Apples, the fruit that famously keeps the doctor away, are getting some help to keep away unwanted visitors themselves. Ontario’s apple trees are facing damage from a new pest – the apple leaf curling midge. The galls (bumps that appear on leaves) produced by the midges can interfere with the normal growth and development of the terminal shoots of young apple trees, which delays or stunts their structural development.
It’s a particular problem in Durham Region, where the amount of land dedicated to growing apples has doubled in the last five years, because young trees are particularly affected, but apple growers across Ontario are struggling with the midges.
In this collaborative project, the Ontario Apple Growers Association approached Durham College for help finding a way to manage apple leaf curling midges. The first step was to select three apple orchards where data could be collected for a degree-day model (which establishes the rate of the midges’ growth, based on temperature). The researchers use that information for predicting and managing the midges’ development.
The researchers also identified biological control agents for the midges in the orchards and evaluated what impact spraying for midges might have on their survivability.
The project team developed two techniques to research the leaf-curling midges in the lab — one for studying the emergence of adult midges from pupa under different temperatures and the other for looking at the transfer of eggs from field samples to potted trees in the lab, to determine how midges successfully establish themselves on new trees.
The field data showed there are four adult “flights” over the summer and a partial flight in the fall. Egg counts increased very soon after each peak adult flight in May, late June, late July and late August. This is crucial information for effective use of insecticides to control the midges.
Two students from Durham College’s Food and Farming program completed the project in six months, collecting data from the three orchards and tabulating and analyzing it for predictions. Using various concepts, tools and techniques they had learned in the classroom to manage and analyze models for pest management gave the students an opportunity to apply their knowledge in a real-world, collaborative project.
All the 235 members of the Ontario Apple Growers Association will adopt management techniques from this project.