Tomato Diseases: How To Fight Buckeye Rot

Tomato Diseases: How To Fight Buckeye Rot

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

tomato stakes and plants with text overlay tomato gardening tips how to prevent buckeye rot

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