White spots on fan leaves?!

white spots on fan leaves

White spots on fan leaves

Have you noticed white spots on your fan leaves or stems? Leaves with white spots that look like small round patches of powdered sugar?

I have bad news for you, this isn’t fairy dust left behind from your guardian weed angel, this is the sign of either a fungal disease or an aphid/spider mite infestation – but don’t panic.

If you haven’t seen bugs and your an indoor grower it’s most likely just White Powdery Mildew which is actually pretty common! and easy to fix if done quick enough.

white spots on fan leaves

As mentioned above, if you’re growing indoors, in a clean environment, what’s covering your leaves is most likely White Powdery Mildew, unless you are growing outdoors, the white dusting could be a sign of other problems such as Spider Mites, which love to lay eggs on the leaves, looking very similar to WPM at first glance, left untreated both can and will devastate crops.

I’ll explain how you can tell the difference between WPM and spider mites, how WPM is caused and how to get rid of it successfully.

What Is White Powdery Mildew?(WPM)

White powdery mildew is a fungal disease that only exists to eat, reproduce and live another day. WPM is quite literally a mold, that grows and leeches from the nutrients in your plants and will eventually cripple the plant if not stopped.

Often occurring due to poor air circulation and high humidity levels, the fungus develops a strong ecosystem within the humidity and shade of the canopy but it can be easily fixed if you catch it early enough – left untreated, WPM can turn into a catastrophe and ruin an entire crop.

white spots on fan leaves

How to identify WPM?

  • Plants infected with mildew look as if they have been dusted with flour/sugar.
  • Powdery mildew typically starts off as circular, powdery white spots.
  • WPM typically covers the upper part of the leaves, however, might grow on the underside of the leaves.
  • The lower leaves are usually affected first, giving the impression that a sudden outburst has bloomed overnight when it fact the fungus would have been “setting up shop” the whole time. The most affected leaves tend to be towards the bottom of the plant.
  • Leaves can also twist, dry and break.
Related image
High humidity is the main cause of WPM

How to control & eliminate WPM?

The main cause of WPM is high humidity – usually as a result of poor air circulation, cannabis plants require a RH level of 40 – 60% with air circulation, remove the air and you can be guaranteed that WPM will colonise.

Start by closely inspecting each individual plant and carefully remove any affected leaves, be careful to not let infected leaves come into contact with unaffected leaves, dispose of all infected leaves separately to be burnt, seriously – burn them.

Once you are confident that you have removed all infected leaves, I would also recommend that you remove the first 1 – 2 inches of soil as it’s likely that spores have fallen into the soil and replace it with new, clean soil.

Now you will need to treat your plants with a natural fungicide to kill the remaining spores and stop it from coming back again.

Natural Fungicides for WPM:

Fungicides can be easily made at home by filling with the help of a hand pump sprayer, a few popular solutions involve:

*Add a drop of washing up liquid to prevent the oil from separating with the water inside the handpump, otherwise, the oil will spray out at a full concentration as a result of sitting on top of the water.

Apply a heavy foliar spray at night time before the lights go off to both the top and underside of the leaves, repeating this process daily. It’s important to wait until the lights are due to go off because the water droplets can be magnified under the intense lights and burn your leaves.

Try to not spray too much of the fungicide solution onto the mature buds because they are oils and can stick around for a while,

Disease Resistant Strains

If your growing environment is susceptible to mold or other diseases, did you know there are mould-resistant cannabis strains that exist?

Identify & Control Spider Mites

Author: tgallone

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