Native to South America, the Tomato Leaf Miner, or Tutaabsoluta, is a huge pest of tomato plants. It feeds on these as well as other plants in the (Solanaceae) potato family. Previous to 2006, these pests were confined only to South America, but in that year reports of the pest were made in Spain, and soon spread across Europe as well as into Sub-Saharan Africa. This Leaf Miner is actually the caterpillar of the Gelechiid moth. When it is in a larvae, the bug tunnels and feeds in between the upper and lower surfaces of tomato leaves that are rich in nutrients and filled with chlorophyll, and these tunnels can be seen with the naked eye. When the caterpillar is larger, it may burrow into the stems and into tomatoes while they are green. If an outbreak becomes uncontrolled, it can drive the crop yield down to zero. At this point it should go without saying that tomato growers in the United States want to keep this awful pest out of the country.
Although their lifespan is around 30 to 40 days, a female leaf miner will produce about 260 eggs. These eggs are stuck to the underside of the tomato stems and leaves. After they hatch, the larvae will eat on every part of the plant and then drop to the ground where they pupate and the cycle continues. The fruits and vegetables that have been eaten on become inedible. This is incredibly damaging considering that tomatoes are one of the most produced and consumed horticulture crops in the entire world, and West Africa alone has more than 500,000 farmers that make their living by growing and harvesting tomatoes. Having no compassion for any tomato, the leaf miners attack tomatoes at any stage, targeting farms and processing plants munching on seedlings to vine ripe tomatoes already packaged.
How to Control Them
In order to prevent these Leaf Miners from invading the United States, some commerce practices will have to change. Vine ripe tomatoes are packaged with a portion of the vine still attached, and these have become more popular over the years with consumers. In the summer these can be produced in the United States which is no problem. But in the off season, these vine ripe tomatoes must be imported. This poses a problem because importing the tomatoes with the stems, leaves, and partial vine attached from areas where the Leaf Miners are carries a high risk of introducing these bugs that may be living in the green parts of the plants. A step to preventing this would be to impose strict regulations like banning the import of tomatoes with stems as well as enhancing the inspection on tomatoes.
To detect the populations of adults, pheromone traps are used and employ the pheromones of the female. Monitoring traps can provide an early warning if these Leaf Miners have invaded. Unfortunately, it is common for pest populations to stay under the radar until they amass to a large size, and then it may be too late for local quarantines and eradication to be effective. To prevent the spread and harvesting of these Tomato Leaf Miners, growers of the crop must be active in recognizing the insect, the damage that it does, and reporting it. Managing the damage that the Leaf Miner does is possible but it adds costs. Ultimately, preventing the entry of these pests into the United States is the best management practice.
To control an outbreak, there are a few steps that may be taken to prevent the likelihood of an outbreak the next crop season. Leaves with newly formed mines should be removed with pruners to stop a new infestation. Plastic trays may be placed beneath the foliage to catch any falling pupae. These trays should be checked daily and any pupae found should be killed by hand. Growers should wait to use insecticides until 10 pupae a day over 3 to 4 days are seen. Any pesticides that are used should be used as directed and Tomato Leaf Miner populations can be minimized the year following an outbreak by immediately plowing under the spent tomato plants. Thoroughly turning the soil will ensure that any leftover pupae are buried deep underground.