Fla., battles whiteflies— and the viruses they carry—in his tomato fields on several fronts.

He starts with clean virus-free transplants, lays reflective metallic mulch over his beds, applies an insecticide at planting, scouts his fields twice a week and performs field sanitation shortly after harvest.

But imidacloprid, his traditional insecticide at planting, wasn’t providing the same length of control as it did when it was first registered about 14 years ago. So Seitzinger had to return sooner than he used to with a foliar insecticide treatment.

He has since switched to Venom, a neonicotinoid applied at planting that is marketed by Valent USA.

“This is not the silver bullet either, but it does definitely help us,” Seitzinger says.

Justin Hood, a farm manager with Collier Pacific Grower Partnership near Immokalee, says he’s lucky now to get a couple weeks’ control out of imidacloprid.

“Five years ago, the imidacloprid was a really good product for the whiteflies,” Hood says. “Now it just doesn’t have the same get up and go that it used to.”

Seitzinger and Hood aren’t alone in their observations. Researchers from universities as well as Bayer CropScience, the chemical’s original registrant, say whiteflies in some locations have become more tolerant to the chemical.

Bayer markets its imidacloprid as the soil-applied Admire Pro and the foliar Provado. Several other companies have generic or off-patent imidacloprid products.

“In some areas, there’s been a gradual decline with imidacloprid control of whiteflies, particularly adults,” says David Rogers, insecticide product development manager for Bayer CropScience in Research Triangle Park, N.C. “There have been no field failures, but the level of activity is less today as it was in former times.

Photo courtesy of the Agricultural Research Service

“This is perhaps not completely unexpected as Admire and Admire Pro have been the backbone for whitefly management programs for many, many years­—longer than the other neonicotinoids currently on the market.”

Researchers also have found whiteflies are more tolerant of thiamethoxam, a neonicotinoid marketed as the soil-applied Platinum and the foliar Actara by Syngenta Crop Protection.


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