Studies On The Ecology Of Pine Woolly Aphid, Pineus Pini (L.) And Its Damage On Pinus Patula Schiede & Deppe In Kenya

Abstract

In the months of February and March, May, June and July the pest was in abeyance. Laboratory and field experiments indicated Exochomus spp. as the most common of the local predators of pine woolly aphid in Kenya. The biology of this predator was briefly described. Results suggested that its effectiveness may be reduced by parasites associated with it. Mechanical action of precipitation by heavy rainfall and hot and dry weather also plays major role in population regulation. Pine woolly aphid infestation produced not only a reduction in length of needles of P. patula, but also a general reduction in the amount of overbark wood volume, the severity depending on the quality of the site. It was also indicated that heavy infestations of aphids were associated with easily detectable decreases in the lengths of needles and eventually death of the whole tree after repeated and continued infestation for 5 years. Stem elongation and diameter growth reductions occur only after crown damage becomes extreme. There is a combination of stunted and normal needles, corresponding at the same time, to stunted and normal branch internodes in trees showing recoveries from infestations It further appeared. that an uninfested stand of P. patula may have from 1.2 to 2 times as much wood volume as an infested stand, but that these relationships interact with site factors. Significant volume differences between non-infested and severely infested trees and between severely infested and light and medium infestations were indicated. Generally non-significant volume differences were obtained between non-infested and light and medium infestations. It was concluded that P. pini need not pose a serious threat to P. patula plantations in correct sites.