Tomato Problems

By Val Whitmyre, U. C. Master Gardener

 

The harvest season is upon us and Master Gardeners receive many calls about tomato problems. Tomatoes are well loved, so it's upsetting to find snails or a gigantic hornworm hanging on the tomato leaves. What can be done to stop their destruction?

The key tactic in any garden is daily inspection and clean-up of unwanted debris on or under the plants. Neglect a garden and you will have a few trouble-free tomatoes. Care for them daily and you will yield enough perfect produce to feed the neighbors.

Here are the most frequently asked questions and answers regarding tomato problems:

There are ragged leaves and half- eaten tomatoes hanging on the plant.
This is the most common problem, and of course it involves snails and slugs or the hornworm. Snails are so prolific that constant baiting or patrolling is absolutely necessary. Bait every two weeks. Pick off any snails or hornworms and destroy. Cut off the lowest branches and any tomatoes growing low on the plant. Make these pesky creatures work for their food.

Blossoms fall off before they can set fruit.
Cold nights are probably the culprit. Tomatoes have to have warm soil, full sun at least six hours a day and deep irrigation. Cool weather also inhibits growth and can cause fungal disease.

Last year the tomato crop was heavy. This year there aren't many tomatoes.
Tomatoes deplete nitrogen from the soil. Next year be sure to amend the soil with manure and/or a well-balanced fertilizer before planting. Also, be sure to wait until the soil is at least 57ºF to plant tomatoes. Before planting, remove the seedlings' lower leaves and plant deeply to encourage lateral root growth from the main branch. This produces a stronger plant, and more nutrients will be able to reach the leaves.

Harvest ripe tomatoes regularly to encourage more production. Improve pollination by planting nearby herbs that attract bees, such as rosemary and oregano. Shake branches to distribute pollen. Keep the soil moist during a heat wave by mulching plants, then water deeply, to a depth of three feet if possible. A rich, crumbly soil will reward the gardener for his or her efforts.

Leaves are curled upward, but are a lush dark green.
This is too much nitrogen and possible over-watering. Neither situation is a serious problem. You are giving your plant too much attention. Too much lush shade may also encourage aphids and other garden pests, like the hornworm. Cut out some of the top foliage to let the sunlight in. Too much nitrogen promotes healthy foliage at the expense of tomato production.

Leaves curl downward and plants are stunted.
Aphids are the culprits. They are also common on eggplants, squash and peppers. Aphids attract ants. Try giving the plants a strong jet of water in the morning to remove the aphids or use an insecticidal soap spray. Bait for ants rather than spraying a pesticide.

The tomatoes have a yellow-orange blotch on the stem end of the fruit, or the tomato has a white papery blotch on the side of the fruit.
This is sunscald. The fruit needs to be protected from hot sun by the leaves. You may prune your plant to improve air circulation and to prevent fungal blight, but give fruit plenty of shade for more perfect maturity.

There is a dark leathery spot on the blossom end of the fruit.
This is blossom-end rot, most often caused by under- or over-watering or by excess salts in the soil. The damage results when the roots can't get calcium to the fruit. Adding more calcium to the soil won't help and may make the problem worse by contributing to salt buildup. Excess nitrogen can also create or aggravate the problem by encouraging leafy growth that robs the fruit of calcium. To avoid blossom-end rot, water consistently and evenly and follow nitrogen fertilizer recommendations. Some varieties, especially the elongated Roma types, are more susceptible than others.

      

Tomatoes, peppers and eggplants look weak and are unproductive in general.
All of these plants are in the nightshade family. They all take nitrogen from the soil and all attract the same problems. Next year, plant these in a different area of the garden. Legumes, such as peas and beans, planted in their place will give nitrogen back to the soil. An unproductive tomato may be a tomato that doesn't do well in our area. Most nurseries in the valley sell tomatoes that perform well here.

There are tiny holes in the tomato leaves.
These are caused by flea beetles. They usually just damage to the leaves.

What is catfacing?
Catfacing is extreme malformation or scarring of the fruit. Cool weather is the source of the problem. Also keep herbicides away from tomatoes as they are forming.