As the growing season gets underway, hemp growers should monitor their fields for beet leafhopper adult populations. Beet leafhopper insects that vector (transmits from a diseased plant to a healthy plant) beet curly top virus can infect a variety of agricultural crops including sugar beet, tomato and hemp.
Below is information focused on beet leafhopper adult monitoring and management tips. To know more about the epidemiology and symptoms of beet curly top virus on hemp, check out Hemp (Cannabis sativa)- Beet Curly Top disease page from Pacific Northwest Disease Management Handbook.
In the fall, beet leafhopper adults overwinter in weedy habitats, and then during the spring and summer seasons they migrate to crop fields and can transmit beet curly top virus into hemp plants. Monitoring for the adults is particularly important if you experienced virus damage in hemp fields during previous years.
In some situations, you may find beet leafhopper adults on hemp plants or in the surrounding landscape, but those plants may not be infected with the virus and not show disease symptoms. Therefore, monitoring and testing the beet leafhopper adults for beet curly top virus presence is important.
Depending on the field size, one or two traps can be used to monitor the beet leafhopper adult population on hemp. A trap can be installed and mounted on a wooden stake, about one to two feet above ground level, and the trap can be secured with a binder clip (Figure 1A). Traps should be checked regularly, sticky cards changed every week and fields monitored until midseason.
Finding beet leafhopper adults on yellow sticky traps can be challenging. Yellow sticky traps are attractive to a variety of insects including flies, thrips, lygus bugs and several leafhopper species (including beet leafhopper).
In general, leafhopper adults are elongate in shape, narrowing from head to tail, their wings appear like a roof over the body while resting and the size ranges from 3 to 10 mm long. When compared with other leafhopper species, the beet leafhopper adult specifically does not have a dark spot on the head; the head is rounded in front; adults have two color forms that include light pale-yellow-colored form and dark-pale-colored forms (Figure 1B). A hand lens or stereo microscope is helpful when identifying the beet leafhopper adults on sticky traps.
You can also send insect samples to the OSU Plant Clinic for identification or contact your local OSU Extension Office/Research and Extension Center for other service sites for beet leafhopper identification and BCTV testing.
Management tips
There is limited information on beet leafhopper and beet curly top virus management on hemp. However, both the pest and the disease are not new, occurring in many other crops (e.g., sugar beet, tomato and peppers); it is therefore applicable to explore the following strategies established for other crops until further research is conducted for the hemp production system.
- Avoiding transplanting very young hemp seedlings may help to minimize beet curly top virus damage although the yield may be compromised. In other crops, the earlier that plant stages are infested with beet leafhoppers that carry the virus, the greater the damage to plants.
- Several weed species (such as Kochia, Russian thistle, bindweed, dandelion, and chicory) can be breeding grounds for the beet leafhopper and are hosts for beet curly top virus. In spring and summer, the removal/control of weeds around hemp field edges may help to reduce the migration of local virus-infected beet leafhopper populations to hemp plants.
- Removal of virus-infected hemp plants will help to reduce the spread of the virus to other hemp plants during the cropping season.
- Although no beet leafhopper pest control products have been tested on hemp, a Kaolin particle formulation (Surround WP) is currently registered for use on hemp in Oregon and has shown to reduce beet curly top virus incidence in chili pepper crop.
