Marijuana Business Magazine

“I’ve got growers out here who are asking for help, asking, ‘What can we do?’ when they see pests,” Pearce said. The good news is that pest-fighting strategies are becoming more available. They range from using rich, healthy soil to being a stickler for cleanliness and employing old-fashioned mechani- cal technologies to combat things like weeds. Persistence also is a must. Moreover, additional help is on the horizon. Some research universities that have been slow to embrace marijuana are putting serious effort into research- ing hemp, a crop that is now legal to grow in 33 states. The 2014 Farm Bill authorized cultivation for research pur- poses and pilot programs. Hemp growers also can tap their cannabis colleagues who are cultivating marijuana. After all, hemp and marijuana are both the species Cannabis sativa and susceptible to many of the same pests and diseases. From leaf-chewing caterpillars to seed-stealing finches and microscopic organisms, plenty of visible and invisible critters can set in. Below are expert tips and advice for managing the weeds, insects, diseases and other threats that can target hemp. Indoor Versus Outdoor The first question for a hemp grower is where to raise the crop.There are pros and cons to growing hemp in a green- house or warehouse versus outdoors, and pest management is a big consideration. Bugs are a problem in either environ- ment. But while greenhouses frequently see pests drawn by heat and humidity – especially mildews and molds – outdoor hemp fields are susceptible to different bugs and even bird attacks. That means a hemp grower needs an action plan to address pests in either environment. “We look at greenhouses differently than we look at a field,” said Nicole Ward Gauthier, a plant pathologist for the University of Kentucky Cooperative Extension Service. “There are different types of disease pressures in each system.” Start with Great Soil It sounds like a no-brainer, but tradi- tional farmers experimenting with hemp are often tempted to try the crop on a piece of marginal land – tucked away from public view and not the farmer’s main revenue producer. That can lead to avoidable mistakes. “It’s not a straightforward thing of just go put hemp in a field and it’ll grow,” said Tom Hutchens, director of research for Atalo Holdings, a hemp research, development and processing company in Winchester, Kentucky. Hemp needs well-drained loam soil – so avoid valleys or anywhere with standing water after a rain. And hemp gobbles nitrogen from the soil, mak- ing it a bad choice in an area with low nitrogen levels in the first place. Even in nitrogen-rich soil, hemp can need an additional 130 pounds per acre of nitrogen before harvest. And don’t put hemp where the soil might already be harboring rots or bor- ers that also attack hemp. Researchers suggest not planting hemp on land that just held canola, edible beans, soybeans or sunflowers – all invite pests that are also known to infect hemp. Greenhouse and warehouse hemp growers need to think about soil or grow- ing matrix, too. Make sure not to recycle soil that might have any pathogens in it, such as gray mold (Botrytis cinereal) or white mold (Sclerotinia scleroriorum). Keep it Clean Cleanliness also is essential. Hemp grown indoors often suffers from the same pests that plague marijuana in EXECUTIVE SUMMARY Hemp farmers have limited resources to fight pests and disease, but growers are borrowing expertise from marijuana and other crops. Here’s a summary of expert advice on battling hemp’s natural enemies: • Start with the best environment. Proper ventilation is key, as is soil or growing matrix rich in nitrogen. • Be a stickler about cleanliness. Avoid dirty hoses as well as used pots or growing media – and do use disinfecting foot mats with an indoor grow. • Don’t cover the plants. Plastic and nets can be tempting ways to repel birds and weeds. But hemp plants can be damaged when they rub against the barriers. • Think of yourself as a pre-modern farmer. Weeds may need to be physically chopped down, using old-fashioned mechanical means or by hand. • Don’t get complacent. It can take a couple years for bugs and other pests to discover a new food source in the area. Nichole Ward Gauthier, plant pathologist. Photo courtesy of the University of Kentucky 48 • Marijuana Business Magazine • November / December 2017