- Author: Lauren Fordyce
Tomatoes are ripening all over California right now keeping many gardeners and tomato lovers busy picking, canning, and eating. But what may not make gardeners happy are seeing curled leaves and not knowing why. There are many reasons why your tomato leaves may be curling or rolling. Being able to narrow down possible causes takes a bit of detective work, but using this article and UC IPM's Plant Problem Diagnostic Tool can make it achievable!
Tomato leaf curl can be the result of:
Environmental stressors
Leaf curl on tomato is often caused by environmental stress, not necessarily pathogens or insects. Too much or too little water or nutrients, can make leaves curl. A wet spring, followed by warm weather can cause physiological leaf roll. Leaves may roll downward and become firm and leathery. Usually, the lowest leaves are affected most and the plant appears healthy otherwise. When conditions become more favorable, like more water if the plant hasn't been getting enough or consistent watering, environmental stressors will often resolve themselves and the plant will recover.
Plant pathogens
Several viral infections can cause tomato leaves to curl. Curly top virus causes leaves to cup downward, become thick and brittle, and stunts plant growth. Tobacco mosaic virus results in mottled leaves that appear stringy and distorted. Tomato spotted wilt virus causes downward-cupped leaves and necrotic spots. It is important to note that viruses can be transmitted to tomatoes, and other garden plants, by sap-sucking insects. Therefore, their control is important in preventing these viruses. There is no treatment for virus-infected plants, so it is best to remove and dispose of them.
Insects
Aphids, whiteflies, thrips and other sap-sucking insects can cause leaves to curl by sucking plant juices out of the leaves. Check the undersides of leaves to look for these insects. Once you have identified the culprit, see the UC IPM fact sheets (Pest Notes) on various methods for managing them.
You may see some ‘good bugs' around the garden too. Many natural enemies will feed on these pest insects, so keep an eye out for lady beetles, lacewings, and minute pirate bugs. Also look for signs of parasitization (like aphid mummies) from parasitoid wasps!
Herbicide injury
If you recently applied an herbicide near your tomato plants, their leaves could be curling from herbicide drift or contamination. When tomato plants come in contact with herbicides, like 2,4-D, their leaves may curl or cup and become distorted.
How can you prevent tomato leaf curl?
- Choose pathogen resistant tomato varieties.
- Harden off plants or wait for the weather to warm up before planting outside.
- Ensure tomatoes receive consistent and adequate water.
- Use the correct amount of fertilizer.
Visit the UC IPM website for more information about tomato pests, issues, and cultural controls. If you have additional questions, please contact your local UC Master Gardeners for more information.
If the new leaves of your peach or nectarine tree become reddish, puckered and severely distorted, chances are that peach leaf curl is the culprit. This disease is caused by the fungus Taphrina deformans and is one of the most common disease problems for backyard peach and nectarine trees here in Butte County. In addition to disfiguring leaves, leaf curl can affect the blossoms, stems and fruit of infected trees. If it is severe enough, leaf curl can significantly weaken a tree and reduce fruit production. Leaf- curl-affected leaves fall off in spring, exposing the main limbs to sunburn injury. And sunburn injury facilitates flatheaded borer attacks, which often result in limb dieback.
The best way to avoid leaf curl is to grow resistant varieties of peaches and nectarines, so if you are planning to buy fruit trees, keep this in mind. Resistant peach varieties include Frost, Indian Free, Muir and Q-1-8. Although the Frost peach variety is very resistant to leaf curl, it must receive fungicide applications in its first two to three years of growth. Red Haven peach and most of the varieties derived from it are rated “tolerant” to leaf curl. On the other hand, Redskin peach and its cultivars are rated “susceptible to highly susceptible” to the disease. Kreibich is a nectarine variety that is resistant to leaf curl.
The most common fungicides available to the home gardener contain fixed copper. The active ingredient, copper, is listed as “metallic copper equivalent,” or MCE. The higher the MCE, the more effective the product will be. Thorough coverage (by spraying the trees until they are dripping) is essential for disease control. Be aware that repeated use of copper products can result in the buildup of copper in the soil, where it may become toxic to soil organisms. The synthetic fungicide, chlorothalonil, is the only non-copper fungicide available for managing leaf curl on backyard trees. When using pesticides, always read and follow the label for usage, rates, toxicity and proper disposal. Proper protective clothing and gear (including goggles) should be used when handling any pesticides.
When the symptoms of peach leaf curl appear on a tree in the spring, nothing can be done to control the disease at that time. Removing diseased leaves or shoots does not control the disease. If your tree has leaf curl now, be sure to treat it next winter to prevent more serious problems the following spring.
For more detailed information on this topic, see the University of California Integrated Pest Management Pestnote #7426: Peach Leaf Curl Management Guidelines--UC IPM (ucanr.edu).
JOB OPPORTUNITY: UC Cooperative Extension has an opening for an individual who can provide administrative and program oversight to the Master Gardener Program, plus technical and educational training to support the creation and maintenance of gardening programs with UC CalFresh Nutrition Education Program clientele in Butte County. For more information and to apply for the Garden Education Coordinator position visit Jobs - Division of Agriculture and Natural Resources (ucanr.edu).
Peach leaf curl is a disease that affects peach and nectarine trees. Although you may not see symptoms right now in the dormant season in California, it's time to think about treatment, especially if your tree had the disease last year.
Symptoms of this fungal disease include distortion, thickening, and reddening of foliage as trees leaf out in the spring. As weather warms, damaged leaves that die and fall off trees are replaced with new, usually healthy leaves. However, after several years without treatment, peach leaf curl will cause tree decline and reduced fruit production.
Avoid peach leaf curl by growing varieties resistant to the disease. For nonresistant peach and nectarine trees, consider spraying with preventive fungicides in the dormant season just before or as buds swell.
See the UC IPM publication Pest Notes: Peach Leaf Curl for more information about the disease and management options. Always read and carefully follow all precautions and safety recommendations given on the pesticide label.
- Author: Lauren Snowden
- Editor: Melissa G. Womack
From the UC Master Gardener Statewide Blog
The tomato is one of the most versatile and rewarding plants to grow in a summer edible garden. According to a 2014 study by the National Gardening Association, 86 percent of homes with vegetable gardens grow tomatoes. It's understandable that the tomato plant is a popular home vegetable garden staple, tomatoes offer thousands of different varieties options and flavors. Plus, nothing beats the flavor of a ripe tomato straight from the garden!
When properly cared for, a single tomato plant can produce 10 to 15 pounds (4.5 to 6.8 kg) or more of fruit. If tomato yields aren't what was expected or the fruit is damaged it could be due to a number of abiotic disorders, diseases or pests. Abiotic disorders result from nonliving causes and are oftentimes environmental, for example: unfavorable soil conditions, too much or too little water, temperature extremes, physical or chemical injuries, and other issues that can harm or kill a plant. Below are five common abiotic disorders of tomatoes and recommended remedies from the UC Agriculture and Natural Resources publication, Growing Tomatoes in the Home Garden.
1. Sunburn
Problem: Fruit turns light brown and leathery on side exposed to sun.
Cause: Overexposure to sunlight.
Solutions:
• Maintain plant vigor to produce adequate leaf cover.
• Avoid overpruning.
• Provide partial shade during hours of most intense sunlight.
2. Leaf Roll
Problem: Older leaves roll upward and inward suddenly, leaves become stiff to the touch, brittle, and leathery.
Causes: High light intensity and high soil moisture, particularly when plants are staked and heavily pruned
Solution:
• Choose less-susceptible varieties.
• Maintain even soil moisture.
• Provide shade during hours of intense sunlight.
3. Blossom End Rot
Problem: Water-soaked spot on blossom end of fruit enlarges and darkens, becomes sunken and leathery. Affects both green and ripe fruit, and is more common on sandier soils.
Causes: Calcium nutrition and water balance in the plant, aggravated by high soil salt content and fluctuating soil moisture.
Solutions:
• Maintain even soil moisture.
• Amend planting area with compost to improve water retention.
• Avoid heavy applications of high-nitrogen fertilizer.
• Soils deficient in calcium may be amended with gypsum.
Problem: Circular concentric cracks around the stem end (concentric cracking), cracks radiating outward from the stem (radial cracking), malformation and cracking at the blossom end (catfacing).
Causes: Very fast growth with high temperatures and high soil moisture levels. Wide fluctuation in soil moisture and or air temperature. Any disturbances to flower parts during blossoming.
Solution:
• Keep soil evenly moist.
• Maintain good leaf cover or provide partial shade during hours of most intense sunlight.
• Mulch around the plant 3 to 7 inches deep to maintain soil moisture and temperature.
5. Solar Yellowing and Green Shoulders
Problem: Yellow or yellow-orange instead of normal red color, upper portions of the fruit remian green even though the lower portion appears red and ripe.
Cause: High temperatures and high light intensity.
Solutions:
• Maintian plant vigor to produce adequate leaf cover.
• Avoid overpruning.
• Provide partial shade during hours of most intense sunlight.
Pests eating your tomatoes?
Other damages that are caused to tomato plants can be caused by a variety of pests. Some examples of common pests, include: hornworms, tomato fruitworms, tomato pinworms, stink bugs, white flies, and leafminers. For information about other pests on tomatoes, visit the UC IPM Tomato Page. For general help identifying and managing pests in your garden, visit the UC IPM website.
Need free gardening advice?
Since 1981, the UC Master Gardener Program has been extending UC research based information about home horticulture, sustainable landscape, and pest management practices to the public. Through a vast network of more than 6,000 certified UC Master Gardener volunteers, the program is administered by local UC Cooperative Extension (UCCE) county offices across California. Contact the UC Master Gardener Program in your county for more information about edible gardening or upcoming educational workshops, mg.ucanr.edu.
Winter is a key time for gardeners to take preventive actions against peach leaf curl in some areas in California. Caused by the fungus Taphrina deformans, peach leaf curl causes distortion, thickening, and reddening of foliage as peach and nectarine trees leaf out in the spring. Damaged leaves often die and drop, but they will be replaced with new, healthier leaves once the weather turns dry and warm. An untreated leaf curl infection will contribute to a tree's decline over several years.
To prevent peach leaf curl in areas where the disease occurs, treat susceptible trees with preventive fungicides during the dormant season, ideally in late November or December. A second application should be made in late winter or early spring just before buds swell. In some places, a third treatment may be necessary. Treatment isn't effective if applied after symptoms appear. Removing affected leaves or shoots will not reduce the problem. A few peach varieties are resistant, including Frost, Indian Free, Muir, and Q-1-8.
Dormant Treatment Materials
When lime sulfur and tribasic copper sulfate were removed from retail shelves, the choices of fungicides available against peach leaf curl for home gardeners became limited. Copper ammonium complex (Liqui-Cop or Kop-R-Spray) is less effective than discontinued formulations, but can be made more effective by applying it with 1% horticultural oil in the solution. Copper soap (copper octanoate) may also provide some protection.
The fungicide chlorothalonil (sold as Daconil, Ortho Garden Disease Control, and others) is effective, but care must be taken in handling it since it causes severe eye or skin irritation and is a likely carcinogen. Proper protective care, clothing, and equipment should always be used.
Bordeaux mixture, which gardeners can mix up themselves, is also effective, but preparing it takes time and planning. The ingredients needed to make Bordeaux mixture are powdered copper sulfate in “bluestone” form, and hydrated lime (calcium hydroxide) or quick lime (calcium oxide). Be sure customers have goggles, gloves, and a dust and mist-filtering respirator to use while working with hydrated lime and mixing up the solution.
For more information, see the UC IPM Pest Notes Peach Leaf Curl.