I enjoy your bi-monthly magazine. I was wondering if you could help me to find a good long term cure for mould on the leaves of my plants. Anything I should be doing? I would appreciate any information you have and look forward to your magazine. Thank you, Mike. Vancouver
Prevention is the best long term cure-bar none. If you have had a mold problem in the past, you must sterilize your growing area and equipment. Before you introduce your next crop to the growing environment. Scrub down the walls and systems with a mild bleach solution. One part of bleach to ten parts water is adequate. Rinse/scrub with lots of fresh water. Irrigation lines can be flushed with a hydrogen peroxide solution.
High humidity in the growing environment is usually attributed to foliar fungus problems. Make sure your humidity is less than 60% during dark cycles humidity is usually the highest. Wire a dehumidistat to your vent fan or dehumidifier. Ensure that the plants are not touching walls or each other, especially floral clusters. Good air circulation in the plant canopy is essential, so have an oscillating fan gently blowing on your plants 24 hours a day. Increased potassium levels have been shown to increase plant resistance to mold problems. If growing in soil, let the top 1/2″-1″ of the growing mix dry out before watering, as this is a breeding ground for mold/fungal spores. Just stick your finger into the soil to determine when to irrigate.
Most plants grown today have been hybridized. Try growing a variety with more of a tropical lineage. Plants that have originated in dry, arid conditions, such as Afghanistan, are more likely to have mold problems when in a humid environment. Tropical varieties generally take longer to mature, but the results can outweigh the additional time spent in flowering.
If you are in mid crop, try using garden sulfur in a foliar spray. It is available in a ready made spray by Safer’s called “Defender.” Always follow the manufacturer’s directions carefully. Good luck.