The citrus leafminer / Phyllocnistis citrella

Found all over the world, including Argentina, Australia, Brazil, China, Corsica, Costa Rica, Cuba, India, Israel, Madeira, Malaysia, Mauritius, Mexico, the Philippines, South Africa, Spain Sri Lanka and other parts of the United States.

The larvae are considered a serious agricultural pest on Citrus species, such as Aegle marmelos, Atalantia, Citrofortunella microcarpa, Citrus limon, Citrus paradisi, Citrus maxima, Fortunella margarita, Murraya paniculata and Poncirus trifoliate. Larvae have also been recorded on Garcinia mangostana, Pongamia pinnata, Alseodaphne semecarpifolia, Loranthus and Jasminum sambac. They mine the leaves of their host plant. The mine consists of a long epidermal corridor with a well-marked central frass line. The mine is mostly lower-surface, but sometimes upper-surface, and rarely on the rind of the developing fruit. Citrus leaf miner larvae are thus protected from many topic insecticide treatments. Pupation takes place in a chamber at the end of the corridor, under an overturned part of the leaf margin.

Each female deposits about 50-130 eggs, placing them on the very young leaves and the youngest twigs. The emerging larvae enter the leaves and burrow therein, forming uneven mines, where pupation takes place. The larvae have 4 instars: the 1st to 3rd instar larvae feed, whereas the 4th instar is spinning larva that does not feed. 

After mating, the female lays single eggs on the underside of host leaves. Eggs hatch about 1 week after being laid. The newly emerged larvae immediately begin feeding in the leaf and initially produce tiny, nearly invisible, mines. As the larva grows, its serpentine path of mines becomes more noticeable. The larvae molt 4 times over a 2- to 3-week period as they develop.

The larva emerges from the mine as a prepupa and rolls the edge of the leaf over causing a curling of the leaf. Inside that curled leaf edge the leafminer becomes a pupa. The pupal stage lasts from 1 to 3 weeks.

The citrus leafminer adults emerge at dawn and are active in the morning. They also fly at dusk and by night. Continuously brooded, up to 13 generations have been reported in a year in India and Egypt, 7 in a year in Tuscany, Italy.

SYNONYM:

Lithocolletis citricola

Phyllocnistis citricola 

Proper use of Pheromone Traps:

The pheromone trap is designed to monitor and reduce pest numbers. In order to determine the population density of pest insects and to identify pest outbreaks (monitoring), it is recommended to use 1 trap per 1 ha.

The trap should be placed in the crown of the tree at a height of 1.5-2 m.  Prior to the first flight of the butterflies, the traps must be checked on a daily basis, and after the first butterflies have been captured, the traps must be checked every 5-7 days. Pheromone dispensers and adhesive tapes can be replaced as needed. Protective measures are based on the results of the monitoring of population density of pest insects.

Trap placement:

For mass capture and sterilization of males, it is recommended to have more than 20 traps per hectare. In case of a large number of pest insects use 30 traps per 1 ha.