Identification, Symptoms and nature

of damage: Leaf miner

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Identification, Symptoms and nature of damage: LeafminerIntroduction

•The scare was caused by a tiny but beautiful species of agromyzid fly, Liriomyza trifolii (Burgess) that entered India accidentally probably, during 1990-91.

•The native country of this pest is USA (Florida). It was introduced probably along with cut chrysanthemum flowers during early 1970s to California, USA .

•The fly was accidentally introduced into Kenya around the same period.

•It is now very widely spread in most countries including Pakistan and India and has now spread to most of the states in India.

• It is a polyphagous species affecting more than 78 annual plant species being especially serious on greens, cucurbits, tomato, castor and ornamental plants

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•Adults look pale yellow in colour.

•Female thrust eggs into the epidermal layer of leaves.

•The emergence of larvae takes place after 2-4 days.

•Then it feeds between the leaf surfaces, creating a meandering track or "mine.“

• At high population levels, entire leaves may be covered with mines.

•Minute orange yellowish apodous maggots mature after 7-10 days then it leaves the mines, dropping to the ground to pupate.

•The life cycle takes only 2 weeks in warm weather; there are seven to ten generations a year.

Identification

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Eggs in the mine Maggot

PupaAdult

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The severely affected leaves may drop.

Liriomyza leaf miner may act as vector of disease, kill seedlings, cause reduction in crop yields, accelerate leaf drop thus exposing fruits like tomato for sunburn and reduce aesthetic value of ornamental plants.

Maggots mines into leaves and causes serpentine mines drying and drooping of leaves.

Symptoms

Life cycle of Leaf miner

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Nature of damage

The adult female makes punctures in the leaf tissue with its ovipositor for both feeding and oviposition.

The ratio of oviposition punctures to feeding punctures varies from 1:6 to 1:14.

The male also uses the feeding punctures made by females for feeding.

The larvae that hatch out from the eggs mine the leaf feeding on the mesophyll region leaving a serpentine structure and thus the common name.

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Leafminer feeding results in serpentine mines (slender, white, winding trails); heavily mined leaflets have large whitish blotches.

Leaves injured by leafminers drop prematurely; heavily infested plants may lose most of their leaves.

If it occurs early in the fruiting period, defoliation can reduce yield and fruit size and expose fruit to sunburn.

Pole tomatoes, which have a long fruiting period, are more vulnerable than other tomato crops.

Leafminers are normally a pest of late summer tomatoes and can reach high numbers.

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ManagementThe most important aspect of leafminer management is conserving their natural enemies, which are often killed by broad-spectrum insecticides applied for other tomato pests.

Reduce the risk of leafminer outbreaks by applying insecticides for fruit pests only when monitoring shows treatment is needed and by choosing insecticides that will not destroy the leafminer parasites.

Biological ControlSeveral species of parasitic wasps, particularlyChrysocharis parksi and Diglyphus begini, attack leafminer larvae; left undisturbed, parasites often keep leafminers under control.

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Cultural ControlCheck transplants before planting and destroy any that are infested; leafminers reach damaging levels earlier when infestations begin on seedlings.

Where a series of tomato crops is planted in the same area, you can reduce early infestations in a new crop by removing old plantings immediately after the last harvest.

Organically Acceptable MethodsBiological and cultural controls as well as spray of formulation of spinosad are acceptable for use on an organically certified crop.

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Lets sum up•Liriomyza trifolii (Burgess) that entered India accidentally probably, during 1990-91.

•The native country of this pest is USA (Florida). It was introduced probably along with cut chrysanthemum flowers during early 1970s to California, USA .• It is a polyphagous species affecting more than 78 annual plant species being especially serious on greens, cucurbits, tomato, castor and ornamental plants•The life cycle takes only 2 weeks in warm weather; there are seven to ten generations a year. The larvae that hatch out from the eggs mine the leaf feeding on the mesophyll region leaving a serpentine structure and thus the common name. Maggots mines into leaves and causes serpentine mines drying and drooping of leaves.

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The most important aspect of leafminer management is conserving their natural enemies, which are often killed by broad-spectrum insecticides applied for other tomato pests.

Several species of parasitic wasps, particularlyChrysocharis parksi and Diglyphus begini, attack leafminer larvae; left undisturbed, parasites often keep leafminers under control.

Biological and cultural controls as well as spray of formulation of spinosad are acceptable for use on an organically certified crop.

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