Effect of apple variety for the detection of apple maggot, Rhagoletis pomonella: How the colour of the fruit influences the attractiveness of the red sphere trap

Several predators are present in orchards in North America, one of the main ones being the apple maggot, Rhagoletis pomonella (Walsh). For effective control, residual insecticide treatments are used in commercial apple orchards when catch thresholds are reached. The hotter summers that we have experienced in recent decades have increased the pressure of this pest. The recommended scouting method uses the sticky red sphere to attract the female when ready to lay. However, for two decades, several new apple varieties were added to the orchard. We noted less efficacy of red sphere trap to scout the apple maggot in the presence of these varieties. The project aims to increase the efficiency of the red sticky spheres to detect the apple maggot, Rhagoletis pomonella (Walsh), in apple orchards with new apple varieties. Red spere traps were placed in six apple varieties, three standard varieties with red fruit (Cortland, Empire and Spartan) and three new varieties with yellow, pink and orange fruits (Primgold, Honey crisp and Delcorf). Trials were done in 2019 and 2020. We note that the red spheres captured more apple flies in the Spartan and Honey crisp varieties, followed by Primgold and Delcorf. The fruits of yellow and orange colours allow a higher apple fly capture than the fruits of red colour. The colorimetry analysis shows the variations in colours that may explain decreasing attractiveness of Honey crisp during the season. The project will help present a more efficient screening tool to reduce insecticide treatments against this pest.