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The Beginner’s Guide to Integrated Pest Management

By David Perkins
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Formulating a Plan

In this article you will learn how to control pests and improve the health of your cannabis plants using integrated pest management, commonly referred to as IPM. This involves a multi-point strategy – there is no quick fix, nor is there one solution that will wipe out all your pest problems. Proper pest management requires patience, consistency and determination.

It is important to understand that not all pesticides are bad. While many are incredibly harmful not only to pests, but also humans, in this article I will educate you about some of the safer alternatives to traditional pesticides. It is possible to safely control unwanted pests in your cannabis garden without harming yourself, your employees or the natural habitat around you.

Every cultivation facility should have a well-thought-out plan for their pest management program. This program should account for the prevention, and if necessary, eradication of: spider mites, russet mites, fungus gnats, root aphids, thrips and caterpillars. These are just a few of the more common pests you’ll find in a cannabis garden. There could also be many other less commonly known bugs, so you have to be vigilant in looking closely at your plants, and the soil, at all times. Complete eradication of a targeted pest can be difficult. Once a pest has established itself, decimating or decreasing the population will require an aggressive regimen that includes spraying daily to control populations and prevent other pests from getting established.

Spraying or applying pesticides to the foliage of plants isn’t the only way to control or eradicate pest populations. There are many other ways that you can minimize the spread of pests without the use of pesticides. In greenhouse and outdoor grows, growing specific types of plants around the cultivation area will attract both beneficial and predator bugs that will naturally control pest populations. Some plants that attract these bugs are: mint, peppers, and marigold. Beneficial and predator bugs, such as ladybugs, predator wasps and predator mites, can control unwanted pest populations in the area before they even have a chance to become a problem in your garden. Plants and flowers that attract bees, birds and insects will also create helpful bio- diversity, making it more difficult for the unwanted pests to thrive.

For indoor cultivation, it is imperative that you have your cultivation facility set up for a proper workflow. If you already have pests, you need to make sure you are not contaminating the rest of your facility when going from one area to the next. Make sure that you only go to contaminated areas at the very end of your day, and when you’re done working in that area, you must immediately exit the building. Do not ever walk back through the uncontaminated parts of your facility or the pests will spread quickly.

An aphid on a plant in a greenhouse

When most people think of pests in their cannabis garden they think of the more common varieties: spider mites, russet mites, aphids and thrips. However, there are also soil-dwelling pests that can exist, without your knowledge. These will decrease the health and vigor of your plants, without you even knowing they’re there, if you’re not careful to check for them. Some of the soil dwelling pests that plague cannabis plants are: root aphids, fungus gnat larvae and grubs. It is just as important to control the pests below the soil, feeding on your roots, as it is to control the pests that feed above soil on your plants.

Maintaining healthy plants is essential to controlling pest populations, both on the foliage and below the soil. Healthy plants will have an easier time fighting off pests than unhealthy plants. Plants have immune systems just like humans, and the stronger the plant’s immune system, the more likely it will be able to ward off pests and diseases. Allowing a plant to reach its full potential, by minimizing pests, means your plants will also have a better quality, smell and flavor, not to mention a bigger yield.

Worker Safety, Regulation and REI times

The application of pesticides requires certification from the state agricultural department. In certain situations, depending on the type of pesticide and method of application, a license may even be required. The application of pesticides without proper certification is against the law. Applying pesticides in a manner that is not in accordance with the label and instructions is also a violation of law.

The proper personal protective equipment (PPE) is required for anybody handling, mixing or applying pesticides. Employees can be a liability to your company if they are applying pesticides improperly. Make sure you and your entire staff are well educated about pesticide use requirements and limitations, prior to usage, and that only a properly certified person is handling the mixing and application at your facility.

The author, David Perkins, In his greenhouse after using insect killing soap.

After a pesticide is applied, you must abide by the re-entry interval (REI). This is the required time period limiting all workers from re-entry into areas where pesticides have been applied. This time period will vary depending on the type of pesticide used and the method of application. In some instances, pesticides applied in the last 30 days may require employee training before work can be done in those areas.

The misuse of or improper handling of pesticides is not only unlawful and dangerous to human health, but can also cause environmental damage to waterways and wildlife. The direct effects of pesticides on wildlife include acute poisoning, immunotoxicity, endocrine disruption, reproductive failure, altered morphology and growth rates and changes in behavior. Pesticides can indirectly impact wildlife through reduction of food resources and refuses, starvation due to decreased prey availability, hypothermia and secondary poisoning. Section 1602 of the California Fish and Game Code governs requirements for permitting of any project where pesticides will be used, and strictly regulates the disposal of all waste and run-off. It is imperative to know the regulations and to abide by them, or heavy fines will ensue!

Using Pesticides in a Regulated Market

Knowing which pesticides you can’t use, to avoid failing mandatory state testing, is just as important as knowing which ones you can use safely to pass required testing. Most states with regulated markets have strict limitations on the pesticides that can be used in cannabis cultivation. Pesticide use in the cultivation of cannabis is the most strictly regulated in the agriculture industry; the pesticides allowed for use in cannabis cultivation are far more limited than any other crop.

Photo: Michelle Tribe, Flickr

Just because a product is certified organic does not mean that it can be used, or that it is safe to be consumed or ingested. Oftentimes when cannabis flower alone is tested it will not fail or show a detectable amount of pesticides or heavy metals. However, when that flower is turned into concentrates, banned substances are then detected in testing, leading to test failures.

Cannabis cultivation facilities that are located on land that was previously used for conventional agriculture, or located near vineyards or other agricultural crops that are heavily sprayed with harmful pesticides, run a very high-risk failing testing. This is because of either spray drift from nearby agriculture, or residual pesticides and heavy metals left in the soil from previous crops that were using pesticides banned for cannabis cultivation. Accordingly, if you’re going to be growing outdoors or in a greenhouse, it is imperative that you get a soil and water test prior to cultivation, so you can determine if there is any potential for test failures due to pesticides or heavy metals in the soil or water in that area. 

Proper Application – Using the Right Tools in the Right Way at the Right Time

One of the most important factors in pest management is proper identification of pests and proper application and coverage of pesticides. It does not require an entomology degree to identify insects, these days there is a lot of information online that can help you identify cannabis pests. Proper identification of insects can make the difference between success and failure. With a good eye and a microscope, if you do your research, you can control most insects in your garden.

In order to control pests in your garden you must get proper coverage of the foliage of the plant when you are applying pesticides. There are different types of equipment that are commonly used to apply pesticides in cannabis cultivation: backpack sprayers, foggers, and airless paint sprayers are the most common. An alternative method involves using an automated dosing system such as a dosatron, which injects fertilizer or pesticides at a specific ratio into your water lines, allowing you to use only the exact amount of pesticide you need. That way you avoid wasting money on unused pesticides. It is also safer for employees because it minimizes employee exposure, since there is no mixing required, and it allows for a large volume to be sprayed, without refilling a tank or a backpack sprayer.

No matter what you are using you must ensure you get the proper coverage on your plants in order to control pests. The temperature and humidity of your cultivation area, as well as the PH and temperature of the pesticide solution, all factor into the success of your IPM. For example, PFR 97 needs to be applied at a higher humidity range, around 70% to be most effective. In some areas this is not possible so repeated applications may be required to ensure the application is effective. A high PH or alkaline PH can cause alkaline hydrolysis which will make your pesticide solution less effective and will dictate how long your pesticides remain effective after they are mixed. It is therefore important to use your pesticide solution as soon as you make it; don’t let it sit around for long periods of time before use or it will be less effective.

In cannabis cultivation there are two different primary growth cycles: vegetative and flower. These cycles require different IPM strategies. In general, during the flowering cycle, pesticides should not be applied after the second week, with some limited exceptions i.e. for outdoor cultivation there is a longer window to spray since the flower set takes longer than a plant being grown inside, or in a light deprivation greenhouse, where there is a 12/12 flowering cycle.

Starting with an immaculate vegetation room is crucial to maintaining pest and mold free plants in the flowering cycle.

For the vegetative (non-flowering) cycle, a strict rotation of foliage spray applications targeting not only pests, but also molds and pathogens, will be necessary to avoid a quick onset of infestation. Starting with an immaculate vegetation room is crucial to maintaining pest and mold free plants in the flowering cycle. Preventative sprays that are safe for use include: safer soap (contact kill) for soft bodied chewing insects; Regalia (biological control) for powdery mildew; and PFR 97 (biological control) for soft bodied chewing insects. It is also helpful to spray kelp, which strengthens the cell walls of plants, making the plant healthier, and thus enabling the plant to better defend itself from pests and diseases. Also, Bacillus thuringiensis (Bt) is useful to prevent or kill caterpillars.

The best way to control a pest infestation in the flowering cycle is at the very beginning on day one. You must start aggressively, with a three-way control consisting of a contact kill and preventative during days 1-14; preventative and biological control during days 10-18; and then release predator bugs on day 25, for optimal results. Knocking back the population with an effective contact kill pesticide early on is essential to ultimately lowering populations throughout the grow cycle, so that you can spray a biological control to preclude them from returning, before you release the predatory bugs at the end of the cycle.

Biological controls can take anywhere from 3 to 10 days before they are effective. Biological pesticides are selected strains of bacteria or fungus. When the plant tissue is eaten by a targeted pest, the bacteria kills the pest from the inside providing control without having to spray pesticides repeatedly. Predator bugs are the last line of defense, used in late flowering. They can be used indoors, outdoors and in greenhouses. An example of a common predator bug is Amblyseius californicus used to control low populations of spider mites, but there are many different varieties and they are specific depending on the type of pest population you seek to control.

A common concern with the use of predatory bugs, is whether they will be present when the flowers are harvested. However, if there is no food for the bugs (i.e. pests) the predator bugs will leave in search of food elsewhere. Further, indoor predator bugs are usually very small in size and difficult to see to an untrained eye. It is very unlikely to see any signs of predator bugs near the end of the flowering cycle, or in the finished flower product. Even when using bigger predator bugs, the bugs will leave the plants when harvested and dried.

Having pests can be very stressful. It is not uncommon to have bugs, pests, rodents, animals and birds cause damage in cannabis gardens. Making an informed decision based on science and not on unproven assumptions can determine how successful you are at pest management. There are many factors that go into pest management and no one situation is the same. You must be dedicated and consistent; pest management never stops. You will always have something ready to invade your garden. Prepare, plan, prevent and repeat!

Applications for Tissue Culture in Cannabis Growing: Part 2

By Aaron G. Biros
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In the first part of this series, we introduced Dr. Hope Jones, who took her experience in tissue culture from NASA and brought it to the cannabis industry and C4 Laboratories. We discussed some of the essential concepts behind tissue culture and defined a few basic terms like micropropagation, totipotency, explants and cloning. Now let’s get into some of the issues with cloning from mother plants and the advantages that come with using tissue culture for propagating and cultivating cannabis.

Time & Resources

Dr. Hope Jones, chief scientific officer at C4 Labs

Taking cuttings from mother plants is arguably the most popular method of propagating cannabis plants. It is a process that requires significant real estate, resources and labor. “Moms can take up a great deal of space that is not contributing directly to production,” says Dr. Jones. “I know from experience that scaling up production and/or adding new strains to the production line requires significant time and resources to raise and maintain new healthy and productive mother plants.” Each mother plant produces a limited number of clones per harvest period and over the course of her life cycle.

By using tissue culture, a cultivator can generate an almost infinite number of clones from one plant cutting. With so many growers calculating their costs-per-square-foot, micropropagation is an effective tool to save space, labor and time, thus increasing profit margins. “Just to put it in perspective: Holly Scoggins’ book Plants From Test Tubes, cites a Day Lily cultivator who uses micropropagation to produce 1,000 plants in 30 square feet of shelf space each week,” says Dr. Jones. “Using conventional methods, one would need a half-acre to produce the same amount of plants.” Cultivators can produce a much greater number of plants-per-square-foot by using micropropagation effectively.

Damage from whiteflies, thrips and powdery mildew is all visible on this sick plant.

Early Health & Vigor

Most tissue culture methods use sterilized vessels that contain sugar-rich media to support growth of plantlets before they can photosynthesize on their own. “The media is prepped, poured into vessels, and placed in an autoclave (or pressure cooker) where it is subjected to high temps and pressure to achieve proper sterility.”

The sterile environment and rich growth media supplies plantlets with an abundance of everything they need. “When plantlets emerge from culture, they are pathogen-free, with a stockpile of food and nutrient reserves that support rapid growth and vigor, superior to conventional cuttings,” says Dr. Jones.

Stress & Disease

As any grower knows, mother plants can sometimes experience stress and disease. This might come in the form under or over-watering, heat stress, spider mites, whiteflies, mold and viruses. “Any stress or infection that a mother plant is subjected too can impact progeny health and productivity in a couple of ways,” says Dr. Jones.

Powdery mildew starts with white/grey spots seen on the upper leaves surface
Tobacco Mosaic Virus symptoms can include tip curling, blotching of leaf mosaic patterning, and stunting.

For example, diseases like powdery mildew and tobacco mosaic virus are often systemic, meaning that pathogens have spread to almost every tissue in the plant. Once infected, it is impossible to completely eliminate pathogens from tissues. Therefore any cuttings made from a diseased mother plant, even if they look perfectly healthy, will also be infected and can eventually present disease symptoms like reduced productivity and/or plant death, according to Dr. Jones.

How does tissue culture get around this problem? Remember that explants (small tissue samples used as starting material) can be extracted from any part of the plant. Meristematic cells in shoot tips and leaves are the source of new plant growth. Dr. Jones explains that these cells, and the first set of primordial leaves are not connected directly to the vascular tissue, the plant’s transport system by which pathogens spread. Therefore, meristematic cells tend to be disease-free, whatever the condition of the mother. It takes a sharp blade, a dissecting microscope, and a lot of experience to learn, but as Dr. Jones explains, “harvesting explants from meristems is a routine micropropagation technique used by ‘Big Horticulture.’ One example is the strawberry. Viruses and pathogens are so prevalent that the strawberry industry must use meristematic culture to ensure pathogen free progeny.”

Epigenetics

Now let’s talk about epigenetics. We know that plants don’t have the option of physically moving away from stress or predation. Instead, they have evolved sophisticated ways of changing their own biology to adapt to and/or protect themselves. “Consider what happens to a mom exposed to a pathogen. The infected plant will start expressing (turning on) genes and making proteins that contribute to pathogen resistance,” says Dr. Jones. “These changes to gene expression are partly regulated by epigenetic modifications, chemical changes to DNA that increase or decrease the likelihood a cell will express a particular gene, but that do not actually modify the gene itself. Like annotations to a piece of music, epigenetic modifications don’t change the notes but rather how loud or soft, quickly or slowly the notes are played.”

There are more than 1,000 different viruses and mixed infections are very common

This is where it gets interesting. “Epigenetic modifications can be systemic and long lived. Plants infected by a pathogen or stressed by drought will present widespread epigenetic modifications to their DNA,” says Dr. Jones. “For an annual plant like cannabis, those modifications are relatively permanent. Thus a cutting from a mom having drought or pathogen adapted epigenetic programming will inherit that modified DNA and behave as if it were experiencing that stress, whether present or not.”

In the wild, this adaptability is critical for plant survival and reproduction, but to a grower, this is a less-than-ideal scenario. “The epigenetic modifications allowed the mother to tolerate the stress, which is great from the perspective of survival and fitness, but it comes at a cost. Some of the finite energy and resources that usually support plant growth and reproduction are instead channeled to stress response,” says Dr. Jones. This trade off results in reduction in overall plant yield and quality. “Those epigenetic changes result in a new phenotype for that mother,” says Dr. Jones. “All cuttings from her will reflect the new phenotype. This is one major mechanism underlying what many in the cannabis industry (incorrectly) call ‘genetic drift,’ or the loss of vigor over successive clonal generations.”

This is again where tissue culture can be such a game changer. The process of dedifferentiation, as explained in part 1 of this series, can rejuvenate a “tired” mother plant by inducing a kind of reboot– clearing accumulated epigenetic modifications that negatively impact progeny vigor and productivity. In the third part of this series, we will discuss the five stages of micropropagation, detailing the process of how you can grow plantlets in tissue culture. Stay tuned for more!