This year has been very wet. We’ve received more cumulative rainfall than we did in 2018 and 2019 through July 1st. Rainfall creates good conditions for a number of different plant diseases. Let’s talk about fungal diseases.
A useful tool for understanding why plant diseases occur is the plant disease triangle. In one corner is plant susceptibility. Susceptibility is predetermined by the plant’s physiology. The second corner of the triangle is the pathogen. It may seem like a no-brainer, but the disease causing pathogen must be present for plants to get sick. The third corner is a favorable environment for the disease to occur. Most diseases like wet conditions, which is why all the rain we’ve been getting can be problematic. If any one of the corners is missing from the disease triangle then disease will not be present in your plants.
Root rots are a problematic disease in Georgia. They love humid, wet conditions, with poorly drained soils. Root rots do most of their damage below the soil line so they may not be obvious at first. Some symptoms to look out for are wilting leaves, yellowing leaves, and poor growth. Root rots attack the roots, decreasing the plant’s ability to uptake water and nutrients. Incorporating organic matter into your soil and reducing plant stress will make a less favorable environment for root rots.
Fungal leaf spots covers a wide range of plant diseases that are often specific to certain plants. Symptoms are small spots on leaves that have tan or gray centers, and dark brown to purple margins. Fungal leaf spots survive on fallen plant debris, so it’s important to remove debris after it’s fallen to keep your area sanitary. Leaf spots also like high humidity. Pruning your plants to increase air flow can help reduce the risk of disease. If you are irrigating your plants try to do it in the morning so that the foliage has time to dry off by the nighttime. Wet, cool leaves is a like an all you can eat buffet to fungal leaf spots.
Rusts are easily identified by the raised pustules on the undersides of the leaves. The pustules will break open and release an orangey powder. Keeping leaves dry and removing infected leaves will help keep disease pressure down.
Finally, Botrytis is a specific disease that loves wet, dead plant material. Quick removal of dead flowers or leaves will keep Botrytis in check. Botrytis will usually only be a problem if a plant is wounded or if air flow is poor.
There are many more types of plants diseases out there, and a variety of different pathogens within the diseases that I’ve described. Removing infected leaves and branches, increasing air circulation, and well drained soils are the best tools against fungal diseases. There are many fungicides that can be used to control fungal diseases. However, proper identification of the fungus so that the correct fungicide is used is highly important.
If you have questions about diseases on your plants contact your County Extension Office or email me at Jacob.Williams@uga.edu.
The Union County Extension Office has a new drop box in place on at the Northeast entrance of the Union County Civic Center. The box has a UGA Extension logo on it. You can drop water and soil samples along with payment in this drop box to increase social distancing.