Common Plant Problems and Solutions by Billy Budd (April 27, 2013):
This document describes, in general, the common problems encountered while growing cannabis. I have provided solutions that I have personally have tried and thus know them to be proven at reducing or eliminating the problem.
Cannabis Plant Problems and their Solutions:
Powdery Mildew: Use milk and baking soda diluted with distilled water. Ratio should be about 10:1 with ten parts water to one part milk. Add some baking soda to raise the PH. PM cannot exist in high PH conditions. You can also use rice water which creates active bacteria which will consume the powdery mildew. You must leave the rice water out for a few days to create the bacteria. You must correct your environment or it will return. Powdery mildew is caused by low light, high humidity, low/no air flow and plants too close/touching.
Aphids: Use ladybugs to kill them. They will eat them. You may have an ant problem as ants milk the aphids for their honeydew. They will protect their slaves by attacking the ladybugs. Neem oil works as well.
Caterpillars: They will be curled up in the leaves and can do a lot of damage. You must manually inspect and remove them by hand. They will be rolled up in the tip of the leaf and quite easy to see.
Spider Mites: Neem oil and pyrethrins work. You can grow chrysanthemum alongside your cannabis plants as well. Pyrethrins are derived from chrysanthemums. Always use good clones are that have not been cloned too many times or from small immature mother plants. Always dip your clones twice, within 3 days, in Azamax or equivalent. The second dose will kill the larvae from the surviving eggs. Maintain a regimen of neem oil until two weeks into flowering or whenever the white pistills begin to appear. Switch up between neem oil and pyrethrins to prevent the mites from acquiring immunity. You can spray the soil, leaves and especially underneath the plant leaves with 50% Isoproply alcohol and 50% water with some high quality lemon dish detergent to act as a surfactant. It will cause slight damage to the leaves but they will recover. It will kills the eggs and larvae at the same time through dehydration. You may want to try a lower percentage of Isopropyl alcohol to start to minimize leaf damage. See my article on Eliminating Spider Mites. That is a holistic approach to spider mites. Please do not use Avid. Avid is very popular for killing spider mites however it is very toxic. It is actually an antibiotic made from mold spores in the earth. It will weaken your immune system and if you are already in such a weakened state as a patient then you will suffer more. You do not want to smoke a plant soaked in Avid either. Avoid this product, the spider mites are actually immune to Avid now in many locations.
Wilting plants: They are either too dry or too wet and drowning. If they are too dry, check the soil, then water them, obviously. If they are too wet and are drowning then use H2O2 (hydrogen peroxide) to save them from drowning. The hydrogen peroxide releases the extra oxygen atom. This allows the roots to absorb the oxygen and thus prevents them from drowning.
Create a solution of food grade 35% and distilled water/dechlorinated water. Mix it 12:1 which is 12 parts water and 1 part hydrogen peroxide. If using different concentrations then adjust the formula accordingly.
Yellowing leaves: Increase the concentration PPM/EC of your nutrients. Yellowing leaves is normal during late flowering but not during the vegatation cycle. Yellowing during vegetation means that the plant is feeding off of its own stored food energy, its leaves. It should be feeding through the roots from the soil or through the stomata as foliar feeding. You should not allow this yellowing to happen, for optimal yield, except during flowering.
Dark leaves / hooking down: Decrease the concentration PPM/EC of your nutrients. Too much nitrogen going into the flower cycle may result in nutrient lockout. The leaves will hook down and you will not get a good yield.
Reading the Leaves: Each strain has its own leaf colour. Indicas are darker green while sativas are lighter green. Hybrids are in between. Learn your strain and its correct leaf colour. Dial in your PPC to maintain that colour.
White on leaves: If it looks like dust then it is powdery mildew. See above. If it is solid white on the edges or middle then it is nutrient burn. Reduce your concentrations of your PPM/EC nutrients. Flush with water several times. Do not feed for a few days and only then with a weaker nutrient solution.
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