Over the past few weeks, you have most likely noticed on your citrus trees some silver to whitish tunnels on the leaves of the last 6 to 12 inches on a branch. This damage is caused by the larval stage of a moth called the citrus leafminer.
During the heat of summer damage caused by the citrus leafminer becomes apparent. Though this problem may appear alarming, there's little to worry about regarding the health of your tree.
The adult citrus leafminer is a very tiny moth with a wingspan of ¼-inch. The female moth lays her eggs on the underside of tender new growth, and the eggs will hatch one to two weeks after being laid. The larvae will immediately begin feeding inside the leaf, creating the serpentine feeding pattern on the foliage.
As the larvae continue to feed on the inside of the foliage, they leave behind a silver sheen — serpentine trails — and ultimately a twisted and deformed leaf. After two to three weeks, the larvae will eventually emerge from the leaf to make a pupal chamber. The pupal chamber is created by folding the edges of the leaf downward and securing it with silk.
The damage that occurs typically does not affect the fruit quality or quantity. But if seeing this damage on your citrus tree is unbearable, just clip off the last 6 to 12 inches to get your citrus tree looking in tiptop shape.
Not all new growth will succumb to citrus leafminer damage. Citrus typically have three distinct flushes of growth each year, all of which can play host to the larvae. Though it is possible for the moth to lay her eggs on any new growth, it is uncommon to see citrus leafminer damage on new growth early in the spring. This is due to low populations during winter. It typically takes spring and early summer for populations to increase to the point where gardeners see the damage.
Insecticides have little effect in controlling the pest because the damage is discovered long after the larvae have disappeared. Using an organic insecticide, such as spinosad, as soon as new growth emerges in late summer can somewhat mitigate the damage. Spinosad can be found at local garden centers sold under such names as Conserve, Green Light Spinosad, Success, Fertilome Borer Bagworm Leafminer and Tent Caterpillar Spray.
The insect was first noticed in Louisiana in 1994 when it was discovered in Plaquemines Parish, where the majority of the Louisiana citrus is grown. It is believed that the insect is native to India or southeast Asia.
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