Citrus Leaf Miner Control: How To Spot Citrus Leaf Miner Damage

Citrus Leaf Miner Control: How To Spot Citrus Leaf Miner Damage

By: Teo Spengler

The citrus leaf miner (Phyllocnistis citrella) is a small Asian moth whose larvae dig mines in citrus leaves. First found in the United States in the 1990s, these pests have spread into other states, as well as Mexico, Caribbean islands and Central America, causing citrus leaf miner damage. If you think your orchard might be infested by citrella leaf miners, you’ll want to learn techniques for managing them. Read on for information on citrus leaf miner damage and what you can do about it.

About Citrella Leaf Miners

Citrus leaf miners, also called citrella leaf miners, are not destructive in their adult stage. They are very small moths, so minute that they are rarely even noticed. They have silvery white scales on their wings and a black spot on each wingtip.

The female leaf miner moths lay their eggs one by one on the underside of citrus leaves. Grapefruit, lemon and lime trees are the most frequent hosts, but all citrus plants can be infested. Tiny larvae develop and mine tunnels into the leaves.

Pupation takes between six and 22 days and happens within the leaf margin. Many generations are born each year. In Florida, a new generation is produced every three weeks.

Citrus Leaf Miner Damage

As with all leaf miners, larval mines are the most obvious signs of citrus leaf miners in your fruit trees. These are the winding holes eaten inside the leaves by the larvae of citrella leaf miners. Only young, flushing foliage is infested. The mines of citrus leaf miners are filled with frass, unlike those of other citrus pests. Other signs of their presence include curling leaves and rolled leaf edges where pupation occurs.

If you notice the signs of citrus leaf miners in your orchard, you may be worried about the damage that the pests will do. However, citrus leaf miner damage is not very significant in a home orchard.

Remember that the larvae of citrella leaf miners do not attack or damage the citrus fruit, but only the leaves. That may mean that you have to make the effort to protect young trees, since their development can be affected by the infestation, but your crop may not be damaged.

Citrus Leaf Miner Control

Managing citrus leaf miners is more a concern of commercial orchards than those with one or two lemon trees in the backyard. In Florida orchards, growers rely on both biological control and horticultural oil applications.

Most citrus leaf miner control occurs via the insect’s natural enemies. These include parasitic wasps and spiders that kill up to 90 percent of larvae and pupae. One wasp is the parasitoid Ageniaspis citricola that accomplishes about a third of the control work itself. It is also responsible for managing citrus leaf miners in Hawaii as well.

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Read more about Citrus Trees

Extension Education in Brazoria County

There are many reasons to love gardening along the Texas Gulf Coast, one being the ability to successfully grow a variety of citrus trees in our landscape. Urban gardeners to small-scale orchard operators in Brazoria County have natural resources of temperate weather and access to full sun to entice sun-colored fragrant fruit from their trees.

Citrus is a general term for fruit that includes the familiar lemon, key and persian lime, the unusual thick-skinned citron, the delectable sweet orange, easy to peel tangerine, huge pomelo, grape-sized kumquat and our beloved grapefruit. Citrus species have their origins in southeast Asia, including south Vietnam, south China and India. Global trade routes via European western expansion eventually brought this precious commodity to be cultivated along the Texas Gulf Coast starting in the 1880’s. It is estimated that approximately 27,000 acres of citrus are now grown in South Texas in the Lower Rio Grande Valley region.

Image courtesy Harris County AgriLife Extension

Since there is a wealth of information regarding citrus production, variety availability and horticultural management, I wish to focus on several inquiries I recently received and related to citrus plant health. A few concerned homeowners witnessed damage to their citrus foliage, reporting black and silver-colored trails on the top of curling and disfigured leaves. One homeowner sent me a great picture of foliar damage to help identify the culprit. I concluded that the leaf damage is due to activity of the Asian Citrus Leaf Miner (Phyllocnistis citrella), a species of moth originating from India to the Phillipines and detected in southern United States in the mid-1990’s. The moth is small and light colored, mostly found active March through October in the Texas Gulf Coast Bend. Regarding life cycle, the female adult will lay eggs on the underside of newly growing leaves in the evening or late night. Larvae hatch and burrow into the leaf, mining as they feed through the leaf tissue. We see the damage as a silver-colored trail along the leaf surface. The larvae proceed through 4 instars (stages of development) and take up to 20 days to form pupae (think of a butterfly cocoon). Right before pupae development, the larvae proceeds toward the margin of the leaf, emerges and rolls the leaf around itself to develop into the adult, causing the leaf to distort and curl. The life cycle can take from 2 to 7 weeks to complete.

Prevent Leaf Miners On Citrus Trees Organically

Citrus leafminers are the wormlike larvae of small, silvery-white moths that flutter around trees at night. These chewing insects tunnel shallow, wandering mines that appear as white trails running throughout the leaves. Leafminer feeding activity causes the leaves to curl and become misshapen. Citrus trees older than 4 years typically tolerate the feeding damage without reduced crop yield or plant growth. This gives the leaves enough time to mature and harden so the larvae won't be able to tunnel inside of the plant tissue. Promptly remove any water sprouts that shoot out from the limbs or trunks of an established tree. Newly hatched wasp larvae promptly start consuming their host leafminers. Planting a few herbs or flowers from those families should encourage the wasps to hang around your outdoor areas. One botanical insecticide available to homeowners is neem oil, which comes from the neem tree and helps prevent adult moths from laying eggs on the foliage.

Citrus Leaf Miner Management

Damage caused by the citrus leafminer (Phyllocnistis citrella Stainton)

As citrus trees produce new flush growth, citrus leafminers may become a severe problem. Normally, citrus leafminers would be a concern primarly in young trees, but older trees that lose significant amount of foliage must be protected from losing the much-needed new flush as well.

The best choice for controlling citrus leafminers on commercial orchards is Spintor 2SC at 6 to 8 fl. oz/acre. Agrimek 0.15EC also is a good alternative when applied at 5 to 10 fl. oz/acre. Apply Agrimek only if it was not used earlier for rust mite control to avoid insecticide resistance development in rust mites to this product. Another alternative for citrus leafminer control is Provado at 10-20 oz. per acre. All work best on citrus leafminer when combined with oils (about 5 gal. oil per acre). Seek the advice of your local specialist on the use of oils as we get closer to cooler months. Depending on the condition of your orchard, your citrus specialist may better describe any possible effects on cold hardiness or on next year’s bloom. Admire as a soil application may provide a longer term protection against citrus leafminers applied at 14 fl. oz/acre. You may use Admire at 1/16 oz per small tree and 1/8 oz per large tree in 10 oz of water applied to the soil. Admire is expensive, but it may be justified on younger orchards and producers can follow up with another Admire soil drench application next spring.

Homeowners who have a few citrus trees in the backyard may obtain excellent control of citrus leafminers by using spinosad formulated for citrus in home gardens. Homeowners may obtain spinosad at local garden centers under different commercial names such as Conserve, Naturalyte Insect Control, Green Light Spinosad, Success, Fertilome Borer, Bagworm, Leafminer & Tent Caterpillar Spray, etc. Citrus leafminer control is important on young, growing backyard citrus trees and mature trees if they have been severely defoliated by storm winds. Citrus leafminer control on backyard trees in turn will reduce sources of citrus leafminer infestations which later migrate to trees in nearby commercial orchards.

Maximum protection for citrus leafminer on both commercial and home garden trees is obtained if sprays are applied when the new foliage is only half emerged and the first affected leaves are just beginning to curl. Remember that protecting trees from additional foliage loss is important because trees use this new growth to accumulate needed carbohydrates to help expedite the recovery, growing and production process. Apply these citrus leafminer management plans in combination with a complete fertilization, disease and weed management program to revitalize your weaken, stressed trees and to protect healthy ones.

Before you buy or use an insecticide product, first read the label and strictly follow label recommendations. 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.

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