Leaf Miner

Marijuana Horticulture

by Jorge Cervantes

Identify

Adult leaf miner flies lay eggs that hatch into one-eighth-inch long maggots. You seldom see the maggots before you see the leaf damage they create when they tunnel through leaf tissue. Leaf miners are more common in greenhouses and outdoors than indoors.

Damage

The tiny maggots burrow between leaf surfaces, leaving a telltale whitish tunnel out line. The damage usually occurs on or in young supple growth. It is seldom fatal, unless left unchecked. Damage causes plant growth to slow and if left unchecked, flowering is prolonged and buds are small. In rare cases the damage is fatal. Wound damage encourages disease.

Controls

These pests cause little problem to indoor crops. The most efficient and effective control is to remove and dispose of damaged foliage, which includes the rogue maggot, or to use the cultural and physical control listed below.

Cultural and physical control

Smash the little maggot trapped within the leaf with your fingers. If the infestation is severe, smash all larvae possible and remove severely infested leaves. Compost or burn infested leaves. Install yellow sticky traps to capture adults.

Biological

Branchid Wasp (Dacnusa sibirica), chalcid wasp (Diglyphus isaea), parasitic wasp (Opius pallipes).

Sprays

Repel with neem oil and pyrethrum sprays. Maggots are protected within tunnels, and prays are often ineffective. Hemp Disease and Pests suggests to water plants with a 0.5 percent solution of neem. This solution works fast and stays on plants for four weeks after application.