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

maggots also foster soft rot and fungal diseases.
    Cultural and physical control: Cleanliness! Use fresh, new store-bought soil when planting in containers. Cover seedlings with Agronet® to exclude flies, and plant late in the year to avoid most adult flies. Place a collar 18-inch (45 cm) of foam rubber around the base of the plant to exclude flies.

    Root knot nematodes cause roots to develop lumps. Fluid flow from roots causes impaired growth.
    Biological: Control with parasitic nematodes, Steinernema feltiae or Heterorhabditis bacteriophora.
    Sprays: Kill root maggots with neem and horticultural oil used as a soil-drench.
Slugs and Snails
    Identify: Slugs and snails are soft, slimy white, dark, or yellow, and occasionally striped. They are 0.25-3 inches (1-9 cm) long. Snails live in a circular shell, slugs do not. They hide by day and feed at night. Slugs and snails leave a slimy, silvery trail of mucus in their wake. They lay translucent eggs that hatch in about a month. They reproduce prolifically, and the young mollusks often eat relatively more than adults.
    Damage: They make holes in leaves often with a weblike appearance. They will eat almost any vegetation, roots included. These creatures winter over in warm, damp locations in most climates. Slugs and snails especially like tender seedlings. They will migrate to adjacent gardens in quest of food.
    Cultural and physical control: A clean, dry perimeter around the garden will make it difficult for them to pass. Spotlight and handpick at night. A thin layer of lime, diatomaceous earth, or salty beach sand two to six (6-15 cm) inches wide around individual plants, beds, or the entire garden will present an impassable barrier. The lime is not thick enough to alter the pH and will repel or dissolve pests. To trap, attach short one-inch (3 cm) feet on a wide board and leave it in the garden. The pests will seek refuge under the board. Pick up the board every day or two, andshake the slugs off and step on them.

Root maggots are found in contaminated soil. They gnaw off root hairs and hollow out larger roots.

Slugs and snails cause most damage to seedlings outdoors. Look for slime trails and holes in leaves to help identify the pests.

Thrips make light abrasions on leaf surfaces.
    Poisonous baits usually have metaldahyde as a base. Confine the bait to a slug hotel. Cut a 1 × 2-inch (3-6 cm) slot in a covered plastic container to make a slug and snail hotel. Place slug and snail bait inside the hotel. The hotel must keep the bait dry and off the soil. In a slug hotel, none of the poison bait touches the soil, and the bait is inaccessible to children, pets, and birds. Place slug and snail hotels in out of the way places. Natural baits include a mix of jam and water and beer. If using beer, it must be deep enough to drown mollusks.
    Biological: The predatory snail, Ruminia decollata –available commercially–is yet another way to combat plant-eating slugs and snails.
    Sprays: Young slugs and snails are not attracted to bait. Spray for young at night or early morning with a 50 percent ammonia-water solution.
Thrips
    Identify: More common in greenhouses than indoors. These tiny, winged, fast moving little critters are hard to see but not hard to spot. From 0.04-0.05 inch (1-1.5 mm) long, thrips can be different colors, including white, gray, and dark colors, often with petite stripes. Check for them under leaves by shaking parts of the plant. If there are many thrips present, they choose to jump and run rather than fly to safety. But often you will see them as a herd of specks thundering across foliage. Females make holes in soft plant tissue where they deposit eggs that are virtually invisible to the naked eye. Winged thrips easily migrate from infested plants to the entire garden.
    Damage: Thrips scrape tissue from leaves and buds, afterward sucking out the plant juices for food. Stipples–whitish-yellowish specks–appear on top of leaves; chlorophyll production diminishes and leaves become brittle. You will also see black specks of thrip feces and little thrips. Many times thrips feed inside flower buds or wrap-up and distort leaves.
    Cultural and physical control: Cleanliness! Blue or pink sticky traps, misting plants with water impairs travel. Manual removal works okay if only a few thrips are present, but they are hard to catch. Thrips can be very vexing to control once they get established.
    Biological: Predatory mites (Amblyseius cucumeris and Amblyseius