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rust spots on cannabis leaves

Do you have problems with rust? We will give you solutions!

Rust is easy to identify. It is a desease with a high destructive power which shows little pumps or little browned spots, with an intense orange surrounded by yellowish mass or even decolored, located at the backside of the leaves and also at the stems. The leaves attacked by this fungus end falling down and the plant keeps weak. In the branches and sprouts may appear red spots as well. The rust may produce a sticking substance that joins to the plant.

Its best conditions for propagation are very low night temperatures with a high humidity rate and lack of aireation, helping spores to be suspended in the air.

To avoid the spread of the spores we must clean carefully our worktools and the rest of the greenhouse, using bleach as antimicrobial agent.

The fungus manifests itself through small lumps or small brown spots, of an intense orange.

The cure is extremely difficult, the main antifungals help to reduce the propagation rate, but don’t eradicate the plague completely, even though we can control it with sodium bicarbonate if the plague is not set up more than two or three days, something very difficult to evaluate, so it can work as a preventive agent.

It is a method which is based in pH control, making it more basic, hence getting hard the biological conditions for fungus proliferation. You only have to do an irrigation with a spray sodium bicarbonate solution direct to the leaves and steams two times a week, watching carefully any signal of fungus appearance.

Any vegetal matter infected by rust must be removed from the greenhouse , cleaning again all tools used for cropping, otherwise we could spread the plague out.

We may use other antifungal agents formulated with synthetic chemical products which are used to treat Oidium and mildiu plagues, but you will have to take security control actions to apply these treatments.

Mentioned treatmens are also basically preventives, and they have to be performed once or two times a week with an interval among 7-10 days, depending on the climate control you have in the crop, increasing the frequency of treatment the more humidity you have in the room (indoor crop) or in the garden (outdoor crop).

You can choose among a wide range of products, even you can make your own product if you prefer to treat your plants naturally. These products always are based on:

  • Macerated or infused garlic in water: Always as preventive antifungal agent.
  • Macerated or infused nettle in water: As preventive antifungal agent, or contact antifungal.
  • Macerated or infused horsetail in water: Always as preventive agent.
  • Cupric sulphate water solution (20% w/w) (Bouillon Bordelais): As preventive antifungal agent, or contact antifungal. It is made of aqueous cupric sulphate solution.
Get a pest-free marijuana crop with this home-made garlic.

Would you mind to tell us about your experience?

Rust is easy to identify. It is a desease with a high destructive power which shows little pumps or little browned spots.

Rust spots on fan leaves during flowering?

Antigen
Well-Known Member

Hello, I have been growing indoors for quite a while now and I have not seen this problem in any of my plants before. I have attached pictures of what is happening.

The problem is only occurring on the older fan leaves near the top of the plant (for now). Newer growth and growth lower down doesn’t seem to be affected (yet).

The plants are grown in Ocean Forest potting soil and I use Earth Juice fertilizers (Grow, Bloom, and Micronute). I always check the water pH before watering to make sure it is around 6.5. I do add all my fertilizers and things to the water first and then adjust pH at the end before I water.

I do not have a soil pH tester or the money to buy a good one (since I’ve heard the cheaper ones do not work well enough to rely on). I’m hoping if this is a soil pH problem someone could tell me based on the pictures if it is too high or too low so I can try to correct it.

I have 2 plants that have been treated exactly the same since they were cut from clones, given the same dirt, water, and ferts, but only one of them is showing this problem. The other plant looks perfectly healthy.

The problem seems to start as tiny rust-colored spots near the veins of healthy fan leaves (see picture 1 below) and it progresses to much larger rust spots along with yellowing and curling/twisting up (pics 2-4).

If anyone has any ideas as to what might be causing these spots, please let me know, or if you need more information than I have provided in order to figure out what is wrong.

Hello, I have been growing indoors for quite a while now and I have not seen this problem in any of my plants before. I have attached pictures of what is… ]]>