On this electron microscope image, the spider mite looks almost harmless with its small head and hair on its back. But this arachnid is a major pest that is not easy to control
The common spider mite (Tetranychus urticae) in our picture is a plant pest that can attack the leaves of over a thousand plant species, pierce them and suck them out from below. To combat the mite, farmers and gardeners have so far mostly resorted to synthetic chemical pesticides, but these also kill many beneficial insects.
Scientists working with Naoki Takeda from the University of Agriculture and Technology in Tokyo have now been looking for a more environmentally friendly remedy for spider mites that also spares their natural predators. They chose an organic pesticide made from safflower and cottonseed oils – both oils that are both also used in food.
The advantage: pesticides based on such oils are generally non-toxic for mammals and, among other things, do not contaminate the soil. In addition, pests develop resistance to these agents less often, so that new types of poison do not have to be constantly produced. To study how the selected organic pesticide called suffoil affects the spider mites, the researchers dipped spider mite eggs in the poison and examined them with microscopes.
It turned out: “The organic pesticide works by preventing the spider mite embryo from turning inside its eggshell in order to hatch,” explains Takeda’s colleague Takeshi Suzuki. This prevents the spider mites from reproducing. In addition, the suffoil had no effect on natural predators of spider mites such as the mite species Neoseiulus californicus. Because their embryos do not use rotation to hatch from their eggs.