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Tomato Diseases and Pests

Swarm of Honeybees - A Welcome Guest
Swarm of Honeybees - A Welcome Guest
Being a gardener comes with the understanding that, for the most part, you are in a cooperative relationship with Nature. It's an ongoing relationship of learning to become a more capable manager of the favorable and unfavorable conditions and variables that present themselves.


In the past I've experienced major disease loss (10,000 plants killed by a blight), periodic infestations and ongoing challenges with weather or soil borne diseases and garden pests. However, I've come to a wonderful part of my gardening life.that of acceptance. that I'm just one part of the whole lifecycle process of nature and my environment.

My influence in my gardening practice is only a temporary one and carries with it a responsibility and respect for all other forms of life. Although I've challenged many times, especially by gophers, deer and a variety of bugs and viruses, I've made the personal choice not to poison.

I support sustainable farming practices and a comfortable degree of cooperation with the critters and the pests that enter my garden.or my life.

In the information that follows I hope to be of some assistance in alleviating some of the frustration that comes with identifying a problem, and how best to alleviate the difficulty.whether that means taking action, no action, or learning to accept what you cannot change, or to prepare you for future successful tomato harvests.

I intend to provide you additional information here in the future. I'm hoping you find this information useful and I welcome your feedback. - Gary Ibsen

Blossom End Rot:

Blossom end rot is most often caused by a calcium deficiency, which can be due to an acidic soil, irregular watering and water-logging, or an ongoing high humidity with a low transpiration generally caused by reduced air movement.

Calcium is an essential plant food in the soil.

When there is an excess presence of soluble salts such as ammonium, potassium, magnesium, or sodium the effective concentration of calcium available to the plant decreases more rapidly than that of other salts. Both excessively dry and excessively wet weather can adversely change the ratio of calcium salts.

Heavily pruned tomato plants appear to be more susceptible to blossom end rot.

Advice: On watering: Do not over water your young plants. Once a seedling is established it should be encouraged to develop a deep and extensive root system by stressing the plant slightly by letting it dry slightly. (Watch your plant. It will let you know when to water again.) With a sufficient root system, the plant is more capable of drawing up sufficient nutrition and water.

Give your plants a good watering on the day of planting so the soil becomes nicely saturated. In the first week of planting, water again every couple of days, then extend the period between watering, cutting back to a good deep soaking once a week in the first month. After 2-4 trusses of flowers have set is the time to increase watering. Then water your plants regularly and evenly.Mulching the soil and watering as needed during dry spells should keep the problem in check.

To help avoid problems developing, I suggest encouraging better air circulation under the plant by planting seedlings sufficiently apart to allow for airflow. I usually trim the bottom 16" of each plant of all stems and suckers other than 4-5 main stems. This serves to reduce the relative humidity around the base of the plants.

To help avoid blossom end rot, add some super phosphate fertilizer, fertilizer that is high in phosphorous and low in nitrogen. Work it into your soil before you plant your tomato plants. You can use calcium sulfate, better known as gypsum, in place of the super phosphate. An application of lime may also assist as a side dressing.

Septoria Leaf Spot:

Leaves on the lower branches of tomato plants are typically affected with brown spots, followed by yellowing or browning of the leaves. Wet weather may encourage the disease to progress up the plant.

Advice: Try mulching to help reduce soil splash onto the plant, which can in turn reduce leaf diseases. Lift your plants off the ground. Staked tomatoes will have better air circulation, which will discourage disease.

Also, it's best to remove the infected leaves as soon as you notice them to help reduce spread. I suggest removing the infected plants at the end of the season and also practice a 3-year crop rotation.


Hornworms can eat considerable amounts of foliage off your tomato plants.

Advice: These can be picked off by hand. Your best control is to keep an eye on your plants for invaders.


Sunscald most commonly appears on immature, green fruit. It first shows up as a white or yellow patch on the side of the fruit that faces the sun. Spot usually developes into a blister then forms a grey-white spot with a papery surface.

Advice: Leaf cover is your best protection. Plants that have been properly watered, and nourished have the best chance of growing a lush, protective canopy of leaves. Trellising or cages are best to protect your tomatoes. Don't buy those wimpy conical cages. Your tomato plant will outgrow these in no time.

I suggest tying up your plants in a trellis between stakes or make your own from concrete-reinforcing wire available at lumber yards. Make these cages about 30 inches in diameter and for better stability you may wish to attach each one to a stake driven into the ground. You'll create a dense, protective canopy of foliage if you tuck the leaf stems into the squares of the tomato cage.


This is a very common problem and not easy to correct since this is most commonly caused by the weather. Many tomato varieties will set fruit only within a fairly narrow range of night temperatures. Temps above 55 degrees for at least a portion of the night are required for the first fruit set and night temps above 75 degrees can inhibit fruit set and cause blossom drop. With night temps below 55 the germination is so slow that the blossom may drop before fertilization occurs. Most of the cooler growing region varieties can set fruit at lower temperatures and there are, as well, varieties that will set at temps above 75 degrees at night. Every area has its good and bad years for growing tomatoes that may show up in only portions of the summer. (Like a heat wave could hit for several days and knock the blossoms off.) Advice: In the early spring you can try to increase the night temperatures by covering the young plants with a fabric cover or tents. Offering some protection from strong winds helps, and you can even try this.daily vibration of the flower clusters to increase fertilization. Probably the best you can do is to keep your plant healthy. (Healthy kids are less apt to catch a cold.that sort of reasoning.) By watering deeply you encourage roots to dig deep and the plant is less vulnerable to minor stresses. Make sure that your soil contains adequate organic matter. Apply a balanced fertilizer at planting and again when fruit forms. And remember that too much nitrogen encourages the plant to grow more foliage. not more fruit. Nothing you do will guarantee fruit set. But having patience will help you feel better till the weather changes.


A problem that occurs to the blossom end of the fruits when they become puckered with deep scars that penetrate the fruit. This most often occurs only to large fruited varieties when bloom set happens during cooler weather. Bloom set during warm weather will probably not result in catfacing. So this is another case where noting can be done except hope for warm weather at the time of bloom set.

Fruit Cracking:

There are two kinds of fruit cracking - radial and concentric. Radial cracking is the most common. This occurs during rainy periods when the temperatures are above 90 degrees, especially when the rains come after a long dry spell. These are conditions that encourage rapid growth to ripening fruit. Tomatoes that are exposed to more direct sunlight, versus having good canopy coverage, are more susceptible to cracking.

Encourage even watering of your plants and an adequate canopy of leaves for shading from the sun.

Leaf Roll:

This is not the leaf roll caused by disease. This is the kind of leaf roll caused by prolonged rains and a saturated soil.or even by pruning your plant too much. (Some varieties are more susceptible to leaf roll than others.) The lowest leaves are the first to roll, and rolling continues throughout the plant's leaves.

The best you can do is to maintain a uniform soil moisture, and an even watering schedule. Using a mulch can help level off moisture level peaks and falls.


The actual damage done by insects is generally minimal compared to the damage done by spreading diseases by the insects. This is the primary reason for controlling insects. The best recommendation I can offer is to remove weeds from around the perimeter of your tomato plants. These are perfect breeding places for insects.


I hear of whitefly problems often.most often from gardeners in the Southeast and in tropical islands. This pest is more than frustrating. Both the adult whiteflies and the larvae can damage tomato plants by sucking the sap from the leaves and excreting a sticky honeydew that coats the leaves and fruits. A black sooty fungus then grows on this honeydew. Whitefly infestation will cause wilting, deformed new growth and plant damage. Whiteflies can also transmit some plant viruses.

Advice: Regularly check the undersides of leaves to monitor for both adults and nymphs. And watch for flying whiteflies by gently knocking your tomato leaves. This is a good way to monitor adult activity because they are easily disturbed and will fly away. Your local garden center may also sell yellow sticky cards for measuring the number of adult whiteflies that are flying. In a small-garden environment, these sticky cards may also manage your whitefly populations by killing the adults.

One of the best methods for avoiding whitefly problems is to buy clean plants. Inspect your tomato plants before you buy them with whiteflies already on them.

Spraying water from the garden hose underneath the leaf can also reduce the number of adults and reduce the number of eggs being laid. You can benefit greatly by trying beneficial insects. In nature there is almost always a predator or parasitic insect that feeds on a pest insect. The insects that destroy plants are 'bad insects' and the insects that prey on the bad bugs are 'beneficials' or good insects. Lacewings and Encarsia Formosa are some of the best beneficials you can release.

Early Blight:

This is a fungus and a problem in moist areas of spring/summer rains. This is not usually a problem in the arid areas of the west. Early blight shows up as small, irregular, brown, dead spots on lower, older leaves. The spots then grow to half an inch in "bulls-eye" patterns. The whole leaf then may go yellow. As fruit begins to occur, when suffering from blight, the older fruits may show dark leathery sunken spots.

Late Blight:

This is a fungus that can be serious during extended periods of muggy, damp weather with cool nights and warm days. Fungus shows up as greasy, black areas on the leaves. A fine gray mold can be seen on the leaf underside during wet periods. Hot dry weather usually impedes the progress of this fungus.

Verticillium Wilt:

The first indication of verticillium wilt is a yellowing of the first, older, leaves along with a slight wilting of the tips. These older leaves soon wither and drop off leading to the whole plant loosing it's leaves. All branches of the plant tend to look weaker than the branches of healthier plants. In the late stages of the disease only the uppermost branches remain alive. And the loss of the plants foliage leaves the fruit open for sunscald.

Advice: Provide well-drained soil for your plants. Crop rotation for 4-5 years with non-related crops.

Fusarium Wilt:

This is one of the most damaging and prevalent, soil-borne, tomato diseases.

This fungus over-winters and survives for many years in the soil. Disease is spread is by seed, transplants, and soil on farm machinery or even footwear. The organism generally doesn't cause serious loss problems unless the soil and air temps are steadily around 90 degrees. Fusarium wilt is noticed in seedlings with drooping of the oldest leaves usually followed by the plants death. Older plants can be affected at any stage of growth but most often during maturing of the fruit.

The earliest symptom is a yellowing of the older leaves. The yellow leaves gradually die off. Frequently a single shoot is killed off before the rest of the plant shows any sign of a problem.

Sometimes only one side of the plant shows problems. If you cut lengthwise the stem of a wilted plant, the woody part next to the green outer cortex shows a dark brown discoloration of the tissue.

Advice: Best way out of this is rotation of crops other than tomatoes for several years.