Marijuana Business Magazine

BEYOND THE BUG: OTHER DAMAGE TO HEMP warm, moist environments – powdery mildew and Botrytis cinereal, a type of fungus sometimes called gray mold or noble rot. “Dirty hoses, used pots, used (growing) media – they can all lead to some nasty outcomes in a greenhouse,” Gauthier said. Indoor growers should use a disin- fectant such as quaternary ammonium chloride (brands include GreenShield or Physan 20) or even bleach to clean sur- faces between every hemp crop. Even a clean crop with no visible pests or disease damage could be grown in soil harboring nasty critters biding their time. Gauthier also recommends that indoor hemp growers install foot mats treated with disinfectant and require workers and visitors to use them before entering a greenhouse.The mats help prevent employees from tracking in microscopic pests from the ground outside. Disinfecting mats are commonly used in marijuana greenhouses and should be used in hemp greenhouses, too. B ugs, birds and disease aren’t the only culprits that can damage a hemp crop. Sometimes well-meaning growers can inflict damage by using cultivation techniques that work great on other crops, but not hemp. The damage is known as “mechanical” wounds – scrapes or cuts on a plant that can act like a skinned knee on a human and invite bacteria. “Mechanical wounds … can serve as entry points for various fungal pathogens like Botrytis,” or gray mold, said Nicole Ward Gauthier, plant pathologist at the University of Kentucky. One cause can be the improper use of plastic covering around the plants, Gauthier said. Opaque plastic sheeting – called plastic mulch – is routinely used to warm the soil for heat-loving plants such as peppers, melons and strawberries. Plastic mulch also inhibits weeds, making sheeting a tempting solution for a hemp farmer who doesn’t want to use chemical weedkiller. But make sure the plastic has room to accommodate a full-grown hemp plant, Gauthier said. “The plants will show damage where they’ve rubbed up against the plastic,” she said. You should also prune judiciously. Cuts on the hemp plant can make it more susceptible to mold and mildew. Other mechanical damage – namely wounds inflicted by hail and wind – can be unavoidable if the hemp is grown outside. In one of the few studies available on hemp production, a Canadian report published in 2000 noted the crop can face “significant” weather damage. “Tall plants with lots of upper leaf mass can be bent quite easily by mid- to late-summer storms,” the hemp researchers wrote. – Kristen Nichols Go Mechanical Even if the hemp is planted in pris- tine conditions, weeds can choke out the individual plants. So hemp growers say they’ve got to rely on old-fashioned mechanical means to keep weeds down. One such method for outdoor hemp farmers is cultipacking, where the soil is compressed to inhibit weed growth before putting down hemp seed. A cultipacker is a heavy iron roller that mashes dirt clods, eliminates air pockets and packs down stones to create a good seedbed. A secondhand cultipacker can be had for less than $500 on eBay, and the tow unit can be dragged behind a four- wheeler or tractor. Graves suggests planting in rows and physically chewing up weeds that grow between the hemp lines with a tractor. “It’s old-school cultivation. You plant in rows and chop out weeds in between, or run them over and mash them down,” Graves said. 50 • Marijuana Business Magazine • November / December 2017 ¬t’s old-school cultivation. You plant in rows and chop out weeds in between, or run them over and mash them down.