Disease Management in Winter Greens

Libbie Johnson
Extension Agent II Agriculture, Aquaculture
Escambia County
libbiej@ufl.edu

For many in north Florida, cooler weather means it’s time to grow a winter garden.  The promise of less insect and disease pressure are two good reasons to get some vegetables growing, but not even the cold weather will keep all pests away.  Greens like turnip, mustard, and collard are easy crops to produce from seed or by transplant in a home garden, but even these crops can develop some diseases. 

Anthracnose on greens Photo Credits: David B. Langston, University of Georgia, bugwood.org

One of the most widely seen fungal diseases on turnip and mustard greens is anthracnose (Colletotrichum).  Anthracnose tends to be a problem when temperatures are in the mid-70s to mid-80s and there is plenty of moisture.  Anthracnose does not disguise itself very well—it shows up on leaves as small, pale gray to straw colored circular spots.  It will show up on stalks as elongated, sunken, gray to brown spots that usually have a black border.       

Cercospora leaf spot on a green Photo Credits: David B. Langston, University of Georgia, bugwood.org

Cercospora leaf spot, Cercospora brassici­cola, also affects greens, but this disease prefers temperatures in the mid 50s to mid 60s and moist conditions.  This disease is also called frogeye leaf spot, and it shows up as spots that can angular or circular and the color of the spots can range from pale green, gray, or white.  In severe cases, if the disease is left untreated, the plants may lose leaves.   

There are a few options to control diseases.  Be it summer or winter, every gardener should practice is sanitation.  Remove any diseased plants, weeds, and any old or volunteer plants.  Starting with a clean slate is ideal.  Secondly, rotate crops.  Try not to plant the same family of vegetables in the same spot repeatedly.  Next, keep overhead sprinkler irrigation at a minimum. Wet leaves are a haven for disease to develop.  If watering is necessary, plan to water in the morning when the leaves will be able to dry relatively quickly.  If all this fails and disease sets in, there are some fungicides that can be used.  Before using any pesticide, check with your local county Extension office to verify the disease and discuss the proper method of controlling the disease.