- Author: Help Desk Team
As tomato growers, we might consider any ailing tomato to have a disease. That would end up making this blog post really, really long. However, we need to consider diseases separately from damage done by pests (both vertebrate and invertebrate—see blog post from July 18: Tomato Diseases in the Home Garden) or environmental disorders such as blossom end rot (see blog post from July 4: https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=57297). We will cover fungal, viral, and bacterial diseases here.
Fungal
The most common tomato diseases are fungal. Many of these fungal spores are nearly everywhere all the time, and given the right conditions, will find a home on your tomato plants. Some fungi prefer cool conditions while some prefer warm. Most prefer wetness and high humidity. Crowding can prevent proper air circulation and encourage fungal diseases. Nutritional deficiencies and injuries also encourage fungal diseases.
Damping Off Disease typically affects seedlings. It's caused by various soil fungi that grow under damp conditions. The affected tap roots of seedlings in contaminated, overly damp soil are dark and mushy and the seedlings usually die. Prevent this by using fresh clean soil and sanitized containers with good drainage. Use alcohol or a 10% bleach solution to sanitize. https://ipm.ucanr.edu/PMG/PESTNOTES/pn74132.html
Septoria Leaf Spot is favored when plants are exposed to cool, rainy weather or splashing from soil. It's relatively uncommon in Contra Costa County. Prune off infected leaves and twigs and keep plants dry. https://ipm.ucanr.edu/PMG/GARDEN/PLANTS/DISEASES/septorialfspot.html
Phytophthora Root and Crown Rot is a soil-borne fungus-like organism transmitted under wet conditions by splashing water or contaminated garden debris, pots, or tools. Plants appear drought-stressed since the vascular system is compromised, and often die. It can also cause damping-off. Look for darkening of the crown, roots, and stems. Good drainage, avoiding overwatering, and sanitizing any tools used on the diseased plants are preventive measures. In previously affected soil, avoid planting members of the Solanaceae family (tomatoes, eggplant, peppers, potatoes) in the infected soil and plant a resistant crop instead such as corn. https://ipm.ucanr.edu/PMG/PESTNOTES/pn74133.html
White Mold, also called Cottony Soft Rot, appears as bleached areas on stems from white mycelia. Fruit can be affected and appears gray. The mold favors hot, moist conditions and often spreads from dying flowers. Bury or dispose of infected tissue; avoid overhead watering, overwatering, and crowding. https://ipm.ucanr.edu/PMG/GARDEN/VEGES/DISEASES/tomwhmold.html
Powdery Mildew looks different on artichoke, pepper, and tomato leaves from its appearance on other plants (see reference). It requires warm weather and living tissue to grow but does not require moist conditions. Prevention includes planting resistant varieties in sunny areas and avoiding crowding. Occasionally a fungicide or a biologic is needed. https://ipm.ucanr.edu/PMG/PESTNOTES/pn7406.html
Early Blight's name is somewhat misleading as it occurs on mature tomato plants and can affect fruit. It is uncommon in our Mediterranean climate. See reference for photos, prevention, and treatment: https://ipm.ucanr.edu/PMG/GARDEN/VEGES/DISEASES/tomearlyblight.html
Late Blight (Phytopthora infestans) occurs in our coastal areas and is favored by average temperatures and high humidity. It can spread rapidly from other Solanaceae family members or their cullings. Avoid overhead sprinkling and crowding of plants and buy certified blight-free seeds and tubers. Dispose of affected plants and debris in green waste. https://ipm.ucanr.edu/PMG/GARDEN/VEGES/DISEASES/lateblight.html
Black Mold typically affects ripe tomato fruit during conditions of warmth and high humidity. It can appear as small dark brown spots or grow into large, sunken areas. Pick fruit as soon as it ripens. https://ipm.ucanr.edu/PMG/GARDEN/VEGES/DISEASES/tomblkmold.html
Verticillium and fusarium wilt are fungal diseases that will be discussed in an upcoming blog.
Viral
Tobacco Mosaic Virus is a disease primarily of Solanaceae, of which tobacco is a member. It is transmitted by infected seeds or by tobacco residue on the hands of smokers. The leaves appear mottled and stringy, but the fruit is edible. Herbicide damage can appear similar. Many tomato cultivars have resistance. https://ipm.ucanr.edu/PMG/GARDEN/VEGES/DISEASES/tobaccomosvir.html
Curly Top Virus and Spotted Wilt Virus are fairly unusual afflictions. Curly Top Virus is carried by the beet leafhopper and causes curling, puckering, and stunting of leaves. Fruit is usually discolored and small. Spotted Wilt Virus is transmitted by the western flower thrip. It can be difficult to diagnose as it presents differently depending on the stage of plant growth. Fortunately, it's rare in Contra Costa County. Both have wide host ranges. For severe infections in the garden, testing may be warranted since the viruses can mimic other diseases. Affected plants will need to be removed and disposed of. Unfortunately, insecticides do not kill thrips or leafhoppers in time once the damage has been noticed. https://ipm.ucanr.edu/PMG/GARDEN/VEGES/DISEASES/curlytop.html
https://ipm.ucanr.edu/PMG/GARDEN/VEGES/DISEASES/tomspotwltvir.html
Bacterial
Bacterial Speck, Bacterial Spot, and Bacterial Canker are all easily confused. They tend to be introduced on infected seeds, and can overwinter on garden debris, flats, and stakes. They all prefer wet conditions. All three cause lesions on fruit. Speck and Spot cause similar leaf lesions and are chiefly distinguished by their appearance on fruit.
Bacterial Speck prefers cooler conditions such as in coastal regions. A Pseudomonas bacterium causes small sunken spots with white halos that can become scabby. The leaf spots are similar and appear greasy, and leaf margins can turn brown in an angular pattern. Stems can also be affected.
Bacterial Spot is caused by Xanthomonas bacteria, resulting in large, black, sunken spots on fruit and irregular black spots on leaves. Warm, humid conditions favor its appearance. The fruit may be eaten once the black spots and any underlying maceration are removed. https://u.osu.edu/vegetablediseasefacts/tomato-diseases/bacterial-leaf-spot/basics/
Bacterial Canker also prefers warm, humid conditions. Stunting, wilting, scorching of leaf margins, cankers on stems, and vascular discoloration are distinguishing features.
https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=27926&postnum=27926
Bacterial diseases can be managed somewhat with copper sprays and these sprays are acceptable for organic farming.
Prevention
Prevention is the ideal way to manage all these diseases:
• Rotate crops
• Don't overwater or spray the plant
• Don't crowd plants
• Remove lower leaves that can touch the soil
• Use mulch to prevent spread from soil
• Buy resistant varieties
• Control weeds to prevent thrip and leafhopper invasions
• Dispose of infected plant parts and debris, sanitize tools, planting flats, and hands
• Baby heirloom tomatoes because they typically have little resistance
For more information about pests and diseases of tomatoes, see this website: https://ipm.ucanr.edu/home-and-landscape/tomato/index.html
Help Desk of the UC Master Gardeners of Contra Costa County (EAS)
- Author: Anne E Schellman
Why Not Move Firewood?
By bringing wood from home, you can unknowingly spread invasive pests and diseases that can harm trees. This includes dry, aged, and seasoned wood. Once you arrive at your destination, pests can emerge from the firewood and spread to the trees and forests where you camp. Invasive and hard-to-control pests kill several million native trees every year, causing environmental and economic problems.
Did you Know?
New infestations of tree-killing insects and diseases are often found in campgrounds and parks as a result of campers moving firewood!
This trip, tell your friends and family why you aren't bringing firewood. For more information about firewood pests and resources for finding good firewood, visit the Don't Move Firewood web site. To learn about many of the invasive wood-boring pests and associated diseases and problems, visit the UC IPM web site.
First posted on August 30, 2021
Anne Schellman has been the Coordinator for the Stanislaus County Master Gardeners since 2018.
/h4>/h4>- Author: Ed Perry
During the first two to four years after planting a new fruit tree, fruit production is either light or absent. However, this is the time when major root growth takes place and the basic framework of the tree is being developed. Actually, the first year that the tree is in the ground is the most important for root development. Stress caused by diseases, nematodes, weed competition or insufficient water can slow or stop root development, and hence top development. If your tree's growth is stunted from the beginning, there is little chance that it will grow satisfactorily in later years. After the first years, young trees become more tolerant to many of these stresses.
The second and third growing seasons are critical ones for developing your tree's framework for fruit production. Deciduous fruit and nut trees must be properly trained for structural strength while developing maximum fruiting area. The system most used is the open center or vase system. Citrus and avocado trees, on the other hand, do not require extensive pruning. Pests such as twig boring insects that cause distortion of early limb growth are most serious during these early years, because their damage affects the ultimate shape of the tree.
Young trees are often most susceptible to certain diseases such as bacterial canker or verticillium wilt. If your trees reach eight or nine years of age without being badly injured by these diseases, chances are good that they will survive future attacks.
Of course the most common and serious cause of poor tree development is improper watering practices. Too much or too little water will prevent the vigorous growth of young fruit trees, and make them more susceptible to pest, disease and sunburn problems as well. More than any other cultural practice, irrigation will affect the growth, development, and long term health and productivity of your fruit trees.
Ed Perry is the emeritus Environmental Horticultural Advisor for University of California Cooperative Extension (UCCE) in Stanislaus County where he worked for over 30 years.
Learn more about planting and pruning bare root fruit trees by watching the recording of our past class on our YouTube Channel.
Take our Pest Management in Vegetable Gardens class to learn how to identify pests and manage them using less toxic solutions. You'll also learn how to recognize beneficial insects, too.
Where: On Zoom. You will receive a link the morning of the class.
When: Tuesday, May 18, 2021 6:00-7:30 p.m.
Cost: Free
Register at: http://ucanr.edu/vegpests/2021
Instructors: Rho Yare & Anne Schellman
- Author: Ed Perry
Do you keep notes on how your garden performs each year to help you remember what is working well and what is not? Maybe this is your year to start. Barb Fick, Home Horticulturist with the Oregon State University Extension Service, explains that there are many good reasons to keep a garden journal. A blank bound book or a ring binder filled with loose-leaf paper can make a great place to record what you do in your garden.
Having a year-to-year record of where things are planted will also help with crop rotation, which is the system of changing the types of vegetables and flowers planted each year in each garden location. Rotation discourages depletion of soil nutrients, pest outbreaks and soil borne disease. Without a good record of where each crop is planted however, it's easy to forget where a particular species may have been growing last year.
By recording each year's seasonal “landmarks” such as rainfall patterns and amounts, unusual weather such as rapid temperature changes, the date of the first daffodil bloom, the first frost and the arrival of the first hummingbird, you will be able to compare different years to one another and relate them to plant performance.
Fick writes that it's a good idea to record pest outbreaks in relation to what plants they are found on. It's also very important to include any control measures used, and the success or failure of those measures. This information will help you prepare for the same problem next year, or may help you decide not to grow that particular species next year. Also, record the appearance and activities of beneficial insects and their host plants. For instance, you may record that aphids on your rose bushes were brought under control by ladybird beetles and other natural enemies by mid-April. This information might help you make a decision on whether to use an insecticide to control the aphids the following year, or to let nature take its course.
To keep track of the amount of money spent on seed, fertilizer and garden tools, a journal can come in handy. It can also be a good way of keeping track of yields and a safe place to record the identities of the things you plant. You can keep a good record of species and varieties simply by taping the plant identification tags onto your journal pages, along with the planting dates and garden locations.
Fick says that along with being very practical, a garden journal can give you a feeling of accomplishment. When you add up the many hours spent, the numbers of species planted and the various garden methods used, most gardeners will feel proud of what they've done.