(Editor’s note: This story is part of a recurring series of commentaries from professionals connected to the cannabis industry. Caleb Johnson is director of customer success at Albuquerque, New Mexico-based Terra Vera.)

Like all plants, cannabis is often vulnerable to pathogens that can affect quality, purity and yield.

As a grower, it’s important to be proactive in both the management and prevention of pathogens.

Many cultivators often struggle with finding solutions that are effective in protecting plants while also safe for staff, consumers and the environment.

What are the common marijuana and hemp plant pathogens?

Powdery mildew

Powdery mildew is one of the most common plant pathogens that marijuana and hemp growers encounter.

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Named for its white/light grayish spots or patches of baby powder-like growth, powdery mildew often thrives in warm, dry climates.

It can spread and eventually cover the leaves of the cannabis plant and put new plant growth at risk.

Botrytis

Botrytis, also known as gray mold, is a type of fungi and commonly affects cannabis plants.

It first appears as a white growth and darkens to a gray color over time.

Botrytis tends to thrive in places with high temperatures and humidity levels.

With its ability to spread rapidly, this fungi can put entire cannabis grows at risk.

Aspergillus

Aspergillus is a saprophytic fungus that is commonly found both outdoors and indoors in the U.S.

It is a common mold that can grow both on the cannabis plant and within the soil.

While most people can breathe in aspergillus spores, exposure can be dangerous to immunocompromised individuals and can lead to aspergillosis, a debilitating and invasive infection that, in some instances, can be fatal.

E. coli

Escherichia coli, commonly known as E. coli, is a group of bacteria that can contaminate food, water and plants such as cannabis.

Exposure to E. coli, even in small amounts, can lead to dangerous infections, leading to diarrhea, stomach cramping, nausea and vomiting.

How do pathogens affect my yield?

Exposure to pathogens can limit the growth and overall yield of cannabis plants, affecting everything from the roots, crown and foliage.

Fungi that affects the buds of the plants can also impact the overall quality of the cannabis.

Medical cannabis patients are most at risk for the dangerous effects of contaminated cannabis, and exposure to pathogens or mold can have dangerous, sometimes deadly, effects on their health.

5 practices to prevent pathogens while protecting the planet

1. Defoliation

Defoliation is the process of removing leaves from a cannabis plant. Many cannabis growers believe that defoliation can help stimulate the growth and yield of cannabis plants.

Some use it as a means to reduce the chance of powdery mildew developing.

2. ScrOG netting and canopy training

Screen of green (scrOG) netting helps form a horizontal and even canopy by bringing the lower branches up and the upper branches down, stretching them across an evenly distributed plane.

By placing netting above the grow, cultivators can weave the branches of the cannabis plants through the mesh as they grow and develop.

Such actions can increase exposure to light and adequate airflow above and below the canopy, reducing the risk of fungal pathogens.

3. Beneficial insects and mites

Introducing beneficial insects and mites can help deter pathogens and keep cannabis plants safe.

Ladybugs and green lacewings feast on aphids, a common garden pest.

Praying mantis enjoy consuming aphids, moths and mosquitoes.

Rove beetles prey on various pests, including thrips, shore flies, and fungus gnat larvae.

Hypoaspis miles (predatory soil mites) and nematodes (parasitic worms) also go after thrips and fungus gnats.

For those looking to grow their cannabis without the use of pesticides and harsh chemicals, these insects and mites can help keep your grow healthy and free of pests and pathogens.

4. Proper environmental controls

Maintaining proper environmental controls is essential to ward off unwanted pests and pathogens in a grow.

For indoor grows, it’s important to maintain a consistent temperature, humidity and airflow as well as light sources.

Failure to do so can often trigger plant pathogens to develop, such as botrytis and powdery mildew.

Indoor growers will often need to have an environmental control system in place to cool, heat and dehumidify the space.

In addition to controlling environmental factors, it’s also important to prevent cross-contamination from staff and tools.

It is advised to use a dedicated set of tools that aren’t used on other types of plants, fruits or vegetables to prevent microscopic “hitchhikers.”

Staff working in the grow area should wear protective clothing and wash it at least once a week. It’s also important to have staff wear disposable gloves when handling the plant to prevent contamination.

These, among other steps, can help prevent outside pathogens and pests from contaminating a grow.

5. Crop-management solutions

To maintain and protect a cannabis grow, it’s important to have crop-management solutions in place to treat not only current pests and pathogens but also as proactive measures to protect the plants from future contaminants.

Cannabis plants are susceptible to many plant diseases, which can put consumers, staff and crops at risk.

While many crop-management solutions are available, it’s important to choose those that not only rid the plants of these pathogens but also do not contaminate the plant or the planet with harsh toxins and chemicals.

Growers should be mindful of the risks posed by these plant pathogens and pests and take proactive, environmentally mindful approaches to keep their grow safe and contaminant-free.

Caleb Johnson can be reached at caleb@terravera.com.

The previous installment of this series is available here.

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