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Integrated pest management (IPM) of Tomato leaf miner
(Liriomyza spp.)

This material addresses aspects of the following syllabus outcomes:

H1.1 explains the influence of the physical, biological, social, historical and economic factors on sustainable agricultural production
H2.1 describes the inputs, processes and interactions of plant production systems.

The work presented in the following section contributes towards understanding the following syllabus content areas:

Students learn about:

Managing plant production

Extract from Stage 6 Agriculture Syllabus NSW Board of Studies Amended 2009

Activity 1

Using your class notes, textbook or the links below to help you, answer the following questions relating to Integrated Pest Management (IPM).

  1. What is IPM?
  2. Identify three benefits of using IPM.

Answers

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Tomato leaf miner (Liriomyza spp.)

The leaf miner flies are small and about 2 to 2.5 mm long. They are greyish to black with yellow markings. The female fly lays very tiny eggs inside the leaf tissue of the tomato plant, just below the leaf surface. Small yellow maggots hatch and feed inside the leaf tissue, leaving long, slender, winding, white tunnels (mines) through the leaf. After three larval stages they are fully grown and about 3 mm long.

The maggots then leave the mines and pupate either on the leaf surface or in the soil. After approximately 15-21 days (depending on the host and temperature) the leaf miner flies emerge to complete the life cycle.

The blister-like blotches that appear on the leaves are where the small maggots have eaten out the tissue between the upper and lower surfaces. Damage may cover so much of the leaf that the plant is unable to function and yields are noticeably decreased. Leaf miner damage to tomato is often confused with leaf diseases by the layman.

leaf miner damage

Tomato leaf miner is rated a Category B quarantine pest in exported produce, and therefore must be constantly monitored.
Control strategies which have been successfully introduced include:

These practices are based on IPM strategies and growers have been encouraged to use them. Over the last ten years growers, seeing the obvious benefits of these strategies, have continued to adopt them, resulting in a significant reduction in crop losses. Monitoring of leaf miner numbers over this time have shown that populations have dropped to 10% of original levels.

Leaf miner damage was considerable prior to IPM strategies being implemented, with growers losing up to 60% of total crop yields in northern Australia. In economic terms, this equated to approximately $10 million loss to the local community. During this time, growers were heavily reliant on chemical insecticides to control the leaf miner and resistance became a major problem. Insecticide susceptibility varies widely, and level of susceptibility is directly related to frequency of insecticide application. Tomato IPM pilot programs were initiated following heavy economic losses from a severe outbreak of leaf miners. During this outbreak, as many as 34 insecticide sprays were used in one 90-day season in a futile attempt to control the leaf miners.

Insecticides also are highly disruptive to naturally occurring biological control agents, particularly parasitoids. Use of many chemical insecticides heightens leaf miner problems by killing parasitoids of leaf miners. Interestingly, leaf miners were (and are) considered a secondary pest of tomato. Control failures were attributed to a build-up of pesticide resistance in leaf miner populations and to high leaf miner natural enemy mortality.

Activity 2

  1. Explain what damage the leaf miner does to the tomato plant and why you think control measures are important.
  2. Evaluate the likely environmentally sustainable implications of adopting IPM strategies to control leaf miner damage in tomato crops.

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