Leafminers

Leafminers feed within the tissues of the host plant. They leave “mining tracks” that wind throughout leaves. The majority of leaf mining insects are moths and flies, although there are some beetles and wasps that exhibit leaf mining behavior.

Leafminer Inspection

Leafminer feeding results in winding mines which are usually slender, white, winding trails; heavily mined leaflets have large white spots. Leaves injured by leafminers tend to drop prematurely. Plants that are heavily infested may lose the majority of their leaves. If the infestation occurs early in the fruiting period, defoliation can reduce yield and fruit size and expose fruit to sunburn.

Leafminer Damage (Photo)

Leafminers reduces the plant’s photosynthetic rate, degrades the plant’s edible anatomic features, and increases the plant’s susceptibility to pathogenic organisms.

Leafminer Treatment

Types: There are many different types of leaf miners that damage agricultural plants, including but not limited to; citrus, tomato, vegetables, rice, corn, onion, garlic and lettuce.

Citrus Leafminer-Phyllocnistis citrella

Description
Citrus Leafminers are tiny moths that are usually less than 1/10 of an inch long. They have silver and white iridescent forewings with brown and white markings and a distinct black spot on each wing tip. They are usually active from dusk until the early morning hours. During the day they are dormant on the underside of leaves. Eggs are laid on the underside of leaves.

Identification
Citrus leafminer larvae creating shallow tunnels, in young leaves. It is most commonly found on citrus such as oranges, mandarins, lemons, limes, grapefruit and other varieties. Patterns on leaves are created underneath the surface and larvae mine on the lower and/or upper surface of the leaves causing them to look curled and distorted.

Treatment
Citrus: Citrus leafminers are attracted to new growth on trees. To help reduce the effect of infestation, do not prune live branches more than once or twice a year. Do not prune leaves that have been damaged because undamaged areas of the leaves continue to produce food for the tree. Citrus Miners are not able to mine leaves once they are hardened. Do not apply nitrogen fertilizer at times of the year when leafminer populations are high, as flush growth will be severely damaged.

Pesticides: IMIDACLOPRID, ABAMECTIN, ACETAMIPRID, DIFLUBENZURON, AZADIRACHTIN

Biological (Eco Aware) Pest Control: Alternate methods of pest control include introducing species of parasitic wasps, particularly Chrysocharis parksi and Diglyphus Begini, which attack leafminer larvae; left undisturbed, parasites often keep leafminers under control.

Traps baited with a pheromone are available for citrus leafminer and are a useful tool for determining when moths are flying and depositing eggs.

 

Here are some additional sources of information about leafminers:

University of California Davis, leafminers

Wikipedia leafminer entry

(Leafminer, also Leaf Miner)

 

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