Disclaimer: This is in no way intended to dismiss the fact that there is peer-reviewed research needed on the interaction between cannabis varietals and invertebrates.
I have noticed, first-hand, some common cannabis-related factors that are limiting, or preventing the success of beneficial insects – and in some cases, even killing them. In most of these cases, there are environmental factors that are the main cause, and in others, dishonest salesmanship is contributing to the problem.
Thus, I have compiled a list that current and potential growers can use both in figuring out what went wrong, and for considerations towards new growing techniques.
So here is what went wrong:
1. Fan Speed
This is first on the list for a reason. From my perspective this is the number 1 reason biocontrols have failed in cannabis grow-ops. In almost every single grow, I have walked into growth chambers that more resemble a wind-tunnel. Forget lab-coats and disposable gloves, it’s time to strap on those sky-diving goggles.
“Why on earth are you doing this?” I first asked. The responses are split: most will say it is to prevent powdery mildew; a few will say “to strengthen the stems.” It seems like those are legitimate concerns…until you remember that people have been growing plants indoors for hundreds of years, and that many of these problems have already been addressed.
Do tomato plants need a wind-tunnel to harden them up so they don’t topple with the weight of fruits? No, you use tomato clips and grow the plant straight up. Could you do this inexpensively with cannabis? Yep.
How does one control mildew? Well, in roses, which are particularly susceptible, growers discovered (a long time ago) that mildew spores may always be present, but they only cause damage and sporulate when there are large, rapid shifts in humidity. So, in some rose houses in Holland, mildew is completely controlled by setting greenhouses to maintain humidity within only a few percentages (using misters and gentle air exchange.) This is difficult for most cannabis growers because they have been taught to grow at such a low rH, that the spay of a fungicide, or a thorough watering will cause a spike in humidity. *Remember, cannabis can be grown above 70%RH – if consistent, no mildew will occur.
Now, imagine you’re sitting outside on a porch on a still evening in the summer; there are bugs everywhere: mosquitos, moths, fireflies…you name it. Also, consider a picnic: wasps, butterflies, ladybugs. Now think back to a time you’re been outdoors at the same time during fiercely blowing winds. Any bugs? Nope.
There is no specific research done on minimum windspeed for winged insects, and it no doubt differs from bug to bug. But know this: as long as those fans are blowing, no winged insect will fly from plant to plant; no insect that depends upon smell to hunt will be able to find food; and as far as we know, even wingless invertebrates like all those predatory mites, may be hanging-on-for-dear-life. (UPDATE: Peer reviewed research on bugs and windspeed has been conducted, and it strengthens my point. 2 miles per hour! That’s it! That’s the threshold for commonly used, winged biocontrol agents to decide to fly or hold on.)
Our president and a distributor once visited a grower who was having a terrible time with aphids. They had bought hundreds of thousands of ladybugs before turning to our aphidoletes – nothing was working. When the two were shown the room, they looked around and saw nothing. Then asked to turn the fans off to speak. As they began to talk in the now quieted room, thousands of ladybugs began to climb up from hiding places and started flying from plant to plant. They had waited out the storm, and flew when winds had died.
Another grower I visited, who supplies ornamentals for a large box-store, found that turning the fans off for 6 hours a day (2 hours before dusk to 4 hours after) was all that was needed for the searching invertebrates to find their food. We also know that aphidoletes use dusk to fly up, mate, and search out the smell of honeydew, produced by feeding aphids. So the still air not only allows for searching, but other essential parts of your beneficials lives.
I encourage all growers to reduce air velocity, have a period without fans or use indirect air movement.
2. Being Reactive:
It is absolutely essential that you start clean and are preventative in your approach to bio control. Once pests get established they will be difficult to eradicate. In many growing environments, small adjustments can favour the conditions for the predator, or at least weaken the conditions for pests. In many cannabis grows, however, conditions are harsh and don’t allow for native predators to freely come in and take care of your problem.
What we tend to see in the Cannabis sector is growers believing they are clean and believing they can maintain that cleanliness. Well, nature will find a way. Put a strong smelling food in a box and I assure you, something will find it’s way in. This belief that they have no pests gives a false sense of security and often causes them to scout the earliest plants too quickly or not at all. It is best to assume you always have aphids and spider mite and treating them now with a small amount of predators will save you money. No space, no matter how much you spend, will keep your plants 100% clean.
Always start a preventative biocontrol program. You can always add more bugs later.
Many crops and growers use a dip for their cuttings to ensure they are starting clean. Most commercially available clones are coming in with pests. Either refuse dirty clones or quarantine and treat them immediately.
Additionally, cannabis has the tricky (and sticky) flowering period. We often run into the problem of pests and predators being stuck to the flowers. This is very simply caused by pests being present before flowering is forced. By being preventative, you will have fewer pests and predators on your plants – they may even appear “clean”. Then, when they enter the dark and get overly sticky, you don’t have to worry about any invertebrates.
3. Know your Chemistry
It is important to know how all of your chemistry might interfere with your biocontrols. A great example is spraying for mildew control. Remember this: “All fungicides and herbicides are pesticides.” It may not be true by definition, but it is true in that both the chemicals and the spreader/stickers are harmful and in some cases lethal to your beneficial insects. When you must spray, be prepared to buy a bunch more beneficials in the following days or weeks.
Compatibility: “There are no pesticides that are compatible with beneficial insects.” Yes, people publish lists of chemicals and how safe they are for bugs – but consider the test: They submerge bugs in the chemicals, pull them out and measure how long it takes them to die. The worst die immediately; but some of the best or “safest” ones kill “only” half of the insects within 24 hours. Consider if that was considered “harmless” for human medicine! If a medicine only kills half the population, then it’s listed as “safe.” The other problem with this testing method is that it does not measure efficacy. Sure, some may survive the chemical exposure, but are they sterilized? Can they no longer fly? Will their offspring be effected? Have they lost their ability to find prey via smell? Are they blind? No one is doing this research.
Be careful with a sales person that says you can spray and use beneficial insects – especially if they are selling you both. *Bio-pesticides and bio-fungicides are often much more compatible.
4. Photo period
In “Being Reactive” I mention the flowering period. Well here is some more food-for-thought. Cannabis naturally flowers in the autumn. It senses a decrease in light or a very specific light to dark ratio. However, it does not need total, high intensity light for the light period, and total, immensely-deep, cavernous-dark for the dark period. On a clear night in September, with a full moon, which is relatively bright, the plant does not reverse flowering. Therefore, total darkness is not essential.
So, consider this: many insects also require specific light. Total darkness will certainly inhibit the effectiveness of your insects. Try adjusting light levels and photo period to both maximize plant performance as well as beneficial performance.
A recent study found a large proportion of methane found in the Amazon was not from the massive bio-density of animals, but actually the trees giving off the tiniest amount of methane during the night when their metabolism changes-gears. It is important to understand that plants are nature, and nature has cycles, and total light for the foliar stages of cannabis is not always best for the plants. Give your plants, and the insects a night time. It may be a short time, it may be a long time. I am sure studies have been done for light and yields, but I doubt anyone is researching the most effective length of time for plants and insects to “sleep”. If nothing else, give plants a night time, because they biologically need it.
Crappy roots, salt build-up, stressed plants: Check your EC’s. The plants in some grows look like crap, because they are. They are pumped full of fertilizer and are majorly stressed. Find out the minimum amount of all macro and micro nutrients needed to get the yield you want and consider pure water rinses from time to time. Your plants will thank you and so will the beneficial insects.
Too much nitrogen produce soft new growth. While you may think the plant is responding well to the nutrients – they don’t have a choice. They absorb it rapidly and pump it through their veins and sucking pests love it! Not only is it worth dropping the available N when you have pest problems, but it is also worth experimenting with different types of N. We know that the nitrogen available via ammonium makes plants far more attractive to pests than other versions of available N, like those calcium based.
When growers tell us they suddenly had a break-out of aphids, we often discover they just switched fertilizers, their EC meter has been off, or they began a “push” to get plants ready for a specific target.
Do not stress your plants! Too much of a good thing is bad. Pests are attracted to stressed plants. (Literally! Some plants reflect a different wavelength when stressed and some pests can visually pick that plant out of a crowd. Other plants produce alcohols or other smells under stress that attracts pests.)
6. Competing Beneficials
Not all beneficials are friends. One of the common products in cannabis, Dalotia Coriaria (the rove Beetle), will eat almost anything – including the other bugs you just spent money on. So if you’re putting it in to control root aphids, be sure that it is eating everything else…and sometimes first.
Other common mistakes with regards to which beneficials play well together are applying different types of Aphidius Wasps, like Ervi, Matricariae, and Colemani. They interfere with each other. In fact, they should not go after the same food, but they are bred on the same aphid, so they are almost the same wasps. Put them all together and they will spend a lot of energy fighting.
Similarly, both wasps for whitefly control (encarsia and eretmocerus) will also interfere.
And the classic mistake is using swiskii, which is great for thrips, unless you plan on using biocontrols for aphids and spider mite. Swiskii will eat all of your aphidoletes, and even some eggs of persimilis. Many of the mites will eat each others eggs, even their own, but most famous is both barkeri and califonicus.
When “mixes” are sold, it is often a marketing strategy used to sell products that have been contaminated with each other. A “package” likely differs. If someone is selling aphid control, spider mite control and russet mite control as a package (and they are each in different containers), you can assume they have figured out what works best together. Sometimes it is best to stick with one IPM person, but draw products from different suppliers. However you plan on building your IPM strategy be sure to find out which are most compatible.
Above: A typical preventative “package” (each sold seperately): Top middle – stratiolaelaps scimitus for in the growing media; Left – neoseiulus fallacis for pest mite prevention; Right – aphidoletes to seach and destroy any aphids.
7. Too many beneficials
This is causing a backlash in the cannabis industry. If you ask one of my ornamental customers what they think of beneficial insects for pest control they will be wildly in favour of it – and so will their staff. Right now, the average cannabis grower will respond “it’s too expensive and it’s not working.” What we want to avoid in this industry is the failure of beneficials in the cannabis crop because it is bad publicity and many people stand to lose a lot of money. So with this article I am hoping to help to make it work, but for this number 7 on our list, let’s talk about the cost.
I recently visited a large-scale cannabis grower who was receiving beneficial insects by the skid. I was shocked, and scared for this grower. Based on normal application rates, they were receiving weekly what might be needed for thousands (if not tens of thousands) of acres. The beneficials weren’t working, and sales people were just throwing more bugs their way – I was embarrassed for our industry.
In our production facility it is difficult to provide enough food to rear our predators on. I know how much our products can eat, so if they aren’t eating, something is wrong. Don’t just throw more beneficials at the problem. More is not better.
As mentioned above, some beneficials will eat each other or each other’s eggs. The more plentiful the number of beneficials, the more the beneficials themselves look like easy food.
Our most successful clients have some wiggle room (unlike the cannabis industry). They achieve a balance by allowing aphids (for example) to exist in their crops at all times. They buy from us aphidoletes and brown lacewing, but only in small enough amounts that they will find enough food to pupate and emerge as 20 times greater numbers naturally. They use their entire crop as their banker system. – put in $100 of bios, let them feed and reproduce and create a next generation worth $2000 – These growers buy very little from us, but have great success.
(When bio-control really took off (in the late 1800’s) the method was called “Pest in First.” Growers actually bought aphids and spidermite and inocculated their crop. A few weeks later they would buy the predators. It sounds crazy, but it works. It is also how we produce our bugs. We can over-load a crop with spidermite to the brink-of-death, put persimilis on it at some rediculously small rate, and a couple weeks later we have millions of persimilis and clean plants. The only reason the Pest in First approach has been largely forgotten is because the two World Wars brought chemical warfare. And those chemicals – diluted – were the begining of chemical pest control.)
Others, like cut flowers and cannabis have to eradicate their pests, so control is maintained with a balance early, but they need to inundate their crop with beneficials to get the late-stage knock down. This can still be done with small amounts of beneficial insects early and consistently throughout the growing period. Then, based on the number of pest you can easily adjust your regular application for a knock-down affect – where the predators actually starve from lack of food. This is seldom more than 10x the bi-weekly preventative rate.
Some application rates, like those for persimilis, can be based upon a ratio of predators to spider mites (1:10-20 for tomatoes). Not all crops have that specific a rate because of too many varying factors. But all of those can give you an idea of how much you need. As I have mentioned in previous posts, if you are not able to scout effectively and regularly, hire a scout!
8. Need for trials
Most of this is trial and error. Each varietal is different, has different pest pressures and different responses from beneficial insects. One common problem with cannabis growers is they have skipped the need for research and development in the plant growing area. All growers should dedicate a room where they can experiment (maybe will all of the above I have mentioned). Try different beneficial insects from different suppliers. Or test out different recommendations. See how fertilizers and windspeed affect your control of aphids…etc. If you cannot find the space and time to do this, at least flag an individual plant to track individual changes. Or, if even that can’t be done, reach out and call some non-cannabis growers, and some other cannabis growers. See what they have found out. Chances are they will be willing to share that information with you. If a cannabis grower doesn’t want to share it is likely because they consider the information proprietary, so, rely on the other growers – that information is sometimes generations deep and comes freely – maybe over a beer or bottle of wine.
This article highlights factors that have caused your biological pest control program to fail. I do not expect any grower to completely change their set-up in complete favour of the beneficials, and ignore the yields. I am expecting people to experiment with a level of compromise. Consider the time (as money) and actual money spent on your beneficial program. Also consider the cost when it does not work. I want to reduce that cost. And if small changes in favour of the beneficials have a small decrease in yield, but is off-set by massive savings in your IPM program, then it is a win-win.
Check out our website: www.appliedbio-nomics.com
The Preventative Tetrahedron of Bio-Control: A simple “how to”
Stethorus – The Ulimate Spider Mite Predator
Great style and very informative. Appreciated.
Thank you David. That is a great read for someone like me just getting into beneficial insects.
A few question I have is about harvesting plants.
Can they affect the end product, can you find beneficial insects in your buds?
Is there a time to cut out using them. i.e use only in veg not in flower, or remove beneficial sachets 2-3 weeks at the start of flower or 2-3 before the end of flower?
Thanks for reading! With a preventative program you’ll have less bugs in general, so going into flowering you can rely solely on the beneficial present, with reduced pests. Predators won’t go into the buds without pests, but you still want them as clean as possible. Large commercial growers use bulk cucumeris in veg and switch to sachets ahead of or during flower (when necessary).
Aphids should also be taken care of long before flower. Nitrogen should be reduced to help that but they too seldom end up in the bud.