Insect Pests of Hemp: Relying on the Power of Integrated Pest Management

Jeffrey A. Davis

The cornerstone of pest control in modern agriculture is integrated pest management (IPM). This concept, born from the over-reliance on insecticides in the 1950s and ’60s, was created to address insecticide resistance, environmental degradation and high chemical residues on food. Today, integrated pest management is defined as a pest management strategy that focuses on prevention of pests through a combination of multiple methods based on ecological principles and socioeconomic considerations. Each pest management system differs by crop, location and production system. By default, integrated pest management programs are dynamic to address changing crop values, input costs, environmental conditions and pest complexes. However, all integrated pest management programs have the key components of monitoring, identification, consulting action guidelines and applying control strategies.

Hemp, defined as cannabis with less than 0.3% tetrahydrocannabinol (THC), according to the Hemp Farming Act of 2018 provisions incorporated into the 2018 U.S. Farm Bill, has a unique history in U.S. farming. For many centuries, hemp production was encouraged for clothing, rope and sailcloth. In Pennsylvania, Virginia and Maryland, hemp was used as money, and in the early 1600s, Virginians were required to grow hemp by law. After the Civil War, hemp production decreased as imports of other products increased. However, at this time, marijuana became a main ingredient in medicines and was sold at pharmacies. By 1937, hemp production was banned within the U.S. with the passing of the Marihuana Tax Act.

Fast forward 81 years, and hemp production is legal again. With the passing of those decades, however, knowledge on production practices has been lost. Furthermore, insecticides, the primary tactic farmers use to control insect pests, have just begun to be registered by the Environmental Protection Agency for use in this crop. In December 2019, EPA approved adding hemp to the use sites of 10 pesticides. Specific information can be found at the EPA webpage titled Pesticide Products Registered for Use on Hemp. Currently, the only other products available for use on hemp are those exempt from EPA regulations — those listed under Section 25(b) of the Federal Insecticide, Fungicide Rodenticide Act (FIFRA). More information can be found at the Minimum Risk Pesticides webpage. Regardless of the type of product, all must be registered with the Louisiana Department of Agriculture and Forestry.

The most important advantage hemp producers today have over those before 1937 is the 70-plus years of accumulated knowledge of integrated pest management. Louisiana producers are already seasoned practitioners in agronomic crops like cotton and soybeans and in horticultural crops such as strawberries and tomatoes. Integrated pest management strategies are used in forestry, ornamentals, urban settings and stored products. Louisiana producers do not rely just on insecticides. They practice cultural techniques, such as planting at certain dates to avoid the highest pest incidences; biological control, which means using natural enemies to control pest numbers; and host plant resistance, which means choosing varieties resistant to pest injury.

This year, 2020, will be the first year that hemp will be grown in Louisiana since 1937. The insect, weed and disease problems hemp producers will face are still largely unknown. An article was recently published describing all known accounts of insects found on hemp in the U.S. Another source of information for insect pests in hemp relevant to Louisiana comes from a video by Katelyn Kesheimer, assistant professor and hemp extension entomologist at Auburn University. In it, she discusses the insect problems Alabama hemp producers faced in 2019: hemp russet mite, fire ants and corn earworm. Likely, these will be insect problems Louisiana will also face.

Using the strategy of integrated pest management, entomologists along with other AgCenter scientists and agents are taking a coordinated, step-by-step approach to helping Louisiana farmers produce the best hemp crop they can.

For more information, go to industrial hemp on the LSU AgCenter website.

Jeffrey A. Davis is a professor and field crop entomologist in the Department of Entomology.

(This article appears in the spring 2020 issue of Louisiana Agriculture, which focuses on entomology.)

People looking at hemp plants growing in pots.

More than 500 people participated in the LSU AgCenter’s first industrial hemp informational meeting on Nov. 13, 2019, held at the State Evacuation Center near Alexandria. They got a firsthand look at hemp plants grown by LSU AgCenter plant breeder Gerald Myers. Photo by Bruce Schultz

A panel of four scientists giving a presentation at meeting.

LSU AgCenter plant pathologist Raj Singh, far left, talks about pest problems that hemp will face in Louisiana during an informational meeting Nov. 13, 2019, held at the State Evacuation Center near Alexandria. Singh is part of an AgCenter hemp working group along with, left to right, AgCenter entomologist Jeff Davis, AgCenter plant breeder Gerald Myers and AgCenter weed scientist Ron Strahan. Photo by Bruce Schultz

Growing hemp.

Industrial hemp in Kentucky. Photo courtesy of the U.S. Department of Agriculture

6/16/2020 7:36:37 PM
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