Damaging populations of spider mites in Delta field corn are most effectively controlled when acaricides are applied before injury occurs to leaves above the 3-foot level on the plants. Premature drying of the corn foliage, caused by mite infestations, reduces grain yields by increasing stalk breakage, lowering moisture content of grain at harvest and causing kernel shrinkage. Mite control has increased grain yields by 100 to 2,500 pounds per acre in recent tests. This is a progress report of experimental work and growers should contact their farm advisors or read current pesticide control bulletins for specific recommendations on mite control.