Emily Chan
Raspberry production faces persistent challenges, especially from pests like spider mites. To minimize the use of chemical pesticides, researchers from the Norwegian Institute of Bioeconomy Research (NIBIO) are exploring environmentally friendly alternatives.
One promising approach has been to simply sprinkle water on raspberry leaves to disrupt and reduce spider mite populations.
The two-spotted spider mite (Tetranychus urticae) is a small arachnid that attacks many types of plants. It primarily poses a problem in strawberries, but it significantly affects raspberries as well.
Nymphs and adults feed on the leaves, which often leads to wilting and stunted growth. They can also cause the leaves to drop too early.
“If you want to get rid of spider mites on raspberries, you either have to use biological control organisms like predatory mites or chemical pesticides,” said Nina Trandem, one of the study’s researchers.
“Fewer and fewer chemical agents are available to the growers, and neither they nor the biological control organisms always yield satisfactory results. This is why we need other good alternative methods.”
The researchers investigated whether irrigation can lower the number of spider mites in tunnel-grown raspberries. Several small chambers, each containing three raspberry plants, were set up inside the tunnel.
A sprinkler nozzle was installed above each chamber to spray the plants with water at specific times. Groups of three raspberry plants were placed outside the chambers to act as control plants. They did not get sprayed.
The researchers recorded signs of spider mite damage and documented the number of colonies on the plants. The mites tend to live on the underside of the leaves. Adults spin webs, but they are very tiny and hard to spot.
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