Thursday, August 4, 2011
Leaf miners are small maggots that chew their way in between plant tissue of veggies and ornamental flowers. They are very easy to spot by the winding tunnels they create in the plant tissue as they mine out the nutrients of the plant. On the left are two example of leaf miner trails. Many times you can usually see and feel the bug inside the plant still.
Spring and summer is when they are most prevalent. They can be frustrating to get rid of and unfortunately there are not many options.
The best defense is a good offense. When you are planting in early spring cover your plants with a row cover to keep the adults from laying eggs that will hatch and crawl into your plants. You can also use a preventative spray containing spinosad that will keep them from penetrating the plant membrane.
If they are in ornamental plants that are not edible you can also use a systemic insect control that will keep them from entering your plant leaves.
However, if they are already on edible crops such as Swiss chard or spinach DO NOT use a systemic or any other spray. You can use a preventative spinosad spray but once they are in the plant it will not be effective at killing them. Sprays will not kill the leaf miners once they are inside your plant and if you are spraying with a systemic or other spray that is not meant for organic gardening, you will be ingesting these chemicals when you eat your plants. They best way of removing leaf miner and keep them from coming back the next year is by cutting the infected leaves off and throwing them away. This will keep them from infecting more leaves and it will keep the next generation of pupae from collecting in the soil and attacking your plants next year. The leaves that you do pick off don't need to go to waste tho, tear the remaining good leaf sections off and use them in a salad. They are still edible, just not the part that has been mined out.