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Purple Power

Leaf Septoria/ Yellow Leaf Spot

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Leaf Septoria/ Yellow Leaf Spot



(Septoria cannabis and S. neocannabina)










Special Species Notes


Leaf septoria or yellow leaf spot is caused by Septoria cannabis and S. neocannabina, both of which are fungal pathogens(or sometimes a bacteria), targeting cannabis in particular; Sativa, Indica, Ruderalis, and Hemp. 


Leaf spot normally affects outdoor more, but if the spore gets in your indoor garden and the right conditions are there, you have a problem.

leaf septoria will not kill your plants, it will reduce yields.


Nitrogen deficiencies can also serve as a catalyst to the disease.


Common Species:


They many verities that cause leaf spot on other plants.




Both species have same symptoms


white/grayish brown/yellow spots on leaves
Usually Circular lesions on lower leaves
 A small pimple looking bump
 Leaves dry and fall of


Leaf spots come in a wide variety of shapes, sizes, and colors. Normally, leaf spot is first observed on the lower and inner branches where humidity is higher and leaves are somewhat shaded. Spots occur randomly on the leaf surface because the pathogens that cause leaf spots are blown there by wind or splashed by rain or irrigation. Depending upon the pathogen, leaf spots may occur on the top, bottom, or both sides of the leaves.


Leaf spots may be angular or rounded, raised or sunken, and have smooth or fringed edges. Colors are extremely variable and can range from yellow to yellow-green to orange-red to light tan, brown, or black. The spots start yellow may have darkened borders and may have a hard growth in the middle like a little pimple, but the thing that makes the spots the most unique is they are often very uniform, like little circles. Each spot is the receptacle of a spore which look like tiny dark specks in the center of each spot.


Frequently a variety of sizes of leaf spots can be observed on one plant. The smaller leaf spots are younger infections, and the larger leaf spots are older infections. At the center of larger leaf spots, it is often possible to see signs of the pathogen such as fungal spores or spore-producing structures. Some leaf spot pathogens cause leaves to drop prematurely, resulting in early defoliation. 






First signs:


Yellow leaf spot will first appear on the lower leaves of the cannabis plant.  The spots can range in color from white to grayish brown to yellow, first appearing as small round lesions.  As yellow leaf spot matures, it takes on a pimple-like appearance, expanding in size.


the plant may start growing slower.


Life cycle


The pathogens that cause leaf spot diseases often overwinter in infected leaf debris. Most leaf spot diseases need either water on the leaves or very high humidity for a prolonged period of time (12 to 24 hours) to start an infection.


It normally occurs on outdoor grown cannabis, triggered by warm weather and rain, or spraying your plants with not enough time to dry before nightfall. It can also appear in plants lacking sufficient nitrogen. 


Yellow leaf spot will first appear on the lower leaves on the top, bottom, or both surfaces of the leaves, grow and spread from there. Yellow leaf spot will damage the leaves and sometimes the stems of your cannabis plants, but will not kill the crop.  However, if left untreated it will reduce yield.  Infected leaves dry at the site of the spot, eventually crumbling and creating a hole where the spot began.  Heavily infected leaves will turn completely yellow, dry up and drop off. 


Leaf spots often mature in one to two weeks. At this point each leaf spot produces spores or bacteria that can be spread throughout the canopy, starting a second set of leaf spots, or causing new infections on other plants. This cycle of infection and spore production repeats whenever weather conditions are favorable. As a result, in years with very high humidity or frequent rain events, leaf spot pathogens can spread throughout the plant and may spread to near by plants. If the fallen leaves are not removed, you have just created a landing ground for spores to overwinter.  This means they lay low until warmer weather arrives which is when they return and do their damage repeating the cycle. 






How it spreads:


Most leaf spot diseases need either water on the leaves or very high humidity for a prolonged period of time (12 to 24 hours) to start an infection.


This fungus spores may stay in the soil over the winter, and attack your plants in the summer. Yellow leaf spot spores rely on the wind, water  (rain, watering,  spraying your plants) and hitchhiking onto passersby for their travels to susceptible plant tissue and easily spread the disease throughout the canopy.


Host plants:



Cannabis sativa

Cannabis indica

C. ruderales ( its a short version of hemp grow 2 feet tall)




What to do




Keep plants healthy, sick plants are much more susceptible to leaf septoria than healthy plants. 'in-bred' monoecious (hermie) varieties are more susceptible to S. cannabis than dioecious varieties. Late-maturing varieties of hemp are more susceptible to disease.


Plants with strong genetics have less change of getting sick and are less vulnerable for pests and diseases. Yellow leaf spot is rarely reported in China, which suggests Chinese landraces may have more resistance to this disease than other European varieties and cultivars.

Clean your entire grow room, especially if you're operating an indoor garden.

 Make sure to keep the ground under your plant clean. Rake away all leaves and vegetation. Adding mulch can also help prevent spores from spreading.


You must have a clean garden space with healthy soils. This is the most important preventative measure you can take. If you have an outbreak, you may need to replace your growing medium before planting again. You can sterilizes your soil it's post 5 of the Quarantine thread     http://freemygreenpdx.com/topic/14249-quarantine-what-is-it-and-why-do-i-need-to/

Remember to water your plants early mornings or early evening time. Never water the leaves, only the soil. By doing this, the sunlight will not burn the leaves. Avoid getting water on the leaves or laying on top of each other - you want to avoid moisture. Use drip lines or soaker hose to water your plants so the leaves don’t get wet. If you need to wash your plants or foliar spray; If outdoors, do this in the morning, so the extra moisture will evaporate during the day. If indoors, wait until light are on and regular temperature is reached.  But I wouldn't do this if the plant has leaf spot.


Space the plants further apart to help keep direct moisture off the plants and the humidity levels down. Prune any leafy parts of the plant to improve circulation through the plant. Untrained bushy/leafy plants with lots of new vegetative growth are especially prone since plants will often have leaves mashed up against each other as they try to reach the light  this will form moisture between them. Cultural practices that can help prevent the disease include carefully monitoring water and nutrient, reducing initial spraying, and removing basal growth or fan leaves. Growers can remove some of the fan leaves that are completely shaded from the grow light, or blocking light lower in the canopy, and bend or tie some of the branches.


Yellow leaf spot can be prevented from attacking your cannabis garden through crop rotation.  This means choosing a different planting site after each harvest.  If this is not possible, then once you have harvested a marijuana crop completely remove any evidence of the previous vegetation and till the soil well, removing all debris.  Prepare the site with sterilized compost and work into the soil.  This should provide enough nitrogen to give the new crop a healthy starting ground.  In the event you have no available compost (every gardener should get into the habit of creating a compost pile) then add blood meal, fish meal or soybean meal to the existing dirt.  This will provide the nitrogen needed for your cannabis.  Be sure to sterilize all gardening tools with peroxide or rubbing alcohol before storing.


If your plants gets infected by yellow leaf spot, immediately and carefully remove all affected leaves to get rid of as many spores as possible. It is important to always remove and completely destroy all affected leaves. You should utilize a plastic bag to remove the leaves that have been affected. Seal the bag and then put it into a disposal container that has a tight lid. The reason for using the plastic bag is to prevent the spores from being sprung into the air and infecting other plants nearby. After removal of the infected areas, treat your plant with fungicide on the stems that held the removed leaves, and the rest of the garden.... don't forget to take a shower after.


Fungicide and sprays


fungicides can also help slow the spread of the disease, not elimination of an existing infection. That’s why it’s important to start a IPM method before powdery mildew occurs or at least at the earliest sign of detection.


Broad spectrum fungicides may be effective at stopping the fungus from spreading though they are best used as a preventative


Bacillus pumilis (beneficial bacteria) is a spore-bearing bacterium found in soil. It is resistant to environmental stresses, include UV light. The growth of Bacillus Pumilus on plant roots prevents Fusarium spores from germinating. A commercial product is available by the name of Sonata. Application boosts the cannabis plants’ immune system, inhibiting fungal germination and growth.


Trichoderma (beneficial fungi) is the best studied of all biocontrol organisms. These species are also abundant in many types of compost and are the most frequently isolated soil fungi from all temperate and tropical soils. The production of antibiotics by these species is well documented.  In fact, Trichoderma species have been found to be highly resistant to a variety of toxins and antibiotics produced by soil microorganisms, antimicrobial compounds produced by plants, and even chemical fungicides. This makes these fungi active colonizers of toxic environments and a strong competitor. Trichoderma (beneficial fungi)- attacks fungal pathogens. brands include shield, root shield, trichodex, biotrek.


Bacillus subtilis is a naturally occurring anti-fungal bacterium found in soils. It has proven to fight blight, gray mold and several strains of mildew, yet has no adverse affects on the environment or humans. For this reason, it has been approved as a fungicide and bactericide for use in organic farming. Bacillus Subtilis compounds prevents pathogens from colonizing crops. This biological fungicide can be procured online under several brand names. Two strains are available; one for foliage applications (QST 713) and one to be used as a soil amendment at the time of planting (GB03 or MBI600).


Neem Oil depending on exactly what's causing your leaf spot Neem Oil will leave an unpleasant taste/smell on buds when used to treat flowering plants, spray all the leaves evenly, since neem oil and water can separate easily. Try spraying just a small part of the plant and see how it reacts first before spraying the whole thing.


Cinnamon, coriander, cloves, and fish oil: They form a sort of shield against the development of mold


Sesame oil destroys molds and spores.


PH up


Eagle 20EW. This product is effective and, therefore, popular with many gardeners. The active ingredient is Myclobutanil. Eagle 20EW acts as a systemic with a residual presence in the plant. For this reason, treating a plant once or twice in its vegetative stage is often sufficient enough to successfully suppress powdery mildew. This is also the reason to avoid treating plants with it during the latter stages of growth. Eagle 20EW can be used as a preventative treatment when introducing new plants to your garden from outside gardens. It can also be an effective knockdown treatment when other options have failed to break the pathogenic cycle. That being said, it should not be overused. Science has proved that overuse of fungicides, like Eagle 20EW, can result in some fungi becoming resistant to them. For this reason, the product label recommends alternating it with other products after two consecutive uses. Use personal protective equipment and carefully read the labels before mixing and using.


Copper based may be effective at stopping the fungus from spreading though they are best used as a preventative, includes Bordeax mixture. Direct contact by sulfur prevents disease spores from developing. When mixed with hydrated lime, the solution will penetrate leaves for even greater effectiveness. A widely available version of this combination includes copper sulphate and hydrated lime, known as Bordeaux mix. However, all of these solutions can burn plant tissue and is damaging to microorganisms in the soil and harmful to beneficial insects. It is also considered moderately toxic to mammals and humans. Do not apply in temperatures above 90F and less than 50 percent humidity. It stays on foliage until washed off. Use sparingly and with caution if at all: Wear a mask, gloves, and safety goggles; cover exposed skin and hair. Avoid skin, eye, ear, and nose contact. Irritates eyes, lungs, and skin.


Sodium bicarbonate (baking soda) To make your own solution—mix one tablespoon of baking soda with a teaspoon of dormant oil and one teaspoon of insecticidal or liquid soap (not detergent) to a gallon of water. Spray on plants every one to two weeks. Some people say one-half teaspoon of baking soda mixed with a quart of water.


Potassium bicarbonate is a contact fungicide which kills spores. Same mixture as baking soda


The link below will take you to "An Intro to beneficial bugs and beneficial insect food" it has a list (been worked on) to pests and beneficial insects











Classy, sassy, and a bit of a smart assy

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