By Max Sargent Reviewed by: Silvia Maroto

Leaf septoria is a harsh plant disease[4] 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 growth, and ultimately affecting the size and quality of their yields.

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


What Is Septoria Leaf Spot?

Leaf septoria is a generic name given to a range of fungal infections that cause brown spots to appear on plant foliage[5], damaging overall growth. Different septoria species are more likely to affect different species of plants, but the one we’re interested in (as cannabis growers) is called Septoria lycopersici.

Cannabis leaves affected by septoria leaf spot, featuring small yellow dots on leaves that indicate fungal infection. This condition can stunt growth and potentially reduce the overall harvest if not addressed.

Septoria can affect tomatoes[6], wheat, and parsley, to name but a few other plants. These fungi tend to develop on fallen, decaying foliage, from which spores make their way to living foliage, where they will grow. Depending on the plant affected, septoria can damage the harvest, or totally destroy it.

In cannabis cultivation, it shouldn’t totally ruin a harvest, but it is likely to stunt growth and reduce the final harvest if left untreated. Therefore, knowing a little about it is important, especially if you’re growing cannabis outdoors.

The Disease Cycle of Weed Leaf Septoria

Knowing about the life cycle of cannabis leaf septoria will help you to understand how it works, and therefore how to prevent it.

These fungi overwinter[7] on infected foliage from the year before, usually on fallen leaves. And these needn’t be cannabis leaves—so it might be present in any fallen leaves. In particular, it thrives in cool, wet environments. As spring appears and new foliage grows, septoria spores can spread and make their way to new growth. On cannabis, the infection only becomes apparent once the plant enters the flowering stage, appearing on the lowest growth first.

The Symptoms of Yellow Leaf Spot

You won’t know that septoria is present until it visibly appears on your plant(s). Here’s what to look out for.

  • Irregular spots: Septoria causes[8] irregularly shaped spots to appear all over foliage. These can appear circular, or elliptical and elongated. Either way, they will have rough edges and won’t be uniform in color. Their centers tend to take on a gray-brown colouration.
  • Bright yellow margins: The outsides of the spots will become yellow[9] as the chlorophyll in the leaves decays. As the spots expand, the yellow margins will move outwards, with the central gray-brown patch also growing.
  • Expanding spots: Septoria spots may start very small, but they can expand until leaves look quite seriously infected. The larger they become, the less leaves will be able to photosynthesise, and the more stressed your plants will become.
  • Development of pycnidia: These are asexual fruiting bodies of certain fungi, in this case septoria species. They develop in the gray-brown spots on infected leaves, and to the eye will appear as small black dots. These are proof that your plants have a fungal infection.
  • Stunted growth: As plants become more stressed and unable to properly photosynthesise, their growth will stall. As septoria usually only appears when plants are flowering, you won’t notice stalled overall growth [10](as cannabis plants no longer get larger at this stage), but you might notice underwhelming flower production.
  • Loss of vigour: Likewise, along with reduced flower growth, you might see that your plants generally look less vigorous. Though septoria doesn’t cause wilting, your plants may still sag and look generally unwell.

Cannabis leaves displaying symptoms of septoria leaf spot, characterized by small yellow dots on leaves, irregular spots with bright yellow margins, and central gray-brown patches. These symptoms indicate a fungal infection that can lead to stunted growth and reduced vigor in the plants.

How to Prevent Septoria Leaf Spot

If leaf septoria appears, you can treat it by removing infected foliage and treating plants with fungicide. However, it’s better if you can avoid it in the first place. While outdoor grows are always at risk of developing conditions—they’re in nature after all—there are many steps you can take as a grower to make this less likely.

Plant Spacing

Keeping your plants at a healthy distance from one another—and from other plants—can make the spread of septoria less likely. If foliage is competing for space and is intertwined, then the likelihood of many different infections occurring is much higher.

Giving every plant space to spread its foliage without competition will reduce the overall chances of septoria appearing, and it will definitely protect the crop as a whole if one plant becomes infected.

Maintain Plant Health

Plants, like animals, have immune systems. And like animals, these immune systems are much more effective when the plants’ overall health is good.

So treating your plants well and keeping them happy is one of the simplest and most effective ways to prevent not only septoria, but all infectious conditions.

In practice, this means:

  • Watering appropriately
  • Feeding appropriately
  • Minimising plant stress
  • Growing in a suitable substrate

Apply Mulch

Mulching the soil that your plants are growing in can help to stop fungal infections from making their way up to the plant’s foliage. As mentioned, septoria overwinters in rotting leaves, which by the next growing season might look much more like soil.

So if you’re growing directly in the ground, then layering mulch over this soil will help to trap all manner of pathogens, and also help to stabilise the moisture and temperature around your plants’ root systems[11].

The image shows a layer of mulch applied to the soil around cannabis plants, which helps prevent small yellow dots on leaves caused by fungal infections like septoria. This practice traps pathogens and stabilizes moisture and temperature in the soil, promoting healthier plant growth.

Stay on Top of Weeds

Keeping your cannabis garden free from excess plant growth is also a good way to reduce the chances of septoria and other pathogens spreading. An abundance of growth around your cannabis plants can have some benefits (in the case of companion plants), but it can also make a richer environment for fungi and bacteria to grow.

Certain companion plants can help to reduce the spread of diseases, but uncontrolled growth can increase the spread—so get weeding!

Control Moisture Where Possible

Septoria, like most fungi, thrives in wet conditions. Now, if you’re growing outdoors, there’s not a huge amount you can do to manage the amount of moisture in the environment. But you can plan ahead and plant your crop in such a way that it will be better able to handle adverse conditions.

Many plants crammed in a dank corner are going to be much more susceptible to fungal infections compared to a crop that is spaced out in a well-ventilated area. Many of us don’t have the luxury of choosing the perfect environment to grow cannabis, but do the best with the space available to you. Well-ventilated cannabis tends to be much healthier.

Trichoderma

Trichoderma are beneficial fungi that live in the soil and can help the root systems of cannabis plants in numerous ways. They can also reduce the occurrence and severity[1] of leaf septoria.

Now, adding Trichoderma[13] to the soil is best done from the beginning of a grow, as it develops a symbiotic relationship with a plant’s root system over time. So the longer this relationship has to develop, the more effective it will be.

These organisms are a must for organic cannabis growing, as not only do they help to protect cannabis plants from diseases, but they also help to deliver a range of nutrients to your plants in a more efficient way, improving overall growth.

How to Treat Weed Leaf Septoria

In case prevention methods fail, the good news is that there are a range of treatments available for cannabis leaf septoria, and they don’t need to be destructive either. Biological controls that pose little risk to the environment can be used to great effect—so there’s no need to spray your plants with synthetic fungicides. In fact, as your plants will be flowering, it’s essential that you don’t cover them in toxic chemicals, as you’ll end up consuming them later.

For best results, follow the approach of integrated pest management (IPM). This means that instead of relying on a single, all-powerful solution (such as toxic fungicides), you incorporate a range of less-damaging solutions, which are equally effective.

Remove Infected Foliage

First, remove infected foliage (usually starting at the bottom of the plant). This should halt or slow the spread of the condition, and will make the following treatments more effective. After handling infected foliage, be careful not to touch any healthy parts of your plants until you’ve thoroughly cleaned your hands.

Lactic Acid Bacteria

Lactic acid bacteria (LAB) occur naturally in decomposing soils. If you use them as an amendment and add them to the substrate in which your plants are growing, then they have been shown to improve growth[2] and help defend plants against soil-borne pathogens—such as septoria.

This organic addition to soil can improve the overall quality of the soil and protect your plants from a number of different diseases, meaning that both the wider environment and your crop benefit.

Compost Tea

Compost teas, made using an aerated brewing process, have been shown to control septoria leaf spot disease when applied as a foliar spray. This is an organic treatment that will not harm either the immediate or wider environment, but can work to get this disease under control. Moreover, it should be safe if it touches flowers that will later be consumed.

If you treat your plants with compost tea, you should act fast. Remove infected foliage and treat the remainder of the plant with the foliar spray. Treat at least once per day for a week after the last signs of septoria disappear.

The image shows a container of compost tea, an organic solution used to control septoria leaf spot disease in cannabis plants, which can cause small yellow dots on leaves. This foliar spray helps manage the infection while being safe for the environment and for flowers intended for consumption.

Trichoderma Foliar Spray

As well as being an effective preventative soil amendment, Trichoderma can also be used as a foliar spray against fungal infections[3]. You can easily buy these sprays online, and apply them liberally to your plants. As with other treatments, it’s still advised to remove infected foliage and apply this spray to seemingly uninfected foliage.

JADAM

JADAM (jayeon-eul dalm-eun salamdeul) translates from Korean to something like: "people who resemble nature". It’s actually an entire holistic farming practice that seeks to bring together natural processes with scientific knowledge in order to farm in a sustainable and effective way.

It’s a world unto itself, and there’s plenty we could say about it.

But in regard to leaf septoria, we will just mention organic pesticides here. JADAM natural pesticides (JNP) don’t harm the environment, but are still effective when it comes to protecting crops. You can make them at home, and they consist of three main ingredients:

  • Wetting agent: Any soap-like surfactant, this forms the base of the pesticide and helps it to stick to leaves and pests. It also increases the penetrative capabilities of pesticides. You can make it with: soft water, canola oil, and caustic potash.
  • Herb solution: This uses herbs or herbal extracts that are repellent to the particular pest we are trying to deal with, in this case, septoria. Some options are: sunchoke, ginkgo, and dried roots of Korean pasque flower.
  • Sulphur: Finally, adding JADAM sulphur to your pesticide makes it particularly effective against fungus. Supplement your JWA with: sulphur, caustic soda, water, phyllite powder, red clay powder, and/or sea salt.

Dealing With Septoria Leaf Spot: Stay Vigilant

While it’s not the worst condition when compared to other cannabis diseases, cannabis leaf septoria can be damaging. Fortunately, it can be dealt with. Good growing practice will go a long way to prevent it, but it’s important to learn what to look out for and how to react if it does appear—because sometimes these conditions do, no matter how well we try to prevent them.

An integrated approach to dealing with this problem is your best bet, and means that you don’t have to resort to environmentally damaging fungicides—so everyone wins.

External Resources:
  1. Biological control of Septoria tritici blotch on wheat by Trichoderma spp. under field conditions in Argentina | BioControl https://link.springer.com
  2. IJMS | Free Full-Text | Application of Lactic Acid Bacteria (LAB) in Sustainable Agriculture: Advantages and Limitations https://www.mdpi.com
  3. Effects of Foliar Treatment with a Trichoderma Plant Biostimulant Consortium on Passiflora caerulea https://www.mdpi.com
  4. Over view of Septoria Diseases on Different Crops and its Management https://www.researchgate.net
  5. Etiology of Septoria Leaf Spot of Pistachio in Southern Spain https://apsjournals.apsnet.org
  6. eptoria leaf spot cause by Septoria lycopersici on tomato https://www.plantpathologyjournal.com
  7. The Most Important Fungal Diseases of Cereals https://www.mdpi.com
  8. Reemergence of Septoria Leaf https://apsjournals.apsnet.org
  9. Analysis and modelling of effects of leaf rust and Septoria https://www.researchgate.net
  10. Analysis and modelling of effects of leaf rust and Septoria https://academic.oup.com
  11. Mulching: A Sustainable Option to Improve Soil Health https://www.researchgate.net
  12. Trichoderma/pathogen/plant interaction in pre-harvest food security https://pdf.sciencedirectassets.com
Disclaimer:
This content is for educational purposes only. The information provided is derived from research gathered from external sources.

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COMPANY NAME: SNORKEL SPAIN, SL (hereinafter ROYAL QUEEN SEEDS)

C/ Vilar d'Abdelà, 5 (nave 1) CP: 08170 de Montornès del Vallès

+34 937 379 846

support@royalqueenseeds.com


The present Privacy Policy sets out the terms on which we will treat personal data at ROYAL QUEEN SEEDS; this includes any personal data collected through our website https://www.royalqueenseeds.com/ as well as any other data we process in the course of our business activities.

ROYAL QUEEN SEEDS collects the following personal data for the purposes listed below:

SECTION 1 – PERSONAL INFORMATION WE COLLECT

1.1 Account purchases

Account purchases can only be made if you are in possession of a personal account. When you create an account or purchase something from our shop, as part of the buying and selling process we collect the following personal information that you provide to us:

This information is required for delivery. In addition, when you browse our shop, we automatically receive the Internet Protocol (IP) address of your computer. Based on this information, we can optimise your online experience and at the same time protect our online environment.

Purpose of data collection

We collect and store account-related data for the following purposes:

(a) to carry out obligations arising from any contracts between you and us, and to provide you with information, products and services that you may request from us;

(b) to set up, manage and communicate with you about your account and your orders;

(c) to conduct market research and analysis;

(d) to confirm your age and identity, and to detect and prevent fraud.

1.2 Newsletters

With your explicit permission, we may send you newsletters about our shop, new products and other updates. We send newsletters based on your explicit consent. In the event that you purchase a product, and in accordance with current regulations, we may send you commercial communications in accordance with the legitimate interest of our company, always about products or services similar to those you have purchased or contracted. In any case, you may exercise your right of opposition through the channels announced in this Privacy Policy. The following information is collected in relation to the newsletter:

We do not need to know the sex of the person in order to send the newsletter (data minimisation: by law we must ask for data that is strictly necessary to provide the service, and in this case knowing the sex is not necessary to send the newsletter).

Purpose of data collection

The data collected is used to:

(a) personalise our emails, including your name and gender;

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You can withdraw your consent at any time by using the link provided in the newsletter or the contact information provided in section 2.

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If you have purchased any of our products, please note that we may process your personal data for promotional purposes, based on Royal Queen Seeds' legitimate interest only to offer you products or services from our company and about products or services similar to those you have purchased. You may exercise your right to opt out of future messages by the means set out in this Privacy Policy or through any notification you receive.

2.1 How do you withdraw consent?

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At Royal Queen Seeds, we will not retain your data for longer than is necessary for the purposes described in this Policy. Different retention periods apply for different types of data; however, the longest period we will normally hold any personal data is 10 years.

4.1 Account information

Data relating to the account remains relevant for as long as the consumer is in possession of an account. Therefore, the data remains documented for as long as the account exists. When our customers delete an account, the associated data will be deleted within a reasonable period of time. Requests regarding the inspection or correction of stored personal data or the deletion of an account can be sent to support@royalqueenseeds.com.

4.2 Newsletters

In the event that you give us your consent to inform you about our products or services, we will keep your data until you express your wish not to receive any further communications from us. However, we regularly (every month) carry out a relevance check. Registered customers (and their personal information) will be deleted whenever customers do not reply to our request. In addition, our newsletter mailing has an opt-out feature. Consumers can withdraw their consent by using this opt-out feature.

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However, certain third-party service providers, such as payment gateways and other payment transaction processors, have their own privacy policies regarding the information we must provide to them for your transactions.

We encourage you to read the privacy policies of these providers so that you can understand how these providers will handle your personal information.

In particular, certain suppliers may be located or have facilities located in a different jurisdiction than yours or ours. Therefore, if you choose to proceed with a transaction involving the services of a third party, your information may be subject to the laws of the jurisdiction in which that service provider or its facilities are located.

Once you leave our website or are redirected to a third-party website or application, you are no longer governed by this Privacy Policy or the Terms of Service of our website.

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On this website we have integrated an element of a web analytics service (with anonymisation functionality). Web analytics can be defined as the gathering, processing and analysis of data about the behaviour of visitors to websites. An analytics service collects, among other things, data about which website a person came from (the so-called referrer), which sub-pages they visited or how often and for how long they visited a sub-page. Web analytics is mainly used for website optimisation and for a cost–benefit analysis of internet advertising.

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To complete deliveries we use a courier service. This courier service carries out the delivery between our company and the consumer's home. To complete these logistics, the company requires access to the consumer's name and address information.

Mailing service

Royal Queen Seeds uses a third-party mail service provider to send its newsletter. This provider has access to limited account information related to opt-in consent (e.g. email address).

Marketing services

Royal Queen Seeds has the support of a company that specialises in marketing and communication activities. Their access to personal information is very limited and mostly anonymous.

Payment services

At Royal Queen Seeds we use external payment services to handle our transactions (e.g. credit card payments).

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To protect your personal information, we take reasonable precautions and follow industry standard best practices to ensure that it is not inappropriately lost, misused, accessed, disclosed, altered or destroyed.

If you provide us with your credit card information, the information is encrypted using secure socket layer technology (SSL) and stored using AES-256 encryption. Although no method of transmission over the internet or electronic storage is 100% secure, we follow all PCI-DSS requirements and implement additional industry standards that are commonly accepted. Information related to the account is protected with a hashing method. This method transforms the information into a generated hash. As a result, confidential information is protected and invisible, even to us. In addition, our databases are exceptionally protected against unauthorised access. For example, access to the database is only possible and permitted via approved IP addresses (e.g. from Royal Queen Seeds headquarters). Other attempts and addresses are rejected at all times.

Furthermore, data is anonymised as much as possible, so it cannot be directly linked to a specific consumer. With this data, however, we may be able to carry out market research and analysis. In addition, the third parties concerned (e.g. mailing service) are examined prior to our collaboration, comply with the GDPR from the EU and receive a processing agreement. Within Royal Queen Seeds, employees are assigned different access permissions. Specific permission provides access only to information that is strictly required to perform a task. Digital security measures are subject to change and must meet high requirements to ensure the safety of online customers. That is why, at Royal Queen Seeds, we appoint a security officer. Regular verification and improvement of security measures (where necessary) are part of the role.

SECTION 7 – CHANGES TO THIS PRIVACY POLICY

We reserve the right to modify this Privacy Policy at any time, so please check back regularly. Changes and clarifications will be effective immediately upon being published on the Website. If we make substantial changes to this policy, we will notify you here that it has been updated so you will know what information we collect, how we use it and under what circumstances, if any, we use and/or disclose it.

SECTION 8 – YOU HAVE THE RIGHT TO: