Curly Top Virus Control: What Is Curly Top Virus Of Bean Plants
By: Amy Grant
If your beans are looking peaked but you’ve been vigilant about watering and fertilizing, they may be infected with a disease; possibly curly top virus. What is curly top virus? Read on for information about beans with curly top disease and treating curly virus in beans.
What is Curly Top Virus?
As the name suggests, curly top virus of bean plants mimics the symptoms of moisture stress, a plant with curling leaves. In addition to curling leaves, beans with curly top disease have foliage that becomes thickened and stiff with leaves that twist and curl upward. The leaves may stay green or turn yellow, the plant becomes stunted and the beans may be deformed or simply not develop.
Curly top virus (CTV) doesn’t just afflict bean plants but tomatoes, peppers, sugar beets, melons, and other crops. This virus has a huge host range and causes disease in over 300 species in 44 plant families. Some plants may become infected while others in close proximity show no symptoms and are virus free.
Curly top virus of bean plants is caused by beet leafhoppers (Circulifer tenellus). These insects are small, about 1/10 of an inch (0.25 cm.) in length, wedge shaped and winged. They infect perennial and annual weeds like Russian thistle and mustard, which then overwinters amongst the weeds. Because a severe infection can decimate a bean harvest, it is important to learn about curly top virus control.
Curly Top Virus Control
There are no chemical controls available for treating curly top virus in beans but there are some cultural practices that can reduce or eliminate infection. Planting virus resistant crops is the first step to preventing CTV.
Also, leafhoppers prefer to feed in sunny areas, so providing some shade by draping shade cloth over some stakes will discourage them from feeding.
Remove any plants that show early signs of curly top virus. Dispose of infected plants in a sealed garbage bag and deposit it in the trash. Keep the garden clear of weeds and plant detritus that offer shelter to pests and disease.
If you are in doubt about whether a plant has contracted the virus, a quick check is to see if it needs water. Soak the soil around the ailing plant in the early evening then check it in the morning. If it has perked up overnight, it’s likely it was just moisture stress, but if not, the plant more than likely has curly top and should be disposed of.
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Plants infected with the curly top virus show a striking down-cupping, puckering, and wrinkling of infected leaves. The leaves become thick and brittle and may turn dark green. Portions between two joints on the stem of infected plants become shortened, resulting in a striking dwarfing and stunting of infected plants, particularly when plants are infected at an early stage of growth. Older plants may turn yellow and die. The upper portion of infected plants resembles a rosette or small flower bouquet. Fruit are small and remain upright instead of drooping. Infected fruit have a dull surface unlike the glossy skin of normal fruit.
The curly top virus has a wide host range that includes beans, tomatoes, peppers, sugarbeet, melons, and other crops. It is not known if a single virus strain infects all these crops or whether distinct strains damage different crops. It is known that the virus overwinters in perennial and annual weeds in areas such as the foothills surrounding the Central Valley of California. The occurrence of curly top follows the seasonal cycle of its vector, the beet leafhopper. Beet leafhoppers overwinter in uncultivated places, where they pick up the curly top virus by feeding on infected wild plants. In spring, when wild hosts begin to dry out, the leafhoppers migrate into the valleys where they settle on crops. Symptoms of curly top appear after the leafhoppers are gone. The disease does not spread from one plant to another new infestations are caused by new flights of leafhoppers.
Plant varieties that are resistant or tolerant to the curly top virus if curly top is in your area. Control of leafhoppers with insecticides will not reduce the incidence of disease.
Curled and wrinkled leaves of curly top on beans
Stunted tomato plant infected with curly top
Stunted cantaloupe plant infected with curly top (lower right) compared with healthy plant
Early ripening of curly top on tomato
Statewide IPM Program, Agriculture and Natural Resources, University of California
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