Friday, September 4, 2015

Curly Top Virus Strikes Again

Curly Top Virus Strikes Again

Image of a tomato plant with curled leaves
Tomato infected with Beet Curly Top Virus
Characteristic symptoms include curled, thickened (stiff) foliage
with purple coloration on the underside of the leaves.
(Photo: N. Goldberg, NMSU - PDC)
Curly top virus (CTV), or beet curly top virus (BCTV) as it is more formally known, is widespread throughout arid and semi-arid regions of the world. The virus is common in the western United States from Mexico to Canada and in the eastern Mediterranean Basin. The virus has a wide host range, causing disease in over 300 species in 44 plant families. The virus appears to be restricted to broad-leafed plants, as no monocotyledonous plants have been identified as hosts for this virus. The most commonly infected hosts include sugar beets (for which the disease was first named), tomatoes, peppers, beans, potatoes, spinach, cucurbits, cabbage, alfalfa, and many ornamentals. The virus also survives in many weeds, such as Russian thistle (tumbleweed) and mustard.

Symptoms vary depending on the host; however, this disease also produces some general symptoms. Other factors that relate to the type and severity of symptom development include virus strain and host physiology. The virus exists in many different strains, which vary in the severity of symptoms produced particularly in relation to the host. Severity of disease is also dependent on the age of the plant when infected. For example, when young plants are infected they will often die shortly after infection. When plants are infected after the seedling stage, the plants survive but are yellow and stunted. Infected leaves of some hosts, particularly tomatoes and peppers, become thickened and crisp or stiff, and roll upward as the petioles curve downward. The leaves turn yellow with purplish veins. Leaves of other hosts such as beets become very twisted and curly. In most cases, yield is reduced, and the fruit that is produced ripens prematurely. The immature, dull and wrinkled fruit is a good diagnostic symptom for tomatoes infected with CTV. If plants are infected after they have begun to set fruit, it is not uncommon to see infected and healthy fruit on the same stem.

Image of three yellow and stunted chile pepper plants in a field
Beet Curly Top Virus on chile peppers (Photo: N. Goldberg, NMSU - PDC)

Image of a yellow and stunted pumpkin plant in the field
Pumpkin infected with Beet Curly Top Virus
(Photo: N. Goldberg, NMSU - PDC)

Image of two bean plants; the yellow one on the left is infected with a virus, the green one on the right is healthy
Beet Curly Top Virus infected bean next to a healthy bean plant
(Photo: J. French, NMSU - PDC)

Image of spinach plants in the field. The yellow stunted plants are infected with virus
Beet Curly Top Virus on spinach (Photo: N. Goldberg, NMSU - PDC)

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