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Pests & Disease Control

Identifying Common Cannabis Plant Nutrient Deficiencies



Just like any other cultivated crop, in order to live and thrive cannabis plants require what are referred to as essential elements. These essential elements each play key roles in plant development and are deemed essential because, without them, the plants would not be able to develop properly. People who grow cannabis will, at some point, experience a nutrition deficiency. In other words, most growers will experience a situation where less than optimal growth occurs due to the plant’s inability to absorb one of the essential elements. In most cases, a nutrition deficiency is treatable and correctable fairly easily. However, finding the source of the problem is extremely important, especially if it becomes a reoccurring issue. Treating the symptoms of a deficiency will help, but if the source of the problem is not rectified, chances are good that the plants will continue to suffer in subsequent grow cycles.

Check Your pH

Most of the plant nutrients made for growing cannabis are balanced and contain all of the essential elements needed for accelerated growth. However, it is not enough to provide just the plants with the essential nutrients; it is important to provide the root system (and the microorganisms in and around the roots) with the proper conditions also. The potential hydrogen, or pH, of a soil, medium, or hydroponic solution represents how acidic or alkaline that soil, medium, or hydroponic solution is. It is actually the pH level of the area around the plant’s roots that mainly influences the availability of nutrients for plant absorption.

The Ideal pH Range

For soil gardening, the ideal pH range falls just below neutral, in the 6-7 pH range; with maximum absorption around 6.3-6.8. A slightly acidic pH is ideal for the reproduction and functioning of the beneficial microorganisms that help break down organic matter into soluble nutrients. When pH values drop below 6, there is a significant decrease in the availability of nitrogen, potassium, sulfur, calcium and magnesium, but the largest decrease is in the availability of phosphorus. Many times horticulturists experience phosphorus deficiencies, not because there is an inadequate amount of phosphorus in the soil, but instead because the pH of the soil has become too acidic.

Hydroponic gardeners will find the ideal pH for nutrient absorption is slightly more acidic than for soil gardening. A hydroponic system is less dependent on the microbial life that is normally harbored in the soil. Hydroponic nutrients are already broken down into a soluble form. This bypasses many of the functions performed by the beneficial microbes, thus changing the optimal pH range for nutrient absorption. The ideal pH range for hydroponic gardening falls in the 5-6 range; with maximum absorption around 5.5-5.8. Unlike soil, the pH value of a hydroponic solution can fluctuate rapidly. This is why it is so important to monitor the pH of the solution daily, if not more often.

Biggest Contributors to pH Fluctuations

The pH of the soil has a large impact on the availability of nutrients so it is of the utmost importance that a grower understands the factors that most commonly affect the pH. The pH of a nutrition solution is most influenced by the water source, the nutrients used, and the growing medium.

Correcting a Nutrition Deficiency

If a gardener is experiencing the signs of a nutrient deficiency, even after he or she has addressed the pH of the growing system, he or she should attempt to treat the specific deficiency being experienced. Many times nutrient deficiencies mimic each other, which makes positive identification even more crucial to correcting the issue. Here are some of the most common deficiencies experienced by cannabis cultivators and ways to quickly correct those deficiencies.


Nitrogen is the most common deficiency experienced by cannabis plants. A plant deficient in nitrogen will have pale or yellowing leaves that start at the bottom of the plant and work their way up to the top of the plant. Plants can be treated with a fertilizer with a high available nitrogen content. Foliar treatments of soluble, high nitrogen fertilizers can help correct this deficiency fastest.


As previously mentioned, a phosphorus deficiency is most often due to a pH level that has become too acidic. Plants with phosphorus deficiencies exhibit slow or stunted growth, regardless of how optimal the environmental conditions may be. Red stems and smaller than normal dark green leaves are also signs of a lack of phosphorus. Plants can be treated by feeding them a blooming fertilizer (even in the vegetative stage) which contains a higher ratio of phosphorus in relation to the other macro-nutrients.


The most identifiable symptoms of a potassium deficiency in cannabis plants are dead, brown spots forming on the lower leaves. Leaves may also suddenly turn yellow and die. Treat plants by supplementing a soluble fertilizer with sufficient potassium or make a tea out of K-mag for a foliar or drench application.


A lack of calcium will generally cause the medium to become acidic and this can cause a series of other problems (such as magnesium, phosphorus, or iron becoming unavailable for absorption). Hollow stems found on harvested plants are telltale signs of inadequate calcium. It is a good idea for growers to supplement a calcium additive during all vegetative and early flowering growth. To correct a calcium deficiency, start by making sure a calcium supplement is part of the fertilizer regiment and then foliar feed 1-2 tsp of dolomite lime per quart of water.


Magnesium is another very common deficiency for cannabis plants. Plants without sufficient magnesium will usually exhibit yellowing leaves on the lower portion of the plant and, in some cases, will turn white. The veins of the leaves will remain green. Leaf blades can crisp and curl upward. A good treatment for a magnesium deficiency is to use 2-3 tsp of Epson salts per gallon of water as a foliar or soil drench.


With a boron deficiency, the new, emerging growing shoots will appear burnt, brown, or gray. This deficiency can be treated with 1-2 tsp of boric acid per gallon of water as a foliar or soil drench.


Usually caused by pH imbalances, iron deficiencies in cannabis plants turn leaves on new shoots bright yellow, while the veins remain green. The best treatment is to supplement a fertilizer with a higher percentage of iron.


Cannabis plants that have white areas on the tips of the leaves or intermittently between leaf veins are displaying a zinc deficiency. This is a common problem in soils that are or have become alkaline. If experiencing a zinc deficiency, a gardener should retest the pH of the solution and medium. In most cases, a zinc deficiency is related to a fluctuating pH. If the pH is in check, the gardener should treat the plants with a foliar application of a fully soluble fertilizer that contains zinc.


When growing cannabis, many horticulturists attempt to push their plants to the maximum. Put another way, the majority of cannabis growers try to provide the ideal atmospheric conditions so their plants will uptake the largest amount of nutrients and grow at the fastest rate possible. In some cases, a horticulturist may make the mistake of believing that more fertilizer will equate to faster growth. Unfortunately, instead of increased growth rates, this usually causes a nutrient lock-out, also known as over-fertilization or toxic salt accumulation.

Over-fertilization in cannabis plants is often misdiagnosed as a nutrient deficiency. If there is leaf burn starting at the tips of the leaves and working its way up the “saw blade” of the leaf, the problem is most likely caused by over-fertilization, not a nutrient deficiency. When a grower experiences over-fertilization, he or she must remove some of the built up salts from the medium. A good place to start is to leach the soil with a diluted fertilizer (1/4 strength) and wait until the plants exhibit signs of recovery before increasing the fertilizer strength again. If over-fertilization occurs in a hydroponic system, the nutrient solution should be drained and replaced with a one-fourth or half strength solution. The gardener can then slowly increase the PPMs as the plants recover.

Cannabis plants require a specific blend of nutrients to thrive, just like any other living organism. When atmospheric conditions are optimal and the plants have everything they need, they can grow at an accelerated rate. However, when a nutrient deficiency or nutrient lock-out occurs, the ideal atmospheric conditions become irrelevant because the plant is unable to access the fuel it needs to complete the photosynthetic process. Cannabis growers who understand that the pH of the soil or nutrient solution is the most important contributing factor to nutrient absorption will be much more likely to have fewer nutrient related problems. Cannabis growers who understand the symptoms and early signs of common nutrient deficiencies will be armed with the knowledge needed to quickly resolve any issues that pop up and get back to doing what they love: growing healthy plants.

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Pests & Disease Control

The Angry Grower: Avoiding and Identifying Pests In Your Garden



Your ability to identify the pests in your garden depends not only on your attention to detail and knowledge but your tools as well, with one of the most important being a microscope. Don’t worry, though, you don’t have to spend hundreds of dollars on a traditional microscope. A quick search on your favorite conglomerate shopping app and you can find handheld digital microscope that connect to your phone or computer for under 50$

Now that you have the ability to see even the smallest of pests, you’ll need to learn the different signs of an infestation. Here are a few off the top of my head;

Spider Mites

Spider mites are often transferred from other gardens and can reproduce very quickly. They are found on the bottom of the leaves but are also easily overlooked. Their bites leave small white specks, and if left untreated, webs can form to the point of buds looking “shrink-wrapped.”


Thrips are larger and more easily spotted than most mites. While looking like small baby worms, they leave silver or bronze marks on the leaves.


Mealybugs are found crawling on buds and leaves and can act as a vector for many plant diseases. Primarily white-colored, with a “fluffy, hairy, waxy, cotton like” material covering their pink bodies

Broad and Russet Mites 

These are possibly the hardest to see and can easily be mistaken for nutrient deficiencies, pH inconsistencies, or heat stress. The leaves will end up glossy, twisted up and blistered. Depending on the severity of the infestation, buds can turn brown as well


These can be a little tricky to identify at first because they can be tiny while appearing different depending on the stage of their life. Their pear-shaped bodies can be found on the bottom of the leaves, as well as on the roots.

Look out for aphids on the bottoms of your leaves!
Photo: Victor Forgacs

Fungus Gnats

Growing mediums such as soil that stays wet for extended periods can be breeding grounds for fungus gnats. They appear to be small dark flies with worm-like larva that lives in damp topsoil.


Due to the wide range of colors these pests come in, they can be challenging to identify at first. Leafhoppers can cause leaves to curl, dry or brown with perhaps the most common sign being clusters of spots

Prevention is Key

Besides making sure that your room is perfectly sealed and that there’s no stagnant water, be sure to check the entirety of your plants – including bottoms of leaves – regularly. Don’t go more than three days without checking WITH A MICROSCOPE, if not every day. That goes for new clones as well. If you receive clones from an outside source, make sure to keep in quarantine and treat them as if they may already be infested.

Don’t make the Grower Angry: PLEASE take the precautions to keep pests off your plants!

One of the most common mistakes is going in your grow room straight from being outdoors or in another grow room. Spraying yourself with alcohol doesn’t guarantee anything, so I prefer to change my clothes and shoes. Having animals like dogs running through your garden is also a bad idea. Even though you don’t always see the bugs directly on yourself, you or your animal could be carrying their eggs

Keep in mind that it’s nearly impossible to be completely bug-free 100% of the time. Identifying, treating, and solid prevention practices can significantly reduce infestations to basically zero. Remember to be vigilant; for every two bugs you find, there’s probably two hundred and counting already!

Stop by the Angry Grower’s column to ask him your grow questions or connect with him on the NUGL App here.

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Pests & Disease Control

Pest Control for Indoor and Outdoor Cannabis Plants

Just like garden vegetable crops, cannabis plants have a variety of pest insects that can hinder or destroy an otherwise healthy crop.



Just like garden vegetable crops, cannabis plants have a variety of pest insects that can hinder or destroy an otherwise healthy crop. Although most pest insects can negatively affect both indoor and outdoor cannabis crops, there are some pests that seem to be more prevalent in either an indoor or an outdoor cannabis garden. For example, slugs rarely, if ever, cause issues for indoor cannabis growers. On the other hand, fungus gnats and spider mites, which wreak havoc in indoor gardens, are usually kept somewhat in check by natural predators in an outdoor garden. Whether the cannabis plants are grown indoors or outdoors, gardeners armed with the knowledge to prevent, identify, and treat garden pests will be able to defend their precious plants from the damage inflicted by uninvited pathogenic guests.

General Prevention for Indoor Gardens

A solid initial step toward pest insect prevention is to reduce the possibility of pests entering the garden in the first place. The number one way pest insects enter an indoor garden or greenhouse environment is by the gardener’s carelessness. When acquiring a new cannabis strain or plant, it is a good idea for the gardener to not only inspect it for bugs, but also place it in an area outside of the indoor garden for a few days of “quarantine”. The quarantine process should include a treatment with a general insecticide. After 5-7 days, if it passes inspection, the grower can introduce the new specimen to the indoor garden.

Another way pest insects enter an indoor cannabis garden is by hitching a ride on an unsuspecting gardener. If possible, gardeners should avoid entering the grow room right after doing yard work or visiting a friend’s indoor garden. If not hitching a ride on the gardener, pest insects make their way into the garden via the ventilation system or other small openings. A fine screen or mesh covering the ventilation ports reduces the chance of pest insects entering the growing space.

A thorough inspection of the grow room may reveal some small cracks or holes which should be caulked or sealed. Sometimes even the most seemingly minor repairs can make major differences in pest insect prevention. Another simple measure an indoor cannabis grower can take to prevent unwanted pests is to keep a clean growing environment. Dead leaves, discarded soil, standing water, and previously used planting containers are all places for pest insects to live and breed. A clean growing environment is beneficial in many ways, but especially in terms of pest prevention.

Pest Insect Identification and Specific Treatments

No matter how clean a gardener keeps his or her indoor garden or how hard they try to eliminate unwanted visitors, chances are, at some point, a pest insect problem will have to be dealt with. Early detection and proper identification are crucial to eliminating the problem quickly. The reason early detection is so important is because most pest insects have relatively fast reproductive rates. The fast reproductive rates teamed with incredibly large birth numbers are the reasons untreated pest insects are capable of taking out an otherwise healthy garden in just a matter of days.

Common Pest Insects for Indoor Cannabis

Spider Mites

Spider mites are one of the most destructive indoor garden pests due to their resilience and extremely fast reproductive rates. The most obvious sign of a spider mite infestation is cannabis leaves that have yellow or white speckling. This speckled look is caused by the mites feeding on the underside of the leaves. Another definite sign of spider mites is their webbing, which looks like a tightly woven spider web. When a spider mite infestation occurs, the cannabis flowers and leaves may be fully encased in webbing. There are many chemical insecticides available that are designed specifically for spider mites. These products are usually referred to as miticides.

Chemical miticides can be very dangerous if not handled properly, so paying close attention to the application directions is a must. For the “conscientious cannabis gardener”, there are organic insecticides that have shown promise in treating mites. Whatever method a grower chooses, he or she must make sure to address the mite eggs. Spider mite eggs are super tough and can withstand most insecticides. Indoor cannabis growers with a mite problem should repeat the treatment program every 2-5 days for at least two weeks. This will catch the new spider mites as they hatch and prevent them from re-establishing.


Thrips are another common indoor garden pest. They can usually be identified by the “track” marks left on the top of the leaves when the larvae are feeding. Adult thrips are winged and generally have a straw-like color. Under magnification, a thrip’s body structure resembles that of a wasp or hornet. The best way to treat thrips is to address all stages of the life cycle. Combining sticky traps for the flying adults, a foliar insecticide for the larvae and adults on the plants, and a soil drench to kill any eggs or larvae in the medium is the best way to simultaneously treat all life cycle stages for thrips. Repeating the treatment every few days for a couple of weeks will only help a grower win the battle against these pest insects.

Fungus Gnats

Fungus gnats are usually identified by swarms of little black bugs that scatter when the soil or medium is watered or disturbed. They appear to resemble fruit flies, but, under magnification, their body structure looks more like a tiny mosquito. Fungus gnats are pesky bugs that seem to keep appearing, even after treatment. Again, the combination of sticky traps, a foliar insecticide, and a soil drench is the best multifaceted approach for a fungus gnat problem. It is also advantageous, if possible, to allow the top three to four inches of soil or medium to dry out. Fungus gnats need moisture for reproduction. Letting the top layer of soil or medium dry out will hinder their ability to reproduce.

Other Indoor Pests

Aphids, mealybugs, whiteflies, leaf-miners, and scales are less common pest insects for the indoor cannabis horticulturist. These soft-bodied insects can be successfully treated with an array of insecticides or beneficial insects. Many cannabis growers find insecticidal soap to be a good cure for these less intrusive soft-bodied bugs.

Integrated Pest Management for Outdoor Cannabis Gardens

Although some of the same pest insects that affect indoor gardens also affect outdoor cannabis gardens, preventing and treating pest insects in an outdoor environment can differ greatly from treatment programs in an indoor garden. It is nearly impossible to use a screen or filter to stop flying insects from reaching the plants in an outdoor garden. Therefore, outdoor cannabis growers must turn to other methods of pest insect prevention. For most outdoor cannabis growers, the best way to approach pest insects is to implement an integrated pest management program. Integrated pest management, or IPM, is the practice of focusing on the long-term prevention of pests and/or pest damage by managing the ecosystem. The idea behind IPM is a comprehensive approach to dealing with pests over the long-term. All in all, IPM is the holistic approach to pest control. The principle of IPM is to look at all of the contributing factors and all of the possible remedies and then make a decision of when and how to take action.

Combination of Treatments

IPM programs normally implement a combination of treatments or control practices that prevent or treat a problem from many different angles. The control practices used in an IPM program can be categorized as biological, physical, cultural, or chemical.

Biological – Biological control is the use of beneficial plants, insects, or microorganisms to control pest insects and pest insect damage. Most pest insects have a natural predator. Ladybugs and beneficial nematodes are just two examples of biological controls.

Physical – Physical control refers to a control that kills the pest insects directly or physically stops them from entering the garden space. Sticky traps to catch flying pest insects and barriers to keep rodents or deer out of the garden are examples of physical controls.

Cultural – Cultural controls are practices that reduce the pest insect’s ability to establish itself. For example, a change in irrigation practices can reduce moisture at certain times throughout the day, thus reducing particular pests.

Chemical – Chemical control is the use of pesticides. For most IPM programs, chemical control is only used when needed and is used in conjunction with other techniques to maximize effectiveness and to create long-term solutions.

Identify the Problem

Even with an IPM program implemented, it is still possible for an outdoor cannabis garden to contract a pest insect problem. Positive identification of the pest will allow a grower to find a combination of treatments specifically designed for that pest. For example, an outdoor grower who discovers aphids may want to plant fennel (known to repel aphids) and release ladybugs. This would be the biological approach. The gardener could also spray the plant with water to “wash off” some of the aphids. This would be the physical approach. If these tactics fail, it may be time to use a chemical control (pesticides).

As long as humans continue to cultivate plants for food and medicine they will have to prepare for potential pest insect problems. As with many problematic issues in a cannabis garden, prevention is key. In both indoor and outdoor cannabis gardens, growers can take steps to reduce the likelihood of acquiring a pest insect problem. Growing cannabis indoors gives horticulturists heightened control over environmental factors. Unfortunately, this “closed ecosystem” also creates a perfect environment for pest insects to establish without the danger of natural predators.

Only a grower armed with knowledge can identify and treat pest insects in an indoor garden. Outdoor cannabis growers can team up with Mother Nature and her natural biological controls. By implementing an IPM program, outdoor cannabis growers can manage their ecosystems to best prevent and treat unwanted guests. Whether indoors or outdoors, cannabis growers who encounter pest insects need to act quickly to positively identify and treat the pest insect before surmountable damage occurs.

By: Eric Hopper

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Pests & Disease Control

Tips for Keeping Pests Out of the Greenhouse



The best way to avoid pest problems in a greenhouse is to keep them out to begin with. The list that follows gives many ways to help keep a greenhouse pest free. The more of these that can be integrate into greenhouse gardening practices, the better chance a gardener will have of winning the war against undesirable garden pests.

Start Plants from Seed

If plants are bought at a nursery or a garden center, one can not be assured that the plants are perfectly clean. If one has been getting plants from a reputable producer and has not had problems in the past, it would be a good idea to stick with that grower, even if the prices are higher. Treated seeds are safer for starting your greenhouse plants. Untreated seeds are more likely to carry a seed-borne bacterial or fungal disease.

Repot Plants Outside the Greenhouse

Repotting plants should be done outside of the greenhouse, and any used pots should be cleaned and disinfected with a 10% bleach solution before use. Commercially available soilless mix should be used as the media for seed starting and potting greenhouse plants. This will allow one to avoid introducing insect and microbial pests that often live in soil.

Protect the Work Area

Protect the ground on the floor of the greenhouse with a barrier to keep soil born pests from digging their way in from the outside. Work in the greenhouse first before working in the outside garden. Outside plants should not be kept near the greenhouse door. These plants can be a safe harbor for bugs waiting for a chance to get in the greenhouse.

Hands should always be washed before going into the greenhouse. This is particularly important after working with plants, or produce in the kitchen.

If one has been in close contact with plants, grass or dirt/mud, a change of clothing may be in order before entering the greenhouse. If one has been walking through grass or mud, it is a good idea to remove footwear, before entering your greenhouse. If one will be walking in the woods or a wooded area under trees, or even just walking on dirt paths, try to do it after working in the greenhouse.

Consider possible contamination by visitors to the greenhouse. Visitors should not enter the greenhouse after being in another greenhouse, a garden or an agricultural field.

Clean the Tools

Insects, mites or diseases can be taken into the greenhouse on garden tools that have been used outside. Tools should be thoroughly washed and disinfected with a 10% bleach solution before bringing them in the greenhouse and in between working on separate plants.

Items that have been exposed to plants or produce are a source of contaminants. Used plant shipping boxes and produce shipping boxes may be very useful, but they should never be taken into the greenhouse.

No Pets Allowed

Dogs and cats, that live or spend time outdoors, should never be allowed in the greenhouse.

A Few More Things

Screen air intakes to the greenhouse with a very fine mesh. The screen area should be at least five times the area of the greenhouse air intake, as to not restrict airflow.

Consider if a double door is possible. This is particularly helpful in keeping moths and butterflies out. Moths and butterflies are not generally a problem themselves, but when they lay their eggs on your plants, they will soon hatch caterpillars and start to eat their hosts. On your daily bases remove any of them that are present.

Sticky fly traps can help in early detection of some flying and crawling pests.

Inspect plants as often as possible for visual predators or damage caused by harmful pests, fungus, bacteria or disease.

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