Wouldn’t it be wonderful if only a few diseases affected the plants in our gardens? Unfortunately, that isn’t the case, and sometimes it seems like every time you turn around, there’s a new pathogen to learn about.
You hear the word “ringspot” for many plant infections, but they’re not always the same pathogen or might be different strains. While they share the name and often have similar symptoms, there are a few different types of ringspot.
Let’s discuss the difference between ringspot viruses, the issues they cause, and the plants they infect so you can use effective control strategies.
What is Ringspot?
Ringspot is a catch-all term for viral diseases that impact plants.
While gardening, you will encounter ringspot when dealing with various plants. Depending on the environment, the variety or strain of ringspot, and the plant, the virus will have different characteristics, modes of infection, and different symptoms.
Here are some of the most common forms of infection that use the term ringspot.
Tobacco Ringspot Virus
This virus can go by other names as well, including cucumber ringspot. It affects many crops and plants, and sometimes the ringspot is named after the particular plant it infects. To make things simple, tobacco ringspot is the name of the virus that infects the following plants with ringspot.
Less commonly, the tobacco ringspot virus has been known to infect:
The symptoms of Tobacco Ringspot Virus normally start with the young plants being stunted, along with damage to both young and established leaves. Often the leaves are smaller than they should be as well.
The leaves get small brown spots with light yellow edges or halos as the virus progresses. You will likely see yellow lines on the leaves when you inspect them closer. In the beginning stages, the leaves may appear to have yellow stippling in the form of numerous small specks of yellow.
In advanced stages of the virus, the buds will become infected. They sometimes bend over and form a hook shape, before turning brown and falling off the plant.
If the plant survives long enough and produces fruit, the symptoms will likely appear on the fruit.
Tobacco Ringspot Virus is commonly spread from infected plants to healthy ones by the dagger nematode (Xiphinema spp.). Other insects that spread the virus between plants are grasshoppers, thrips, and flea beetles.
Usually, Tobacco ringspot is introduced to the garden by infected seeds and plants. Use only certified seeds and get plants from trusted sources.
Tobacco ringspot has no cure, so prevention is the only method to concentrate on. The virus can overwinter on surrounding weeds and wild plants, so clear the garden and surrounding area.
Remove dead and dying leaves as they fall from the plants. Practice good hygiene by cleaning tools well. Any plant with this virus needs to be removed and destroyed well away from your other plants and compost pile. Burning is best if you can do that in your area.
Tomato Ringspot Virus (ToRSV)
Tomato ringspot virus is very similar to tobacco ringspot virus, and it has even been called tobacco ringspot virus no. 2. Hey, I did say this gets a bit complicated.
Tomato ringspot virus can affect many other plants, and often the name changes to reflect the infection of that type of plant.
Tomato ringspot virus can infect:
Flowers and ornamental plants that can be infected include:
Other plants can be infected depending on the local conditions and the strain of the virus.
The symptoms of tomato ringspot virus are similar to tobacco ringspot, but there are small differences. The plant may be stunted or fail to thrive and, at the same time, have no other physical signs of infection. On top of that, the plant will decline slowly.
The foliage will often suffer chlorosis, which makes the leaves go yellow as if it isn’t getting enough sunlight. Chlorophyll is then affected.
Cane fruits often go dry and crumbly.
When members of the Prunus genus are infected, the leaves turn pale and wilt early in the growing season before turning purple or red. The fruit size is severely affected, and the quality is poor. This is because the flow of water is affected by the virus.
One key sign to look for is the bark, both above and below the soil line, becomes spongy. In bad infections, this can actually cause the tree to collapse.
Yellow Bud Mosaic
Yellow bud mosaic is a disease caused by ToRSV. It infects peaches, almonds, and other closely related trees. It’s sometimes called Peach Yellow Bud Mosaic Virus (PYBMV).
First, the lower branches lose all the leaves, and as the virus spreads upwards, the upper branches also lose them. Leaf veins turn white, and this, combined with defoliation, has detrimental effects on the fruit and overall tree health.
Although symptoms vary depending on the plant infected, some common signs exist:
- Stunted growth
- Obvious yellow spots
- Soft yellow spots on the fruit
- Plant decline
- Small fruit
- Yellowing of leaves
Once tomato ringspot infects your garden, you can only go into defensive mode. It can’t be cured.
Remove infected plants and destroy them. This also goes for those plants nearby, in case they are infected. If you don’t want to remove trees you suspect are infected, get a second opinion from an expert.
Don’t replant in that spot for at least 12 months. Try to starve out the nematodes that spread the disease.
If you think a plant has tomato ringspot, and the symptoms disappear, that plant can still infect others. Cane berries will often show signs of infection in spring and be clear by summer. This plant is still infected and will be a vector for the disease.
Try these tips to keep tomato ringspot from your garden or orchard:
- Quarantine new plants until you are certain they are disease free
- Ask your local garden center if they have disease-resistant varieties
- Disinfect your tools often with bleach and water
- Remove and destroy infected plants and those around them straight away
Papaya Ringspot Virus (PRSV)
Papaya ringspot virus affects papaya and cucurbits. It is sometimes called watermelon mosaic virus type 1 or papaya mosaic virus.
Along with infecting papaya in warm areas, it will also infect:
In papaya infections, the leaves develop spots and a mosaic patterning, causing yellowing. This can cause the plant to struggle and it may become stunted.
The petioles develop marks that look like water stains or oily streaks. The leaves may become so thin and distorted they look as thin as a shoelace.
If a papaya tree is infected early in its life, it will unlikely grow to its full potential and produce any decent fruit.
In severe cases, the foliage becomes necrotic, and the fruit is covered in large bumps and yellow spots.
In cucurbits, the disease can be confusing for many gardeners. You could be forgiven for thinking someone has carved intricate designs in the fruit’s skin, leaving the inner layer untouched.
Like the other types of ringspot viruses, there are differences in the ringspot that affects papaya and cucurbits.
PRSV-P affects both papaya and cucurbits, while PRSV-W affects only cucurbits. So if you’re wondering how papaya ringspot virus got to your pumpkin patch when there are no papaya trees around, thank PRSV-W and the insect that spreads it.
Aphids are the main spreader of this virus, and once an infected insect gets to your cucurbit plants, they can be infected within three weeks.
Papaya ringspot virus is easier to control, and it’s not necessarily as big a problem as the other ringspot viruses we’ve covered.
Control the aphids, and you can eliminate the risk of the disease. It’s important to note that aphids sometimes spread the disease, and sometimes they don’t. It’s what is referred to as a non-persistent vector.
Use homemade bug sprays, insecticides specifically to target aphids, or regular sprays of neem oil.
Clear away weeds that can harbor the virus, including clovers, pigweed, lamb’s quarters, and mallows.
Introduce or attract beneficial insects in the garden that love to eat aphids like ladybugs or lacewings.
Unlike the other ringspot viruses, all is not lost when you get this in your cucurbit patch because the virus lives in the aphid, not in the plant, so it generally doesn’t spread from plant to plant unless the aphids carry it.
One season you may have it, and the next, it doesn’t appear.
You can still save the seeds of your infected cucurbits, eat the harvest, and allow the plant to grow and produce throughout the season. If you get the aphids under control, the spread will be minimal.
Once the season is over, remove the vines and destroy them. I prefer not to put infected plants in my compost heap, regardless of how the infection spreads.
Far less common in home gardens are:
- Pepper Ringspot Virus
- Coffee Ringspot Virus
- Shamrock Chlorotic Ringspot Virus
- Tomato Spotted Wilt Virus
- Groundnut Ringspot Virus