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brown spots on leaves during flowering

Leaf Septoria (Yellow Leaf Spot) On Cannabis Plants

Cannabis plants, unfortunately, are susceptible to a wide variety of diseases and pests. Leaf septoria is one such disease, and can greatly damage the foliage, development, and yield of your cannabis plant. Learn how to properly treat and prevent leaf septoria from devastating your crop.

Leaf septoria is a harsh plant disease that regularly affects the foliage of a variety of plants, including cannabis.

If not handled properly, leaf septoria can be devastating to plants, destroying foliage, stunting their growth, and ultimately affecting the size and quality of their yields.

In this article we take a close look at cannabis leaf septoria, what it is, and how to treat/prevent this disease from affecting your cannabis crops.

WHAT IS LEAF SEPTORIA?

Leaf septoria, also known as septoria leaf spot or yellow leaf spot, is a plant disease caused by a specific kind of fungus known as Septoria lycopersici.

This fungus usually overwinters on dead foliage or common garden weeds. Fungus spores can also spread onto equipment like garden stakes and netting, before germinating when conditions are right.

Leaf septoria can be an extremely damaging disease, greatly affecting the foliage and growth of a variety of plants, including tomatoes, parsley, and obviously cannabis.

As the name suggests, leaf septoria is characterized by yellow and brown spots forming on both the upper and lower sides of leaves. The spots tend to be circular with dark brown margins and tan or greyish centers. They usually measure between 1.5 to 6.5mm.

Leaf septoria usually affects plants just after they enter the flowering stage and usually forms on lower leaves first. As the disease develops it spreads its way upwards, quickly affecting multiple leaves all across the plant.

Affected leaves will usually turn slightly yellow, then brown, and eventually wither completely. Leaf septoria rarely spreads on to fruit, so it generally won’t affect cannabis flowers.

If left uncontrolled, the disease can destroy a lot of foliage. This ultimately creates a lot of stress for plants and stunts their growth as well as the size of their harvests. Leaf septoria is particularly prevalent in areas affected by extended periods of wet, humid conditions.

HOW TO TREAT LEAF SEPTORIA IN CANNABIS PLANTS

As with most garden pests and disease, early detection is extremely important when dealing with leaf septoria. Make sure to pay close attention to your plants during extended periods of hot and humid weather, as well as during the early stages of the flowering cycle.

Once you’ve identified the disease, make sure you follow the following steps to control it and stop it from spreading:

1. REMOVE INFECTED FOLIAGE

The first step to effectively dealing with leaf septoria is removing infected leaves. If caught early, you can usually prevent the spread of the disease by simply removing all infected lower leaves and burning/destroying them.

However, if the disease has spread to the height of your flowers, you’ll generally want to skip this step. Removing foliage from flowering areas will greatly weaken a plant and reduce the quality of its buds.

2. IMPROVE AIR CIRCULATION

Proper air circulation is extremely important for cannabis plants and plays a big role in the management of pests/diseases.

If you’re growing indoors, improving air circulation can be as simple as adding an extra fan into your room and creating some space between your plants. If you’re working outdoors, however, this might be a bit more difficult.

Pruning is also a great way to help create airflow in and among plants. Try trimming down extremely bushy areas of your plants and avoid having leaves touching or laying on top of each other.

If you’re working outdoors, you may want to try elevating your plants slightly so that they catch a bit more wind. Alternatively, also consider running an electric fan on outdoor plants if possible.

3. AVOID MOISTURE

Moisture is another major player in the spread and germination of fungal spores. Hence, you’ll want to avoid moisture as much as possible.

Avoid overhead watering as this will wet the leaves of your plants and consider watering slightly less regularly in order to give the soil a chance to really dry out. Also water early in the day to allow the soil to dry out during daylight hours.

4. MULCH

Fungal spores often spread into soils where they hang out over the winter until conditions are right for germination.

While you won’t be able to change your growing medium mid-grow, there are some steps you can take to avoid any spores from the ground spreading onto your plants further.

Start by removing any dead foliage and raking the soil to remove any possibly infected vegetation. Next, dry out your soil properly. Finally, apply a thick layer of mulch to the top of your soil then water your plants.

This will help stop the spread of fungal spores from the soil up onto your plants.

5. REMOVE WEEDS

Night shade and horsenettle are common hosts of Septoria lycopersici spores. Hence, make sure you run through your garden and remove any weeds that could possibly host the fungus.

6. KEEP TRACK OF TEMPERATURE AND HUMIDITY

Remember that leaf septoria naturally strikes in hot, wet conditions. Hence, if you’re dealing with an infection, try driving down the humidity and temperature levels in your grow space (where possible).

7. APPLY FUNGICIDES OR NATURAL OILS

If you’re dealing with a minor case of leaf septoria, steps 1-6 might be enough to kill the disease and stop it from spreading any further. However, if you’re dealing with a more serious infection you may need to rely on some heavy-handed fungicides.

Broad spectrum fungicides and disease control sprays will usually do the trick. For extra protection, try opting for a copper-based fungicide. Either way, remember to carefully follow the package instructions when using any kind of disease control agent, and avoid getting any of it on your buds.

If you’re after a more natural alternative, we suggest turning to essential or horticultural oils like neem. Neem oil is commonly used to treat all kinds of garden pests and diseases and can easily be applied to your plants using a mister.

Alternatively, consider trying eucalyptus, rosemary, lemon, and cinnamon oils. Either way, remember that these oils have strong aromas and should never go near your buds to avoid contaminating their aroma/flavour.

Neem oil serves as a completely natural way to protect your cannabis plants against pests.

Leaf septoria, also known as yellow leaf spot, is a fungal disease that can greatly damage cannabis crops. Here's how to deal with leaf septoria on weed plants.

How to Spot the 7 Most Common Cannabis Plant Deficiencies by Leaf Symptoms

A cannabis plant is hardy, but its health and vigour will be negatively impacted if it is deprived of essential nutrients. If this is not corrected, it can cause plants to stop growing or even die. Deficiencies in cannabis can be hard to identify, so we have compiled a basic list of what to look out for if things go wrong, and how to fix them.

New cannabis growers are bound to come face to face with a problem or two. Thankfully, cannabis plants are resilient and can stand up on their own in the face of pests or improper growing conditions for a while. But if the problem isn’t rectified in a timely manner, there’s going to be consequences.

One of the biggest mistakes new growers make is overreacting, though. If an iffy situation is spotted, growers should simply acknowledge that and take the time to learn what the problem is and how to properly fix it.

This guide will go over some of the most common problems that can be identified by simply inspecting the leaves. It also will explain how to proceed and get those plants on the road to recovery… and a better yield!

While this definitely isn’t a conclusive list, here are some common growing problems and how they may be identifiable on cannabis leaves (read the rest of this guide for more in-depth help):

  • Yellow leaves: Could be a sign of all deficiencies mentioned below, or light burn
  • Leaves that curl upward: Could be a sign of potassium deficiency, or overwatering
  • Brown leaves: Could be a sign of phosphorus, potassium, magnesium, sulphur, manganese deficiency. Could also be nutrient burn (more solid brown colouring) or heat stress (brown on the edges)
  • Leaves droop: Could be a sign of overwatering
  • Leaves curl downwards: Could be a sign of potassium or phosphorus deficiency, or overwatering

Nitrogen deficiency in a cannabis plant

Nitrogen deficiency is probably the most common deficiency reported by cannabis growers. It’s usually easy to identify and correct as soon as it becomes apparent, although it shares a basic resemblance to several other deficiencies in the early stages.

In the early stages of nitrogen deficiency, leaves appear to be too light in colour—almost yellowish-green—compared to the desired deep green of healthy leaves. Nitrogen-deficient leaves also typically have slightly darker veins compared to the very light colour of the leaf tissue itself—although the contrast is not as marked as in some other deficiencies.

At the other end of the spectrum, nitrogen toxicity results in leaves taking on a very dark green hue that can look almost black in extreme cases.

In severe cases of nitrogen deficiency, the leaves appear lighter and lighter in colour, and eventually begin to dry out and die. The larger leaves on the lower and outer parts of the plant are often the first to be affected and the first to die.

How to fix nitrogen deficiency

If nitrogen deficiency becomes apparent in the later stages of flowering, it doesn’t need to be corrected. In fact, it’s natural for the older leaves to drop off and die at this point as they are no longer needed.

However, a nitrogen deficiency in vegetative growth or early flower can severely impact overall yield and quality, as it affects the plant’s ability to photosynthesize energy. Nitrogen deficiency can usually be corrected by simply increasing the strength of your normal NPK-based feed, but if fine-tuning is required then nitrogen-only additives are not hard to find.

Phosphorus deficiency in a cannabis plant

Phosphorus deficiencies are rare, but should be cause for concern. If it affects plants in the vegetative stage, it can cause reduced growth rates, small leaves, weak roots, and plants that are generally lacking in vigour. In the early stages, phosphorus deficiency usually causes leaves to appear dark but washed-out, with very dark veins and somewhat lighter leaf tissue.

As it progresses, purplish discolourations begin to appear on the main part of the leaves and the leaf edges begin to turn brown and curl downwards. The leaf petioles (the small stalk attaching the leaf to the main stem) may also begin to turn a purplish colour. In the final stages, large patches of the leaves become purplish-brown and dead, while the remaining sections turn mottled yellowish-green.

Again, phosphorus deficiencies usually affect the outer, lower leaves first. Unlike nitrogen deficiency though, phosphorus deficiency at any stage is cause for concern, as the plants continue to require high levels of phosphorus throughout the flowering period.

How to fix phosphorus deficiency

There are several ways you can fix a phosphorus deficiency. Just remember to take it slow. If any remedy is overdone, the plant could end up not getting enough of other nutrients and fare worse than if it had been left alone. With that said, here are a few methods for fixing it:

  • Temperature – Don’t let the temperature drop below 15 degrees Celsius, as colder temperatures make it difficult for cannabis plants to absorb phosphorus.
  • Water correctly – Ensure the plants are watered correctly. Too much water and soil that’s too packed can lead to a phosphorus deficiency.
  • pH Products – Use a pH up or pH down to ensure the roots have the correct pH level. It should be between 6 and 7.
  • Add Phosphorus Sources – Add sources rich in phosphorus to the soil. Some sources that can be used are fish meal, warm casting, soft rock phosphate and crab shell. (Or simply use a good organic fertilizer that automatically ensures balanced soil)

Once the problem is corrected, new leaves shouldn’t show the discolouring signs of phosphorus deficiency. Keep in mind that old leaves will likely not recover and that’s perfectly normal.

Tutorial: Cannabis plant nutrient deficiencies can be hard to identify. Use this guide to help you figure out what’s wrong and how you can fix it.