by Matt Gibson
About Buckeye Rot
Buckeye rot is a soil borne infectious plant disease that is caused by the fungus Phytophthora parasitica. There are three species of the fungus, P. capsici, P. drechsleri and P. nicotiana var. Parasitica. These species vary by growing locations. Buckeye rot is a common problem in the southeastern and south central United States.
The infection affects tomatoes, eggplants, and peppers, causing damage to the fruit, as well as the plant itself. After prolonged rains and warm, soggy conditions, buckeye rot is known to pop up and damage crops. Usually occurring where the fruit touches the ground, the disease can easily be identified by the distinctive ringed greenish brown stain-like spots that look much like a buckeye, from which the fruit-rotting fungal disease gets its name.
Luckily, buckeye rot, especially for gardeners with small home-gardens, can be avoided by taking a few precautions. Since the disease usually enters the plant by attacking the fruit, where the fruit makes contact with the soil, the goal is to keep the fruit from ever touching the soil. This can easily be achieved by providing a support for your tomato plants, in the form of a trellis, or stake. Gardeners can also lay out a thick layer of mulch around the base of their tomato plants, to put plenty of space (and mulch) between the fruit and the soil.
Causes And Symptoms of Buckeye Rot
The fungus is introduced to the garden through transplants, infected seeds or volunteers that pop up between growing seasons from the previous crop. The disease is known to attack both green and ripe fruit and can spread from plant to plant by splashing rain and surface water.
Fungal spores grow when the soil is above 65 degrees F and soggy. In areas with poor soil drainage, when the area has been exposed to excessive rain, and temperatures between 75 and 85 degrees F, buckeye rot is likely to occur.
Buckeye rot begins on tomatoes as a small brown, wet-looking spot that typically occurs due to the heavy fruits of the plant making contact with the surface of the soil. In the early stages of the infection, the spot is both firm and smooth, but as the spot increases in size and starts to develop its signature alternating rings, the spots become rough and sink in at the spot’s margins, sometimes producing a fungal growth that produces a white, cotton-like fungus.
Treatment and Control of Buckeye Rot
There are a few precautions that can prevent the occurrence of buckeye rot in your garden completely. If you are growing your tomatoes in an area that is prone to warm weather and in soil that has inadequate drainage, you will be more vulnerable to fungal infections. Here are some steps you can take to control buckeye rot in your garden:
- Mulch around the base of your tomato plants to reduce the possibility of direct soil to fruit contact.
- Practice proper crop rotation, rotating where your tomatoes are grown every three to four years.
- Water your plants less often, but deeply, with lots of water, rather than more often with less water.
- Encourage better drainage in your soil by amending with lots of organic material.
- If using containers, use potting soil that is specifically formulated for container gardening.
- Use fungicidal sprays on a regular basis, treating soil before infections occur. Follow the directions on the bottle. Fungicides that will work for buckeye rot should contain one or more of the following ingredients: chlorothalonil, maneb, metalaxyl, or mancozeb.
- Use a soil fumigant to fumigate soil that has become severely infected before reusing that soil or planting anything else in that part of your garden. Fumigants are usually available in liquid or granular form, and should be worked into the soil prior to a deep soaking. Then the soil should be covered with a thick layer of plastic sheeting. Use the directions provided by the manufacturer when attempting a soil fumigation.
Common Questions and Answers About Buckeye Rot
How should I treat for buckeye rot?
Gardeners can treat buckeye rot with cultural controls, such as avoiding excess moisture in the soil (reducing irrigation, using raised beds, increasing soil drainage) and staking or mulching to prevent tomatoes from touching the soil. Fungicides with the active ingredients chlorothalonil, mancozeb, or metalaxyl can also be used to fight buckeye rot, but fungicides have reduced effectiveness against soil-transmitted fungal diseases like buckeye rot. Gardeners should apply these fungicides according to the directions provided by the manufacturer.
Is buckeye rot contagious?
Buckeye rot is contagious between plants. The bacteria behind it spread through splashing water from rainfall and standing water on the surface of the soil. To prevent buckeye rot, reduce standing water in the garden by using raised beds, reducing irrigation, or using soil that offers plenty of drainage. Gardeners can also prevent tomatoes from touching the soil by staking or adding a layer of mulch.
What are the symptoms of buckeye rot?
Buckeye rot begins to show up as small grayish or brown water soaked lesions on green or ripe tomatoes, almost always affecting tomatoes that are touching the soil. The initial lesions spread and enlarge to form concentric rings of alternating light and dark brown. The edges are smooth, and lesions start out firm but, as time progresses, turn softer and eventually decay. Aside from symptoms affecting fruit, buckeye rot can also cause damping off, stem cankers near the soil line, and leaf blight.
What causes buckeye rot?
Three species of Phytophthora cause buckeye rot: P. capsici, P. drechsleri, and P. nicotiana var. parasitica. It is a soilborne disease. Many factors can increase crops’ susceptibility to buckeye rot. These include warm and moist weather, moisture in the soil from frequent rainfall or excess irrigation, high humidity, and low-lying fields. To prevent buckeye rot, gardeners can plant in raised beds, avoid planting where soil is heavy and drains poorly, avoid using compacted soil, use staking or mulching to keep fruit from touching the soil, or rotate to non-solanaceous crops.
What is buckeye rot?
Buckeye rot is a fungal soilborne disease caused by the P. capsici, P. drechsleri, and P. nicotiana var. parasitica species of Phytophthora. It causes gray or brown water soaked lesions on fruit with smooth edges. The lesions are initially firm, but form concentric rings of light and dark discoloration and become softer and eventually decay as the disease progresses. The disease can also cause leaf blight, damping off, and stem cankers near the soil line.
Want to learn more about buckeye rot on tomatoes?
Texas A&M University covers Buckeye Rot
University of Massachusetts Amherst covers Tomato, Buckeye Rot
Gardening Know How covers Buckeye Rot of Tomato Plants
SFGate Homeguides covers How to Avoid Buckeye Rot in Tomatoes
NC State University covers Tomato Diseases: Buckeye Rot
Plantwise Knowledge Bank covers Buckeye Rot on Tomatoes
Alabama Cooperative Extension System covers Buckeye Rot