Swiss scientists have been testing netting as a way to exclude spotted wing drosophila from cherry orchards.
Researchers at the Breitenhof Stone Fruit Centre in Wintersingen, near Basel, covered Staccato cherry trees with two types of insect netting: a black net with a mesh size of 1.7 by 1.7 millimeters and a white netting with a mesh size of 1.2 by 1.2 mm, European Fruit Magazine reports.
The larger mesh did not keep out the flies, but the 1.2 by 1.2 mm mesh did keep them at bay. However, the mesh size is so small that the netting decreases ventilation and potentially increases the risk of fruit rots developing.
Scientists at the Brietenhof Centre also studied the effectiveness of using postharvest pesticide treatments in order to reduce spotted wing drosophila populations the following year. They tested dimethoate, acetamiprid, spinosad, and pyrethrum products, which were applied to unpicked Regina cherry trees.
Results were disappointing, the magazine reports. Although the products were somewhat effective, more flies would appear a few days later, effectively negating the results of the insecticide treatment.
Researcher Thomas Schwizer concluded that growers would need to use a combination of chemical and mechanical measures, such as netting, to protect their cherries. When fly populations are high, pesticides alone will not be enough.