Marijuana Horticulture: The Indoor/Outdoor Medical Grower's Bible

after applying.
Verticillium Wilt
    Identify: Lower leaves develop chlorotic yellowing on margins and between veins before turning dingy brown. Plants wilt during the day and recoup when the light goes off. Wilt soon overcomes parts of the plant or the entire plant. Cut the stem in two and look for the telltale brownish xylem tissue. The fungus blocks the flow of plant fluids, causing wilting.
    Control: Cleanliness! Use fresh, sterile soil. Good drainage. Use amonical nitrogen as a source of nitrogen. Do not overfertilize.
    Biological: Bio-Fungus® (Trichoderma species), Rhizo-Plus® (Bacillus subtilis).

Right: Verticillium wilt is less common than Fusarium wilt, but the symptoms are similar. Cut a stem and look for discolored xylem.
    Sprays: No chemical spray is effective.
Viruses
    Identify: Viruses are still a mystery. They act like living organisms in some instances and nonliving chemicals in other cases. They must enter plants via wounds. Once a virus takes over plant cells, it is able to multiply. Viruses are spread by insects, mites, plants, animals, and human vectors. Aphids and whiteflies are the worst. Infected tools also transport viruses from one plant to another. Typical symptoms of viral infection are: sickly growth, leaf and stem spots, yellowing, and low yields. Viral diseases move into the plant’s fluid distribution system and destroy it, which often causes leaf spots and mottling. A virus can completely take over a plant in a few days. Once a plant gets a virus, there’s little you can do.

    Control: Cleanliness! Always use fresh, sterile growing medium. Disinfect tools before cutting foliage on different plants. Destroy all plants infected with virus.
    Biological: None.
    Sprays: No chemical sprays are effective against viruses.
Troubleshooting
    This simple troubleshooting chart will solve 90 percent of the grow problems encountered when growing cannabis. This chart started with an article in High Times magazine and borrowed from the “Problem Identification Keys” presented in Hemp Diseases and Pests: Management and Biological Control, by J. M. McPartland, R. C. Clarke, D. P. Watson. Please see that book for much, much more information. One word of caution–this troubleshooting chart assumes the grow room is clean.
    Clones are relatively easy to root. Success rate depends on the proper combination of heat, humidity, light, rooting hormone, and growing medium aeration/moisture. The more precise the combination, the faster and stronger roots grow.
    The vegetative growth stage is when problems begin to show. Often, these problems continue through flowering. Remedy problems before they progress. If allowed to persist through flowering, yield will be substantially diminished.
    Flowering is the last stage in life and only six to ten weeks long. Problems must be solved within the first two weeks (at the absolute latest, three weeks) of flowering, or yields decrease in relation to the severity of the problems.
    Note: Keep growing area super clean to help prevent problems. If you notice insects or fungus on foliage, remove them and check them against color photos and drawings in this book and the troubleshooting chart below.

Troubleshooting Chart

----
Spraying
    Use only contact sprays approved for edible fruits and vegetables.
    Warning: Do not use TOXIC SYSTEMIC CHEMICALS! Read the entire label on all sprays. The toxic or active life of the spray is listed on the label. Wait twice as long as the label recommends, and thoroughly wash any foliage before ingesting it. Toxic life is many times longer indoors, because sunlight and other natural forces are not able to break down chemicals.
    Sprays are beneficial if not overdone. Every time a plant is sprayed, the stomata are clogged and growth slows. At 24-28 hours after spraying, rinse leaves on both sides with plain water until it drips from leaves. Avoid sprays that leave a residual during the weeks before harvest. Spraying increases chances of gray (bud) mold once dense buds form.
    Phytotoxicity is the injury to plants caused by sprays. Symptoms include burned leaves, slow growth, or sudden wilt. Spray a test plant and wait a few days to see if spray is phytotoxic. Water plants before spraying. Phytotoxicity is diminished when more liquid is in foliage.
    Temperatures above 68°F (20°C) make virtually all sprays, even organic ones, phytotoxic and damaging to foliage.
    Intense light causes leaves to take in the chemicals too quickly and will often cause