Tomato spotted wilt (TSW) is the No. 1 disease of tomatoes that we encounter these days. It can also affect peppers, celery, eggplant, peanuts, lettuce, pineapple, many legumes, and many ornamentals. TSW is caused by a virus spread by two species of thrips, tiny insects with scraping and rasping mouthparts. Thrips carry the wilt virus from various host plants (weeds) and can transmit the virus within minutes of active feeding.
Symptoms of TSW include stunting of the tomato plant, drastically reducing yields and causing irregular ripening and yellowing of tomato fruit. Leaves may turn yellow and have red, brown, or black discolorations, forming a ring. Veins on the undersides of affected leaves may turn purple and thicken. If the fruit are set before infection, they may be distorted or develop blotchy orange ring spots as they ripen.
If you have a history of problems with TSW in your garden, be aware that you are more likely to have disease pressure due to the presence of infected weeds in the landscape. Weed hosts identified as potential virus carriers include spiny amaranthus, wild lettuce, pasture buttercup, curly dock, sowthistle, lambsquarters, chickweed, clover, jimsonweed, morningglory, pigweed, among others.
Once tomatoes are infected with TSW, there is no control. Spraying for the culprit thrip is not effective once the damage is done. The best approach to controlling the TSW is the use of resistant varieties. Tomato varieties that have confirmed resistance to this virus include Amelia, Quincy, BHN 640, Crista, Bella Rosa, Talladega, Red Defender, BHN 444, Redline, BHN 602, Top Gun, Mountain Glory, Fletcher, Finishline, Tribute, and others. Most of these are commercial varieties, but some may be available to the home gardener. Commonly grown varieties such as Better Boy, Big Boy, Beefsteak, Beefmaster, Big Beef, Early Girl, Goliath, etc. offer no known resistance to the virus.
Perhaps the best non-chemical approach for reducing thrips is the use of metallic-reflective mulch. This mulch serves to disorient and therefore discourage the thrip from feeding on the tomato plants.
To summarize, while the elimination of TSW may not be possible, the incidence and severity of the disease may be reduced by using cultural practices such as starting with virus-free and virus-resistant plant material, removing all infected plants (once virused, there is no cure for the diseased plant), controlling weeds, rotating crops, and the use of reflective mulches under plants.
I trust you will have a long and prosperous gardening season free of the dreaded tomato spotted wilt virus.
The beach morning glory (Ipomoea pes-caprae) is a beautiful flowering vine that grows well in coastal environments. However it is susceptible to tomato spotted wilt virus (TSWV) a potentially devastating disease. TSWV causes stunted growth, withering, leaf yellowing and necrosis, and can even kill infected plants. Fortunately, with proper management techniques, TSWV can be controlled in beach morning glories.
Understanding TSWV
TSWV is caused by the tomato spotted wilt tospovirus, and is spread by tiny insects called thrips. When thrips feed on infected plants, they pick up the virus. They then transmit TSWV to healthy beach morning glory plants as they move between plants and feed. TSWV infects over 1000 plant species, including many ornamentals and vegetables.
On beach morning glories, TSWV initially causes ring spots and bronzing on leaves. As the infection worsens, leaves yellow, plants become stunted, and vines wilt. Fruit may develop necrotic ringspots. Without control measures, TSWV can destroy an entire planting.
It’s crucial to scout regularly and remove any infected plants immediately to prevent spread. TSWV management focuses on controlling thrips and their access to plants.
Cultural Control Practices
Start with Healthy Plants
Always inspect new plants closely for thrips and symptoms before bringing them to your garden. Ask suppliers about TSWV resistance. Resistant cultivars can reduce, but not eliminate, the risk of infections.
Sanitation
Thrips and TSWV can overwinter in crop debris and weeds. Remove all morning glory vines and weed hosts at season end. Control weeds in and around the garden during summer. Promptly dispose of any infected plants. Keep the garden free of debris that thrips can use as shelter.
Reflective Mulches
Use reflective silver mulches around plants. The intense glare repels thrips, preventing them from reaching and feeding on plants. Reflective mulch also suppresses weeds.
Monitor Thrips
Use yellow or blue sticky cards just above plants to detect thrips. Check weekly and track numbers. Increase monitoring if plants show symptoms. High populations signal it’s time to implement other controls.
Physical Controls
Row Covers
Install fine mesh fabric row covers over plants at planting time. Secure edges with soil. This forms a physical barrier preventing thrips from reaching plants. Remove covers when plants start blooming to allow pollination.
Screening
Small fiberglass screening can be used to cover vent windows, doors, and other openings in greenhouses and tunnels. This blocks thrips entry while allowing airflow. Screening helps protect indoor and semi-protected plantings.
Biological Control
Predatory Mites
Release predatory mites onto plants. These mites prey on thrips eggs and larvae but won’t harm plants. Make releases every 2-3 weeks starting when thrips are first seen. Follow release rates on product labels. Combine with insecticidal soap for best results.
Nematodes
Apply nematodes to soil around plants. Nematodes seek out and kill thrips pupae in soil and leaf litter. Make monthly applications, following label rates. Irrigate soon after application to disperse nematodes into soil. Nematodes work well with foliar sprays.
Parasitic Wasps
Small wasps that parasitize thrips can provide biological control. Look for products containing Ceranisus, Thripobius, or Montandoniola wasps. Make releases every 2 weeks according to label directions. Combines well with other controls.
Chemical Control
Insecticidal Soaps and Oils
Insecticidal soaps and oils kill thrips on contact through their mode of action. Spray plants thoroughly, especially undersides of leaves and flowers, when thrips are first seen. Repeat every 5-7 days as needed. Direct contact is required, so good coverage is key.
Botanical Insecticides
Botanical insecticides like neem, pyrethrins, and azadirachtin made from plant extracts also kill thrips on contact. Rotation between these products helps prevent resistance. Follow label rates and reapply every 5-7 days. Thorough coverage is essential for control.
Other Insecticides
Other insecticide options include spinosad, spinetoram and abamectin. Rotate between chemical classes to reduce resistance risk. Limit use only when needed, combine with non-chemical tactics. Always follow label precautions when applying any pesticide.
TSWV can be difficult to control once established. Prevention through early thrips management and removal of infected plants offers the best protection for beach morning glories. Reflective mulches, row covers, predatory mites, and insecticidal soaps are effective and eco-friendly options. When issues persist, rotational use of targeted insecticides integrated with other measures can successfully manage TSWV. With a thoughtful IPM approach, your beach morning glories can thrive TSWV-free all season long.
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Why Are My Tomato Plants DYING? Managing Tomato Wilt Disease
FAQ
How do you get rid of tomato wilt?
Is it safe to eat tomatoes with spotted wilt virus?
Where does the tomato spotted wilt virus come from?
What are the host plants for tomato spotted wilt?
What is tomato spotted wilt virus (TSWV)?
Tomato Spotted Wilt Virus (TSWV) is a virus that has been documented on multiple farms in each of the last several years in New Hampshire; in some cases, causing significant plant and revenue loss. TSWV is often introduced on asymptomatic plants and then is transmitted by thrips to vegetable seedlings or other plants that were started by seed.
What causes tomato plants to wilt & die?
Look for plants labeled with ‘VF’ on the plant tag. Dozens of tomato viruses can cause tomato plants to wilt and die. Two of the most common are Tomato Spotted Wilt Virus (TSWV) and Tomato Mosaic Virus (ToMV) which cause stunted growth, wilting, and unattractive fruit. The source of the virus can be other plants, seeds, or insects.
How does thrips move the virus from plant to plant?
The virus is moved (vectored) from plant to plant by the piercing-sucking feeding of tiny insects called thrips. So, managing this disease requires strong and continued efforts to: (1) manage the source of the virus (other plants that are already infected), and (2) manage thrips, which move the virus from infected plants to healthy plants.
What is TSWV & how does it affect tomato plants?
TSWV is a well-known virus in other regions of the country. In the state of Georgia, for example, it is estimated to cause approximately $9 million in losses in tomato and pepper each year, and growers on the west coast have reported losing up to 50% of tomato plants to the virus.