tiny silverleaf whiteflies are resisting the latest crop of pesticides in fields of melons and peppers in the lower Rio Grande Valley, Texas, us . Tong-Xian Liu, researcher at the Texas a&m University, in the us , and his assistants, searching for signs of the tiny silverleaf whiteflies say there are signs that the species is evolving. "Whatever you use, sooner or later it will become resistant,' says Liu.

The tiny whiteflies weaken crops by feeding on plant sap, producing waste that encourages fungus to grow, blocking photosynthesis. They also carry plant diseases. Liu's project intends to check whether the flies are developing resistance to