Novel Chemistry for Effective Control of Dry Bean Disease

Phaseolus dry beans are the leading grain legume crop with an annual world production of 20 million metric tons (mmt) and the U.S. is the leading export nation marketing 40% (0.4 mmt) of all dry bean production overseas. Dry or dry edible beans (DEB) are produced in the U.S. on 1.7 million acres by nearly 11,000 farms with estimated sales at $1.8 billion. Production occurs in fourteen states and includes fifteen different varieties of beans. However, dry bean diseases can dramatically reduce yield, quality of harvested beans and therefore, greatly affect grower profits. White mold in particular is a key pest of dry beans in Michigan. Serious losses can occur when weather conditions are favorable for disease development and disease organisms are present. Except for the driest seasons, 100% of crop acres are at risk and up to 40-50% can be affected, with yield losses as high as 50% occurring within 2 weeks late in the growing season. Under irrigated production in California and the Northwest, losses can be 100%. Intervention with chemical treatments at early flowering suppresses white mold but does not completely eradicate the disease. Generally growers are delighted to obtain 50% suppression of white mold with a single fungicide application but of course, growers also expect to have a yield increase over untreated crops. An additional spray treatment can provide extra protection but more often than not, two applications of current fungicide products for dry bean is cost prohibitive. Identifying a novel fungicide that is cost-effective for two applications would be highly advantageous; especially for use in fields with a history of disease and during periods of prolonged and/or heavy rainfall particularly at time of flowering. Moreover, nearly all labeled fungicides are listed as carcinogens or suspected carcinogens and some have high chronic toxicity. Many are either highly toxic to fish/ aquatic life (Topsin, Blocker 4F, Switch) or have issues of pathogen resistance (Rovral, Endura and Switch). Topsin-M, Rovral and Ronilan are on the California list of "Known Carcinogens and Reproductive Toxicants". Blocker 4F is listed in California as a toxic air contaminant. Due to the serious health and safety issues related to these products, re-registration under the Food Quality Protection Act (FQPA) could be jeopardized or severe restrictions could be implemented. Hence, growers seek safer, less costly products to effectively control white mold infestations. It is anticipated that EPA registration for most, if not all, of the experimental ingredients will likely include acute toxicity testing and minimal (if any) chronic toxicity trials on animals; i.e., teratogenic and carcinogenic studies. Use of more environmentally friendly products by growers would lower consumer risk. The discovery of alternative chemicals that protect food safety would agree with some of the goals for sustainable agriculture and protect quality of life. Pesticides obtained from renewables and not derived from petrochemicals would also be in the public interest.