To help plants better fend off insect pests, researchers are considering arming them with stones. The University of Delaware’s Ivan Hiltpold and researchers from the Hawkesbury Institute for the Environment at Western Sydney University in Australia are examining the addition of silicon to the soil in which plants are grown to help strengthen plants against potential predators.

The research was published recently in the journal Soil Biology and Biochemistry and was funded by Sugar Research Australia. Adam Frew, currently a postdoctoral research fellow at the Charles Sturt University in Australia, is the lead author on the paper.

Silicon is the world’s second most abundant element after oxygen in the Earth’s crust, but because it is in a stone or mineral form, it is not readily available for use by plants.

By amending the soil with silica, a form of silicon that plants can easily take up, the researchers helped the plants build up tiny particles called phytoliths, or “plant stones,” to defend against herbivorous insects and possibly rodents.

In experiments with two sugarcane varieties grown in a greenhouse, root-feeding insects, primarily the cane grub, fed on the plants. The immune function of the insects was assessed by measuring their immune response to entomopathogenic nematodes—small organisms that kill insects in the soil—while insect growth and root consumption were assessed in a feeding trial.

The researchers found that high levels of silicon concentrations decreased insect growth and root consumption, the latter by 71 percent. Because the silicon doesn’t affect grazing livestock it also will not affect humans when, for example, a person consumes boiled carrots or sweet corn.

The option of using silicon to naturally strengthen the plant’s defenses against the cane grub would be both environmentally friendly and economically attractive to growers, as they would not have to spray as much to protect their crops.