It is reported in this further paper on the damage caused by Pineus pini (Gmel.) to Pinus patula in Kenya [see preceding abstract] that reduction in the elongation of the needles and stems occurs only after crown damage and aphid infestation become extreme. Lighter infestations are reflected in slight reductions of needle length. Damage to the trees and consequent losses of wood volume are most severe under warm dry conditions. Severely stunted needles caused by aphid feeding result in loss of half the tree yield. Infested stands may incur up to 5% economic loss in wood volume. These relations are, however, affected by site factors such as rainfall and altitude. With stands of P. patula at suitable sites. Pineus pini need not pose an important threat to plantations in Kenya.