Combatting Gray Mold on Tomato Plants: Guide on Identifying, Controlling & Prevention

Our experienced writers spend hours deep researching, considering both scientific and experimental info to bring the insights you can trust.  

This is a comprehensive guide to aid you in understanding the identification, control, and preventive measures of gray mold on tomato plants.

Scroll down for more!

What Is Gray Mold And How Does It Harms Tomato Plants?

Gray Mold is caused by the fungus, Botrytis cinerea which affects many plants, including tomatoes. It affects the dead plant or weak plant tissue and then spreads to living tissue. It is more prevalent in greenhouses.

It will affect the leaves, stems, and buds of the tomato plants.

How To Confirm That Gray Mold Is Troubling Your Tomato Plants?

A typical characteristic to confirm the occurrence of gray mold is a gray fuzzy coating on the plants. You may observe grayish-white spots near a wound. These spots may turn brown, grow to the entire leaf, and cause the leaves to fall.

You may observe grayish webbing on the leaves under highly humid conditions.

Eventually, all parts of the plant, including branches, buds, and flowers, will be affected.

Here is how an infected plant looks like –

Natural Ways To Control Gray Mold On Tomato Plants

Some gardeners have tried neem oil and baking soda to manage gray mold in tomato plants. These may not cure but help to control further spread. But, more research studies are required to confirm their effect.

1. Apply Neem Oil

Neem oil can be used to prevent or kill fungi on your plants. It has lesser side effects on beneficial insects and humans.

  • Dilute neem oil– Purchase organic neem oil and dilute it with water. Shake well and transfer to a spray bottle.
  • Spray on susceptible plants– Spray on the affected and susceptible plants. Repeat application every seven to 14 days. Avoid spraying in the hot sun to prevent the burning of leaves.

Here is a video on applying neem oil to control diseases:

2. Spray Baking Soda + Vegetable Oil

Baking soda, also known as sodium bicarbonate has shown antifungal activity on the molds. Vegetable helps in sticking baking soda to the leaves.

More studies are required to confirm the effects.

  • Prepare baking soda+ vegetable oil spray– Mix one teaspoon of baking soda and 1 ml of vegetable oil in a gallon of water. Mix well.
  • Spray on the affected foliage– Spray on the affected parts of the plant. It is preferable to spray in the early morning or evening.

Check out this video on controlling gray mold using baking soda:

Physical Ways To Control Gray Mold On Tomato Plants

The best way to control gray mold spreading is by pruning the infected parts of the plant. Also, provide good air circulation around the plants to manage the disease.

Method 1- Prune The Infected Parts Of The Plant

Pruning the infected parts of the plants will help to control the spread of gray mold to the other parts.

Also, it may help in improving air circulation between plants. It minimizes the size of stem scar which can further reduce the incidence of grey mold.

  • Remove the infected parts– Observe the infected parts. Wear gloves and remove the infected stems, leaves, and fruit using sterilized tools.
  • Place fan- You may place a small clip-on fan to improve airflow especially if grown indoors.
  • Destroy them– Clean up the infected parts and place them in a plastic bag for disposal. Do not toss them in a compost pile.

Chemical Ways To Control Gray Mold On Tomato Plants

Chemical fungicides are available to control gray mold on tomatoes. Chlorothalonil has shown promise as a fungicide but is recently banned by EPA due to its harmful effects.

So, chemical fungicides should be used as a last option once cultural practices have been implemented.

Method 1- Spray Liquid Copper

Copper fungicides can be effective against gray mold especially applied to the plants before they are infected with pathogen spores. But, the excess application may lead to productivity losses.

  • Prepare the fungicide spray– Check on the product label for when and how to dilute the concentrate. Dilute the concentrate and transfer it to a spray bottle.
  • Apply on the infected foliage– Apply on the infected foliage. It is better to spray in the late evening to avoid affecting pollinating insects. Repeat after 7-10 days.

How To Prevent Gray Mold In Tomato Plants?

The preventive measures to control gray mold in tomato plants involve reducing the amount of moisture on your plants, following appropriate sanitation practices, and ensuring proper spacing between the plants to allow for good airflow.

1. Follow Good Sanitation Practices

Collect and remove the infected plants immediately after harvest. Do not throw them in a compost pile. Also, sanitize the tools after use with one part of bleach to four parts of water.

2. Allow Good Ventilation

Gray mold survives in shaded and crowded areas. So, provide enough spacing between tomato plants. It helps in providing adequate ventilation and preventing gray mold in tomato plants.

3. Inspect New Plants

If you are transplanting new seedlings, keep them quarantined for some time. It helps in inspecting for fungal spores and prevents spreading them to the garden.

Method 4- Practice Good Watering Technique

Ensure that you are watering in the morning to give them time to dry out. Also, avoid overhead watering of leaves to avoid the spread of fungi by splashing.

You may also install a drip line or use a soaker hose to prevent the disease.

Also, mulch around the plants to prevent contact of plant with the soil and prevent spores from being splashed onto the plants.

What Causes Gray Mold Attacks In Tomato Plants?

Gray Mold attacks tomato plants if there is high humidity, cool temperatures (60-7oF), and a damp environment. Also, it is prominent when there is rain, heavy dew, or fog before harvesting. It also infiltrates through injured tomatoes.

It can also spread via wind, and the spores will stay in the host plants long.

Frequently Asked Questions

What are the plants commonly affected by gray mold?

Gray mold affects flowers with thick succulent petals, including begonias, peonies, and geraniums. It also affects a variety of fruits, vegetables, and berries especially after being harvested and stored in cool areas. It can be seen in apples, strawberries, peaches, plums, raspberries, tomatoes, and beans.

Can you use chlorothalonil for treating gray mold?

Chlorothalonil is a broad-spectrum, non-spectrum fungicide that has been used to control gray mold. But, EPA recently banned them for use in home gardens as it is acutely toxic if inhaled. Long-term exposure may cause kidney damage and is a possible human carcinogen.

How to save a plant with gray mold?

Once you spot gray mold on your plant, remove the diseased leaves and branches. Also, prune the affected branches about four to six inches below the infection with a clean cut. It will help in saving the plant. But, it may be difficult to save a heavily infected plant.

Can you control gray mold on tomato plants using biological agents?

Some studies have shown that microbial agents can be used to manage gray mold through competition for nutrients, parasitism, and plant defense.  A study showed that M.anisopliae can be used as a biocontrol agent against tomato gray mold in the greenhouse. Further studies are warranted.


Hopefully, this guide has provided you with many measures to tackle gray mold affecting tomato plants at your home.

Have you had any problems with gray mold in your tomatoes? If yes, let me know your experiences in dealing with it!

Do share the guide with your friends and family to help them out too!

Check out information on other tomato diseases here>