Plant Protection in a World of Pests: Q&A With Dr. Raymond Cloyd

Plant Protection in a World of Pests: Q&A With Dr. Raymond Cloyd

Cannabis growers must understand the pests that love their plants.

July 26, 2022

Pests are everywhere, and they happen to love the crop that your team is growing. Whether you’re working indoors or outdoors, a host of tiny antagonists await your plants.

So, what’s a cannabis grower to do?

One of the great fronts against mite pests is the world of biological control agents. These predator mites fight back against the problem. This process is called integrated pest management or “plant protection,” as Kansas State University entomologist Dr. Raymond Cloud puts it in this interview.

We spoke with Cloyd ahead of his research-based panel discussion at Cannabis Conference 2022 to learn more about how to combat pesky pests. 

Eric Sandy: What drew you to study insects in the first place?

Raymond Cloyd: I've always been interested in biology and the sciences throughout my life. Around high school, I really was fascinated by the diversity of insects, the number of them and just all the wonders of insects. I liked the different morphology and their evolution processes. It's very fascinating dealing with a group of organisms that is by far the largest on the planet.

ES: Were there certain crops you found yourself working with early on?

RC: I'm primarily in horticultural entomology, which includes ornamentals in greenhouse, nursery and landscape. I do turfgrass and vegetables and fruits, Christmas trees, cannabis, hemp, and I also work with the pollinators—beekeepers and such—but it's mostly horticulture crops. I don't deal with the fuel crops, like corn, soybeans, cotton, rice. That's handled by other entomologists. So, it’s quite diverse.

Cannabis, as a result of being grown in greenhouse production systems or outdoors, has its cadre of insects or mite pests that we deal with, which are almost the same as those that deal with ornamental plants. Aphids and mites and thrips are probably at the top of the list. And then you can talk about fungus gnats and the infamous hemp russet mite, which is a different mite than the two-spotted spider mite. The insect mite pests that are common in ornamental production and greenhouses are going to be similar to what a cannabis grower will experience when they're growing indoors.

ES: When did you start getting involved with cannabis?

RC: It was four or five years ago. I was contacted by several producers in Colorado. This is when Colorado was taking the lead in both medicinal and recreational cannabis. They really had nobody to go to, in terms of greenhouse production systems. These were either warehouses, or they were growing greenhouses. As a consultant, I went out there and helped them to develop what I call ‘aggressive plant protection programs.’ It’s a proactive way to minimize pest problems because cannabis growers don’t have any materials to spray—or, if they do, they're very limited in scope.

You’re talking about a plant that's consumable in a sense, so you’ve got to be careful for THC content and CBD oil composition. I've been really involved with that, working with two of the big producers in Colorado, and the reputation must have been going around. Now, I’m dealing with a number of operations, not just in the Midwest, but across the U.S.

ES: Did the cannabis plant provide a different set of challenges that other plants don’t have or that you hadn’t seen before?

RC: That’s an interesting question, because early on the plant really has no hairs. But later on, as it develops and gets buds, it has trichomes or hairs. That becomes a problem when you're dealing with spider mites. When I went out to these operations, they were dealing with spider mites when cannabis was in bud and there are all these hairs and trichomes on it. At that point, it was a lost cause.

As a consequence of that, we started developing these proactive, aggressive programs for early on [in the plant’s growth cycle] when the plant doesn't have the trichomes or hairs that would impede the ability of predatory mites and other biological control agents to manage the pest population. That would go for any crop, but specifically for cannabis because of that change of morphology later on when it's getting into the bud stage.

ES: Could you define “IPM” and what that might mean in the context of cannabis?

RC: IPM refers to integrated pest management. It’s a holistic system that integrates many of the approaches—cultural, physical, chemical and biological. I have personally don't use ‘IPM’ anymore, because we've overused it [as a term]. Some people refer to as ‘I pay more.’ I now say ‘plant protection,’ and plant protection is protecting your crops from harmful organisms, which can include fungi, bacteria, and viruses.

LISTEN: Beyond the Show with Dr. Raymond Cloyd

When we talk about plant protection, it's going through the typical scouting strategies, cultural strategies, physical strategies, all the management strategies that can be employed. The key is scouting, because you need to detect populations early on if you're going to release these biological control agents. That's really critical. I gave a talk this weekend to some cannabis growers, highlighting the importance and the need to scout to detect populations early. Then you can make your decision to purchase biological control agents ahead of time.

ES: What does a good scouting strategy look like?

RC: What you're doing with scouting is you determine the trends or patterns in those insect populations during the growing season. It could be either passive scouting—where you put up traps, yellow sticky cards, blue sticky cards—or it can be active when you're out there doing visual inspections. Now, remember only some insects will be caught on yellow sticky cards. Some will not, like spider mites which can't fly. So, you're going to have to do visual inspections, whether it be looking at plants or what we call the beat method: You put a clipboard to a white piece of paper, you shake the plants and you look at what's on the paper. That's a really good indication about what is active at that time of year.

ES: When you’re scouting, should you be hitting different parts of the room?

RC: You can do this two ways. You can do what we call the random search, going through the greenhouse and then randomly picking out plants. Or you can flag certain plants, use those as indicator plants throughout the greenhouse, and always go to those when scouting. Either way, you're not having to go through the entire crop. Both of those methods will be successful, but the reason I like the flagging method is because you're always going after the same plant. That gives you an idea of what the trends are on that plant. Now, is that representative of what's going to occur in the greenhouse and the rest of the crop? It could, but maybe not, but at least it gives you a heads up about what's happening on certain plants throughout the greenhouse.

ES: What are some misconceptions about plant protection that you tend to correct when you go out and talk to cannabis growers?

RC: There are several misconceptions, and one of them is that, when releasing biologicals, you can't release them when the insects or mite pests are present and reproducing. It's too late. You have to release biological control agents almost before you see the pest, because of the fact that they take time to attack and feed in the pest population.

We do know that dead insects don't kill live insects, so we really focus in on making sure that our biologicals are alive. Don't assume that they're alive when they come in. You need to check the mites or the parasitoids. In our laboratory, we've been doing this for five years, and I believe I presented it at a recent Cannabis Conference: making sure that what you order is alive prior to releasing into the greenhouse. If you're predatory mites are dead, they're not going to manage the population.

ES: This might be a cheesy question, but do you have a favorite pest? Or is there a pest that might be the most interesting to you?

RC: I like them all. There's a million of them, but the ones I've been dealing with over my career, like Western flower thrips and fungus gnats and mealybugs, are fascinating. Mealybugs and thrips are very difficult to deal with because of their propensity develop resistance or develop means of avoiding contact with insecticides and even biological control agents. There’s a whole plethora of insects that I find very fascinating because of their biology or morphology or just how they've evolved. Monarch butterflies, to me, are very fascinating: how they've evolved with milkweed plants. You have this arms race between the plant defending itself and the butterfly larvae needing to eat it to get the cardenolide so that it's a poisonous predator as an adult.

ES: Over the last six to 12 months, what have you been working on lately in cannabis?

RC: We haven't done much research because of the restrictions in the Midwest, but what we have been doing—and it's very enjoyable—is working with cannabis producers to implement biocontrol programs, and they've all been successful. It’s a learning curve, but, again, they have to develop an established scouting program. That allows them to implement the release of biologic control agents. It’s been very satisfying to me to see these successful programs being implemented, because, to me, cannabis is a 100% biological control program. It does work. I'll be highlighting some of the previous experiences and our newest [project] in St. Louis [at Cannabis Conference].

ES: To a business team that might be just getting off the ground, or to a team that might be building out an indoor facility right now, what are some early considerations to begin educating themselves on pests?

RC: The structure can be an issue. This one operation, their irrigation system was not conducive for the crop. We thought it had been designed for another crop. They are making the adjustments, but I think the key really is just trying to get a handle on what your potential pests are. If you're growing indoors, we know what those are. Thrips, aphids and spider mites are the big three. We recommend just reading the information—and other colleagues and I have written articles—and there's plenty of information out there understanding the biology and the life cycle of these [pests] that will help you develop these scouting programs. Consequently, you’ll determine what biological control agents are commercially available for use against these insect mite pests. We have predatory mites for thrips. We have predatory mites for two spotted spider mite. We have parasitoids for aphids. Most of the companies out there have these commercially available. That’s where the success of these programs is contingent on availability of these biological control agents.

ES: We mentioned indoor environments, of course, and it seems to me like the outdoor environment opens a whole other can of worms, so to speak. In a general sense, what are some baseline outdoor considerations for pests?

RC: When you're talking about growing cannabis and hemp, which I deal with also, outdoors, you're dealing with a whole different complex of pest problems—because these insects are out there. You're putting in a field crop, so you're getting a host of caterpillars, leaf hoppers, beetles, sucking insects. The complex of the insect of mite pests is much more diverse and it's larger than a grower or producer would experience in an indoor-type situation. In that case, scouting is critical. You really can't do biologicals. Scouting is really critical in that case. For example, when a soybean or corn crop is harvested, and your cannabis crop’s grown outdoors, it’s going to be a magnet for certain insects that might pass through, for them to feed upon.

ES: In terms of them being a magnet, are there different phases of the cannabis plant growth cycle that are more alluring to pests?

RC: It’s a good question because it goes into what we call the seasonality of insects. You’ll get pests—now that we're talking outdoors—you'll get pests that might be a problem early on like aphids or leaf hoppers. Mid-season, maybe some beetles, like cucumber beetles, might be a problem. Later on, when the crop is in bud, then you get corn earworm, which is a major pest outdoors in cannabis and hemp. There’s a seasonality of when these insects or mite pests show up, and that's what producers need to be aware of.

ES: We’re talking about plant protection, but on the other side of that coin is a lack of plant protection. What are the consequences of just letting this go? I mean, certainly crop failure is sort of where this is all leading to, but what does that look like?

RC: If you basically put your crop outdoors and let the insects or mite pests have a free-for-all, you're probably going to have a very low yield as a result. You get the ones that come in early on, and they may kill the plant directly. Later, they’re going to impact the crop and also the yield. The do-nothing approach is not going to succeed if you want to make a profit and pay the bills. You have to implement an aggressive scouting program out there once or twice a week to detect these populations early on. That will allow you to choose a plant protection management strategy, although they are limited. But you could use mass trapping with the yellow sticky cards or vacuuming or even hand picking or whatever means to deal with them early on, which will be easier than when you're dealing with 10,000 mites or aphids later on in the season—or when corn earworm is feeding on your buds.

ES: What are you hoping attendees take home this year from your presentation?

RC: I'm trying to get the point across that biologic control does work, because I've had the experience with the producers. Biocontrol is a lot of work, but it is successful. The inputs are less so than you would see for insecticides, and the indirect benefits are helpful: no personal protective equipment, no resistance issues, no residue issues. The growers and the employees like to work in there because there is no residue issues.

If you make your releases timely and you do quality assessments, it will work. This comes from my experience with some really wonderful producers that have decided to go that route. I know there are not very many options, and that's what I like about cannabis. It's a monoculture crop. You can make some mistakes, but it's a learning experience. I'm willing to help producers as much as possible, because I've seen the producers that are successful. They're committed and they want it to work. And consequently, as a result, it does.