Kali Zammit, Schmit, Rene A.
One of the most common insect pests of citrus trees is the citrus leaf-miner. It is a tiny maggot larva that mines its way through the inside of a leaf feeding on the upper and lower surfaces of the leaf at the same time. Thus the reason for the name miner! As it feeds, it leaves behind a line of whitish trails that serpentine throughout the leaf. The leaf-miner destroys the cell tissue which in turn causes the leaf to crinkle and fold. These symptoms are easily distinguishable and can quickly indicate that a leaf minor infestation is present. Depending on how severe the damage is, the leaves will either remain on the tree or eventually be shed. However, leaves that do remain often provide little benefit to the tree due to a lack of functional tissue available enough to conduct normal photosynthesis.
Leaf minors tend to infest mostly the newer leaves of citrus trees that form during flushes however; they also will mine some of the older leaves but generally ones that are still somewhat tender. Generally, there are about 5 to 6 flushes that occur in a single growing season for citrus and it is during that time when leaf-minor flies lay their eggs and the larva hatch and move into the new leaves. Normally, citrus leaf-miners are more of a concern for young trees, but older trees that lose a significant amount of foliage from leaf-miner damage as well should be protected from losing a much-needed flush of new leaves.
The best line of defense and control for leaf-miners on all citrus is to layer the new foliage as they are being formed with an insecticide that controls the flies keeping them from laying their eggs. Citrus leaf-miner control becomes important on both young and mature growing citrus trees especially if trees become partially defoliated by storm winds or other conditions that create stressful situations to trees. A routine control of leaf-miners on backyard trees will also aid in helping reduce sources of citrus leaf-miner infestations which can later migrate and infest near-by vegetables gardens.
Homeowners may obtain excellent control of citrus leaf-miners by using spinosad – a natural, organic insecticide formulated for citrus trees in the home garden. Spinosad can be obtained at most local garden centers including most hardware stores under different commercial names such as Conserve, or Naturalyte Insect Control, or Green Light Spinosad, or Success, or Fertilome Borer, Bagworm, Leafminer & Tent Caterpillar Spray, and etc.
Spraying for leaf-miners should involve one spray every 5 to 7 days in late evening hours. A total of 2 to 3 treatments may be necessary to gain a good, effective control. Be sure to read and follow the label correctly to ensure a proper and safe mixing and application. Mention of trade names or commercial products in this article is for informational purposes only and does not constitute endorsement by Louisiana State University AgCenter.Rene’ Schmit is the LSU AgCenter county agent for St. Charles Parish and assisting St. John Parish. He can be reached at 985-785-4473 or 985-497-3261.