Chapter 9 Growing Top Shelf Buds
Avoidance is the best cure–we really mean it too. Starting from seeds means that your crop has a fresh, clean start–no pests or diseases originate from quality cannabis seeds.
Problems Do Occur
Grow a plant or a garden for long enough and it’s likely you’ll wind up with some sort of growing issue. The severity level can range from minor hassle to major crop loss.
The most common pests for indoor cannabis crops are spider mites, thrips, whitefly, and fungus gnats. There are others, but this is the usual list of suspects.
As far as foliar diseases go, powdery mildew (white mold) and downy mildew (grey mold aka bud rot) are most common.
Always keep a vigilant eye out. The majority of growing problems can be controlled or eliminated with early detection and swift action. Doing nothing about it is NOT an option. Things can get out of hand very fast. Inspect the top and undersides of foliage daily. Take a random leaf sample from time to time and examine under a magnifying glass.
Pest problems start out small but grow fast. If you follow this grow guide and maintain the environmental conditions as recommended, problems are unlikely and will be easier to control if they do surface.
Don’t let friends or pets visit your garden. They can carry problems in on their hair or clothes. Same goes for you, if you have been in another garden, nursery, etc. don’t enter your cannabis garden without showering and changing your clothes first. While it may sound like a hassle, it can save you bigger costs later on.
Learn the life cycle of pests or problems. Understanding their nature, different life stages, optimal environments, etc. is key in knowing when and how to treat and protect your crop. To quote Tsung Tzu’s Art of War “know your enemy”.
There are very few pest control products registered for use on Cannabis plants. Do not use poisons on plants you intend to consume or especially smoke. Just because something is only required in a very small amount does not make it harmless. Toxicity can be measured in parts per billion.
The only products we can recommend for controlling pests and foliar diseases in cannabis are insecticidal soap (insect control) and potassium bicarbonate (mold and mildew control). Believe it or not, if applied as preventative measures or used to treat crops in the early stages of problems they are very effective. They are also safe enough to use up until the last few days before harvest, if absolutely necessary.
There are spray additives available that allow you to apply your control products with the lights on. They will prevent foliage from scalding under bright light when sprayed and make what you spray a lot more effective with better coverage.
For prevention and control of either or both insects and foliar issues we recommend the following, added to one liter of fresh, clean filtered water:
5 ml Safeer’s Insecticidal Soap Concentrate (or Bug B Gone insecticidal soap), 7.5 ml Optic Foliar Transport and 15 ml Food Grade Potassium Bicarbonate (available from beer and wine making suppliers).
Mix well, and gently shake when spraying to keep the mixture stirred up. Always wear a respirator, gloves and eye protection when spraying.
Fine Mist Sprayers
Using a sprayer that creates a fine mist with a wand is desirable. This makes it easy to reach all parts of the foliage including the leaf undersides. We recommended this versus cheap hand sprayer that does not offer good coverage or control.
Shut off fans when spraying so you have control over the application and to help prevent foliage from scorching.
If you are inexperienced with foliar applications, it’s best to try a few plants first and wait a couple days to make sure you aren’t damaging plants. Avoid spraying directly onto buds. It’s the foliage around them that typically has the pest or problem. If you spray the buds directly it tends to hurt bud quality and may leave bad tasting residuals.
If you have sprayed your crop within a few weeks before harvest, it is advisable to do a couple of sprays with fresh water only prior to harvest. Again, the products we have recommended are safe to use for people on cannabis crops. It doesn’t mean that improper or over application won’t hurt quality or yields, however.
IPM (integrated pest management)
This is the practice of using natural biology to control pests. Basically, it’s about releasing good insects to eat bad insects. If you have a severe pest problem, it’s not likely IPM will eliminate pest levels sufficiently. However, with some fine tuning and a bit of research, IPM can be an effective management tool for avoiding and controlling crop pests in Cannabis.
Beneficial insects can be obtained by mail order and sometimes directly from your local hydroponics store. Different insects will control different pests. They all have their advantages and disadvantages. One of the biggest challenges is that the ideal environment for your cannabis plants may not be the ideal environment for your predatory insects. We are not discouraging growers from exploring IPM, it can be effective. However, there is often a learning curve involved.
Yellow Sticky Traps
Do not underestimate the effectiveness of yellow sticky traps for flying insects like fungus gnats, thrips, whitefly, etc. Insects are attracted to the bright color and land on the sticky, nontoxic surface, only to never leave again. Yellow sticky traps are great for both prevention and control of some types of common garden pests found in cannabis crops. It’s also easy to identify and monitor potential problems, as the contrast between the bright yellow and a tiny dark insect is easy to spot with the naked eye.
A Note on Neem
Neem oil (extract of the neem tree) and its derivatives may come up if you research “safe” pest and foliar control. More recent studies and observations have found that residual neem in smoked cannabis can have some serious side effects on some people including seizures. Remember, we eat tomatoes and don’t smoke them. What is ok for veggies isn’t necessarily ok for cannabis.
A Final Note on Controls
Stick to products that are registered for use on cannabis crops. If you are unsure, you can visit Health Canada’s website for cannabis. Look for listings (very short at this time) of products that are registered for use in cannabis. Always follow control product labels to the letter.