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The females drill holes in leaves with their ovipositor to feed on plant saps. In some of these "nutrition spots" they lay an egg. The male miner flies do not have an ovipositor and use the feeding holes made by the females when they feed. Immediately after the eggs hatch, the larvae start eating and devour all of the tissue between the upper and lower layers of the leaf. This creates small tunnels (mining). In severe cases this is at the expense of photosynthesis with inhibited production as a result. These small tunnels reduce the ornamental value of plants.

Different types of leaf miners differ in appearance in their larval stages:

• Florida Leaf Miner (Liriomyza trifolii): the larvae are ochre yellow and not transparent. Host plants include plants such as various vegetable- and ornamental crops such as chrysanthemum, gerbera and peppers. 
• Pea Leaf Miner (Liriomyza huidobrensis): the larvae are pure white. Intestinal contents are invisible. As the larvae mature, their heads turn yellow. Host plants are mostly leaf crops - such as lettuce and Chinese cabbage, tomato and chrysanthemum. The small tunnels mostly run along the veins in the leaves.
• Tomato Leaf Miner (Liriomyza bryoniae): the larvae are transparent white. Their intestinal contents are visible. As these larvae mature their head turns yellow. Host plants are various vegetable- and ornamental crop species such as tomato, pepper, lettuce, chrysanthemum and the gerbera. 

Just before the larvae pupate, they make a hole in the leaf and drop down. The larva then crawls into the ground or hides in other protective places such as folds of plastic and pupates there. A small number of the larvae lingers on or under the leaf to pupate there. Temperature has a major impact on the duration of this cycle.

The duration of development from egg to adult at 15 °C is 41 days, at 20 °C it is 26 days and at 25 °C it is 17 days. This may vary by species of leaf miner by a few days. Adult miner flies are small flies from 1.5 to a maximum of 2.5 millimeters in length. They are black and yellow in color and have a distinct yellow spot on the back of the thorax.

To avoid leaf miner infestation, you can choose to cover the air vents with insect netting. This reduces the chances of adult miner flies entering the greenhouse via the air vents.

Leaf miners can be controlled by using various natural enemies. The types of natural enemies are;

• Parasitic wasp: Diglyphus isaea (DIGLYcontrol)
• Parasitic wasp: Dacnusa suberic (DACNUcontrol).
• Predatory bugs: Macrolophus pygmaeus (MACROcontrol) can also contribute to leaf miner control.
• Signal rollers and sticky traps: can be used to detect the presence of this pest and to catch the adult leaf miners.

Leaf miners can also be controlled by using chemical crop protection substances. Products such as Vectine Plus, Mainspring and Vertimec Gold work well against leaf miners. 

Not all products can be used in combination with natural enemies. For more information about side effects refer to the Agrobío Effects App.

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