Alternatives to EBDC fungicides in grapes

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.  

Fungicide supplies are tightening due to increased demand for fungicides in the United States and other countries. In addition, a plant that produced Dithane was shut down by Dow AgroSciences and the supply of the fungicide Pristine has also been reduced by BASF. In addition, rising fossil fuel costs have increased the cost of producing fungicides. The shortage may already be noticeable as fungicides are harder to obtain and also more expensive. Unfortunately, these developments will definitely affect fungicide choices for grape growers. Alternatives to Dithane are Penncozeb, Manzate, Ziram, and Captan. All of these are broad spectrum fungicides that have more or less the same spectrum of activity against grape diseases, including Phomopsis cane and leaf spot, black rot, and downy mildew. I would expect Penncozeb and Manzate to be similar to Dithane. Ziram is rated as moderately good against Phomopsis, black rot, and downy mildew. Captan is rated as very good against downy mildew, moderately good against Phomopsis cane and leaf spot and moderate against black rot.

Whereas Captan was not allowed to be used on juice grapes grown for Welch’s previously, the National Grape Cooperative has now approved use of Captan before bloom on juice grapes to ease any fungicide shortage that growers may be experiencing. Wine grape growers do not have any restrictions on Captan other than what the label indicates. Growers will have to decide what the most cost-effective fungicide options are this growing season. As far as Captan is concerned, there are several formulations available, including Captan 50 WP and Captan 80 WDG. Our experience in blueberries is that the 80WDG formulation is easier to work with and works as well as or better than the 50 WP formulation. The label for Captan 80WDG for instance, suggests a use rate of 1.25-2.5 lb in 20-200 gallons of water per acre. Captan may be applied up to the day of harvest. However, the REI is 72 hours.

Another good option for early-season disease control is phosphorous acids, such as ProPhyt and Phostrol. These fungicides have good to excellent activity against Phomopsis and downy mildew and are moderately good against black rot: three pt per acre is a good rate for effective disease control. Advantages of phosphorous acids are that they are systemic and therefore rainfast once dry, and they are relatively inexpensive. For the past five years, phosphorous acids have shown good efficacy against Phomopsis and downy mildew in small plot field trials in vineyards in Michigan. Phosphorous acids can also be used to tankmix with a half rate of Dithane or Ziram. This way, the amount and cost of these products can be reduced.

Dr. Schilder’s work is funded in part by MSU‘s AgBioResearch.

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