By Xavier Martini
Citrus leafminer (CLM) is a recurring pest in citrus groves that lays eggs on new growth shoots (flush). After hatching, larvae penetrate directly into the leaf and begin feeding on sap and leaving a serpentine mine in the leaf.
CLM population dynamics are mostly driven by flushing pattern, with two flight peaks in early spring and late summer/early fall. While CLM is easily detected during the larval stage, by the time the serpentine larval mines appear on the underside of new leaves, it is often too late to act.
The best control methods for preventing mines in young citrus shoots require an assessment of the leafminer population beforehand. For instance, systemic insecticides such as neonicotinoids or diamide need one to two weeks following the drench before being translocated into the leaf tissue. Similarly, pheromone disruption should be deployed when adults mate in the citrus grove, but pheromone disruption has no impact on eggs and larvae already present in the flush. Therefore, for both systemic insecticide application and pheromone disruption, it is critical to have a sampling method in place before mines start to show up in the grove.
The best tools to monitor CLM are delta traps equipped with a sticky liner on the bottom and baited with a lure that releases CLM sex pheromones. The trap should be placed on a branch at shoulder height. When CLM capture starts to increase, this indicates the best time to release a pheromone dispenser or to drench trees with systemic insecticides. It is recommended to deploy one trap per 3 to 5 acres. Trap captures are influenced by the pheromone release rate. Therefore, be sure to change the lure after six to eight weeks to keep maximum efficacy.
Learn about citrus leafminer control here.
Xavier Martini is an assistant professor at the University of Florida Institute of Food and Agricultural Sciences North Florida Research and Education Center in Quincy.