For those of us who are familiar with growing herbs and vegetables it should come as no small notion to say that pest and disease in the garden can be a real source of headache as well as heartache. For those of us only recently finding interest in horticulture, take heed that the threat of pest and disease pressure should not be underestimated or ignored.
Throughout gardens, greenhouses, and grow rooms worldwide the vast diversity and tenacity of mother nature are a constant presence. As gardeners, we would be foolish to find ourselves fighting nature. Rather, we would be best to consider ourselves adept observers and manipulators of the natural systems in which we live, and which we try to mimic.
Plants are food and sustenance to humans as well as other animals. Most frequently the most pressing threats to any garden garden are insects, arthropods, mollusks although any outdoor gardener may contend that deer are as great a threat as any flying swarm.
Utilizing Integrated Pest Management (IPM)
Frequently gardeners find themselves confronted with a pest or disease issue and are either unprepared to tackle the issue, underestimate the scale of the infestation, misdiagnosing the malady, or completely overlooking the problem and wondering why harvest results were less than ideal. Herbaceous plants such as cannabis are especially susceptible to insects and pests, and left unchecked they can ruin a garden and cause problems that may takes cycles to recover from.
Integrated Pest Management or IPM is a protocol which aims to limit insect and disease pressure while also leaving the lightest impact on the plants. As we seek to grow high quality cannabis we must be mindful of our inputs and their residual impact on final product. Many controls are incredibly effective while leaving zero impact, while some controls such as those designed for the ornamental/floral/landscape industries can give your cannabis medicine a more detrimental taste and effect rather than a healing effect.
Being Proactive As First Control
When growing craft cannabis it isn’t a matter of if, but when insects and diseases will strike, an adept gardener may never have to destroy a crop or bleach every square inch of a grow-room. The first step is to understand the weak points in a grow room and how mitigate them.
Irrigation frequency, temperature, relative humidity, and airflow can play a huge roll in how rapidly insects can move and breed. An example of this with two spotted spider mites and the fact that they reproduce most rapidly in environments where relative humidity is low, temperature is high, and limited air circulation allows them to travel unimpeded by high winds. Highly saturated grow mediums are the perfect place for fungus gnats to breed and destroy healthy root systems.
Grow room cleanliness and personnel hygiene are another major component that is easily controlled and has zero impact on plants. By utilizing airshowers, footbaths for shoes, and sterile clothing, and washing ourselves before starting work in the garden, we can greatly reduce the potential vectors for transporting pests and pathogens may carry. Dirty hands and fingernails can harbor millions of pathogenic bacteria and fungus, so washing hands and trimming fingernails is a must for gardeners!
Scouting For Signs of Pests and Disease on Cannabis
Scouting is one of the key tenants to a proper IPM strategy. By scouting, we as growers are being attentive to the changing visual signals that plants give, positive identification of pests and pathogens, and the indication of damage caused by these invaders.
When scouting we take note of any changes in the plants, where in the room these changes occur, and the scale of the issue at hand. By keeping thorough records we can track the impact and how effective treatment is, and how we must approach the problem at hand. Yellow sticky cards are wonderful indicators for many bugs, and noting which species are found along with the size of the population on the card can be vital in applying the proper control measures.
After signs of something wrong has occurred, it is important to figure out where it came from. Are there signs of bites? Are there flying critters? Does it look like mold, or bacteria? Leaf spots? Fruiting fungus bodies? Is my medium too wet? Do I need to clean my reservoir or irrigation lines? Is there plant material accumulating anywhere in the grow room? Does my trash need to be emptied? All of these are important questions to ask, while always looking for ways to make a room more efficient and maintaining the highest standard of cleanliness
Utilizing Inputs for Low Impact Assistance
Using inputs such as pesticides and fungicides along with biological controls in a proactive way combined with diligent scouting and a well designed and maintained grow room are the pillars to a robust and effective IPM program.
Understanding the difference between bio-control measures as well as chemical control measures, along with their respective modes of action determine which control to use, and when. This means taking into account whether or not a chemical control is organic or synthetic, whether they are systemic or non-systemic, and what safety precautions must be taken into account for personnel who are applying the controls, and whether or not their will be residual presence of the control to the end user.
Using synthetically and organically derived inputs should be done on a rotational basis. The main reason for this is to prevent pests from developing an immunity towards certain controls. This was seen to be case where pyrethrin was heavily used on the west coast as an organic and short half-life knock-down style control. As this one control was used every few days in heavily effected gardens, the exponential rate of reproduction inevitably caused the two spotted spider mite on the west coast to become widely immune to suppression, spurring on the need for other more costly organic solutions.
When using chemical controls, be aware of the difference between systemic and non-systemic, while also striving to use products which are approved by the Organic Materials Review Institute (OMRI). These are widely considered safe for the environment and workers where proper safety measures and re-entry times are followed. Many OMRI listed ingredients are derived from or mimic naturally occurring compounds found in nature.
It is best advised that systemic and systemic pesticides and fungicides are used only during vegetation period, while non-systemic pesticides may be used up to 2 weeks into the flowering period. After two weeks of flowering it is advised to use biological controls such as probiotics and beneficial fungi along with beneficial bugs to fight pests and pathogens. These are often grouped into the category of biological controls.
My favorite organic pesticides include
- Azamax (systemic, pre-flower)
- Spinosad
- Insecticidal soap derived from fatty acids of potassium salts
- Blends of botanical oils
- Companion plants (when used outdoors, these attract beneficial pest predators)
My favorite organic fungicides are
- Regalia
- Serenade
- Green Cure
- Flying Skull (also a knock down insecticide and destroyer of pest eggs, a very nice, but expensive all-in-one)
Biological Controls
Bio-controls can include not only pest predators, but also bacterial and fungal spores which may propagate and act as competitors to pathogens. These probiotics and other beneficial microbes may consume and/or out-compete pathogens while living in symbiosis with the host plant. Beneficial microbes such as bacteria and fungi are widely seen some of the best proactive and low-impact controls.
Predatory bugs such as mites, beetles, and many insects in the mantid family are voracious and skilled hunters. Seeking out and devouring hundreds of mites, aphids, and caterpillars a day. It is important to keep in mind the possibility of beneficial insect/mite populations and microbes being impacted by application of chemical controls. Another thing to keep in mind when working with pest predators is that some may have the tendency to bring in the very pest you seek to control with prevention, specifically spider mite predators. Because predatory mites are fed spider mites, it is inevitable that you will be introducing spider mites to your garden if they haven’t been already. With this knowledge, it is highly advised that predatory bugs be used only when positive identification of a pest has been made. My #1 favorite predatory control is Green Lacewing Larvae. Skip the lady bugs. Use predatory mites only after positive ID of pest mites
While all of this may seem daunting just keep in mind that being proactive and being away of vectors of pest and disease transmission will be your greatest asset. A mindfully designed grow room and strict protocol and procedures governing who enters a grow room and how they conduct themselves while in there will be the #1 way to ensure a healthy garden and a happy harvest.
