Using Water To Turn down Spider Mite Pressure on Berries

Researchers at NIBIO (Norwegian Institute of Bioeconomy Research)  are studying how sprinkling with water can reduce the pressure from spider mites on berries.

The two-spotted spider mite (Tetranychus urticae) is a small arachnid that can attack a wide range of plants. It is especially problematic in strawberries, but also poses significant challenges in raspberry production. Both nymphs and adults feed on the leaves, which can lead to wilting, stunted growth, and early leaf drop.

“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,” researcher Nina Trandem explains. “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.”

Together with colleagues at NIBIO, Trandem initiated a study to investigate whether irrigation can reduce spider mites in tunnel-grown raspberries. Inside the tunnel, several small chambers were set up, each containing three raspberry plants. A sprinkler nozzle above each chamber sprays the plants with water at set intervals.

“We observed a 40% to 50% reduction in spider mites on plants that were regularly sprinkled with small amounts of water compared to those that were not sprayed,” Trandem says.

The same was seen in strawberry trials. “The effect was on par with spraying once with a miticide, if we count the mites a couple of weeks after spraying. Spider mites simply don’t thrive in a moist environment. Predatory mites, on the other hand, which are natural enemies of spider mites, prefer a slightly humid environment. In other words, this treatment can also create favorable conditions for biological control.”

Trandem emphasizes that the treatment does not completely eliminate the mites but keeps their numbers low enough to prevent significant damage to the plants.

For more, continue reading at Phys.org.