Actually (to the best of my knowledge),
PyrethrOIDS (such as those listed in the original email) are not OMRI approved. Some formulations of PyrethrINS (e.g. Pyganic) are. The differences being that the "oids" are artificially synthesized compounds while the "rins" are chrysanthemum extracts. Functionally the "oids" are quite a bit more active than the "ins", to a large extent because some formulations can provide 7+ days of residual activity whereas the "ins" residual activity can be as short as several HOURS. Please also note that any pyrethrin formulation including PBO (piperonyl butoxide; a synergist) also lack OMRI approval (e.g. Pyranyl).
So, unless the organic grower is spraying pyrethrins on a very regular basis (i.e. 4+ times per weekI doubt resistance from his/her local population would be much of a problem; of course immigrating resistant critters might be another story.
As far as Spinosyns go, Entrust has OMRI approval and is functionally about the same as Spintor (the conventional product).
On Jul 23, 2008, at 10:11 AM, Vicki Morrone wrote:
Please note this concern for resistanct to two organically allowed pesticides (pyrethroid as a natural botanical pesticide) is restircted (allowed following NOP rule)and Spinosad (allowed). From: Tony Shelton [mailto:[log in to unmask]]
Sent: Tuesday, July 22, 2008 11:04 PM
To: Great Lakes Vegetable WG
Subject: Resistance in ECB
Has anyone done tests to determine if European corn borer is becoming resistant to pyrethroids and spinosad? A local extension educator in New York says that his sweet corn farmers are telling him that they are experiencing resistance. A few years ago we published a paper that indicated a dramatic decrease in efficacy for pyrethroids and spinosad against ECB with increased temperature after some growers claimed 'resistance'. So now we are wondering if anyone has done some actual lab test for resistance. Musser, F. P and A. M. Shelton. 2005. The influence of post-treatment temperature on insecticides to Ostrinina nubilalis. Pest Management Sci. 61:508-510 Abstract: The influence of post-treatment temperature on the toxicities of two pyrethroids (lambdacyhalothrin
and bifenthrin), a carbamate (methomyl) and a spinosyn (spinosad) to Ostrinia nubilalis
(H¨ubner) larvae was evaluated in laboratory assays. From 24 to 35 ?C, the toxicities of the pyrethroids
decreased 9.5- and 13.6-fold while spinosad toxicity decreased 3.8-fold. The toxicity of methomyl did not
change significantly. The results demonstrate that the most effective insecticide against a pest may vary
with environmental conditions. In situations where comparable products frommultiple insecticide classes
are available, temperature should be included as a factor in the decision-making process.
Professor, Department of Entomology International Professor; Associate Director International Programs Cornell University/NYSAES, 630 W. North St., Geneva NY 14456
PH 315 787-2352 FAX 315 787-2326
If you would like to access a searchable archive of the all the previous Mich-Organic listserv postings copy this URL and paste in your browser address field http://list.msu.edu/archives/mich-organic.html
Matthew Grieshop PhD
Assistant Professor of Organic Pest Management
Michigan State University
205 Center for Integrated Plant Systems
East Lansing, MI 48824
Phone: (517) 432-8034