The Beet Leafhopper Strikes Again!

 

Southwest Yard & Garden

By Bethany Abrahamson

 

Photo credit: K. DeHoff. 

 

QUESTION: What could be causing my tomatoes to die mid-season?

                                        --K. DeHoff, Sandoval County 

ANSWER: Samples from this unfortunate situation were collected and sent to the folks at the NMSU Plant Diagnostic Clinic. While there are many diseases that affect tomatoes (check out Bernalillo County Extension's Tomato Resources website for some of the major culprits), the clinic immediately identified the cause in this case as beet curly top virus (BCTV). This virus affects hundreds of broadleaf plant species, including beets, tomatoes, peppers, beans, pumpkins, and more. This has been an ongoing problem for New Mexico chile growers, particularly this season. Symptoms vary by host, but infected plants generally exhibit curled leaves, dull wrinkled fruit, and reduced yield. Once infected, there is no cure for the virus. 

From my conversations this year it seems that BCTV is especially prevalent once again, possibly because of the warm winter, and this innocuous looking little bug, the beet leafhopper (Circulifer tenellus):

Beet leafhopper adult. Photo credit: A.C. Magyarosy, Bugwood.org, CCBY NC 3.0

While most garden insects are harmless or even beneficial, beet leafhoppers can be deadly to crops. This topic was discussed on Southwest Yard and Garden back in 2021, but I thought I'd take the opportunity to take a closer look at the culprit behind the disease. 

Beet leafhoppers are true bugs that belong to the family Cicadellidae, and are related to cicadas, treehoppers, and planthoppers. They are about 1/8th of an inch long and their color can vary from pale green to gray to tan. They can be difficult to identify without some practice. Leafhoppers go through incomplete metamorphosis, so instead of having a larval stage and an adult stage (like a bee, beetle, or butterfly), they go through several immature nymph stages that look like tiny versions of the adults. 

 

Beet leafhopper nymph. Photo credit: Whitney Cranshaw, Colorado State University, Bugwood.org CCBY 3.0

These insects use their piercing-sucking mouthparts to feed on plant tissues. When disturbed, leafhoppers hop to escape. These behaviors together are what cause such a big problem. If a beet leafhopper feeds on a plant infected with BCTV, then hops to another plant to feed, it can transfer (or vector) the virus to the new plant. Only beet leafhoppers are capable of spreading BCTV. It takes less than a minute of feeding to transmit the virus to a new plant, and then it's too late. 

The typical life cycle and wide host range of the beet leafhopper contribute to the problem. In the winter, beet leafhoppers survive on annual mustards like London rocket, flixweed, and Russian thistle. 

London rocket. Photo credit: Joseph M. DiTomaso, University of California - Davis, Bugwood.org , CC BY NC 3.0  

A warm winter means leafhoppers have even more weeds to live on and are less likely to die off. Leafhoppers then emerge in early spring, moving into crops and completing their lifecycle in just a few months. Multiple generations can develop during a single growing season, especially during the long growing seasons we have across much of New Mexico.  

Wondering if you have beet leafhoppers? A yellow insect sticky card, common in the integrated pest management arsenal, can be placed near the plants of concern to find out. You can also try monitoring your crops with a fine-mesh insect net. A dissecting scope, jeweler's loupe or hand lens can help with identification. Make sure sticky cards are out of reach of children and pets, and always follow the label. 

If you have beet leafhoppers in your area, there are some opportunities to protect your tomatoes from the worst of the virus. Row covers or netting with very small holes can keep the bugs out (check now and then under the cover to ensure that other pests didn't sneak in). Also, don't forget to do your weeding even as your crop growing efforts die down this fall-- keeping on top of London rocket stands reduces overwintering spots for beet leafhoppers. 

 

NMSU Agricultural Science Center at Los Lunas staff work on a row of tomato plants covered by shade fabric during a study on curly top virus. NMSU Gallery photo.

Shaded planting areas (like those under row covers) can discourage beet leafhopper activity since these insects prefer to feed in sunny spots. There are also some varieties of crops that are more tolerant of beet curly top virus or do not get the virus at all (such as onion, garlic, and corn). Even if your plants are exposed to infected beet leafhoppers, you can still get a great crop.  

The beet leafhopper is one pest where chemical control can do more harm than good. Leafhoppers are extremely mobile, so a pesticide application may just as likely harm beneficial insects that feed on beet leafhoppers and other pests. Some of these garden 'good guys' include big-headed flies, ants, and assassin bugs. See if you can find any in your garden, or consider creating an insectary habitat to attract them for even more natural pest control!  

 

This striking assassin bug was found at the Sandia Natural History Center near Albuquerque. Photo credit: Bethany Abrahamson.  

There is a happy ending to this story: netting saved the next crop of tomatoes at this location! The up-side to our long growing seasons is that even if you lose some plants to BCTV, there is still hope for another planting. So, don't give up!

If you suspect beet curly top virus in your garden, bring a sample to your local Cooperative Extension Office where it can be sent to the NMSU Plant Diagnostic Clinic for analysis. Remember, there are lots of leafhopper species and only some of them are pests. Be sure to correctly identify insects before trying to control them and your garden will thank you!

For more information on beet leafhopper and BCTV:

Integrated Pest Management (IPM) Strategies for Common Garden Insect Pests of New Mexico by A.J. Freeman, M.L. Kersten, A. Skidmore, and M.Y. Thompson, NMSU Extension Guide H-176 (2021).  

Curly Top Virus revised by N. Goldberg and P. Lujan, NMSU Extension Guide H-106 (2021).

Beet leafhoppers by D. Wickwar and E.J. Winnegar, University of Idaho Extension (2023). 

Beet leafhopper (Neoalitarsus tenellus) and beet curly top virus, Colorado State University Extension (2022).  

For more gardening information, including decades of archived Southwest Yard & Garden columns, visit the NMSU Extension Horticulture page (http://desertblooms.nmsu.edu/), follow us on social media (@NMDesertBlooms), or contact your County Extension office (https://extension.nmsu.edu/county.html).

 

Bethany Abrahamson is a Cooperative Extension Agriculture Agent for Sandoval County.