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

controls the maggots; unfortunately, it is available only in large one-gallon (3.8 L) containers. Difficult to find at garden centers, check hydroponic stores.
    Cultural and physical control: Do not overwater, and keep ambient humidity low. Do not let growing medium remain soggy. Cover growing medium so green algae won’t grow. Yellow sticky traps placed horizontally 1-2 inches (3-6 cm) over growing medium catches adults.
    Biological: The aforementioned Bt-i works best. Alternatives include the predatory soil mite (Hypoaspis (Ceolaelapumites) and the nematode (Steinernema feltiae).
    Sprays: Apply neem or insecticidal soap as a soil-drench.
Mealybugs and Scales
    Mealybugs:
    Identify: Somewhat common indoors, these 0.08-0.2 inch (2-7 mm) oblong, waxy-white insects move very little, mature slowly, and live in colonies that are usually located at stem joints. Like aphids, mealybugs excrete sticky honeydew.
    Scales:
    As uncommon indoors as mealybugs, scale looks and acts similar to mealybugs but is usually more round than oblong. Scales may be white, yellow, brown, gray, or black. Their hard protective shell is 0.08-0.15 inch (2-4 mm) across. Mealybugs rarely or never move. Check for them around stem joints where they live in colonies. Scales sometimes excrete sticky honeydew.
    Damage: These pests suck sap from plants which causes growth to slow. They also exude sticky honeydew as a by-product of their diet of plant sap which encourages sooty mold and draws ants that eat the honeydew.
    Controls: These pests present little problem to indoor growers. The easiest and most efficient control is listed under Cultural and physical below.
    Cultural and physical control: Manual removal is somewhat tedious but very effective. Wet a Q-Tip in rubbing alcohol and wash scale away. A small knife, fingernails, or tweezers may also be necessary to scrape and pluck the tightly affixed mealybugs and scales after they are Q-Tipped with alcohol.
    Biological: There are numerous species of mealybugs and scales. Each has natural predators including species of ladybeetles (ladybugs) and parasitic and predatory wasps. There are so many species of each that it would be exhaustive to list them here. For more specific information see Hemp Diseases and Pests.
    Sprays: Homemade sprays that contain rubbing alcohol, nicotine, and soaps all kill these pests. Insecticidal soap, pyrethrum, and neem oil are all recommended.
Nematodes
    Identify: Of the hundreds and thousands of species of microscopic nematodes–sometimes, big ones are called eelworms–a few are destructive to plants. Most often nematodes attack rootsand are found in the soil; however, a few nematodes attack stems and foliage. Root nematodes can often be seen in and around roots with the help of a 30X microscope. Often growers just diagnose the damage caused by destructive nematodes rather than actually seeing them.
    Damage: Slow growth, leaf chlorosis, wilting several hours during daylight hours from lack of fluid flow–symptoms can be difficult to discern from nitrogen deficiency. Root damage is often severe by the time they are examined. Root knot nematodes are some of the worst. They cause roots to swell with galls. Other nematodes scrape and cut roots, compounded by fungal attacks. Roots turn soft and mushy.
    Cultural and physical control: Cleanliness! Use new, sterilized potting soil or soilless mix to exclude nematodes’ entrance. Nematodes rarely cause problems indoors in clean grow rooms.
    Biological: French marigolds, Tagetes patula, repels soil nematodes, fungus (Myrothecium verrucaria, trade name DeTera ES®)
    Sprays: Neem used as a soil-drench.
Root Maggot
    Identify: Both the seed corn maggot and the cabbage maggot attack cannabis roots. The seed corn maggot is 1.5 to 2 inches (5-6 cm) long. The seed corn maggot converts into a fly and is a bit smaller than a common housefly. Cabbage maggots are 0.3 inch (1 cm) long, and the adult fly is bigger than a housefly. These pests winter over in the soil and live in unclean soil. In the spring, they emerge as adult flies and soon lay eggs in the soil at the base of young plants. The squirmy, whitish larvae hatch several days later with a ravenous appetite.
    Damage: Root maggots chew and burrow into stems and roots. The seed corn maggot attacks seeds and seedling roots. Cabbage maggots attack roots, leaving hollowed out channels and holes in larger roots. Both maggots destroy small hairlike feeder roots. Wounds made by the root