Multiple sources are reporting that there will be a shortage of the fungicide chlorothalonil, which is widely used in peanut and vegetable crops, according to Austin Hagan, Auburn University Extension plant pathologist.

The fungicide is marketed under numerous trade names such as but not limited to Bravo WeatherStik, Bravo Ultrex, Echo 720, Equus 720, Chloronil, Chlorothalonil 720 and others. “Issues with product formulation are the likely cause of chlorothalonil shortage but I’m not sure it refers to U.S. or foreign sourced material,” says Hagan. “There are also chlorothalonil combination products such as Muscle ADV and Echo Eminent Co-Pack that are available for use in peanuts, but supplies of these products are also likely to be limited.”

In peanuts, says Hagan, chlorothalonil is a critical broad-spectrum anchor in nearly all fungicide programs due its good activity at relatively low cost against early and late leaf spot diseases as well as peanut rust. It also has value as a resistance management tool with strobilurin and triazole fungicides.

“Due to the existing risk of resistance-related control failures for triazole fungicides like tebuconazole, metconazole (Quash), and propiconazole (Bumper, Propimax, Tilt) as well as potential for risk for resistance-related control failures with the strobilurin fungicides azoxystrobin (Abound 2SC and Azaka), pyraclostrobin (Headline 2.09SC), and fluoxastrobin (Evito), total application numbers of these fungicides is limited to half or less of the total number of fungicide applications in a peanut disease control program,” says Hagan.

With the limitations to the use of the above systemic, single-site fungicides, there are not a lot of broad-spectrum alternatives to chlorothalonil in peanuts or other crops with a similarly high efficacy level, says Hagan, but there are some options for stretching chlorothalonil supplies.

“Reducing chlorothalonil application rates from 1 ½  to 1 pints per acre is a possibility. Field trials over the past few years have shown that there’s little drop off in leaf spot control at chlorothalonil application rates of 1 pint versus 1 ½ pints per acre (0.9 vs. 1.4 pounds per acre for Bravo Ultrex).

“Going with reduced chlorothalonil rates season-long will be much riskier where peanuts are cropped every year or every second year, and irrigated peanuts regardless of location, as well as high rainfall areas such as Baldwin, Mobile and Escambia counties. A tropical storm also can trigger a leaf spot or rust control failure when using reduced rates or numbers of applications of chlorothalonil,” says Hagan.