Grow Your Tomatoes
Start Growing: • Home • Grow From Seed • Store-Bought Plants • Container Growing • In the Garden • Tomato Pests • Tomato Diseases • Heirloom or Hybrid • Popular Varieties • Companion Planting • Fertilizers • Grow Lights • Saving Your Seeds • Contact	Tomato diseases and disorders These are some diseases I have documented myself, as well as a link to additional disease info and photos. Late Blight Late blight is encouraged by cool, wet weather conditions and severe cases of it can kill crops of tomatoes. Common symptoms are brown areas on fruit, brown areas on the stem, and gray-brown lesions on the leaves. The brown rot on the fruit is not the same as blossom-end rot and may appear similar to buckeye rot. Blossom-end rot affects only the blossom end of the fruit, while late blight can cause rot on any part of the fruit. Buckeye rot is caused by soil contacting the fruit, and won't be found higher on the plant. Click image for full size. The brown areas on the stems (not shown) are common on late blight-infected tomatoes. Leaf lesions may have a very fine, white "fuzz" growing on them and the affected leaves will eventually die out. Late blight is also found on other plants in the same family as tomatoes. It can infect and devastate crops of potatoes, and it can also affect peppers, eggplant, and wild plants such as nightshade, ground cherry, etc. Tomatoes and potatoes seem to be affected the most by late blight. In the spring of 2009, shipments of Bonnie^® tomato plants infected with late blight were sent across the US to thousands of stores. Favorable conditions for the blight, especially in the Northeast, promoted rapid growth and spread of the disease. Late blight spores may be killed in the ground overwinter, if the ground freezes. Airborne spores do not last long, especially in dry or hot weather. The airborne spores can travel with the wind and can be transmitted to other plants by wind and sometimes by rain. Any infected tomato plants must be pulled, and sealed in an airtight trash bag and disposed of in the trash. Do not compost any infected tomato plants! Damping Off Young seedlings may die from one or more species of fungus that causes the plant to collapse. A section of the stem wilts or rots just above the soil level, causing the entire seedling to topple over and die. The disease can be soil-borne and may be transmitted by watering the plants if water splashes up onto the stem. It is also more prominent in cooler weather. To help prevent this disease, use sterilized soil-less seed starting mix, and water the mix carefully and don't splash the stems. (Bottom watering is preferred by some as a better way to water seedlings.) Some people like to give seedlings "cold treatment," a period of a couple weeks long with lowered temperatures, which helps develop stronger plants. The period of colder temperatures increases risk of damping off, but if other preventative measures are taken, you can grow seedlings in cooler temps without much worry. Blossom-end rot (BER) Blossom end rot is not a true disease; it happens when tomatoes are do not receive enough water. While overwatering can cause excessive cracks in tomatoes, underwatering can cause blossom-end rot. The rotten patch starts from the blossom end (bottom) of the tomato. If it gets bad enough, it can consume half of the tomato. I have only had mild cases of BER because I frequently water. Some varieties are more prone to BER than others. Cherry tomatoes, for example, rarely get BER if at all. Plum tomatoes, such as Roma, on the other hand, are much more suceptible to BER. If you have tomatoes with blossom-end rot, you can eat the undamaged portion of the fruit. BER does not render the fruit inedible unless it has consumed a substantial portion of the fruit. BER like that in the photo above is mild and can be sliced off. Catfacing Also not a disease, catfacing is common when temperatures are cool. It happens as the bud is just forming. Catfacing is not noticeable till a fruit is set. The fruit is often misshapen at the blossom end, with creases or folds and tough, brown scarring. The above picture is of some severe catfacing that happened to one of my White Wonder heirloom tomatoes. Unlike the tomato in the picture above, catfacing is usually less severe and may appear as creases and/or indentations in the blossom end surrounded by thin brown scarring. Like blossom-end rot, catfacing is more likely in some varieties than in others. To avoid catfacing, pick off flowers during cool weather and/or select varieties that aren't as suceptible to catfacing. Tomatoes that are not severely catfaced may be eaten; catfacing does not effect edibility of tomatoes. Sun Scald Not a disease. It can happen to green or ripe tomatoes. When the fruit are exposed to direct, strong sun for extended periods of time, they will develop sun scald. It can take days for the scald to appear, but continuous sun exposure will eventually create yellow or white, bleached areas on the fruit that may be slightly shriveled. Sun scald happens when there isn't enough leaf cover to shade the fruit. Heavily pruned plants, or diseases that kill the leaves, can result in sun scald because of loss of leaves. Artificial shade (paper plates, fabric, etc) can be used to protect tomatoes from the sun. Cloudy Spot This disorer is caused by stink bugs. The immature and adult bugs pierce the fruit much like a mosquito would do to a person. The result is often yellow or otherwise pale-colored irregular spots under the skin of the fruit. I have found tomatoes with mild to moderate cases of cloudy spot to be fine for eating. The damage is usually just below the surface of the skin, and from my experience, the fruit can be eaten. If you ever see stink bugs on your tomato plants, kill them right away. Don't use insecticide spray on or near your tomatoes - pick the bugs off by hand or crush them with pliers. Dodder Click image for full size. This parasitic plant is not common on tomatoes. However, it is possible that it may grow in your area and seed could be dispersed and reach your garden. It's unlikely that you'll ever see this in your garden unless it's a big problem in your area. Dodder is an orange or yellow, parasitic vine that does not photosynthesize. Instead, it steals the nutrients it needs from host plants, by winding around and attaching to the stems. When dodder sprouts from seed, it must find a hostplant within a few days or it will die. When it finds and attaches to a host, it detaches from its roots and continues to grow on its host plant without roots. Dodder is an annual plant that will die out during the winter, but the seeds can survive a few years in the soil. The leaves are almost nonexistent - they are merely bumps at the stem nodes. Dodder flowers mid to late summer. It can only feed on plants that are dicotyledons, which includes tomatoes. Grasses are monocotyledons and are not host to dodder. If you ever were to see a yellow or orange, string-like plant sprout in your garden, you would need to pull it up immediately before it could reach your tomatoes. Even if you detach dodder from its host plant, it can re-grow from haustoria that are left inside the stem. Dodder haustoria are basically parasitic roots that grow inside the host plant's vascular systems and suck nutrietns from the host. They cannot be removed simply by pulling, and will re-grow if the main dodder stems are removed. If you ever find yourself in or around a patch of dodder during late summer, you should change clothes before going near your tomatoes to prevent stray dodder seed from spreading to your garden. In California, Dodder has caused some problems for commercial tomato growers. But like I said, it usually doesn't invade home gardens. Other diseases and disorders Click here for a Web page with plenty of photos to help diagnose many common tomato diseases and disorders.
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Grow Your Tomatoes

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Tomato diseases and disorders

These are some diseases I have documented myself, as well as a link to additional disease info and photos.

Late Blight

Late blight is encouraged by cool, wet weather conditions and severe cases of it can kill crops of tomatoes. Common symptoms are brown areas on fruit, brown areas on the stem, and gray-brown lesions on the leaves.

The brown rot on the fruit is not the same as blossom-end rot and may appear similar to buckeye rot. Blossom-end rot affects only the blossom end of the fruit, while late blight can cause rot on any part of the fruit. Buckeye rot is caused by soil contacting the fruit, and won't be found higher on the plant.

Late blight leaf lesion on tomato leaf. Click for larger version

Click image for full size.

The brown areas on the stems (not shown) are common on late blight-infected tomatoes. Leaf lesions may have a very fine, white "fuzz" growing on them and the affected leaves will eventually die out.

Late blight is also found on other plants in the same family as tomatoes. It can infect and devastate crops of potatoes, and it can also affect peppers, eggplant, and wild plants such as nightshade, ground cherry, etc. Tomatoes and potatoes seem to be affected the most by late blight.

In the spring of 2009, shipments of Bonnie^® tomato plants infected with late blight were sent across the US to thousands of stores. Favorable conditions for the blight, especially in the Northeast, promoted rapid growth and spread of the disease.

Late blight spores may be killed in the ground overwinter, if the ground freezes. Airborne spores do not last long, especially in dry or hot weather. The airborne spores can travel with the wind and can be transmitted to other plants by wind and sometimes by rain. Any infected tomato plants must be pulled, and sealed in an airtight trash bag and disposed of in the trash. Do not compost any infected tomato plants!

Damping Off

Young seedlings may die from one or more species of fungus that causes the plant to collapse. A section of the stem wilts or rots just above the soil level, causing the entire seedling to topple over and die.

The disease can be soil-borne and may be transmitted by watering the plants if water splashes up onto the stem. It is also more prominent in cooler weather. To help prevent this disease, use sterilized soil-less seed starting mix, and water the mix carefully and don't splash the stems. (Bottom watering is preferred by some as a better way to water seedlings.)

Some people like to give seedlings "cold treatment," a period of a couple weeks long with lowered temperatures, which helps develop stronger plants. The period of colder temperatures increases risk of damping off, but if other preventative measures are taken, you can grow seedlings in cooler temps without much worry.

Blossom-end rot (BER)

Blossom end rot is not a true disease; it happens when tomatoes are do not receive enough water. While overwatering can cause excessive cracks in tomatoes, underwatering can cause blossom-end rot.

The rotten patch starts from the blossom end (bottom) of the tomato. If it gets bad enough, it can consume half of the tomato. I have only had mild cases of BER because I frequently water.

Some varieties are more prone to BER than others. Cherry tomatoes, for example, rarely get BER if at all. Plum tomatoes, such as Roma, on the other hand, are much more suceptible to BER.

If you have tomatoes with blossom-end rot, you can eat the undamaged portion of the fruit. BER does not render the fruit inedible unless it has consumed a substantial portion of the fruit. BER like that in the photo above is mild and can be sliced off.

Catfacing

An unripe, catfaced tomato will be edible when ripe, but the damaged areas may need to be cut off.

Also not a disease, catfacing is common when temperatures are cool. It happens as the bud is just forming. Catfacing is not noticeable till a fruit is set. The fruit is often misshapen at the blossom end, with creases or folds and tough, brown scarring. The above picture is of some severe catfacing that happened to one of my White Wonder heirloom tomatoes.

Unlike the tomato in the picture above, catfacing is usually less severe and may appear as creases and/or indentations in the blossom end surrounded by thin brown scarring.

Like blossom-end rot, catfacing is more likely in some varieties than in others. To avoid catfacing, pick off flowers during cool weather and/or select varieties that aren't as suceptible to catfacing. Tomatoes that are not severely catfaced may be eaten; catfacing does not effect edibility of tomatoes.

Sun Scald

Not a disease. It can happen to green or ripe tomatoes. When the fruit are exposed to direct, strong sun for extended periods of time, they will develop sun scald. It can take days for the scald to appear, but continuous sun exposure will eventually create yellow or white, bleached areas on the fruit that may be slightly shriveled. Sun scald happens when there isn't enough leaf cover to shade the fruit. Heavily pruned plants, or diseases that kill the leaves, can result in sun scald because of loss of leaves. Artificial shade (paper plates, fabric, etc) can be used to protect tomatoes from the sun.

Cloudy Spot

This disorer is caused by stink bugs. The immature and adult bugs pierce the fruit much like a mosquito would do to a person. The result is often yellow or otherwise pale-colored irregular spots under the skin of the fruit. I have found tomatoes with mild to moderate cases of cloudy spot to be fine for eating. The damage is usually just below the surface of the skin, and from my experience, the fruit can be eaten.

If you ever see stink bugs on your tomato plants, kill them right away. Don't use insecticide spray on or near your tomatoes - pick the bugs off by hand or crush them with pliers.

Dodder

Click image for full size.

This parasitic plant is not common on tomatoes. However, it is possible that it may grow in your area and seed could be dispersed and reach your garden. It's unlikely that you'll ever see this in your garden unless it's a big problem in your area.

Dodder is an orange or yellow, parasitic vine that does not photosynthesize. Instead, it steals the nutrients it needs from host plants, by winding around and attaching to the stems. When dodder sprouts from seed, it must find a hostplant within a few days or it will die. When it finds and attaches to a host, it detaches from its roots and continues to grow on its host plant without roots.

Dodder is an annual plant that will die out during the winter, but the seeds can survive a few years in the soil. The leaves are almost nonexistent - they are merely bumps at the stem nodes. Dodder flowers mid to late summer. It can only feed on plants that are dicotyledons, which includes tomatoes. Grasses are monocotyledons and are not host to dodder.

If you ever were to see a yellow or orange, string-like plant sprout in your garden, you would need to pull it up immediately before it could reach your tomatoes. Even if you detach dodder from its host plant, it can re-grow from haustoria that are left inside the stem. Dodder haustoria are basically parasitic roots that grow inside the host plant's vascular systems and suck nutrietns from the host. They cannot be removed simply by pulling, and will re-grow if the main dodder stems are removed.

If you ever find yourself in or around a patch of dodder during late summer, you should change clothes before going near your tomatoes to prevent stray dodder seed from spreading to your garden.

In California, Dodder has caused some problems for commercial tomato growers. But like I said, it usually doesn't invade home gardens.

Other diseases and disorders

Click here for a Web page with plenty of photos to help diagnose many common tomato diseases and disorders.