Spraying Methodologies for Integrated Plant Management
This page will cover both spraying as controls for pests and pathogens, as well as foliar feeding of nutrients and biological agents. We have included an important section on WARNINGS. Foliar application is an important component to cannabis horticulture, but since cannabis' mode of ingestion is through inhalation, it is very important to become acutely aware of what kind of residuals might be left on the flowers. Whether it's simply to pass testing, or medically sensitive patients, learning proper foliar methodologies can provide long standing commercial success as well as clean medicine.
It is important to remember that just because it's labeled Organic, doesn't make it the holy grail of safety. More specifically, as a cannabis farmer, you CANNOT rely on the application recommendations of pre-harvest intervals. Furthmore, certain OMRI listed products are being flagged by certain State's Dept of Agriculture for containing non-label chemicals, so it is not enough to rely on the OMRI label solely.
We highlighted Azatrol as a two-fold example.
First azatrol can be applied as directed to any food or non-food crop up to and including the day of harvest. This unfortunately has only been studied on methods of ingestion, not inhalation. There is a markedly different reaction when chemicals are broken down in the stomach vs being absorbed into lung tissue.
Secondly, Azatrol was flagged by the Oregon Department of Ag for containing off-label pesticides such as permethrin, bifenthrin, cypermethrin, cyfluthrin, and chlorphyrifos, which are prohibited on cannabis cultivation. For more information on flagged off-label pesticides please visit our PESTICIDE ALERTS page.
It is important to remember that spraying flowers should be avoided at all costs. Other IPM management strategies using predator mites or introducing companion plants to create environments for beneficial insects should be employed as alternatives to spraying.
Organic certified chemical controls typically seen applied in commercial and hobbyist settings are Sulfur, Neem Oil, Citrus Oil, Pyrethrum, Mineral Oils, Potassium Salts, etc. These chemicals are deemed reasonably safe to ingest in small amounts, BUT again, there is no data from combustion studies that shows the safety of inhalation. Extreme caution should be used spraying any of these chemicals past week 2 of flowering. Even then, that is just a recommendation and does not provide clear-cut answers on particular photo-degredation rates. Sulfur is especially detrimental to spray during flowering and it is not safe to inhale while be combusted. Additionally, sulfur also taints the taste of the flowers or concentrates. Many concentrate producers will cringe at hearing that sulfur has been used through flowering. This also includes the use of sulfur vaporizers. Sulfur can be a very important tool against pest and pathogen protection, but its role belongs in the vegetative and very early (1-2 weeks max) phase of flowering. The general rule of thumb given by professionals is, if you can see calyxes and pistils setting, along with any trichome coverage, it is too late to spray sulfur.
Biological controls are rapidly emerging as alternatives to chemical or biochemical controls. They can be considered MICROBIAL INSECTICIDES or MICROBIAL FUNGICIDES. But they should also be understood as MICROBIAL ANTAGONISTS. Microbial antagonists can be considered any type of beneficial biological foliar spray. Compost tea and other marketplace products that contain beneficial strains of bacteria and fungi fall under this category. The preventative spraying of biological controls can be the greatest ally for plant health and preventing pathogen outbreaks. The important thing to remember again, is that proper IPM management always begins when the plants are small and is consistently applied during the vegetative stage. For more information for preventing pathogens, please visit:
Preventative Foliar Solutions to Pathogens
The best methodologies will consist of a strong Integrated Pest Management (IPM) plan that focuses its time and resources on treatment during vegetative growth. A strong IPM control program during the vegetative phase will set the stage for a clean environment and low pest pressure during flowering.
Spray intervals 2-3 x week. 90%-100% coverage must be achieved to ensure adequate control. This rate will depend on the biochemical used and recommended instructions on the label. The IPM protocol that must be met is a spray regimen of 2-3 x week for maintenance in systems that have documented pest pressure that has exceeded the Economic Injury Level (EIL).
Spraying is stopped after 1-3 weeks of flowering. The duration of time into flowering depends on resin production, floral set and particular biochemical used.