Introduction, Spread and Control of the Pine Woolly Aphid,Pineus pini(L.), in Rhodesia

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Abstract
In 1968 the pine woolly aphid Pineus pini (L.) was found in Rhodesia (and Kenya) and these are the first recordings of Pineus spp. in Africa south of the Sahara. This pest was probably introduced into Rhodesia in 1962 on Pinus taeda L. scions from Australia. Pineus pini spread rapidly and by 1974 had reached all the important afforestation areas in Rhodesia. Nearly all the hard pines introduced into Rhodesia have been attacked but with varying degrees of severity; Old World species of the Silvestres group are most susceptible and Mexican pines, particularly those of the subsection Oocarpae, are among the most resistant. All the introduced soft pines are Immune. A gamma-B.H.C. spray used initially to try to isolate the outbreak was not successful. A population buildup of coccinellid predators started when spraying ceased and this, together with the possibility of introducing a predacious fly, indicates promise for biological control. Trees under physiological stress are particularly susceptible to attack by Pineus and it is clear that the correct siting of species is important in silvicultural control. Prospects for genetic control are excellent. Analysis of Pineus attack in Pinus kesiya Royle ex Gordon and Pinus patula Schiede & Deppe provenance trials illustrate the principle of adaptation to plantation and local climatic conditions as insurance against possible catastrophe when a new injurious organism is introduced. Analysis of an assessment of Pineus attack in a Pinus elliottii Engelm progeny test indicates high heritability for resistance. Pineus pini need not pose a serious threat to pine plantations in Southern Africa.

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