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Article on Leaf Miners from todays paper

strawboss10
16 years ago

Citrus leaf miner

I know: Your freshest bright green citrus leaves look as if they've been bound and gagged with Saran Wrap. When you look closer, you see that the Saran Wrap is actually the thin clear skin on the surface of the leaf, which has been raised by the serpentine burrowing of the citrus leaf miner.

All citrus lovers, from California to Florida, are scowling at the damage produced by the Asian leaf miner this time of year. Auburn University citrus expert Monte Nesbitt worries that growers around Mobile Bay may be seeing more damage than most, perhaps because we don't yet have the full complement of leaf-miner predators that keep the pests in check in central and southern Florida.

But in spite of all that, the damage from leaf miner is not nearly as harmful as it looks. Unless the leaf falls off, it's largely unaffected, and continues to absorb and transform energy from the sun.

And that's fortunate. Because it's nearly impossible to effectively treat for leaf miners. Citrus experts in Florida, California and Alabama strongly recommend that you DO NOT use conventional chemical pesticides to treat leaf miners, unless your citrus is very young (less than 4 feet tall or 4 years old).

Because these insects tunnel under the cuticle of the leaf, they're protected from contact with most chemical sprays. And treating citrus leaf miner with complicated chemical insecticides can backfire, as you're more likely to kill the insects that control leaf miners than the the leaf miners themselves.

If you time it just right, you may be able to limit citrus miner damage by spraying the plant with summer horticultural oil, such as All-Seasons oil, as soon as the new green growth starts appearing in late summer and early fall (there's no need to spray earlier, since the miners are never a problem until late in the season). You'll probably need to spray once a week until the new growth hardens off after a month or so.

Some people make the mistake of using systemic insecticides in an attempt to control leaf miners. This not only eliminates beneficial insects, it also eliminates the possibility of eating your citrus. Systemic insecticides are quickly transferred into the flesh of your citrus, making it unsafe to eat.

Meanwhile, Nesbitt promises to look at our citrus leaf miner problems in Mobile more carefully, in hopes of reducing this largely aesthetic damage in future years.

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