'An ounce of Prevention is worth a pound of Cure!'
You're not the only one who likes to enjoy your cannabis plants. No, unfortunately there are plenty of others who are preying on your green ladies, so watch out! And then I am not even talking about the real thieves who are lurking around, no I'm talking about other organisms that want to feed on your cannabis: PESTS. Insects that want to eat your lovely ladies before you can reap the benefits from them, and believe me there are plenty of this kind of potential enemies lurking around! I came into contact with some of these pests myself, so I will highlight this matter from my personal experience: Spider mites, Thrips & Mildew and bud rot.
The most common mistake when it comes to pests: thinking that it will never happen to you. But unfortunately you'll quickly find out that it can happen to anyone, that's why pest prevention is an important aspect in the cultivation of cannabis. Make sure you don't take anything to your growing room from outside. And keep a close eye on your plants, pay attention to the top of the leaves as well as on the bottom. If you notice spots on the top of the leaf that shouldn't be there, check underneath the it to make sure that there aren't any other surprises waiting for you. In my personal experience you can really see if there's something going on when you check underneath the leaf. I've had some dark spots and silver colored ones on a leaf myself, seemed pretty innocent, but it wasn't until I checked the bottom of the leaf with a little microscope when I saw what was really going on: my plants were suffering from thrips larvae! Within a few days all my other plants had the same spots on their leaves and were covered with thrips. I had to do something about it fast!
You can fight plant pests the a chemical or biological way. You can also opt for a foliar spray, which has a natural and mechanical action. Cannabis is a product that's consumed by both recreational and medicinal users. When using pesticides (chemicals) during the cultivation process, the end product will be harmful to the health of the user.
That is why I personally am against the use of pesticides and didn't want to use it as a pesticide again thrips. I chose an alternative: organic pesticides (organic). After having used two products (Ed Rosenthal's Zero Tolerance & Aptus Dislike) without getting the desired result, I continued to look further. They are good preventative products, but I recommend to always use an organic pesticide product in the growing phase (foliar spray), just to be safe, but once the little creatures are there then these products are not as effective though in my experience
When you start with seeds, then you know for sure that you haven't started with traces of spider mite/thrips. The biggest problem with cuttings/clones is that spider mites/thrips often come along with it. When you come from outside you could carry traces of vermin, so it is important that you never, no not even quickly, enter with clothes from outside in your growing room. Because it's an enclosed space without any natural predators, spider mite/thrips can multiply in a rapid pace and ruin your crops as a result..
Pests are an issue with indoor as well as outdoor cultivation, but it varies with indoor because there are no natural enemies of the pests present. This means that a plague may spread easily in an enclosed environment, with disastrous consequences. The solution I've found is the release of natural enemies (can also be preventive): insects that feed on the weed-eating organisms. Releasing predatory bugs like Orius proved to be very effective against my thrips plague, it was the only 'natural' solution that worked, so I highly recommend it!
It's important when preventing pests that your plants are all as healthy as possible, so ensure the optimal conditions for them, and make sure that essential plant nutrients aren't left out. When the plants are less healthy they will be extra susceptible to thrips, spider mites and other pests.
Recognizing & Preventing
Mildew & Bud Rot
Mildew and/or bud rot are in contrast to spider mite/thrips not caused by an organism. They are a type of fungus that get the chance to thrive due to high humidity. In the Netherlands and surrounding countries the humidity level is very high at the end of the outdoor season. During this period (usually in September), mildew/bud rot are a disaster for your crops.
When you discover bud rot it often already too late, once it's in one of your buds it's impossible to get out. This means that preventing is actually the only solution. You can tell if you have bud rot if the leaves that come from the bud start to turn brown, when you gently pull on these 'rotting leaves' they'll easily tear off (without any resistance). When you can pull out a brown leaf from a bud without any resistance then alarm bells should go off. Chances are very high that there is bud rot present in the spot where the leaf used to be, deep inside the bud itself. If the bud rot is in a further stage then you can't really miss it. The top will be visible on the outside, and it will show brown-gray spots that are a little fuzzy. If you'd place the fuzzy part under a microscope you could see all the fungal hyphae, and if that's the case there's only one solution: cut off the entire bud and throw it away (no not just cut a small piece and smoke it, this can be very harmful to you health!). Then check all the other buds in the same room according to the previously mentioned directions and completely remove them as well. Try to avoid only removing a part of the bud, it will only cause the bud rot to spread even faster. Fungi contain spores, and these spores will spread under ideal circumstances, so when you don't remove the top entirely but only a small part it will only cause the spores to release.
Mildew is a fungus that usually starts on the leaves, which can then lead to bud rot. So it's well worth it to detect mildew at an early stage and fight it. Mildew manifests itself as white powder or white spots on the leaves. You can fight mildew with a mixture of 100 ml of skimmed milk, preferably non-fat milk, 900 ml of water and four teaspoons of sodium carbonate. Sodium carbonate is available as baking soda in many health food stores in the Netherlands. If you are about to harvest, you can also omit the milk. Spray the mixture on your plants with a plant sprayer every few days, keep the buds in mind, you don't want the buds to be soaking wet with the mixture. So only try to spray the affected leaves.
- Thrips, pest identification
Adult thrips are small, elongated insects with typical fringed wings. They are about 1 mm in size, and grayish or yellowish to brownish color. The thrips occur on the top as well as the bottom of the leaf.
The female thrips deposits her eggs in the plant tissue. They make an opening in the plant tissue where then the kidney-shaped egg is laid. Once the larvae hatch they immediately start to eat. They suck the leaf cells dry which causes silvery colored spots on the leaf.
The total cycle from egg to adult is about 20 days at 20°C and 12 days at 30°C. Under ideal circumstances 1 thrips female can produce more than 100 offspring.
Thrip damage can be recognized by spots on the leafs, often silvery colored. Thrips suck out the plant juices. They do this by scraping the leaf. This causes spots on the leaves. The thrips leave droppings on the leaf behind that look like dark spots. Moreover, growth is inhibited and deformation of the leaves occurs. Some thrips can also transmit viruses.
A good tool for pests detection is hanging up blue roller traps.
- Combating Thrips
The predatory bug Orius seems the most voracious biological thrip fighters. It is the only natural enemy that attacks adult thrips. Often enough you can see an Orius with thrips impaled on its nose walking over the leaf.
The predatory bugs are packaged in a plastic bottle. Each bottle contains about 500 adults and nymphs mixed in an easily dispersible carrier substance to combat about 25 square meters.
You can release the predatory bug by dispersing large heaps on a leaf and let it sit for a few days. This way the bugs get a chance to mate and spread out over the crops.
If necessary Orius can be stored in a cool temperature of about 8°C-10°C.
- Spider mites, pest identification
The spider mite is a 0.5 mm sized yellow-brown mite with two dark green spots on the flanks that lives off plant juices. The spider mite is active the most at a temperature of 25ºC to 30ºC and likes a low humidity. An adult spider mites lays 50 to 100 eggs at a time on average. At a temperature of 30°C, the duration from growth from egg to adult spider mite is about 1 week.
Spider mite damage can be seen by the white-yellow spots on the upper side of the leaf of the plant and silky threads on the bottom of the leaf. To feed themselves the spider mites suck up the plant juices. This causes a yellow discoloration of the plant cells, which is often visible on the top of the leaf and appear as yellow dots. On the bottom of the leaf there are very tiny spider like creatures that suck the phloem from the leafs. With severe infestations the leafs fall off and the silky threads are clearly visible.
A good tool for pest detection is hanging up yellow roller traps.
Often cuttings come with spider eggs. It recommended to release predatory mites when putting up the cuttings.
- Combating spider mites
Spider mite can be combated successfully with the predatory mite Phytoseiulus persimilis. The predatory mite is a 0.6mm red mite that moves fast and quickly goes on the hunt for spider mites. This predatory mite mainly feeds off spider mites and spider eggs which it then sucks empty and eats. The predatory mites are packaged in a bottle of about 1000, sufficient enough to treat a surface area of 25 square meters, if the infection is not too severe. The application is simple: scatter the contents of the bottle over the leafs of the plant (and not the flower).
It's recommended to treat spider mite every 14 days.