Citrus Leafminer

It's always a little sad when we start noticing a pest problem cropping up with more frequency. Such has been the case with the citrus leaves like the one pictured left. The wavy trail running through this young leaf is a sign that something has burrowed inside. Or perhaps an older leaf has just started to look gnarled and bumpy. In either case, the culprit is most likely the citrus leafminer. The adult leafminer is a tiny moth that looks like a slightly dustier version of a whitefly, almost invisible to the naked eye unless you are looking closely. But it isn't the adults that do the damage, once again, it's the kids. The adult (who has a lifespan of about 1-2 weeks) lays its eggs on citrus trees and once the young hatch, the larvae burrow into the leaf creating the wavy maze-like pattern . Over the next several weeks, the larvae will continue to burrow through the leaf and molt several times. The larvae then burrows out of the leaf as a prepupa and curls the leaf around itself. Inside the curled leaf it becomes a pupa, hatching into an adult about 1-3 weeks later. The entire life cycle takes about 3-7 weeks and normally occurs when temperatures are between 70-80 degrees.

Although the wavy mines and the curled leaves can look unsightly, in normal cases, the leafminer offspring don't do enough damage to the tree to affect its health or fruit production. Chemicals like Greenlight's Spinosad may be used to control the adult populations, but adults are difficult to see and without pheromone trapping it may be near impossible to know when they are most active. Probably one of the best controls is to maintain trees in a way that will make them less appealing to the larvae. Because the larvae prefer new, succulent growth, avoid continually pruning trees which will result in more new growth. Also do not apply nitrogen fertilizer when when leafminers are most active (normally summer and fall) so that trees won't produce succulent new growth on which the larvae will feed. (Instead feed with an organic slow release fertilizer in early spring and late fall.) Also remove suckers which tend to grow vigorously and produce new leaves often to help reduce the larvae population.