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Home-grown tomatoes are by all measures the most popular of all garden items. More gardeners grow these than grow any other edible plant. From large tomato patches to the single plants tucked into flower beds or in containers, tomatoes are growing in Utah gardens.
Obviously the most popular fruit in America is also popular for the pests. Diseases, insects and different growing conditions all take their toll. Knowing what problems are likely to happen and how to prevent them will assure an unending supply of these tasty treats.
The most common complaint this year is slow growth. This is directly attributable to cool, moist spring weather. Tomatoes are warm-season crops. Without heat they sit and sulk and never grow. Gardeners in cool, moist climates have trouble getting any varieties to ripen - let alone the tasty ones we like to grow here. Patience is the way to overcome this problem. When we have tomato weather we have tomatoes.
Wilt is probably the next most common complaint. The name is very descriptive of the symptom. Plants grow well for a time and then suddenly wilt and die. Some plants have one side start to wilt first and then the symptoms progress until the whole plant is affected. In other cases, the whole plant suddenly collapses.
Verticillium is the most common wilt organism, and it's a tough problem to control. The organisms live in the soil and then attack the plants grown in infested soils. These fungi and their spores have a long life span. They can survive in the soil for up to 20 years. There is no practical control for verticillium or any other persistent soil fungi. Chemicals are not available to control the problems, and rotation doesn't work because the fungus lasts for so long. Avoid problems by always planting seeds or transplants with the letters VF on them. This means the varieties are resistant to verticillium and fusarium wilt. Keep in mind that resistance does not mean immunity.
Problems may still develop, but that is not as likely as when varieties without resistance are used.
The above-mentioned fungi are not the only reason plants wilt. Overwatering decays the tiny absorbing roots and causes the plants to wilt. Underwatering also causes wilting, and when it gets hot and dry and windy, temporary wilting may hap-pen. Plants will recover in the evening or when you apply more water. Overfertilization or mechanical damage to the stems also causes wilting.
Spotted leaves are another concern. Early blight is a problem that starts as yellow spots on the leaves. These dry out and turn brown, leaving target spots with brown concentric rings on the leaves. This is common but isn't a serious problem in most gardens. Fungicide sprays are not usually warranted. With the wet weather this disease may be more prevalent. When this problem troubles plants, stop sprinkling the plants and water with drip or furrow irrigation. If problems persist, Daconil is an effective fungicide.
Brown spots on the bottoms of the fruits are an environmental problem called blossom end rot. As the fruits grow rapidly, the plant does not move sufficient calcium to the end of the fruit. Brown, leathery spots appear at the blossom end, making the fruit very unattractive. The fruit isn't toxic, but it's not highly desirable to eat. Control this problem by controlling the water. Too much or too little interferes with calcium transport and makes the spots appear. Avoid wide swings in soil moisture by mulching the plants. The problem is less severe during periods of moderate weather.
Other misshapen fruits result from a variety of factors. Genetic makeup of the tomato is a big factor. Some varieties are smooth with few problems while others always seem to get a gnarled, wrinkled appearance. Certain insects also cause the fruit to be misshapen. Some feed when the fruits are small and green, while others feed on ripening tomatoes. Carefully inspect for the pests and take appropriate control measures.
Curled leaves are another symptom. Some curling is natural as the plants go through various water, wind and heat cycles. The serious problems come when plants get curly top or are damaged by lawn weedkiller. Curly top is a virus disease spread by the sugar beet leafhopper. This small insect pest is related to the aphids and feeds by sucking the plant juices. They have an aversion to tomatoes and never feed on them for any length of time. One feeding allows them to inject the curly top virus into the plant. The plants then develop yellow leaves with purple veins. The fruit ripens prematurely, and, of course, the leaves curl up. Once the plants have the disease they are infected for life, and there is no cure.
Tomatoes are extremely sensitive to 2, 4-D and other chemicals in lawn weed-killers. These cause tight twisting of the leaves. The youngest growth is most affected and the leaves remain green. They also develop a parallel venation pattern.
Several insects also attack the tomatoes. By far the most noticeable and repulsive is the tomato hornworm. These giant worms will get up to 4 inches in length and will consume voluminous quantities of leaves in a few hours. They are easy to control by picking them off and destroying them. Dipel or Thuricide are also effective if the pests become extremely numerous. The tomato fruit worm is simply a confused corn earworm. They occasionally get on the fruit and eat the green or the ripe ones. Again, handpicking is the preferred method of control.
Whiteflies are usually pests in greenhouse tomatoes. Some gardeners have serious problems in their outdoor crops. Whether the whiteflies manage to survive in plant residues in mild winters is unclear. They are usually introduced into the garden in the spring from infested plants. Likely carriers include fuchsias, Martha Washington geraniums and lantana, although many other plants and ornamentals harbor the pests. Control is very difficult. Spray the undersides of the leaves weekly with insecticidal soap. If that doesn't work, use a pyrethrum spray that is labeled for edible vegetables.
After reading this, you may think tomatoes are difficult or impossible to grow. They show few problems in most situations. I grow dozens of plants each year and almost never lose any plants or have to spray them. The best rewards are those tasty home-grown tomatoes fresh from your garden. They make dealing with any and all problems well worth the trouble.