How to Kill Leafminers on Beet Leaves
- 1). Control weeds adjacent to growing areas as a first line of defense against leafminers. Chickweed, nightshade, amaranthus and lambs-quarters all serve as food sources for leafminers. Reducing the number of weeds makes infection of beet leaves more difficult.
- 2). Spray beet leaves with insecticidal oils to control visible insects. Horticultural oils are effective against leafmining insects, as is Neem oil. A wide variety of commercially available formulations exist, but household mineral or vegetable oils are also effective. These oils are safe and non-toxic, and pose no threat to plants or gardeners. Avoid applying oils in rain, freezing weather or temperatures above 100 degrees F.
- 3). Spray insecticides, such as malathion, Pyrethrin and spinosad, onto leaf surfaces when eggs are visible to coincide with hatching season. Insecticidal soaps are also effective against leafminers, and are easily applied with a spray bottle.
- 4). Reapply insecticides at 14 day intervals throughout the growing season, until insect populations have been visibly reduced. Visual inspection is sufficient for population monitoring. Check for thread or blotch-like lesions on leaves, or visible insects or eggs on the underside of the leaf surface.
- 5). Examine plant leaves for signs of infestation. Cut away infected leaves with pruning shears, and place into the trash. Crush any visible egg masses with gloved hands before discarding into a trash receptacle. Leafminers lay small, white eggs in rows on the underside of beet leaves. The eggs are cigar shaped, approximately 1 mm in length. Keep infested plant material away from compost heaps to avoid contamination of soil.
- 6). Cultivate the surrounding soil frequently, on a weekly basis if possible. Leafminers develop as pupae in garden soil and produce approximately four generations per growing season. Mechanical disturbance disrupts their lifecycle and prevents leaf infestation.
- 7). Rotate crops once per growing season to prevent infestations. Planting beets in the same location season after season increases the likelihood of leafminer infestations.
- 8). Cover plants with fine mesh cloth, such as cheesecloth or tobacco cloth, to prevent infestation.
Source...