Browsing by Author "Rose, D.J.W."
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Item Establishment of pine woolly aphid, Pineus pini (Gmelin) (Adelgidae) on some host trees in Kenya(1982) Mailu, A.M.; Khamala, C.P.M.; Rose, D.J.W.; Kenya Agricultural Research Institute; C.P.M. Khamala Department of Zoology, University of Nairobi; D.J.W. Rose Centre for Overseas Pest Research, U.K.The establishment of Pineus pini (Gmelin) on six common Pinus species is examined with references to possible causes for observed differences in the rates of infestations, on the different host species. Pine woolly aphid crawlers are positively Apoptotic, but do not settle onto surface exposed to strong light. They appear negatively photostatic to strong light and consequently tend to settle in hidden and tight crevices. The undersides of lateral branches which receive only moderate light tend to harbor a higher concentration of aphids than the upper surfaces. Possibly, positive thigmotaxis and' negative phototaxis operate together, tending to bring crawlers into situations satisfying feeding and thigmotactic instincts.Item Evaluation of Pine Woolly Aphid Damace to pinus patula and its effect on yield in Kenya(1978) Mailu, A.M.; Khamala, C.P.M.; Rose, D.J.W.; Kenya Agricultural Research InstituteThe pine woolly aphid, Pineu pini (L.) is currently regarded as one of the most serious pests of exotic pines in Kenya. Odena (1972) has described the basic life history of this pest, but 'its impact on Pinus is essentially unknown. Its distribution is widespread in Kenya, as well as in Rhodesia. The first sign of damage is stunted needles, followed by abortion of buds. The effects of repeated attacks are cumulative so that growth reduction, tree deformity and at times 'outright tree mortality are encountered.Item Population dynamics of pine woolly aphid, Pineus pini (Gmelin) (Hemiptera Adelgidae), in Kenya(1980) Khamala, C.P.M.; Mailu, A.M.; Rose, D.J.W.The population dynamics of Pineus pini (Gmel.) was examined in two locations in the Kenya Highlands where the mean annual precipitation ranges from 620 to 1400 mm. Variations in population densities were related to rainfall. Generally, there was a marked decrease in population during the three months of heavy rainfall in March to May and a significant increase during dry weather from August to October. This was followed by a slight decrease in the rate of population build-up, until the long rains in April again resulted in another population collapse. Nine species of predatory insects were identified, and population fluctuations of the most common of these, Exochomus spp., was studied. Predators seemed to remove about 12% of the aphid population. Other mortality factors included heat and crawler dispersion. The greatest mortality occurred early in the life cycle and was mainly due to eggs and crawlers being washed off the host-tree by rain.Item Sampling Techniques for Populations of Pine Woolly Aphid, Pineus Pini (Gmelin)(Adelgidae)(1982) Mailu, A.M.; Khamala, C.P.M.; Rose, D.J.W.; Kenya Agricultural Research Institute, Muguga, Kenya.; Department of Zoology, University of Nairobi, Kenya; Centre for Overseas Pest Research, U.K.From observations on Pinus patula at 4 places in Kenya, procedures for sampling populations of all stages in the life history of Pineus pini (Gmel.) are given. The distribution pattern of the aphids within the tree crown branches is described, and tables are presented giving the numbers of trees to be sampled in order to estimate populations with a known precision, either by measurement of pine needle lengths or by counts of aphids present. A highly significant negative relationship between needle lengths and aphid numbers suggests that measurements of needle lengths alone are adequate to estimate the intensity of infestation.Item Sequential Surveys for the Pine Woolly Aphid, Pineus pini (L.) Homoptera: Adelcidae in Kenya(1978) Mailu, A.M.; Rose, D.J.W.; Khamala, C.P.M.; Kenya Agricultural Research InstituteMany pest management programmes do not require exact estimates of population density but rather require that pest populations are categorized into density classes which are related to predictable levels of crop loss.
