Tomatoes, Leafminers, and the Blues

I have never noticed leafminers on my tomato plants, but I received an email from Freeda who sang the blues for her tomatoes because of these insect pests.

Here’s an account of the crises involving her gorgeous tomato plants and the reclusive leafminers:

“Please, do you have any suggestion to help save my tomatoes? The plants are like six feet tall with beautiful large tomatoes. Some have like eight tomatoes to the cluster. Leafminers have almost destroyed my beautiful plants.”

“Last year the miners were a small problem so I contacted the County Agent and was advised to dump the dirt from my containers and spray the inside of the pots with a 10% clorox solution. I did that and bought new soil to fill my pots for this year. The plants were just perfect until about 10 days ago and now they are covered from top to bottom with leafminer damage.”

Leafminers: A Big Deal or Minor Nuisance?

I’m familiar with the frustration of dealing with leafminers; they always attack the Swiss Chard plants in early summer. The damage is usually cosmetic though, as they don’t kill the chard plants and the infestations tend to lessen or disappear as the season continues. Therefore the leafminers have never been a major concern in my organic garden.

That’s a blessing, because the way that leafminers attack a plant makes it very difficult for a gardener to fight back. The larvae burrow inside of the plant’s leaves where they create the unsightly trails that are the obvious sign of their presence. It also places the critters where they are safe from a topical application of insecticide.

The Backyard Leafminer Tomato Plant Connection

This is the first that I have heard of leafminers being a problem with tomato crops so I did a little investigating and discovered that Freeda’s insect issue isn’t a unique one. There are varieties of leaf miners that feast on tomato crops and can cause problems!

Here are a couple of informative links with details and photos of leafminers and the damage that they inflict on tomato crops:

IPM Pest Management – Tomato Leafminers

American Serpentine Leafminer

Organic and Biological Leafminer Controls

Tomato leafminers are especially difficult to control because of the manner in which they live inside of plant leaves where normal insecticidal sprays can not reach them. There are some chemical controls for leafminers but their effectiveness is questionable, they are not ideal for use on edible crops, and these agents may actually be part of the problem leading to serious leafminer breakouts.

Aside from complications related to leafminers developing a resistance to the sprays, a bigger issue may be that the chemicals destroy the natural leafminer deterrents found in the garden: parasitic wasps! Both of the articles linked to above emphasize the importance of these beneficial insects in keeping leafminer populations in check.

Maybe that explains the absence of leafminers on the tomatoes in my organically-grown garden, or the reason that the leafminers on the chard don’t get totally out of hand. I don’t apply any chemical sprays that are hard on beneficials and give an advantage to the destructive insects.

Coming to Grips with Leafminers in the Vegetable Garden

I don’t have a quick-fix solution for the problem with the leafminers infesting tomatoes, but sometimes it pays to step back and take a look from a longer-term and wider perspective:

• Are you gardening organically, or do you continue to use substances in the yard and garden that could upset the natural checks and balances?

• Do you grow a variety of plants including flowers and herbs that help encourage diversity and may even create confusion for insect pests that target specific crops?

• Is your garden an inviting and hospitable place for beneficial insects to take up residence and fulfill their role of natural insect control? Do you provide adequate food, cover, water, and a safe (pesticide-free) environment to attract and harbor these good bugs?

• Are you supplying the nutrients, moisture, and other essentials that your plants need in order to grow strong and remain healthy despite the occasional insect infestation?

• Is the problem merely a cosmetic one, or does the threat warrant a drastic intervention on the part of the gardener? And if you don’t step in will those plants survive to produce a harvest of delicious home-grown tomatoes in spite of the presence of the leafminers or other pests?