Beet Leafhopper (Neoalitarsus

tenellus) & Beet Curly Top Virus

Order: Hemiptera
Family: Cicadellidae

Description

Leafhoppers are generally small, torpedo shaped insects that have long bodies relative to their width, and their hindlegs have one or more rows of spines. Some species are brightly colored while others camouflage with the host plant. Both adults and nymphs are highly mobile and will jump away from physical disturbances.

In Colorado, the most common leafhopper in hemp is Ceratagallia uhleri, which does not cause injury to plants. Ceratagallia spp. are typically brown or dark gray with brown markings. Adults of beet leafhopper are pale green in the summer and roughly 3.3-3.6 mm (0.13-0.14 inches) long. There are no markings on the head unlike many other leafhopper species, and this feature can be used to distinguish beet leafhopper from other leafhopper species found in hemp.

Quick Facts

• Beet leafhoppers are small insects in the order Hemiptera. They have piercing-sucking mouthparts and are major pests of sugar beets. It is an important vector of the beet curly top virus (BCTV), which can significantly reduce plant health.
• BCTV is much more prevalent in western Colorado than in eastern Colorado. In 2019, there was a damaging outbreak of BCTV in the state.
• Hemp appears to be highly susceptible to BCTV, which was first reported in hemp grown in western Colorado in 2015. Young plants are especially susceptible to this virus.

Beet leafhopper

Beet leafhopper adult
A.C. Magyarosy, Bugwood.org

Beet leafhoppers are small insects in the order Hemiptera. They have piercing-sucking mouthparts and are major pests of sugar beets. Beet leafhoppers are also vectors of the beet curly top virus (BCTV), which is capable of infecting various cultivated plants including hemp. Young plants are the most susceptible to infection and this virus can significantly reduce hemp yields. Management recommendations for beet leafhopper in hemp primarily involve cultural and chemical control.

Nymph of Ceratagallia uhleri

Nymph of Ceratagallia uhleri on a hemp leaf
Melissa Schreiner, Colorado State University, Bugwood.org

hemp plant infected with bctv

Hemp plant infected with beet curly top virus. Note the curling of leaves
Whitney Cranshaw, Colorado State University, Bugwood.org

Hemp plant yellowing

Hemp plant infected with BCTV. Note the yellowing and stunted growth of the plant, even in the absence of leaf disfiguration.
Whitney Cranshaw, Colorado State University, Bugwood.org

Witches broom on jujube tree

Jujube tree with multiple witches’ brooms, caused by infection of a phytoplasma.
William M. Brown Jr., Bugwood.org

Life History and Habits

Females of beet leafhopper begin laying eggs in the early spring, and each female can lay hundreds of eggs. There are typically multiple generations per year. Eggs are elongated, slightly curved, and white or yellow, and they are deposited singly inside leaves and stems.

Nymphs develop through five instars. The first instar is transparent white after emerging from the egg but within a few hours it becomes yellow or green, and later instars have black, brown, and red spots. The beet leafhopper acquires BCTV by feeding on infected weeds and can transmit the virus to nearby cultivated plants.

Injury

The transmission of BCTV through beet leafhopper feeding poses a significant threat to hemp cultivation, even though the feeding itself does not significantly injure the plant. Infected plants will display various symptoms depending on the plant’s growth stage at the time of infection. Young plants are the most susceptible.

Leaves of young hemp infected with BCTV have light green color and yellowing of new growth is common. Older leaves of infected plants tend to display dark and light green mottling due to chlorosis. The mosaic mottling continues into mid growth of the plant and includes more severe yellowing. Infection at this stage will cause curling and twisting of new leaves. Leaves of the apical meristem will also be stunted with a shortened stem at the internode, producing a symptom known as “witch’s broom”.

The symptoms described above typically appear at or above the infection site and seem to occur on individual branches. Some branches show no symptoms and will cover and outgrow symptomatic branches. Symptoms of late-stage infection include severe curling and possibly twisting of leaves, stunting, and necrosis of yellow leaves. All these symptoms will significantly reduce yields, and dwarfed plants with severe infections tend to experience high mortality later in the season. It is unknown whether BCTV is seed transmitted.

Monitoring

Treatment thresholds have not yet been established for beet leafhopper in hemp, but the pest should still be monitored to determine whether control measures are necessary. Note that other leafhopper species may be present in hemp fields, therefore accurate identification of beet leafhopper is crucial. To monitor beet leafhopper in hemp, yellow sticky cards can be placed on the field edges, inspected weekly, and replaced as needed. Sweep nets can also be used to conduct surveys in fields.

Biological Control

There are many natural enemies of beet leafhopper, including spiders, green lacewings, assassin bugs, bigeyed bugs, and certain species of parasitic flies and wasps. When possible, these natural enemies should be promoted in the field through appropriate means of conservation biological control.

Cultural Control

Since young plants are the most susceptible to BCTV infection, deploying a physical barrier over seedlings can help protect against beet leafhoppers. Trap crops can also be planted on the edge of fields to concentrate the pest in these areas for targeted sprays. Sugar beet is the preferred food source of the beet leafhopper and makes for an ideal trap crop.

Scouting nearby crops and weeds for the presence of beet leafhopper is recommended. When beet leafhopper is present, these breeding areas should be treated with both soil and foliar applications. This will help knock down beet leafhopper populations before they begin migrating to nearby hemp fields.

Chemical Control

Beet leafhopper is resistant to many commonly used pesticides in its preferred host – sugar beets – and utility of pesticides commonly used in hemp in Colorado is still under investigation.

References

California Department of Food and Agriculture. (n.d.). Beet Curly Top Virus Control Program. Available https://www.cdfa.ca.gov/plant/ipc/curlytopvirus/ctv_hp.htm

Colorado State University. (n.d.). Leafhoppers. Available https://webdoc.agsci.colostate.edu/hempinsects/PDFs/Leafhoppers%20Revision%202020.pdf

Hu, J., and Masson, R. 2021. Beet Curly Top Virus in Industrial Hemp. The University of Arizona: Cooperative Extension. Available https://extension.arizona.edu/sites/extension.arizona.edu/files/pubs/az1931-2021.pdf

Oregon State University. (n.d.). Hemp-Leafhoppers. Pacific Northwest Pest Management Handbooks. Available https://pnwhandbooks.org/insect/agronomic/hemp/hemp-leafhoppers

University of California. (n.d.). Pests in Gardens and Landscapes: Leafhoppers. University of California – Statewide Integrated Pest Management Program. Available http://ipm.ucanr.edu/PMG/GARDEN/VEGES/PESTS/leafhopper.html#:~:text=Leafhoppers%20have%20one%20or%20more,not%20resemble%20that%20of%20adults.