Author: Kari Arnold, PhD, Western Region IR-4 Associate Director, Environmental Toxicology Dept., UC Davis\u00a0<\/p>\n\n\n\n
On\u00a0October 22, 2024,\u00a0EPA\u00a0prohibited the use of\u00a0all products\u00a0containing\u00a0the herbicide\u00a0dimethyl\u00a0tetrachloroterephthalate\u00a0(Dacthal\u00a0or DCPA) under the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA). Although the reason for the cancellation was based in\u00a0science, the decision left many vegetable growers in California\u00a0at a loss for how to manage weeds at planting.\u00a0CDFA\u2019s\u00a0Office of Pesticide Consultation and Analysis<\/a>\u00a0(OPCA)\u00a0has been supporting\u00a0research into herbicide alternatives through the\u00a0IR-4 Project<\/a>, a\u00a0federal research program ensuring that specialty crop farmers have legal access to safe and effective crop protection products as regulations evolve. Through IR-4, OPCA has funded researchers spearheading the effort to register\u00a0pyraflufen-ethyl, an alternative to\u00a0Dacthal.\u00a0<\/p>\n\n\n\n EPA\u2019s cancellation came in response to robust studies\u00a0demonstrating\u00a0thyroid toxicity related to unborn babies of mothers exposed to\u00a0Dacthal\u00a0via handling or working in areas\u00a0where\u00a0it\u00a0was recently applied.\u00a0Prior to cancellation,\u00a0Dacthal\u00a0filled a niche\u00a0use pattern most herbicides\u00a0couldn\u2019t.\u00a0As a \u201cpre-emergent\u201d\u00a0herbicide, it could\u00a0limit\u00a0the\u00a0emergence of existing weed seed populations in the soil.\u00a0Dacthal\u00a0provided this type of protection long enough for a vegetable crop canopy to grow in, but with little\u00a0to no\u00a0injury to the various crops listed\u00a0allowed to use it.\u00a0This\u00a0unique\u00a0capability made many vegetable crops\u00a0reliant\u00a0on\u00a0Dacthal\u00a0as an integral step in their\u00a0Integrated Pest\/Weed\u00a0Management\u00a0(often referred to as\u00a0IPM)\u00a0Program.\u00a0<\/p>\n\n\n\n Steven Fennimore, a retired UC Davis Professor of Cooperative Extension, invited me down in early 2023 to visit his USDA Salinas station weed management studies. While walking to the trials, he remarked that many specialty crops have been reliant upon the same herbicide chemistries for 60 years, and that we need to see if there are applicable alternatives. Part of Steven\u2019s career consisted of collaborations with registrants and IR-4 to broaden the range of options for vegetable growers to accomplish that goal. In terms of Dacthal alternatives, pyraflufen-ethyl was one material of interest. Although this is a contact herbicide, meaning it must contact the weeds to work and cannot be used before weeds emergeSteven and the registrant, Nichino America Inc., had been testing varying rates and application times to determine an acceptable crop injury use pattern for an over-the-top application to onions and garlic. If successful, this material could control early emerging weed populations during the initial stages of crop development. <\/p>\n\n\n\n Although there was till on-going research at that time, I encouraged Steven to submit the request in 2023. With support from CDFA-OPCA, the registrant, and Western Growers, submission was prioritized at the IR-4 Food Use Workshop and moved forward for the 2024 field research season. Given our current timeline, the product should be available to growers by 2030. <\/p>\n","protected":false},"excerpt":{"rendered":" Author: Kari Arnold, PhD, Western Region IR-4 Associate Director, Environmental Toxicology Dept., UC Davis\u00a0 On\u00a0October 22, 2024,\u00a0EPA\u00a0prohibited the use of\u00a0all products\u00a0containing\u00a0the herbicide\u00a0dimethyl\u00a0tetrachloroterephthalate\u00a0(Dacthal\u00a0or DCPA) under the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA). Although the reason for the cancellation was based in\u00a0science, the decision left many vegetable growers in California\u00a0at a loss for how to manage … Continue reading An Alternative to\u00a0Dacthal\u00a0<\/span>