As we move into the latter part of the cotton season, we are seeing areolate mildew (also called “false mildew”) in our South Carolina crop. Our hot, humid conditions, along with rain showers, have caused this disease to become active and spread in some fields. In most cases, areolate mildew is either absent or at low levels (Figure 1), but I have seen some fields where the infection is severe (Figure 2). In cases where infection in severe, this disease can cause premature defoliation throughout the canopy.
Management of areolate mildew depends on the age of the cotton with regards to defoliation timing. If the crop is more than a month away from defoliation, a fungicide application could help slow the spread of the disease and protect yield. On the other hand, if we are less than a month away from defoliation, a fungicide is probably not needed. Ideally, a fungicide is sprayed when symptoms of the disease first appear in the field. If you would like to spray, there are three fungicides that are considered very good against areolate mildew: Miravis Top, Priaxor, and Revytek. Additionally, Quadris (or generic azoxystrobin products) is expected to do a fair job against areolate mildew.
A take-home message for areolate mildew in South Carolina is to scout your cotton for this disease. The last time we saw significant yield losses from this disease across the state was in 2021; however, losses in particular fields vary year-to-year. If you need help identifying areolate mildew or management recommendations, please contact your county agent.
