Pests, Bugs & Viruses
Unfortunately, bugs or pests can totally mess up your marijuana harvest.
Some bugs live in soil, while other pests are airborne. Mold can be a big problem too. But you don't have to sit back and take it.
This page aims to be a comprehensive resource on the different types of bugs / pests / mold that can affect your marijuana crop, along with tips for preventing and solving each problem.
Pests that can affect your marijuana plants include aphids, spider mites, ants, whiteflies, white powdery mildew / white powdery mold, stem rot, and even mammals such as gophers and rats.
It's time to fight back against bugs, mold and pests!
If you have anything that you would like added, please contact me!
Most pests can be erradicated with SM-90.
Mist your plants in a solution made of 1 part SM-90, 5 parts water.
When you spray the plants, make sure you get the undersides of the leaves.
You'll want to do this when the lights are about to go off(or else the leaves will get burned). You can get a sprayer like this one on amazon.com, or at Home Depot for about $12.
Diseases of Cannabis are caused by organisms or abiotic sources.
Organisms include fungi (first and foremost), nematodes, parasitic plants, bacteria, and viruses.
Abiotic (non-living) causes include nutrient deficiencies, pollutants and genetic diseases. Different diseases prevail in different crops (e.g., drug cultivars versus fiber cultivars). Disease prevalence is also modulated by geography and climate.
The claim that Cannabis has no diseases is not correct, Cannabis suffers over 100 diseases, but less than a dozen are serious.
Serious diseases include gray mold, hemp canker, damping off, assorted leaf spots, blights, stem cankers, root rots, nematode diseases, broomrape, macro- and micronutrient deficiencies, and genetic diseases.
Environmentally stressed plants become predisposed to diseases. Stress includes drought, insufficient light, untoward temperatures, or growing plants in monoculture.
(McPartland, J. M., 1996. A review of Cannabis diseases. Journal of the International Hemp Association 3(1): 19-23.)
(McPartland, J. M., 1996. A review of Cannabis diseases. Journal of the International Hemp Association 3(1): 19-23.)
That quote was taken from a great page on Cannabis diseases <http://www.hempfood.com/IHA/iha03111.html> that everyone should read.
Aphids
Aphids are soft-bodied insects which can be green, yellow, black, brown or red.
They are usually small and oval-shaped, and may have dicernable wings or antennae.
Aphids use their piercing, sucking mouth-parts to feed on the sap of plants and usually occur in colonies located on the undersides of stems or leaves.
If a plant becomes heavily-infested, its leaves can turn yellor or wilt due to the excessive sap removal.
Aphids produce large amounts of a substance known as "hondeydew," a sugary liquid waste.
Honeydew drops from these insects and can causes spots on the windows and finish of cars which are parked under infested plants.
A fungus called sooty mold can grow on honeydew deposits which accumulate on the leaves and branches of your plant, turning them black. Many times, an aphid infestation is only noticed after the first appearance of sooty mold.
The drops of sweet honeydew can also attract other insects such as ants.
An infestations is generally the result of a small numbers of winged aphids that fly to the plant and take it up as their new host.
Winged aphids deposit several wingless young on the tender undersides of leaves/steams before moving on to find a new plant.
Immature aphids, or nymphs, that are left behind, feed on plant sap and increase gradually in size.
They mature in 7 to 10 days and then are ready to produce live young. Usually, all of them are females and each is capable of producing 40 to 60 offspring.
The process is repeated several times, resulting in a tremendous population explosions. Less than a dozen aphid "colonizers" can produce hundreds to thousands of aphids on a plant in a few weeks.
Aphid numbers can build until conditions are so crowded, or the plant is so stressed, that winged forms are produced. These winged forms fly off in search of new hosts and the process is repeated.
Solution: Early detection is the key to reducing aphid infestations.
The flight of winged colonizers cannot be predicted, so weekly examination of plants will help to determine the need for control.
Examine the bud area and undersides of the new leaves for clusters or colonies of small aphids. The presence of these colonies indicates that the aphids are established on the plants and their numbers will begin to increase rapidly.
Fatty acid salts or insecticidal soaps are very good against aphids. They apparently work to disrupt insect cell membranes. They require direct contact with the insects and leave no residual effect.
Nervous system insecticides, such as malathion, Dursban (chlorpyrifos), and Orthene (acephate), are labeled for use on many shade trees and ornamental plants for aphid control.
As with soaps, coverage is very important and a follow-up application may be necessary. Sevin (carbaryl) is not effective against many aphids so it is generally not a good choice for control unless recommended specifically.
In fact, applications of Sevin may reduce the number of beneficial insects, such as lady beetles, and increase the potential for aphid outbreaks.
Beneficial insects, such as lady beetles, lady bugs, and lacewings may eat large numbers of aphids but the reproductive capability of aphids is so great that the impact of the natural enemies may not be enough keep these insects at or below acceptable levels.
To keep aphids and other pests off your plants just finely chop1 onion and 2 medium cloves of garlic. Put ingredients into a blender with 2 cups of water and blend on high. Strain out pulp.
Pour liquid into spray bottle. Spray a fine mist on plants, making sure to coat both tops and bottoms of leaves.
Spider Mites
Spider mites (also called spidermites) are not insects but are more closely related to spiders.
Read complete tutorial here:
http://www.growweedeasy.com/how-to-get-rid-of-spider-mites
http://www.growweedeasy.com/how-to-get-rid-of-spider-mites
These arachnids have four pairs of legs, no antennae and a single, oval body region.
Most spider mites have the ability to produce a fine silk webbing. Spider mites are very tiny, being less than 1/50 inch (0.4mm) long when adults.
Spider mites have tiny mouthparts modified for piercing individual plant cells and removing the contents. This results in tiny yellow or white speckles.
When many of these feeding spots occur near each other, the foliage takes on a yellow or bronzed cast. Once the foliage of a plant becomes bronzed, it often drops prematurely.
Heavily infested plants may be discolored, stunted or even killed.
Web producing spider mites may coat the foliage with the fine silk which collects dust and looks dirty. Spider mite species seem to be warm weather or cool weather active pests.
The two spotted, European red, honeylocust, and oak spider mites do best in dry, hot summer weather. The spruce and southern red spider mites do best in cool spring and fall weather.
All spider mites go through the same stages of development. Adult females usually lay eggs on their host plants.
The eggs hatch in days to weeks into the first stage, called a larva. Larvae are round bodied and have only three pairs of legs. The larvae feed for a few days, seek a sheltered spot to rest and then molt into the first nymphal stage. The first nymph now has four pairs of legs.
The first nymphs feed a few days, rest and molt into the second nymph. The second nymphs feed, rest and molt into the adult stage.
The males are usually the size of the second nymph and have pointed abdomens. The females have rounded abdomens and are the largest mites present. Most spider mites spend the winter in the egg stage but the twospotted spider mite over winters as adult females resting in protected places.
This cannabis leaf shows the first signs of a spider mite infestation: dozens of tiny yellow spots.
Solution: Early detection of spider mites, before damage is noticed, is VERY important.
The tiny spider mites can be detected only by a full and thorough leaf inspection (on both sides of the leaf). If you find Spider Mites you must act fast and hit them hard.
The thing about spider mites is they are very quick to take over your plant, and even quicker to evolve and adapt to whatever methods you are using to try to kill them. They will soon develop resistance to almost any method you use to get rid of them.
If you have problems with spider mites, keep a constant and varied offence for the best chance at success.
If you already have an infestation, start hitting them hard with something that will kill them on contact.
Follow up in 2-3 days with something different that kills their eggs as well as a different method to kill the remaining adults (these ones will already be more resistant to your original method).
Repeat those two step at least one more time to ensure that you have really cleaned out your grow room.
Shake the plant, then kill the spider mites with something that kills them on contact, like:
- A bleach solution (1 tablespoon of bleach to 1 gallon of 95°F, pH balanced, water in a spray bottle.)
- Alcohol and water mixed togther will also kill the bugs on contact and shouldn't hurt the plant as long as the solution contains at least 30% water.
- SM-90 mixed with water (1 part SM-90 to 5 parts water) kills spider mites on contact and is organic (it even smells good!)
- Neem Oil works in a similar way to SM-90, though doesn't smell as nice
Using a mix of all the methods seems to work best for getting rid of spider mites.
I tend to avoid chemical sprays, or miticides with Abamectin or lindane because these are harmful to humans.
There are also insect predators that can help in providing some CONTROL but this does not mean 100% eradication. The insect predators can help to control spidermites if your infestation is out of control and chemical sprays are not your thing.
Spider Mite Prevention - The Clean Grow Room
Now it's all about prevention.
If you've had spider mites in the past, chances are you are unintentionally doing something to encourage or attract them.
There are many preventative products such as sprays or neem oil, which make plants less tasty to annoying spidermites. However, these should only be used to supplement good practices.
The most important aspect of spider mite (or any marijuana pest) prevention is a CLEAN GROW ROOM.
- Never move other plants from the outside world into your grow room - this is the most common way people get spider mites. If you get a clone or plant, keep that plant away from your other plants in quarantine for at least a couple weeks to ensure it has no bugs. Get ahandheld microscope and use it to look for bugs on new plants, too.
- No old dead leaves in your grow room at any time - you must collect old leaves regularly and completely remove them from your growing space. It doesn't count if you put them in a neat pile or trash can in the corner, you need to keep dead plant matter out of your grow room
- Make sure that you or anyone who comes into your contact space is clean (don't ever walk into your grow room directly from outside)
- No dogs, cats, rabbits or any other pets in your grow space
White Powdery Mold / White Powdery Mildew
What causes white powdery mold?
- White Powdery Mold is usually caused by too much humidity in a closed area or not enough airflow
- If plants are kept close together in an enclosed space without air circulation, this can be a breeding ground for white powdery mold.
- Plants which are very leafy, or which have lots of leaves touching each other, are more prone to WPM. Therefore pruning old leaves that are no longer needed can sometimes help prevent WPM.
Solution: ·What to do if you have WPM:
- Carefully wipe mold off affected leaves using plain water.
- Afterwards, make sure you have good air circulation moving over your plants(like with a fan) and a working exhaust fan. Fresh, clean, moving air will prevent powdery mold
- Get SM-90. Mix 1 part SM-90 to 5 parts water and spray your leaves right before lights out time. You can repeat if you see further outbreaks, but SM-90 often works with just one application. If SM-90 isn't available where you live, then neem oil is a great alternative (though it doesn't smell as nice as citrusy fresh SM-90).
- Learn more in our tutorial about white powdery mildew
More pictures of white powdery mildew
White Flies / Whitefly
White flies behave just like spider mites.
The insect hides underneath the leaf, sucks dinner from the essential nutrients in the plant.
This results in white spots on the top side of the leaf.
White flies are easily spotted with the naked eye. If you shake the plant a little, they'll fly around. They look like little white moths, around 2 millimeters in size.
Solution: ·A white fly problem can be solved basically the same way as aphids. My favorite way to get rid of them is misting your plants in a solution made of 1 part SM90, 5 parts water.
When you spray the plants, and make sure you get the undersides of the leaves(that's where they lay eggs).
You'll want to do this when the lights are about to go off(or else the leaves will get burned). You can get a sprayer like this one on amazon.com, or at Home Depot for about $12.
Thrips
Thrips are small, fast-moving insects with wings.
They rasp, or grate the marijuana leaves open, and suck the sap out.
Thrips prefer flowering tops, and fresh, young leaves.
Affected leaves have shiny, silvery spots. This is caused by the thrips sucking the chlorophyll out of the leaves.
In spite of the fact that they're small, you can see them marching in columns on an infested plant.
Solution: Thrips can be fought with your favorite insecticide. Or predatory insects, the thrips' natural enemy is Amblyseius cucumeris.
A thrip problem can be solved basically the same way as aphids. My favorite way to get rid of them is misting your plants in a solution made of 1 part SM90, 5 parts water.
You'll want to do this when the lights are about to go off(or else the leaves will get burned). You can get a sprayer like this one on amazon.com, or at Home Depot for about $12.
Grey Mold / Bud Rot / Fungus (Botrytis cinerea)
Botrytis blight or gray mold is a common fungus disease which can cause blights; the most common is Botrytis cinerea.
Botrytis infections often thrive in cool (60 degrees Fahrenheit or 15 degrees Celsius), rainy spring and summer weather.
Gray mold can be particularly damaging when rainy, drizzly weather continues over several days.
Look for masses of silver-gray spores on infected plant parts that are growing in humid areas.
Tiny, black, shiny specks might also be seen embedded in diseased plant tissue.
These are sclerotia of Botrytis: they allow the fungus to survive the winter.
Botrytis blight can affect leaves, stems, crowns, flowers, flower buds, seeds, seedlings, bulbs, and just about any other part of a plant with the exception of the roots.
Solution: The best way to manage this disease is keeping humidity low, maintaining good air circulation, and by regularly inspecting and removing of infected parts of the plant immediately.
NEVER SPRAY YOUR BUDS WITH ANYTHING. Once a bud has been infected, you need to remove the affected parts.
Remove infected flowers, leaves, or the entire plant if it's infected at the base, and take it far far away from your grow area to dispose if it.
Low humidity slows down and prevents mold (50% or less humidity is optimal, especially towards the end of the flowering stage). Also try to maintain lots of air movement with oscillating fans, and lots of air exchange if possible ( via Exhuast air and Supply air).
If you find mold remove it immediately. Once you first find mold, you need to watch your plants like a hawk, as mold spreads quickly.
It is best not to do any mold removal while plants are wet since this could help spread fungal spores during conditions which favor infection.
Also avoid overhead watering, or misting plants, especially if you have had trouble with grey mold in the past.
To promote rapid drying of plants, try to space them to allow good air circulation, and don't hesitate to use fans to help promote good air circulation.
Sanitation and cleanliness alone is not sufficient to control this fungus.
The fungus can produce 60,000 or more spores on a piece of plant tissue the size of your small finger nail.
Even one spore can infect a plant and cause disease.
So, avoid injuring plants in any way.
Do not leave large stubs of stems when taking cuttings.
Ventilate your grow space to prevent high humidity conditions.
Even lowering the humidity slightly can have a significant effect on Botrytis.
Outdoor planting should be planned to provide good air circulation patterns.
This is the most important means of stopping this fungus.
Added protection is available for many crops by applying a fungicide or combination of fungicides.
However, Botrytis can develop resistance to certain chemicals.
An ozone treatment is also an option, ozone is excellent for decimating spore counts in the grow room and a decent UV tube unit placed high in the room with a fan blowing through it can reduce dramatically the risk of botrytis.
Don't spray or burn Sulfer in the flowering stage! You will ruin your crop as Sulfer makes your bud taste really bad, like REALLY TERRIBLE.
However, it is safe to use sulfur in Veg to treat mold, before the buds have started forming. Sulfer seems to get right into the essence of the bud and the taste/smell is impossible to remove. Sulfure will TOTALLY ruin your crop if used in the flowering stage!
Root Rot / Pythium Root Rot (Pythium spp.)
Pythium root rot can be caused by several different species of the fungus Pythium.
These fungi are common in field soil, sand or sediment of surface water supplies, and dead roots of previous crops.
Pythium has also been found in some commercially available soilless potting mixes.
Pythium is easily introduced into pasteurized soil or soilless mixes by using dirty tools, dirty pots or flats, walking on or allowing pets to walk on the mixes and by dumping the mixes on benches or potting shed floors that have not been thoroughly cleaned.
When introduced into pasteurized soil or soilless mixes, Pythium can cause severe root rot because it has few competitors to check its activity.
Root rot is also a common problem for those growing directly in water, such as via deep water culture or bubbleponics and this fungus poses a threat to crops grown in just about any hydroponic system.
A great way to prevent root rot in hydroponic systems is to properly aerate the water!
If the reservoir is heavily contaminated with debris or soil harboring Pythium, the fungus can spread to a large number of plants quickly.
If the fungus infests a cutting bed or if contaminated water is used in propagation, large losses usually occur.
Almost all plants are susceptible to Pythium root rot.
Root tips which are very important in taking up nutrients and water are attacked and killed. Pythium also can rot the base of unrooted cuttings.
Symptoms of Pythium include: Stunted plants, root tips are brown and dead, Plants yellow and die, Plants wilt at mid-day and may recover at night, rot may proceed up the stem, brown tissue on the outer portion of the root easily pulls off leaving a bare strand of vascular tissue exposed, and the cells of roots contain many microscopic thick-walled spores.
Solution: Pythium root rot is difficult to control once it has begun.
However, at GrowWeedEasy after much trial and error, we've discovered that we've always been able to control and erradicate root rot with Aquashield.
We HAVE NOT had good luck with Subculture B, Great White and SM-90 to treat root rot, though other growers have reported success killing root rot using those treatments.
Still, even with the amazing power of Aquashield in treating root rot, every effort should be directed toward preventing the disease before it begins.
Pasteurize soil and sand with heat (a microwave) or chemical fumigant treatments.
If the water supply is suspected of being the primary source of Pythium, it may be necessary to treat the water before use.
Slow sand filtration has been shown to be an effective, simple, and inexpensive method for removing Pythium from water.
Cover the treated soil and store it or the soilless mix in an area that will not be contaminated through the introduction of non-treated soil.
Likewise, cover ebb and flow system reservoirs. Disinfest all surfaces, tools, and equipment that will contact the potting mix.
We have also found that Hydrogen Peroxide (H2O2) will work for controlling Pythium in both dirt and hydro for short amounts of time. However, I highly recommend getting Aquashield for a more permanent solution.
Damping-off (young marijuana seedlings dying)
Damping-off generally refers to sudden plant death in the seedling stage due to the attack of fungi.
These fungi are soil borne and are stimulated to grow and infect the seed or seedling by nutrients released from a germinating seed.
However, seedlings may be injured or killed by something other than fungi, for example, toxic materials in the soil, excess or deficient soil moisture, seed defects, temperature extremes, toxic gases in the air, etc. A correct diagnosis is the key to effective control measures.
Damping-off disease of seedlings is widely distributed and is a problem on a worldwide basis. It occurs in most soils, temperate and tropical climates, and in greenhouses.
The disease affects seeds and seedlings of various crops.
The amount of damage the disease causes to seedlings depends on the fungus, soil moisture, and temperature. Normally, however, cool wet soils favor development of the disease.
Seedlings in seedbeds often are completely destroyed by damping-off, or they die after transplanting.
Frequently, germinating seeds are killed by damping-off fungi before they emerge from the ground, which accounts for poor stands in many crops.
Older plants are seldom killed by damping-off fungi mainly because the development of secondary stem tissue forms a protective barrier and limits fungal penetration.
However, portions of the roots and stems still can be attacked, resulting in poor growth and reduced yields. When seeds are planted in infested soils, damping-off fungi may attack them at any stage.
The damping-off fungi may attack the seed prior to germination, or they may attack after the seed has germinated but before the seedling has emerged above the soil line.
Infected seed becomes soft and mushy turning a brown to black color, and it eventually disintegrates.
Seeds that have germinated and become infected develop water-soaked spots that enlarge and turn brown.
The infected tissue collapses, resulting in death of the seedling.
Penetration and death of seeds before they emerge is termed preemergence damping-off.
Seedlings that have emerged are usually attacked at or below the soil line. The organism can easily penetrate the young soft stem tissue.
The infected stem portion becomes discolored and begins to shrink.
As this occurs, the supportive strength of the stem's invaded portion is lost, and the seedling topples over. The fungi continue to invade the remaining portion of the seedling, resulting in death.
This phase of the disease is termed postemergence damping-off. Older established plants also can be attacked by damping-off fungi.
Usually the new developing rootlets are infected, resulting in root rot. Infected plants show symptoms of wilting and poor growth.
Solution: Proper conditions for seed germination and seedling emergence also favor vigorous growth of fungi that cause damping-off.
Seed and roots must be kept moist and warm until the roots have penetrated the soil and the seedlings have emerged.
As the seedlings continue to grow, moisture at the soil surface can be decreased, and the damping-off fungi then will have less of an advantage.
When watering, thoroughly saturate the soil and then apply no more water until soil approaches the point at which plants wilt.
This procedure will keep surface soil dry for a maximum time.
Pasteurization of Soils is the best way to protect yourself. Soil for growing transplants in flats can be steam pasteurized.
If steam is used, the entire soil mass should be maintained at a temperature of 160 degrees F for 30 minutes.
The home gardener obviously does not have facilities to steam soil; however, pasteurized, packaged soil mix is available from many garden centers.
To prevent soil recontamination, all items such as tools, pots, and flats, etc., must be clean. The items can be cleaned in hot water (160 degrees F for 30 minutes) or in a chlorine bleach solution (1 part bleach to 9 parts water; soak for 30 minutes).
It is important to use fresh chlorine bleach-water solutions.
Lice
Lice are found inside as well as outside. And thrive during the summer months. Lice are the most interested in plants with questionable health.
It's unusual to have a lice problem with a healthy marijuana harvest.
Solution: There are two methods to kill lice, spraying with incecticide SM-90, and setting out assassinator wasps.
The problem with most flying predatory insects is that they're attracted to the high-pressure gas lamps we all love to use, which sends most of them to a quick and fiery death.
Slugs/Snails
The common slug is too common a pest to even need much of an introduction. Slugs attack a wide range of plants, causing anything from slight damage to death.
Unfortunately, these annoying pests attack leaves AND buds, and they can do a surprising amount of damage in a short time, so you want to watch out for them and get rid of them quickly.
They often stay hidden, attacking your plants at night, so stay vigilent for slug and snail damage!
Solution: There is no foolproof method for eradicating slugs.
All one can hope for is to reduce their numbers and protect plants when they're at a vulnerable stage.
Toads, frogs, and beetles eat slugs and are worth encouraging in your garden. One of the best ways of dealing with slugs is to use physical barriers.
Place plastic bottle cloches around plants, or sprinkle circles of lime, eggshells, Diatomaceous Earth,or sawdust around plants.
Slugs are attracted to saucers, orange rinds, and plastic pots of milk or beer (they drown themselves in ecstasy).
How to Make Beer Trap for Slugs and Snails: mix flour with some stale beer and use it to fill a shallow container. Place in garden with the rim 1 or 2 cm above the ground so that slugs and snails can climb in. Substitute beer for wine, sugar water, juice, or water mixed with yeast.
BE WARNED, the trap will fill up quickly so come back often to empty.
To be sure you're keeping your slimy slug population under control; collect them by hand at night or on damp days. T
ry collecting them under a tile or wet cardboard, and squash all eggs you find while digging. Placing a saucer of salt is another method that will kill snails and slugs.
Martha Stewart recommends coiling a piece of wire around the base of your plants to give slugs a shocking experience.
Tobacco Mosaic Virus
The tobacco mosaic virus can attack a wide range of plants, including tomato, pepper, eggplant, tobacco, spinach, petunia, marigold, and our beloved herb marijuana.
On marijuana the virus infection causes light and dark green mottled areas on the leaves.
The dark green areas tend to be somewhat thicker than the lighter portions of the leaf. The leaf mottling is seen more easily if the affected plant surface is partially shaded.
Stunting of young plants is common and often is accompanied by a distortion and fern-like appearance of the leaves. Older leaves curl downward and may be slightly distorted.
Certain strains of the virus can cause a mottling, streaking and necrosis of the buds. Infected plants are not killed, but they produce poor quality buds and low yields.
Tobacco mosaic, is incited by a virus. The tobacco mosaic virus is very stable and can persist in contaminated soil, in infected plant debris, on or in the seed coat, and in manufactured tobacco products. The virus is transmitted readily from plant to plant by mechanical means.
This may simply involve picking up the virus while working with infected plant material, then inoculating healthy plants by rubbing or brushing against them with contaminated tools, clothing, or hands. Aphids are not vectors of the virus, although certain chewing insects may transmit the pathogen.
Solution: Virus diseases cannot be controlled once the plant is infected.
Therefore, every effort should be made to prevent introduction of virus diseases into the garden.
Sanitation and cleanliness is the primary means of controlling virus diseases.
Infected plants should be removed immediately to prevent spread of the pathogens.
The use of tobacco products during cultural practices should be avoided to prevent inoculation of plants with the tobacco mosaic virus.
Those people using tobacco or working with infected plant material should wash their hands thoroughly in soapy water before handling your plants.
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