How to Safeguard Your Citrus Trees from Leafminer Infestations

Citrus trees hold a special place in the hearts of many Panhandle residents. However, every year, these beloved trees face a formidable adversary – the citrus leafminer (CLM). A small moth and its larvae inflict extensive damage on the trees by burrowing between the layers of new leaf growth, resulting in the formation of serpentine mines beneath the leaf cuticle. This feeding activity causes curling, distortion, and stunted growth of the leaves. Moreover, severe infestations of CLM can provide a gateway for citrus canker, a bacterial disease that has recently emerged in the Florida Panhandle, Georgia, and Alabama.

Chemical Control

While commercial citrus growers have access to systemic insecticides to combat CLM, homeowners face limited options. However, there are some systemic insecticides available for home use, such as imidacloprid (Bayer’s Tree & Shrub Insect Control™, Merit®, etc.) and dinotefuran (Greenlight Tree and Shrub Insect Control™, Safari®, etc.). For optimal efficacy, these insecticides should be applied two weeks before the start of the flushing season. This timeframe allows the insecticide to move from the roots into the canopy. To prevent leaching, soil applications should be made within a 24-hour period without rain. In the Florida Panhandle, most citrus cultivars experience two significant flushes in May and September.

It’s important to note that systemic insecticides are most effective against CLM in small and immature trees. For mature trees, foliar sprays are the recommended solution. Options such as horticultural oils or insecticides containing spinosad (like Monterey® Garden Insect Spray) can be utilized by homeowners. However, controlling leafminers on mature trees through foliar applications can be challenging due to unsynchronized flushing. Timing the sprays with the appearance of the first visible leaf mines is crucial. Remember, always read and follow the label directions of any product used.

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Cultural Practices and Non-insecticidal Methods

For those with isolated citrus trees in their backyard, cultural practices and non-insecticidal methods can often suffice in controlling CLM, making the use of insecticides unnecessary, especially for mature trees. One essential cultural practice is the removal of stems that grow below the bud union or from the rootstock, commonly known as ‘suckers.’ These rootstock shoots compete with the scion shoots and serve as significant reservoirs for CLM. Removing them can greatly reduce the CLM population.

Mass trapping, along with cultural practices, is another effective method. By employing pheromones specific to CLM, mass trapping can yield favorable results. A delta trap, baited with a lure emitting a substantial amount of CLM sex pheromone, is used in this approach. The odor attracts male CLM, who then become trapped in the sticky liner of the delta trap. While these traps are typically used by growers to monitor CLM populations, they can also be effective in controlling CLM on a single tree for homeowners. One trap, combined with a lure, is usually sufficient to protect a single tree for approximately three months.

Lastly, biological control presents another option. Various natural enemies, such as ants, lacewings, spiders, and the parasitic wasp Ageniaspis citricola, actively prey on or parasitize CLM. These natural predators can significantly reduce CLM populations, with some cases reporting up to a 90% reduction.

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By adopting a combination of cultural practices, non-insecticidal techniques, and utilizing suitable insecticides when necessary, citrus tree owners can effectively manage and minimize the impact of citrus leafminer infestations, ensuring the health and vitality of their beloved trees for years to come.

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