| dc.description.abstract | The pine woolly aphid, Pineus (L) (Homoptera:
Adelgidae), was first known as a pest in the northern
temperate zones of holartica and in the northern orient.
Heavy infestation by the pine woolly aphid was first
discovered in the estates of the East African Agriculture
and Forestry Research Organization (EAAFRO) at Muguga in
January, 1969, where it was established on pines.
The taxonomic status of the pine woolly aphid is
briefly reviewed and it is concluded that only one species
is present in Kenya.
The history of the introduction of pines is
discussed in relation to the occurrence of P. pini in East
Africa, and it is concluded that the pine woolly aphid was
introduced from Australia on pine scions, about six years
ago. Subsequent spread has since occurred in all
Two isolated outbreaks have been
reported from seed orchard plots in West Kilimanjaro and
in the southern highlands of Sao Hill of Tanzania.
The development of the pine woolly aphid in Europe
according to Marchal (1913) is reviewed. The life history
at Muguga presented
The larvae are mobile for about three days, then insert
The eggs are laid on the bark.
their stylets into the bark and become sessileo They
become adults after four moults. Each apterous female
may lay from 12 to 104 eggs. The virginoparae are less
prolific than the apterous exsules, and one insect lays
from 1 to 4 eggs.
The habits and behaviour of the pine woolly aphid
are discussed and evidence for dispersal of wineless
crawlers and eegs by wind is demonstrated. Flight
behaviours of the alatae indicate a possibility of
migration.
A method for the routine quantitative estimation
of the pine woolly aphid population trends and their
relationship with the physical and plant environment are
outlined. Development occurs continuously throughout
the year, and about four to five and a half generations
of apterous parthenogenetic females are recorded. Winged
insects which are also parthenogenetic occur in smaller
f .El!!i has been reported on 35 specio.s of pines.
Pinus massoniana Lambo, f.o elliottie Engelme, E- contorta
Dougl. ex Loud. and Po radiata Do Don. were the most
favored host while Po patula Schl. and Charno was less
readily attacked. The majority of trees in a st and where
the infestation is well established often develop heavy
infestation, but a few trees remain abs91~tQly untouchedo. ayacahuite Ehrenb. and Po strobus var. chiapcnsis
Martinez. were ~g~~letely resistant to attacko
P. ~ feeds in the bark of all parts of the tree
from the crown to the stem. The feeding method of the
aphid is described, and it is shown that the injury and
damage to the plant tissues is mainly due to the effect
of salivary secretions which the insect injects into
the plant when feeding. Death of the tree is gradual
and usually progresses' from the top to the base, and from
the outside to the centre of the crowne Damage is most
severe on unhealthy trees.
In a final discussion, it is argued that the pine
woolly aphid is a primary pest, capable of killing healthy
trees unless its population is regulated within endemic
proportions. Complete eradication is unlikelyo Lmpor c ant
factors in the control of the pine woolly aphid include
predaition by Syrphid larvae and various Coccinelllds, and
starvation in the first instar during dispersal.
Preventive practices that are designed to.reduce the rate
of spread of the pest are recommended. Biological control
by introduced predatory insects is suggested.
It is suggested that some of the extensive pine
mono-cultures should be selectively replaced by mixed
crops, consisting of soft and hard-wood trees. | en |
