AGRO 16 |
| Loss of methyl bromide makes alternatives for nematode control an urgent need. The stilbene 3,5-dihydroxy-4-isopropylstilbene (DST), isolated from Photorhabdus luminescens bacteria that live inside nematodes of the genus Heterorhabditis, has paralytic/lethal activity against a variety of nematode species, including Caenorhabditis elegans and Meloidogyne incognita (K. Hu, J. Li, J. Webster. Nematology 1:457-469, 1999). Interestingly, the symbiotic nematodes within which the bacterium lives were completely insensitive to DST at concentrations up to 200 µg/ml. Since DST is structurally similar to 4,4'-diisothiocyanato-2,2'-stilbenedisulfonic acid (DIDS), a well-established blocker of anion transporters, the two compounds may share a similar mode of action on cell membranes which could be the basis of insecticidal or nematicidal activity. Accordingly, we have screened DIDS and related materials for nematicidal activity in the laboratory. In vitro toxicity assays showed that DIDS, NPPB, IAA-94, and 9-AC were paralytic/lethal to M. incognita in the low ppm range, but not to H. bacteriophora at 200 ppm. Thus, bona fide blockers of anion transporters showed a cross resistance pattern similar to that previously observed for DST. Studies using longer term exposures of M. incognita found that the endpoint LC50 for DIDS occurred at 72 hr indicating a slowly developing toxic action. Similar results were observed on nematode egg hatch in vitro. Activity in whole plant screens remains to be determined. |
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Alternatives to the Use of Methyl Bromide in Pre-Plant Soil Fumigation and Stored Commodities
8:00 AM-11:35 AM, Sunday, 10 September 2006 San Francisco Marriott -- Salon 2, Oral
Division of Agrochemicals |