Fungus Troubles in Cannabis

Fungus issues during flowering

Fungus is one of the most common cannabis pests both growers and hobbyists have to deal with. Some of them are seasonal while others tend to occur regularly. You often use pest control products and organic solutions to eradicate this problem, but they just keep on coming. Read on to find the answer on how to prevent and control this common marijuana pest problem.

Damping Off

damping off in cannabis seedling

Damping off is a kind of fungus that is found in soil mixtures. It attacks seeds and seedlings before and after they emerge from the shell. Seedlings that get attacked by this fungus usually die, considering the plant doesn’t have a fighting chance nor a system set up to help fight the fungus. Leaves, roots, and stems can be affected. The plant can be attacked in a range of growth stages – from three leaf nodes up to the time it develops eight sets of true leaves. 

Damping off can be easily confused with excessive fertilization (nutrient burn), high levels of salts from either water or nutrient solution build-up, extreme heat or cold, excessive or insufficient soil moisture. The cotyledons that emerge on the soil surface can wither and die or healthy looking seedlings may suddenly fall over. Infection first starts right below the soil line. Once attacked, the seedling and vegetative stage plants will start to rot and show any or all of these following symptoms– the lower part of the stem will be soft and brown, leaves will turn to a purplish hue, or can yellow or brown and then fall over or shrivel up. Seedlings or vegetative stage plants will then start to fall over from the stem being so soft and starting to rot inside out. 

One factor that contributes to this problem is overwatering, especially when putting seedlings or small plants into a big pot. When you water your plant, the soil lower down soaks up excess water and ends up sitting in the middle to the bottom part of the pot. When this happens fungus begins to build up due to them not having a deep or big enough root system to absorb all the excess water, so it ends up turning into damping off. In vegetative stage seedlings, leaves typically turn yellow and droop during the later part of damping off, often looking like the plant has been overwatered. Stems will be severely weakened and may fall over from being underdeveloped and skinny. 

Older plants can build up a resistance to damping off but if they do not, these will show long skinny stems, stunted roots, and stem discoloration. Soil that is rich in nitrogen, soggy soils, soil that stays wet for long periods, and warm soil or temperatures all encourage damping off. Even hydroponics systems can get damped-off; growing media that stay too saturated raise the risk but you have a less likely chance of getting damped off in hydroponics systems.

Prevention and Control

In order to help control or prevent damping off, you should grow seedlings in “starter cups” which are the standard drinking cups you get from the store. Putting drainage holes in the bottom of the cups is extremely important in helping avoid damping off, allowing excessive water to drain so the bottom half of the mixture will not stay wet.

This is why cups are great for starter seedlings; you can still over water, but your chances of getting damped off are much less than that of a seedling put into a big pot with lots of soil. It helps a lot to make sure you have a good amount of perlite in your potting mixture and your pots have holes. Putting seeds into the soil at a low depth helps out – just putting it an inch or 2 at the most helps avoid the fungus.

cannabis seedlings in starter cups

Avoid planting in rich soil mixtures –not only can you burn cotyledons when they emerge from the soil, but too much nitrogen can lack root growth and aggravate damping off. Try using a seed starter mixture and do NOT water heavily. Avoid watering every day; instead, water your seedlings every other day. Seedlings with 2 to 3 sets of leaves in cups can start to be watered more heavily when the water starts to drip out the drainage holes. Only then should you water like this every 3 days. 

Overwatering is one of the biggest causes of damping off. Also, using soilless mixtures like growing peat mixed with other stuff can help deter it. If you decide to get mostly soil with peat moss, you must make sure there is dolomite lime added to adjust the pH; otherwise, you will have pH issues that can lead to locking out nutrients that are in the soil but are not absorbed because the pH is off. Using sterile soil helps greatly. Moreover, allow great airflow and circulation in your grow room and let the surface dry out before watering again. Use moisture meters or stick your finger down in the soil near the edge of the pot to test for wetness down below. Make sure to test soil along pot edges in order not to disturb root development. 

Once seedlings that have already emerged from their seed shell end up getting affected by damping off, there’s a very high chance they will not survive and there is nothing you can do about it. By the time it shows in seedlings, it will already be too far off for corrective measures. Using a fungicide on the seed before putting it into soil mixtures helps to avoid post-emergent damping off. Plants in the vegetative stage (having a few sets of leaves) have better odds at fighting off fungus. Depending on the extent of the fungus infestation, you may use a fungicide to address the problem. Using organic-based fungicides can help avoid or kill damping off, especially when cultivating cannabis using seedlings or seeds. Chemical control should only be used on older plants and not on seedlings and should be avoided as much as possible.

Fungus issues during flowering

Fungus issues during flowering

When your cannabis plants are in the flowering stage, they are more susceptible to fungus infestation or bud rot. Growing conditions for fungus are best when temps are between 60 and 80 ℃ and the humidity is high. Fungus in cannabis is very destructive and spreads quickly. These kinds of fungi are airborne and can travel to other bud sites. If you already have been infected by them, the best thing you can do is cut off and remove the infected section and discard out of the grow area. Next, find some kind of antifungal spray and apply.

Fungi can kill your crop quickly, so invest in some safe fungicide and spray down the plants as much as you can and as soon as you can. The faster the safer. If you have had problems with fungus before, do NOT spray them – you will contribute to the fungus becoming resistant to the chemical sprays you are using. Try to keep the humidity down to the range fungi do not grow too well in. Keep a good amount of ventilation around your grow and if you have plants outside, always keep them quarantined away from your indoor plants until you know they are safe.

Most fungicides are very nasty and dangerous when used on food crops or cannabis crops, so it’s best to use something that is safe for human consumption in the end product. There is a variety of safe and organic fungicides that contain only sulfur in solution and works well on fungus issues.

Controlling Fungus on cannabis

To control and prevent fungus from forming there are a few things you should do:

  • Do NOT foliar feed at night as this tends to raise humidity compared to when you do it at daytime when moisture has time to evaporate. At night it will linger in the air.
  • Same goes for watering plants during night time – better to wait till the following morning or afternoon to water!
  • Keep a happy plant and it will not become prone to infections. Checking your cannabis plants often can aid in getting rid of any fungus that may attack other leaves and/or buds!
  • Have a lot of air circulating around the plants. Poor ventilation always results in sick plants and a breeding ground for spores!
  • Keep leaves away from the soil making sure they do NOT touch the surface.
  •  Keep cooler temps at night while plants are on their downtime.

If you have already gotten some kind of fungus there are many things you can use: Neem oil works wonders! Potassium bicarbonate, baking soda, and other chemical agents are available and you can also use Plant Shield, Serenade, and pythium. There’s a wide range of other chemicals and organics that work but these more popular ones deliver amazing results.

Organic Fungus Pest Control – Ant & Garden Solutions Beaverton

Fungus is a common cannabis problem that can infect and damage your marijuana babies and give you a headache. The only way to eliminate fungus is to be patient and hands-on with your cultivation procedures. You’ll need some good cannabis organic pest control advice from someone who’s OLCC-certified to help you with these. The answer to your problem is simple – effective and organic pest control knowledge and application methods. Ant & Garden Solutions in Beaverton is here to help! I have the most pest control licenses than anyone else in Oregon.

With a general pest license, I’ll treat your structure and building to get rid of pests. An agricultural insecticide license also enables me to treat your cannabis plants with OLCC-approved products. My ornamental insecticide fungicide license lets me treat your environment and surrounding property and my herbicide license ensures I get rid of weeds surrounding vegetation with professional and reliably trusted products. Ant & Garden Solutions will treat your high-valued cannabis plants safely and properly for your peace of mind. Contact Us today to speak to our master technician for some good organic pest control advice!

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