By: Darcy Larum, Landscape Designer
In springtime we put so much work into creating our ideal garden beds…weeding, tilling, soil amendments, etc. This can be back breaking, but we are driven by the vision we have of a full heathy garden and a bountiful harvest. When this vision gets destroyed by fungal or viral plant diseases, it can feel devastating. Continue reading for information on beet curly top virus in spinach.
Curly top spinach disease is a Curtovirus that affects many plants besides just spinach. Certain herbs and even specific weeds are all susceptible to spinach beet curly top infections, as are:
This viral infection is spread from plant to plant by the beet leafhopper. When leafhoppers feed on infected plants, they get the virus on their mouthparts and spread it to the next plant they feed on.
Curly top spinach disease occurs in hot, arid regions. It is most prevalent in the western half of the United States. Arizona, specifically, has had many serious beet and spinach crop failures due to beet curly top virus. Symptoms of this disease appear within 7-14 days of infection. These symptoms include chlorotic or pale foliage, puckered, stunted, curled or distorted foliage. Infected leaves may also develop purple veining. As the disease progresses, infected plants will wilt and die.
Unfortunately, there are no treatments for infected spinach plants with beet curly top. If the disease is discovered, plants should be dug up and destroyed immediately to reduce the risk of spreading the virus. Prevention is the only helpful course of action to defend plants against spinach beet curly top infections. There are also no spinach varieties which are resistant to this disease.
Weeds, specifically lambsquarter, Russian thistle and four-wing saltbush, are susceptible to spinach beet curly top. These weeds are also a food source and provide safe hiding places for beet leafhoppers. Therefore, weed control can help reduce the spread of this disease.
Chemical insecticides can be used to kill leafhoppers on weeds, but it is not recommended to use these chemicals on the edibles in the garden. Leafhoppers are most active in hot, humid weather. Delaying fall planting by a few weeks can help reduce the risk of spinach beet curly top. Covering young garden plants with row covers can also prevent the spread of this disease.
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Curly top  is a viral disease that affects many crops. This disease causes plants to become smaller in size, have shriveled petals and leaves, and are twisted and pulled out of shape. They are often caused by curtoviruses (genus Curtovirus), members of the virus family Geminiviridae. This disease is important in western United States, such as California, Utah, Washington, and Idaho.
Curly top is characterized by stunting of the plant and deformation of leaves and fruit. The petioles and blades of the leaves curl, twist, and become discolored. 
Weeds may act as virus reservoirs and should be removed. However, weed removal will not necessarily prevent virus infections from taking place. No resistant spinach cultivars are available. Spraying for the insect vector will not prevent virus infections from occurring however, growers should still attempt to manage vector populations when possible (for more information, see section on APHIDS).
UC IPM Pest Management Guidelines: Spinach
UC ANR Publication 3467
S.T. Koike (emeritus), TriCal Diagnostics, Hollister
M. LeStrange (emeritus), UC Cooperative Extension Tulare County
Curly top virus is widely distributed in Texas. It is most noted for destruction of tomatoes, peppers, and sugar beets, but watermelon, beans, spinach, and squash are also susceptible as well as many weeds and ornamentals.
Symptom expression changes from barely noticeable stunting and leaf puckering to death of the entire plant. Infected plant leaves become distorted through curling, twisting, and rolling. Tomato leaves become thickened and leathery. Branches bend down, leaves cup upward and twist on their petioles. Veins on the underside of leaves will turn purple in some varieties. Smaller tomato plants often turn yellow and die after expressing the other symptoms. Tomatoes, melons, and cucurbits in general appear to ripen prematurely, but have an odd taste.
See Photo 1, Photo 2, Photo 3 of the Curly Top Virus on Tomatoes.
Transmission is by the sugar beet leafhopper (Curculifer tennelus). The virus is not transmitted to leafhopper eggs. True seed transmission does not occur but persists in potato seed pieces. The leafhopper can retain the virus in as little as 1 minute, but maximum retention occurs after 2 days. Usually a minimum incubation of 21 hours is required within the leafhopper before it can be transmitted to another plant. Very high temperatures can reduce this time to 4 to 6 hours. Symptoms appear in 24 hours in high temperatures, 14 days in normal temperatures, and up to 30 days when cool. Severe infection is related to high light intensity, prolonged summer heat, and high evaporation. Relative humidity above 50% reduces curly top and below 35% makes it severe. It is thought that high humidity delays visits of leafhoppers.
Attempts to control leafhoppers with insecticides is not effective. Fine mesh mechanical barriers over tomato plants on ground or around tomatoes in wire cages is effective. Elimination of infected weeds to drive off leafhoppers before transplants are planted should be tried. Resistant varieties include Roza, Rowpac, Columbia, and Saladmaster. All four are also resistant to Verticillium and Fusarium. Seed of these varieties can be obtained by contacting Dr. Harold Kaufman, Texas Agricultural Extension Service, at Lubbock (806) 746-6101.