All the Master Gardeners in the Tri-County area got an e-mail recently that should have some folks worried. I know it does me. Apparently, because of the weird weather we have been having there have been cases of Anthracnose fruit rot found.
This major tomato disease was first noted in 1879. It is now found in North America, Europe, and Asia. The disease results in a fruit rot which reduces the
quality and yield of tomatoes. Colletotrichum coccodes is the plant pathogen that causes it. Many common weeds and crop plants are hosts and they become inoculum reservoirs. The pathogen can overwinter on seed, in the soil, and in infected plant debris. This is a good place to stress sanitation in your garden. ALWAYS, keep leaf and dropped fruit litter cleaned up.
Symptoms of Anthracnose appear first as small, circular, slightly sunken lesions on the surface of ripening fruits. Most infection takes place on ripe or over-ripe fruit. The spots quickly enlarge, become deeply depressed, and develop a water-soaked appearance directly beneath the skin (epidermis) of the fruit.
The fungus forms small, dark survival structures called sclerotia (a compact mass of hardened fungal mycelium containing food reserves) in the centers of the fruit spots. These sclerotia can survive in soil for up to three years and cause infections either directly or by producing secondary spores. Green fruit are infected but do not show symptoms until ripening. The fungus then spreads from infected to healthy fruit as spores are splashed by rain, overhead irrigation, or by picking fruit from wet plants.
To control it, you need to harvest fruit as soon as possible after ripening. Make sure you remove infected or rotting fruits from the plant as soon as possible. Avoid excessive overhead irrigation or use drip irrigation to reduce moisture levels on fruit and humidity in the plant canopy. Fungicide sprays used to control leaf diseases help reduce losses from Anthracnose when applied on a regular schedule and in a manner to achieve thorough fruit coverage. Mancozeb or Chlorothaonil are two examples, I am sure there are others. Always follow label directions! There are no organic controls that are effective. A three-year rotation may reduce chances for infection. For example, do not plant your tomatoes where peppers, eggplants, potatoes or a previous tomato crop has been grown in at least two years. Using disease-free seed is also recommended. Resistant varieties are available and should be used whenever possible. Allow the proper spacing between your tomato plants and stake them to allow for the proper air circulation.
Here are some pictures of what it looks like:
Just so you know, there are times that you can follow all the recommendations and still get this disease. I removed one of my plants today because I discovered it. I am hoping that the rest of the varieties I am growing are the resistant ones. In the mean time, I will keep an ever vigilant watch for the signs and will try to get some fungicide this week.