Researchers are continually looking for ways to control pests without using synthetic pesticides. Biological, cultural or physical control measures would (ideally) be less costly to both the environment and the pocketbook. One area where significant progress is being made is with insect control in the apple orchard.

Three major insect pests account for most of the damage done to apples. The adult apple maggot is a clear winged fly which lands on the fruit and lays its eggs. The infested apple becomes irregular and "lumpy" and small larvae may be found inside. The plum curcullio leaves a crescent shaped scar on the fruit where it lays its egg. Again, a little worm is found inside. Codling moths also lay eggs on the surface of the fruit. Their larvae are the little worms that are found near the seeds at the center of the fruit. The majority of insecticide applications currently used on apple orchards are to control these three pests.

Scientists have discovered that the females of many insect species attract males by emitting a strong chemical scent called a pheromone. The pheromones of many insects including the codling moth have been isolated and can be reproduced in the laboratory.

A very small amount of this substance will attract males from long distances. Researchers began to wonder what would happen if an area were saturated with pheromone. They conducted experiments in which plastic "twist tabs" were impregnated with the pheromones and hundreds of the tabs were placed on trees in the test orchards.

They found that the poor confused male moths flew frantically from tree to tree in search of females but found only indifferent pieces of plastic. Eventually, the males gave up and mating did not occur. The females had few fertilized eggs to lay on the fruit so damage was greatly minimized.

Preliminary results have been encouraging but there are still problems to overcome. This process called, mating disruption, only works on the codling moth and does nothing for the other major pests. It is more expensive than conventional spray programs. Also, they discovered that some secondary pests such as leaf rollers became a greater problem since they hand normally been controlled as a by product of spraying for codling moth.

Progress is being made with trapping for apple maggot but plum curcullio is proving more difficult to control with alternative approaches. Research continues.

• Parasitoids
• Pathogens
• Pheromones

• Predators
• Weed Consumers