Root Maggot

Marijuana Horticulture

by Jorge Cervantes

Identify

Both the seed corn maggot and the cabbage maggot attack cannabis roots. The seed corn maggot is 1.5 to 2 inches long. The seed corn maggot converts into a fly and is a bit smaller than a common housefly. Cabbage maggots are 0.3 inch 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 rots. 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 hair-like feeder roots. Wounds made by the root 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 of foam rubber around the base of the plant to exclude flies.

Biological

Control with parasitic nematodes, Steinernema feltiae or Heterorhabditis bacterophora.

Sprays

Kill root maggots with neem and horticultural oil used as a soil-drench