Uniform, mottled yellow spots appear on the leaves of marijuana, which is that marijuana has yellow leaf spot.
This is marijuana suffering from black leaf spot, and there are concentrated and uneven black spots or areas on the leaves.
This is that hemp has brown spots, and brown spots of different sizes and uneven distribution appear on the whole hemp, which looks a bit like withered.
This is that hemp is suffering from round spot disease, and light yellow or light gray, very round spots appear on the hemp leaves. It is evenly distributed and scattered on the cannabis plant.
Cannabis suffers from keratoderma, which turns into a light brown after being water-stained at first, showing an irregular polygonal shape, and is gray-white in the later stage, easily perforated, and perishable. Smelly.
Cannabis suffers from wheel spot disease, with round or semi-circular spots on the leaves, which are light brown or light white, and there are obvious round patterns on the lesions. When it is hot and humid, black mold grows on the back of the lesion.
Cannabis is suffering from spot blight. At the initial stage, brown round spots appear on the leaves of hemp, and then gradually expand into large polygonal spots, which are off-white or light brown, with dark brown edges, scattered or whorled many small black spots in the spots. Point, and gradually expand to the edge of the leaf and the stem, and the expanded area begins to wither noticeably.
When similar spots appear on our cannabis plants, we are about to start paying attention. There are many reasons for spots on cannabis leaves, such as insect gnawing, burning by the sun, physical damage to the leaves, these are common and occasional situations. Even the self-shedding of cannabis leaves starts from yellowing.
However, if these spots proliferate in a large amount in a short period of time, appear on still young leaves or even new leaves, or these spots begin to appear on cannabis stalks, then we can determine that cannabis is suffering from leaf spot.
Leaf spot disease is divided into black spot disease, brown spot disease, gray spot disease, round spot disease, angular spot disease, wheel spot disease, spot blight and other spotted plant diseases. Different spotted plant diseases have different bacteria or It is caused by fungi, and the specific symptoms are similar, so many growers refer to the spotted plant diseases that appear on the leaves as leaf spot diseases.
Because the fungi and bacteria that cause leaf spot disease all like high temperature and humid environment in their living habits, and they are widely distributed in nature. So once marijuana suffers from one of the leaf spot diseases, it will soon also suffer from other leaf spot diseases. These leaf spot diseases usually appear on plants together, or as other leaf spot diseases worsen, new leaf spot pathogens will multiply and multiply in the decaying place, causing new leaf spot symptoms.
These fungal bacteria that cause leaf spot disease are usually found in wilted plants and will spread around with wind and running water. It is not obvious when it first invades healthy plants. After 3 to 5 leaves are affected, it will grow explosively and quickly kill the plants in a short period of time.
How to prevent leaf spot disease?
- Control humidity and temperature. The pathogenic bacteria of various leaf spot diseases generally like high temperature and high heat environment. Controlling the humidity below 60% and the temperature below 32 degrees Celsius can effectively prevent various leaf spot diseases.
- Strengthen air circulation, most of the pathogenic bacteria of leaf spot are anaerobic bacteria. Enhancing the ventilation of the planting space can not only prevent the growth of leaf spot pathogens, but also prevent these pathogens from attaching to the cannabis plant.
- Control watering, or use sterilized soil. Generally, the soil contains these pathogenic bacteria. Watering at low temperature and letting the soil dry out at high temperature can effectively delay the reproduction of these bacteria. Or simply use sterilized soil.
- Prevent pollution. Most of these strains exist in the branches and leaves of rotting plants, so as to avoid direct or indirect contact between our hemp and these spoilages.
- Pyraclostrobin fungicide, this kind of broad-spectrum fungicide will kill many pathogenic bacteria including leaf spot. It is also toxic to humans and other animals. It can only be used during the growth period of marijuana. When using it, take care to protect the skin and eyes.
- Cut off the infected leaves. When the infection is too serious, cut all the leaves with obvious disease, and spray other branches and leaves with a fungicide.
The initial damage of leaf spot disease is not obvious, and lowering the humidity can effectively prevent this plant disease. It is not difficult to control this kind of plant disease by using a fungicide to disinfect the whole plant and the soil at the beginning of the infection.