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The Fundamentals of IPM for Indoor Grows

October 15, 2018

  • Healthy Plants, Healthy Genetics
  • Utilizing a Suit in the Grow
  • Sanitizing Grow Spaces and Common Areas
  • Pruning & Defoliating in Vegetative Phase
  • Defoliating in Flower Phase
  • Proper Environmental Conditions
  • Regularly Spraying Minimal Risk Pesticides
  • Beneficial Bugs

Healthy Plants, Healthy Genetics

There are many concerns regarding the ability to successfully deter cannabis plant pests and diseases as integrated pest management (IPM) strategies need to be multifaceted in scope and indoor growers are seen as having a disadvantage by lacking a complete ecosystem by excluding predators in many cases. It is important to understand that different strains of cannabis exist for a reason. The genetics differ from strain to strain which means these different strains may have slightly different environmental needs, slightly different nutrient needs, and possibly significant resistance differences. A plant may be more resistant to infestations and infections because of superior genetics which is an important consideration when growing and maintaining a healthy cannabis grow. Although certain cannabis genetics may produce more desirable terpenes or higher potency, their difficulty to maintain their health may prove too difficult to find worthwhile for large-scale growers because diminished health will diminish yield and quality.

Besides genetics, a plant that has not had the proper care may also become more susceptible to pests and diseases. There are many factors that are to be considered to maximize the potential of a cannabis plant. The first is that often times hydroponic cannabis growers lack a more balanced ecosystem within each of their plant’s rhizosphere. What hydroponic mediums lack are microbes. These microbes play a big role in terms of overall plant ecology. Some of the benefits of adding microbes to your grow medium include nitrogen-fixation, improved water retention, improved nutrient uptake, and suppression of possible root diseases. Some of the best microbes for the cannabis plant rhizosphere are endomycorrhizal fungi, ectomycorrhizal fungi, and azospirillum bacteria (Winston, 2014). Even though this much is known about microbes, there is still little that is known about microbial associations with cannabis plants. Besides adding microbes to a grow medium, cannabis growers should take the time to develop their feeding schedules and recipes that will allow a cannabis plant to thrive. Besides using the right amount and type of nutrients, this also includes finding a balance between underwatering and overwatering to maintain the health of a cannabis plant. Microbes can only help a plant so much, other edaphic factors such as pH, nutrients, and water are more crucial for a cannabis plant’s health.

Utilizing a Suit in the Grow

An indoor cannabis grow is susceptible to outside contaminants such as powdery mildew, spider mites, hemp russet mites, rice root aphids, and thrips which all thrive on various sections of a cannabis plant (Lieberman, 2017). One effective preventative IPM measure to combat outside contaminants is to utilize suits and shoe covers. Powdery mildew spores, spider mites, and aphids can be tracked into an indoor cannabis grow from a person’s shoes (Martyny, 2012). It can be extremely difficult to eradicate pests and diseases once they have entered your grow, it is best to take preventative measures. Disposable coverall suits can protect from inadvertent contact with plant pests and disease pathogens which can prevent possible contamination from one area or room of the indoor grow to another area.

Sanitizing Grow Spaces and Common Areas According to the Food and Drug Administration (FDA), hydrogen peroxide is a dependable high-level disinfectant in healthcare facilities which is defined as providing complete elimination of all microorganisms in or on a surface or instrument, except for small numbers of bacterial spores. Cleaning up dirt, debris, and miscellaneous items coupled with high-level disinfection is recommended to eliminate enough pathogens to prevent transmission between plants.

Using Hydrogen Peroxide 32% food-grade solute diluted with water creates an effective disinfectant solution for cleaning common areas such as hallways and entryways. When cleaning grow rooms it is also an effective solution and a great alternative to a bleach solution or simple green. Isopropyl alcohol is effective for disinfecting various indoor grow tools such as pruners, tables, and small surfaces, but it can be more cost-effective to use hydrogen peroxide for larger cleaning projects such as routine grow room cleaning in-between room flips. (CDC, 2008).

Pruning & Defoliating in Vegetative Phase

There are several aspects of defoliation including: remaining time until harvest, plant size, plant age, and genetics. As plants are in the vegetative phase there is an importance placed on providing optimal airflow throughout the plant canopy to help prevent contaminants from taking hold as cannabis plants are usually stationed closer together during the vegetative phase. It is important to leave enough plant matter to allow the plant to grow optimally, the frequency of defoliating such as every other week is more important than defoliating more plant matter in a single sitting. Some cannabis strains can tolerate or would appreciate a higher rate of defoliation than other plants and the opposite is true as well for other strains. While spending time defoliating plants, it is a great opportunity to monitor and inspect for pests and disease symptoms to ensure cannabis plants are healthy.

Defoliating in Flower Phase

There are several theories as to why defoliating in the late flower phase of cannabis may increase yields, it honestly may be the result of several factors such as increased light penetration through the plant canopy, increased airflow through the plant canopy, and possibly simulating the plant’s natural life cycle in nature as cannabis plants are annuals as they cannot bloom and revert back to the vegetative phase an infinite number of times. A female cannabis plant can increase its odds of reproducing for survival by creating larger buds or flowers to create possible surfaces to be pollinated to produce seeds. This is just one theory as to why defoliating can increase cannabis bud yields as it has been proven anecdotally many times by many growers over the years. As the cannabis plant ages, the window of time shrinks in terms of opportunities to resolve pest and disease issues because utilizing sprays in late flower can run the risk of producing bud rot and other additional issues.

Proper Environmental Conditions

Ensuring cannabis is being grown in the proper environmental conditions is fundamental to growing quality cannabis flowers. Before plants are placed into a growing environment whether it is a tent or a room, the room should already have the proper conditions and precautions in place for when the humidity raises after watering or spraying plants or for when the temperature rises when the lights are on full power. If the humidity is high, the conditions become more favorable for mold and mildew growth while sapping the plant’s ability to fend off these spores. Also high temperatures can be beneficial for the reproductive cycle of many pests including spider mites, root aphids, and thrips which is why it is important to be able to control the indoor environmental conditions of your grow space.

Regularly Spraying Minimal Risk Pesticides

The application of any pesticides is very controversial within the residential and commercial cannabis grower communities. There are many minimal risk pesticdes which fall under section 25b of the Fungicide and Rodenticide Act (FIFRA) according to the EPA. (Feldman, 2015). These pesticides that are found to be of minimal risk under the previously stated guidelines are exempt from federal registration. Minimal risk pesticides include citric acid and many different essential oils such as castor oil, cinnamon oil, lemongrass oil, clove oil, neem oil, and rosemary oil.

There is a grey area with using federally registered pesticides on cannabis plants as the EPA is barred from registering a pesticide for use on cannabis or for setting tolerance limits for pesticide residues on cannabis crops at the federal level. This means several states have taken different approaches to the use of pesticides on cannabis. The state of California allows the use of FIFRA 25b exempt pesticides as well as other pesticides that have a broad enough definition on the label for crop applications that could include cannabis (California, 2019). Colorado has adopted an approved pesticide list for use on cannabis crops and in the state of Illinois it is only legal to apply pesticides to cannabis crops in the vegetative stage. Overall, most states allow the use of minimal risk pesticides or pesticides that are FIFRA 25b exempt on cannabis crops which means when used correctly they can be beneficial to keeping your plants healthy while providing minimal risk from pesticides to people and the environment around them.

Beneficial Bugs

Many individuals and companies decide against using any pesticides in their garden. This is just another approach that can work if done properly. If pesticides are not going to be applied to the garden, then the obvious next step is to fill in the gap within the ecosystem more naturally with predatory insects or beneficial bugs some including Amblyseius andersoni mites, Dalotia coriaria beetles, and Stratiolaelaps mites. These predatory bugs feed on various common cannabis pests such as spider mites, root aphids, thrips, and gnats at various stages of their life cycles (Bioline, 2019). They can be introduced in a variety of ways, but companies commonly sell these beneficial insects in sachets which can hang near or in the plant’s canopy.

Introducing and maintaining beneficial insects is a form of bio-control that more naturally keeps pests at a minimum. Some beneficial insects and minimal risk pesticides can even be used in continuous cycles, but each individually should be researched before applying pesticides on beneficial insects.

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