(Note: This article was contributed by my colleague, Mariah Simoneaux. Mariah is the LSU AgCenter Horticulture Agent serving Ascension and Assumption Parishes.)
Citrus is one of the most popular and low maintenance fruit trees grown in Louisiana. Most years, established trees require little attention besides an application of fertilizer in the spring and occasional pruning. However citrus production is not completely free of disease and insect related issues. So when an insect related problem does occur, the first and most important step is to correctly identify what is causing the damage to your tree.
One of the most common insect pests of citrus trees is the leafminer. This tiny caterpillar feeds on the foliage of the tree. It creates winding tunnels throughout the leaves which causes them to appear twisted and deformed. While this damage is unsightly, it does not usually affect the health of the tree or the production of fruit. For established trees treatment is usually unnecessary. In some cases, young trees, less than three years old, can be significantly set back by a heavy leaf miner infestation. Chemical treatments include the use of horticulture oil, and insecticides containing spinosad or imidacloprid. Always be sure to read and follow the label when using any pesticide. Additionally, the leafminer has a number of natural enemies, including several species of parasitic wasps.
The orange dog caterpillar is another insect often found on citrus trees. It is the immature stage of the giant swallowtail butterfly. The orange dog caterpillar has a unique type of camouflage that strongly resembles bird droppings. You can imagine when the caterpillar is still small it can be quite difficult to spot! One or two of these can completely strip a young tree of its foliage, while older established trees are more tolerant of feeding damage. Homeowners who tolerate a little damage from this funny looking insect are rewarded with the presence of beautiful giant swallowtail butterflies. If control is necessary caterpillars can be removed by hand and destroyed. Insecticides containing Bacillus thuringiensis (Bt), a naturally-occurring soil bacterium, are an effective option for caterpillar control.
Leaf-footed bugs and stink bugs are sometimes found on citrus trees in late summer and early fall. Both have straw-like, piercing sucking mouth parts and cause similar injury to fruit. Feeding damage from these two insects can cause premature color break and fruit drop. Leaf-footed bugs are easily identified by the white stripe across their abdomen (or backside) and a pair of expanded, leaf-like hind legs. Stink bugs have a shield-like shape and are green or brown in color. Both can be removed from the tree by hand and destroyed.
Let me know if you have questions.
Dr. Mary Helen Ferguson is an Associate Extension Agent with the LSU AgCenter, with horticulture responsibilities in Washington and Tangipahoa Parishes. Contact Mary Helen at mhferguson@agcenter.lsu.edu or 985-277-1850 (Hammond) or 985-839-7855 (Franklinton).
