Dr. Curtis Swift, and Bob Hammon, CSU Extension, Tri River Area, Grand Junction office.

Photos by Swift and Hammon unless otherwise indicated

Curly top is one of several insect-vectored viral diseases that affect tomatoes. Seventy-five percent losses can occur in Western Colorado when conditions are favorable for the spread of the beet leafhopper (Circulifer tenellus), the vector of the virus.

Ideal conditions occur when springtime winds from the south or southwest carry infected beet leafhoppers from neighboring states into Western Colorado. These winds dry out vegetation in dry-land areas increasing the movement of leafhoppers into and through tomato fields. Weather conditions have been ideal this year for the movement of the beet leafhopper.

The following two photographs show stunting and rolling of leaves in the early stages of development of curly top virus on tomato.

As the disease progresses, the leaves yellow and veins turn purple. Infected plants eventually turn yellow and die. Note the size and color differences in the following two photos.

Symptoms on other vegetable crops: Beans, Beets, Bell Pepper, Pumpkin various Squash, and more tomatoes

The Beet Leafhopper (Circulifer tenellus)

Identification characteristics of this insect are:

lemon green base color, with dark banding on the abdomen, which may make some appear brown
slight roof shaped face, devoid of any spots
square terminal abdominal segment on males
semi-circular terminal abdominal segment on females

  Courtesy of http://www.ent3.orst.edu/kgphoto/index.cfm

Control Options

The beet leafhopper avoids dense plants, thus densely planted fields are less attractive to this insect. Shading and the use of row covers also reduces infections.

The beet leafhopper is a transitory insect in tomato fields spending little time to feed before moving to the next field or weed patch. This insect can build up in large number in weed patches and vegetables more to its liking. Weeds around tomato fields should be controlled. Sprays should focus on kochia and other Chenopodiaceae plants. These include lambsquarter, halogeton, Russian thistle, greasewood, and Atriplex (four wing saltbush). When spraying an insecticide on or near vegetables, check to ensure the product is labeled for vegetables.

Spray with a contact insecticide, such as a pyrethroid, to kill any insects present before implementing any form of weed control. Contact/residual insecticides applied to crops adjacent to the tomato field will help kill leafhoppers present and leave a residual to control leafhoppers landing in the treated barrier.

Curly Top Virus can be confused with Tomato Spotted Wilt Virus

Symptoms of tomato spotted wilt, caused by a virus spread by thrips, can be confused with curly top symptoms. The upper young leaves of tomato plants infected by tomato spotted wilt virus (TSWV) bronze and develop small dark spots or flecks. Curly top infected plants do not exhibit spots or flecks on the foliage. TSWV is responsible for the distinctive concentric rings seen on green and red fruit. The same conditions responsible for the movement of beet leafhoppers into tomato fields are also responsible for the increase in TSWV problems.

Note: Warm windy springs always result in an increase in tomato virus problems. Preventative treatments should be implemented as soon as such conditions occur. Do not wait until symptoms appear in the field before taking action.

For information on biology and identification of the Beet Leafhopper check out the web site at http://highplainsipm.org/HpIPMSearch/Docs/BeetLeafhopper-Sugarbeets.htm