“These bactericides give us hope,” said Mr. Petteway’s son, R. Roy, 33, as he watched his father treat the family’s trees, some of them 50 years old.

A further elevation from 37 C. to 45 C. renders nonyl and decyl resorcinol also potent as bactericides in aqueous solution. Because of the increased solubility of the alkyl resorcinols in alkali, the ...