As explained in an article from University of Arizona Cooperative Extension, curly top disease in spinach can be caused by two viruses in the Curtovirus group, the beet curly top virus and the spinach curly top virus. Both are transmitted from infected to uninfected plants by the same vector, the beet leafhopper.

The beet leafhoppers will leave drying vegetation in the fall to feed on new growth in agricultural fields. Those nymphs that aren’t infected will soon get the disease by feeding on weeds and infected plants. When a spinach crop is infected, you’ll notice stunted growth and leaf discoloration and distortion.

There are a few ways to help prevent the infection and spread of curly top virus:

• Late plantings are helpful to avoid the beet leafhopper migration. Not only are leafhoppers more likely feed on other vegetation before your plants, but because the temperatures are dropping, their feeding frequency will decrease.
• Scout your fields and remove plants that you know are infected with the disease. Eventually the disease will take over the plant and it will no longer produce. While it may be hard to detect these insects, if there are large populations on a plant, a quick shake of the plant will reveal their location.
• Because weeds are a great location for beet leafhoppers to set up residence, a program to help control weeds is a good start to keeping these pests away.

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