WDC56: Hemp pest management and production in the western USA

(Multistate Research Project)

Status: Active

WDC56: Hemp pest management and production in the western USA

Duration: 02/01/2023 to 09/30/2024

Administrative Advisor(s):

NIFA Reps:

Non-Technical Summary

Statement of Issues and Justification

Hemp Cannabis sativa has been produced legally in the USA beginning with the 2014 Farm Bill and Hemp Farming Act of 2018 which allowed for the renewed legal cultivation of the crop. The 2014 bill provided a formal definition of the crop as "the plant Cannabis sativa L. and any part of such plant, whether growing or not, with a delta-9-tetrahydrocannabinol (THC) concentration of not more than 0.3 percent on a dry weight basis".

In much of the western USA, this prompted a surge in industrial hemp cultivation. In 2019, hemp production was 206, 965 hectares with 16,877 grower licenses across 34 states, according to "US Hemp Report" (www.votehemp.com). This is a greater than 455% increase over 2018 licensed acreage. Colorado, the leading state in hemp production increased production from 4,873 licensed hectares (346 growers) in 2017 to 12,525 licensed hectares (835 growers) in 2018. The US retail sales of hemp products was reported at $1.2 billion in 2018. The most profitable market for North American hemp is oilseed production and cannabidiol (CBD), a nonintoxicant cannabinoid with promising therapeutic use as a pharmaceutical product. Current CBD sales are estimated at $190 million and are projected to reach $2.5 billion by 2022.

That renewed beginning of hemp production led to a steep learning curve in how to successfully cultivate industrial hemp and major adjustments to the CBD/hemp markets. The learning curve has included AES and CES personnel from western states with no previous experience with the crop, its cultivation, and its pests.

Hemp is grown throughout the world, with the plant optimal temperatures listed as 60-80 F and sensitivity to daylength for seed set (USDA, 2000). Much of the breeding work for hemp has traditionally been done in Canada and China. All these factors suggest that most hemp varieties are not ideally suited for the warmer conditions in the western USA.

Unlike hemp grown in the USA in the 1940’s, industrial hemp is now grown for three components: CBD, grain, and fiber. However, in the western USA, CBD production has dominated. The lack of infrastructure, markets, and reliable sustainable sources of seed/clones have been a major stumbling block for hemp production. CBD hemp production has relied on the use of clones, while grain and fiber varieties are grown from seed. There are few to no pesticides registered for the crop, which leads to difficulties in the organic production needed for CBD hemp production.

Hemp grown in the western US faces many unique problems from pests and cultivation issues that differ from that grown in other parts of the US. There are a variety of fungal root rots and viruses that infect hemp and several insects that cause damage. For example, curly top virus caused significant losses or greater than 90% to hemp fields in western Colorado in 2019. Hemp grown for CBD in Colorado averages more than $50,000 per acre.

Hemp genetics research and plant resistance to pests has been quite limited and are really just in the initial stages. Sustainable management programs for pests and pathogens of hemp are mostly in the research and development stages but will require an integrated approach only possible when individuals with different areas of expertise work together.

We propose the initiation of a WERA group to address these problems.  This committee will meet to discuss, assess, and prioritize required research into hemp genetics, pests and their management, hemp cultivation, and hemp processing.  Individuals will share their best practices, which is the greatest benefit for active participation in the group. The committee will coordinate action plans to determine who will accomplish which aspects of the needed research, including who will work together to seek funding for the highest priority research.  The group will also coordinate research to provide preliminary information needed to secure grant funding.

Related, Current and Previous Work

Hemp is a relatively new crop for the USA. Sales of hemp products in the United States have been growing at a very rapid rate since legalization of the crop with the 2018 farm bill. The market is highly volatile. The prices of CBD raw biomass, dried CBD flower, crude hemp oil, refined hemp oil, and CBD isolates have all dropped within the past two years, due to market saturation. However, the market for hemp for grain and fiber are less defined in much of the US and are expected to grow substantially through the next few years. For hemp to be highly successful, it will also have to provide expected returns equivalent to returns for competing crops.

In addition, there is a highly structured permitting process with state and federal oversight, and sometimes local laws, governing production. There are some differences between states, but all require permits before planting hemp and testing for THC level prior to harvest. In some locations, local ordinances prevent growing hemp outdoors if it could pollinate cannabis crops.

Other concerns for hemp production are market development, proper storage, and access to reliable seed or clones. While some of the hemp being produced is done on a contract basis, in other situations, the market is not well established. Most of the contracts do not pay the producer until the processor has sold its final product. In addition, hemp for grain, fiber, and CBD need to be stored until it is time for them to be used.

For grain and fiber crops, conventional production practices from seed are followed. In contrast, CBD hemp is grown from clones in greenhouses or fields. CBD hemp is often grown using organic production practices since the CBD could be consumed. In addition, there are no herbicide, insecticide, or fungicides currently labeled for use in hemp. It is possible that legalization of pesticides for fiber, and possibly grain hemp, would be pursued through minor use registration.

Access to certified reliable seed and clones is a problem for many producers. Much of the current stock of seed has been developed from northern climates and leads to premature flowering in warmer southern climates. Genetic selection is very important because some clones grown for CBD extraction contain illegal levels of THC (>0.3%) at harvest, necessitating destruction of the crop. Compliance with THC levels is less of a problem for grain and fiber producers but requires that they have a reliable seed source. Harvest can be a problem for some producers. There is a 30-day harvest window that begins with the final regulatory test for THC levels, which can cause time constraints due to labor intensiveness of harvest for CBD hemp.

The hemp industry in the western U.S. needs concentrated crop testing. Efforts to better understand yield potential, production factors, harvesting methods, handling, storage, and processing for crops grown in the region are essential. Hemp is not adapted to desert environments and cultivation of the plant in hot arid field conditions needs additional research.

Industrial hemp is produced for three components: 1) CBD extraction, 2) Fiber, 3) Seed/grain. Currently in the western US, little of the crop is grown for fiber or seed/grain.

  • CBD hemp

Cannabinoids have been used for many potential medicinal properties including aiding sleep, pain relief. The flower buds of unfertilized female hemp plants are used for extraction of CBD or sometimes as smokeable flower buds. Similar to marijuana cultivation, plants begin from clones of feminized plants. Efforts are made to remove any male plants and to discard any plants that produce seed, which indicates fertilization. Light intensity is manipulated to achieve optimal flower bud production. Plants grown outdoors are generally harvested in September to early October. Since levels of THC increase with increased CBD levels, plants are usually harvested by hand based on laboratory testing of CBD/THC levels to avoid illegal levels of THC. After harvest, the plants are trimmed, dried, and stored.

2) Fiber

The stalk is largely used for fiber. Fiber from the plant can be utilized in numerous ways ranging from yarn and fabric to electrical super-capacitors manufactured from carbon nanosheets. While traditional use of the fiber was for rope, it is not cost effective to use hemp fibers for products that are generally imported from China.

Dioecious hemp crops produced for fiber typically are harvested when the male plants have finished flowering, typically in August-September. Traditional hay making equipment can be used for hemp fiber harvest, but cuts the fibers into shorter lengths (Ehrensing, 1998).  Harvesters and collection systems developed for cotton production have been used experimentally for collecting hemp fibers since the plants are chopped and less tangled during harvest.  Such systems also require less handling through the collection and process stages, allowing for longer fiber lengths.  This requires modification of the harvesting equipment, but in areas already producing cotton, the equipment is available. Prior to processing, the hemp fibers must be decorticated. The decortication process for hemp mechanically removes the tough woody interior (the hurd material) from the softer, fibrous exterior of the stalk. (In wetter areas that can be done in the field with water over 2-6 weeks.) Equipment for this process is not readily available in much of the western US near where hemp is grown, thus increasing costs associated with hauling the hemp to a processing facility. It is also possible to modify the cotton processing equipment to decorticate the hemp. Ultimately the optimum harvest system will depend on the market value of the fiber.

3) Seed/grain

Hemp seed is sold as grain and also has is useful for oil production and animal feed.  Hemp grain is relatively high in oil content; generally containing 30% or more by weight. This oil is very healthful as a dietary constituent or supplement for humans. It is rich in omega-3 fatty acids and has a very favorable omega 3 to omega 6 ratio of about 3:1. This is much higher than that found in many other oil seeds. The grain is also high in protein and contains all 20 amino acids (Russo and Reggiani 2015).

Hemp grain processors in Canada produce a wide array of consumer products including toasted hemp seed, hemp seed oil, hemp flour, and even hemp coffee.  It is also used as bird feed and livestock feed, either whole or in part (as a high protein hemp seed meal and hulls), much the same as soybean meal and hulls are used today.  Hemp grain is an important commodity crop in Europe, where approximately 80% of the grain is used as animal feed. 

Harvesting industrial hemp grain by combine is the norm in other countries and has been successful in the northern US.  Variety selection is key as the growth habits of those varieties bred primarily for grain production are more conducive to harvest by combine. Crops grown for seed oil production need to be harvested once seeds are mature. After harvest, the grain is cleaned and dried to prevent spoilage.

The S1084 Industrial hemp production, processing, and marketing in the US regional project has addressed portions of this topic. That project, which runs through 9/30/2022, has focused on hemp production in the southeastern US, which has very different growing conditions than the western US. As a result, hemp grown in the western US has different cultural and pest problems than that grown in the southeast. 

Our WERA group was developed after a meeting of the Western Hemp IPM working group (funded by the Western IPM Center). That working group already contained sustainable collaborations among group members and sharing of information.  For example, the Nachappa and Creamer labs have been involved in studying the ecology, epidemiology and disease mitigation strategies for beet curly top virus in hemp (funded by FFAR - Foundation for Food and Agriculture Research).


  1. Assess the current status of hemp cultivation and management and set priorities for integrated research on hemp pest management and cultivation in the western USA.
  2. Characterization of biology of hemp pathogens, insect pests, weed pests, and nematodes including identification, genetic diversity, and detection.
  3. Organize research on the ecology and epidemiology of the pathogens and their insect vectors and transmission, insect movement, and the role of weed hosts in carry over of insect and pathogens of hemp in the western US.
  4. Organize research to improve management of pests and pathogens of hemp important in the western USA.
  5. Organize research on hemp cultivation in the western USA including factors such as seed/clone selection, transplant difficulties, irrigation, heat stress, early maturity day length issues, and excess THC levels.
  6. Organize research on hemp production at and after harvest in the western USA including factors such as harvest, extraction of CBD, equipment necessary for harvesting grain hemp, equipment needed for processing fiber hemp, and marketing essentials.
  7. Provide a national platform for education on hemp, pathogen and pest ecology and management, hemp cultivation and processing, and collaboration among scientists involved in these activities, and extension of research-based information for producers.


Measurement of Progress and Results


Outcomes or Projected Impacts


Projected Participation

View Appendix E: Participation

Outreach Plan


Literature Cited


Land Grant Participating States/Institutions


Non Land Grant Participating States/Institutions

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