Four field trials were conducted over three seasons to determine the optimum plant growth stages for single and follow-up insecticide applications for the control ofChilo partellusin grain sorghum. The insecticide was applied at various vegetative and reproductive plant growth stages. Different infestation levels were obtained by using different planting dates. A significant infestation level×treatment interaction (P<0.001) was observed. Yield losses ranged between 10.7% and 24.7% for the most effective single application and 3.9% and 48.0% for the most effective follow-up application. The most efficient single application was at the mid-whorl or flag leaf stage. The most efficient follow-up application involved the flag leaf stage application combined with either a boot or soft dough stage application. An increase in infestation levels resulted in an increase in the efficacy of mid-whorl stage applications. Applications before the flag leaf stage appear to be necessary when approximately 20% of the plants exhibit whorl damage. The necessity for different control strategies for specificC. partellusinfestation situations is emphasized.