Target spot has been a little later this year than it was last year but we are beginning to find the disease in area cotton fields. Here is a picture of a target spot lesion on a cotton leaf:
Here are some common questions that I have been receiving regarding Target spot in the recent days and the answer to those questions:
Question 1: Do I need to spray my cotton for Target Spot?
Answer 1: It depends. Some fields may need treatment as a result of Target Spot and others will not. My suggestion would be that growers do not make entire cotton acreage decisions in regards to spraying for this disease, but rather determine the need for a fungicide treatment on a field by field basis using proper scouting techniques.
Question 2: Which fields am I more likely to find Target Spot becoming a problem?
Answer 2: Target spot is more likely to be found in fields that have one or more of the following factors.
- Field History. Target spot is likely to occur again in fields where it has been severe in the past if environmental conditions are favorable.
- Rank cotton growth. The development and spread of target spot seems closely tied to extended periods of leaf wetness. Foliage within the dense canopy of cotton stays wet longer and is thus more prone to target spot.
- Irrigation. As above, irrigation can both improve the growth of the cotton plants and extend periods of leaf wetness, thereby increasing the risk to target spot.
- Extended periods of rainfall and cloudy weather. Such conditions create conditions where disease is favored.
Question 3: If I find Target Spot in my cotton field does that mean that I should treat that field with a fungicide?
Answer 3: Not necessarily, but it definitely increases the likelihood that a fungicide treatment may be warranted. Growers need to consider the age of the crop, the risk to the disease (see answer 2), and the presence of the disease before applying a fungicide. A cotton crop that is 6+ weeks into bloom will most likely not need a fungicide application. Data has shown no reliable increase in yield from a fungicide application when made after that growth stage. However, if a small amount of disease is detected in a cotton field that is still in the first few weeks of bloom, growers should consider applying a fungicide before the disease becomes established in the crop, before significant defoliation occurs in the lower portion of the plant, and before the canopy of the cotton foliage closes preventing appropriate coverage of the lower cotton leaves.
Question 4: Ok, I have decided to treat my cotton field with a fungicide for Target Spot. What fungicide do I use?
Answer 4: Growers need to consider using either Headline, Quadris, or Twinline fungicides for the management of Target Spot in Georgia cotton.
If you have other questions about Target Spot in Cotton, contact your local extension agent.