NC State Extension Publications

Description and Biology

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The citrus leafminer, Phyllocnistis citrella, is a relatively new pest in North Carolina. It was first discovered in the United States in Florida in 1993. The tiny caterpillars feed just under the epidermis, leaving a cellophane-like, transparent covering over the mine. Each leafminer produces a meandering mine that has a line of pale frass down the middle so that the mines resemble an aerial view of a mountain road with numerous switchbacks and a no-passing line between the lanes. Eventually the leafminer emerges from the mine (the spot where it emerges is killed so that a brown spot is formed on both sides of the leaf), crawls to the edge of the leaf, and folds it over to form some protection. The tiny caterpillar then pupates and a tiny moth emerges some seven to 21 days later. The moths are tiny (about 1/8 inch long), silvery, with brown markings and a distinct black spot at the end of each wing. The mining and leaf rolling cause infested leaves to be greatly distorted. Citrus leafminer moths are most active during the morning but are usually not noticed. After mating, females lay one egg at a time on new, tender leaves. Eggs hatch about a week later, and the extremely small caterpillar bores into the leaf to feed, forming an almost invisible mine. These caterpillars molt four times as they grow in the two to three weeks they spend in the mines during which time the mines become much more noticeable. We have several generations per year in North Carolina.

The citrus leafminer is a tiny, almost transparent, yellow, lobe

Citrus leafminers pupate under the curled edge of a leaf.

Citrus leafminers pupate under the curled edge of a leaf.

The moths of citrus leafminers are very small.

Host Plants

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Citrus leafminers infest on oranges, mandarins, lemons, limes, grapefruit, kumquat and calamondin as well as other related plants. Citrus leafminers do not kill citrus plants, but they make them look awful. Young trees that have more succulent foliage tend to be more heavily damaged. Constant grooming of container-grown citrus encourages citrus leafminers as new growth is attractive to the moths for egg laying.

Citrus leafminers tunnel just under the epidermis.

Citrus leafminers tunnel just under the epidermis.

Plants infested with the citrus leafminer look ragged and tatter

Plants infested with the citrus leafminer look ragged and tatter.

Residential Recommendations

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Citrus leafminers are often most damaging when they first arrive. Natural biological control agents such as very tiny parasitic wasps help suppress these leafminers. Do not prune off leaves damaged by citrus leafminer since undamaged areas of leaves continue to produce energy for the tree. Insecticides containing imidacloprid are effective for this leafminer. However, citrus red mites and other spider mites sometimes become unusually abundant after an application of imidacloprid so be alert to this possibility.

References

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For assistance with a specific problem, contact your local Cooperative Extension Center

This Factsheet has not been peer reviewed.

Author

Professor Emeritus
Entomology and Plant Pathology

Publication date: Oct. 21, 2017
Revised: Sept. 12, 2019

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