Five field trials at Moshi examined control of white grubCochliotis melolonthoidesfor 3 years given by a single treatment of controlled‐release granules containing 140 g chlorpyrifos a.i./kg. In the first 2 years CR‐chlorpyrifos (2.94, 5.88 and 7.84 kg a.i./ha) and preplant and pre‐first ratoon ethylene dibromide (118.8 kg a.i./ha) treatments effectively reduced white grub densities compared to the untreated. Yields at harvest of the plant and first ratoon crops showed that treatments of CR‐chlorpyrifos at 5.88 and 7.84 kg a.i./ha, yielded significantly higher than EDB, except CR‐chlorpyrifos at 5.88 kg a.i./ha in plant cane in trials 1 and 3, and at the highest rate in plant cane in trial 3. There were no significant differences between the two higher rates of CR‐chlorpyrifos. In the third year EDB was not reapplied, and EDB and the untreated plots were totally damaged by white grubs. The two higher rates of CR‐chlorpyrifos reduced white grub densities in the second ratoon crop to a greater extent than the 2.94 kg a.i./ha rate in four of the five trials. In the second ratoon crop there were no significant differences between cane yields given by the three CR‐chlorpyrifos rates in two trials, but in the other three trials both the higher rates resulted in greater yields: in these three trials there were no significant (P< 0.05) differences in the yields given by CR‐chlorpyrifos at 5.88 and 7.84 kg a.i./ha.