Citrus Leafminer

Phyllocnistis citrella — the citrus leafminer — is one of the most economically important PESTS OF CITRUS worldwide and one of about 800 species in family Gracillariidae (the leaf miner moths). The species is native to South Asia (probably southern India and Southeast Asia) but has spread globally via citrus commerce since the 1990s — first detected outside South Asia in Florida in 1993, then invaded California (1994), Mexico (1994), Caribbean and Central America (mid-1990s), South America (late 1990s), Mediterranean Europe (1994 in Italy, then France, Spain, Portugal), Africa (late 1990s through 2000s), and Australia (1995). The global invasion has been one of the most rapid documented insect range expansions of the past 30 years. Adults are 4 mm wingspan (extremely tiny), small silvery-white moths with darker markings — rarely noticed by humans because of the small size. Larvae are 3-4 mm long when fully grown, pale yellow-green, with reduced legs adapted for the leaf-mining lifestyle. The species is unlike most Lepidoptera in DEVELOPING ENTIRELY INSIDE LEAVES. Female moths lay tiny eggs on the underside of YOUNG CITRUS LEAVES; larvae hatch and BURROW INTO THE LEAF, developing entirely INSIDE the leaf tissue (between the upper and lower epidermis layers) for 2-3 weeks. The larva creates a CHARACTERISTIC SERPENTINE 'MINE' as it feeds — a winding tunnel through leaf tissue that is visible from outside as a SILVERY-WHITE WINDING TRAIL on the leaf surface (the silver appearance comes from the air space where the larva has consumed the green photosynthetic tissue). Each mine is made by a single larva and shows the larva's complete life history through the leaf tissue from initial entry to pupation site. The serpentine mines are one of the most-recognized signs of citrus leafminer infestation worldwide. Damage: leafminer feeding directly damages photosynthetic capacity of citrus leaves, reduces tree growth and fruit yield, and provides ENTRY POINTS FOR CITRUS CANKER BACTERIAL DISEASE (Xanthomonas citri) — the leafminer wounds can vector or facilitate citrus canker infection, adding secondary pathogen damage to the direct feeding damage. Annual global ECONOMIC LOSSES to citrus leafminer total HUNDREDS OF MILLIONS OF DOLLARS — combining direct feeding damage, citrus canker facilitation, and ongoing control costs. The species is the focus of major international citrus pest management programs and is featured in essentially every modern textbook discussion of leafminer biology and citrus pest control. The species is harmless to humans (way too small to bite or sting) but is a major economic pest of global citrus production.