Late Blight was confirmed in the Tulelake Lease Lands last week. It's been over 15 years since the last reported case of late blight in Tulelake. All growers should be on high alert as this is a devastating disease that can wipe out an entire field in a short period of time. Late blight spreads extremely quickly and few varieties are resistant to the disease. Brian Charlton put together an excellent write-up on late blight in his Friday issue of Potato Bytes. Brian's article is attached to this post and I encourage all potato growers to read it carefully. As an update to Brian's article only 2 fields that sit adjacent to one another on the east side of the lease lands have confirmation of the disease. The grower and PCA are following appropriate steps to manage the disease and they are doing everything possible to prevent spread. I strongly encourage Tulelake growers to consider preventative fungicide applications, especially growers in the lease lands. As Brian mentioned, thunderstorms and wind can spread spores over long distances, and current environmental conditions are favorable for the disease. Below are some points I think are very important to consider when protecting fields from late blight.
- If you find disease symptoms that you suspect are late blight, call your PCA or local extension agent immediately to get confirmation of the disease.
- If you walk or drive equipment in diseased areas, make sure you wash clothing and equipment before going to other potato fields to prevent spread.
- Fungicides work best when applied BEFORE infection, and they need to be applied every 7 to 14 days until the end of the growing season. Read the label or consult your PCA for application instructions.
- Chlorothalonil (Bravo) and EBDC fungicides such as mancozeb (Manzate) are two economical fungicide choices that provide protection from late blight when applied before infection occurs. They can be applied alone or tank-mixed with compatible fungicides.
- Curzate, Tanos, Omega, Ranman, Revus Top, Forum, Gavel, Zampro, and Zing also provide good protection from late blight. These products can be more effective in reducing the tuber blight phase of late blight than standard protectants like Bravo and Manzate. Keep in mind some of these fungicides are pre-packaged mixes of multiple fungicides such as Tanos (famoxate + curzate) and Revus Top (mandipropamid + difenoconazole).
- Endura and Luna Tranquility are effective on early blight and white mold, but they are NOT effective on late blight.
- University research has shown chemigation and aerial application are both effective fungicide application methods for late blight.
- Some copper products have organic certification approval and can provide late blight protection for organic growers.
Brian and I will be providing more information on late blight management in the near future. Feel free to call Brian Charlton at OSU KBREC or Rob Wilson at UC IREC (530-667-5117) for information on identification and management of late blight.