Cannabis cultivators are up against many day-to-day challenges, from compliance and legal issues to plant health. Nutritional, physiological and pest issues are among those that can negatively impact cannabis crops, but knowing the potential problems and how to identify them will help cultivators treat them early, before too much damage is done.
Here, Dr. Brian Whipker, professor of floriculture at North Carolina State University, provides insight into common disorders that affect cannabis plants and shares tips on how to diagnose them.
Cannabis Business Times: What are some of the most common nutritional, physiological and pest issues that affect cannabis crops?
Dr. Brian Whipker: Nutrition-wise, nitrogen rates are probably the biggest [concern], [followed by] the substrate pH. I think those two are the biggest ones, and then, what kind of nutritional balance do people need?
Physiological [issues include] guttation, [or] water droplets appearing on the leaves, and then you can get salts on there.
Pest-wise, the biggest pests that we run into [are] broad mites, russet mites, spider mites and hemp aphids. Those are probably the biggest pests [in greenhouses]—I know people are trading those around.
CBT: What are some best practices for avoiding these kinds of nutritional disorders?
BW: We have a system—basically, it’s PVC pipes in the greenhouse—for veg and clones. We have four benches, [and] we use fertilizer salts that are pure, and a recipe. It we want to use magnesium, we have a recipe for magnesium fertilizer to balance it.
CBT: What is your advice for identifying pest issues?
BW: Most of the ones I talked about, the bigger ones, you can see with a 10x hand lens, but in reality, with a russet mite, you may need closer to an 80x or 100x microscope for identification. [Cultivators should implement] pre-screening and ID if [plant material is] from an outside source. [As] part of the inspection of any new plant material coming in, there’s screening they can do. [They should] have a 10x lens, but also an 80x to 100x, so they can see things in the microscope and see what’s going on.
That’s probably where the need is because by the time they see symptomology, you have a significant infestation. [For example,] with russet mites, they’ll make the leaves [hang down,] but that’s not one or two—that’s [close to] 1,000 of them on the leaf because they’re really small.
CBT: What do you hope attendees will bring back to their business from your session at Cannabis Conference 2020?
BW: On the disorders, I hope they’ll learn the symptomology of those and realize that if they see those [symptoms,] then there’s a problem that needs correction.
Editor’s Note: This interview has been edited for style, length and clarity.
