Posted on 23 January 2012 by

Travel the Path Less Taken: Organic Control of the Leaf Miner

By Mindy McIntosh-Shetter

The other day I was watching a movie about a coal miner and it made me think how life mimics the natural world.

This coal miner was trying to control an environment that he did not understand.

He felt that following the same path that his father had followed would lead him to a different conclusion.

We all know how that ends and the same applies to gardening.

When we see a pest, we seem to fall to the same habit that has caused so many problems.

This habit, one may ask, is chemical application. While this technique works quickly in the short term, it never works out in the long run. Which is where the movie comes into play along with the simple leaf miner.

The adult leaf miner attacks tomato plants by lying white, cylinder shaped eggs on the underside of leaves. When the eggs hatch, pale, translucent white or pale green larvae appear that are about 1/3 inch long. This larva tunnels its way through the lamina layer and eats the chlorophyll rich mesophyll cells or the middle of the leaf. This activity causes dead tissue or leaf scars called “stipples.” These “stipples” cause the leaf to stop functioning and in turn cause stunted growth and reduced yield.

This behavior continues for two to three weeks, until the larva fall off and pupates in the soil for two weeks to one month. This cycle can occur at least twice in one growing season. Once you understand the cycle, what do you do about it?

The first step in control is to know your tomato plants. Visit them often and observe the leaves. If there seems to be a change, such as those described above, it is time to take action and not chemical action.

The second step is to remove any leaves with questionable damage. The third approach is to squish any pale green eggs that may be on the underside of the leaves. If leaf miners have been a problem in the past, place row covers over young plants. This will prevent the adult leaf miner from laying its eggs on the leaves.

Trapping the adult leaf miner is another approach. This can be done by color or favorite plant. It has been discovered that this pest loves the color yellow and blue. Commercially made cards are available in these colors that are treated with a sticky substance. The insect lands on the card and never leaves. You can also make your own cards with colored poster board and a sticky, horticulture glue. To maximize the effectiveness of this approach, remember to hang these cards above the plants.

Another way of trapping is through a trap crop. The adult leaf miner loves dock and lamb’s quarter. To use this approach, requires the gardener to plant these plants near but not among the tomato plants. These plants will “ host” the leaf miner insects without killing them while keeping them away from the tomato plants.

The last way of protecting your tomato plants from the leaf miner is to encourage a healthy population of natural predators. These include lacewings, ladybugs, purple finches, chickadees, and robins.

So until we blog again, to become a responsible gardener, we must first learn about our own space.

For more information about tomatoes, please visit our sister website Tomato Casual.

One Response to “Travel the Path Less Taken: Organic Control of the Leaf Miner”

  1. The Sage Butterfly Says:

    I don’t have too many problems with leaf miners, but when I do I use a concoction with neem oil that seems to help. The parasitic wasps help as well.

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