I just received a phone call from our plant pathologist, Dr. Kelly Ivors. Late blight has been confirmed in a commercial tomato field in western North Carolina. Now is the time to start protecting your tomatoes. If you are a conventional grower, you can access the tomato spray guides that Kelly has prepared for recommendations.
If you are an organic grower, the product that is most effective is copper. If you are certified organic, please check with your certifier to make sure that you can use copper and how frequently. Kelly recommends that if possible, your first spray should be copper. You can then rotate with other products such as Regalia, Serenade, Sporatec, and Oxidate. eOrganic has an excellent article on Organic Management of Late Blight. There is also a webinar for Late Blight Management on Organic Farms and one for Late Blight Control in Your Organic Garden.
More information from Dr. Kelly Ivors. She is sending this out to growers and it will be posted as a Pest News Alert:
Late blight confirmed on tomatoes in WNC
Table 3-55 of the SE Vegetable Crop Handbook provides efficacy ratings against this disease. If you do not have a hard copy of the handbook, you can access it online