Farmers lose more than $1 billion a year when wind-borne rust fungi attack wheat, coffee, and other crops. Threadlike rust cells invade plants through tiny breathing pores called stomata, cutting crop yields by as much as half. Cornell University plant pathologists Harvey C. Hoch and Richard C. Staples speculated that the ridges surrounding the stomata signaled the fungi where plants were vulnerable. To test their hypothesis, they grew fungi on silicon wafers etched with different-size ridges by electron beams. "It was a marriage of cell biology and nanotechnology," says Hoch.
It turned out that fungi couldn't recognize stomata if the ridges were slightly taller or shorter than half a micron. The pair have identified the optimum ridge height that fungi can recognize for more than 30 crops. Efforts to discover plant varieties with stomata invisible to fungi have so far been unsuccessful. But Hoch thinks that introducing genes from plants that have ridges all over could confuse the fungi's sense of direction and leave a plant unharmed in its wake. Fungi could then be controlled by changing the architecture of, say, a leaf rather than zapping it with chemical sprays.