Mepiquat chloride recommendations developed for Acala cotton in CA are based upon the concept that growth regulators should be used when within-season plant mapping information indicates low to moderate fruit retention combined with moderate to high vigor measured as plant height or growth rates. Field history which indicates consistent problems with too high vigor can also be used as an indicator that growth regulator responses would likely be positive. In more recent studies with Pima cotton conducted over a long time period, results indicate that mepiquat chloride materials can be effective in helping manage vegetative growth, but impacts on yield are smaller and less consistent than found with Acala cotton. Results also show that the potential impact of delayed irrigations in combination with growth regulator use on plant growth and lint yields depends to a significant extent on fruit retention and the intensity of water stress.