Contents - LAC Biosafety

286 Insect pests in plantations: case studies
Pest profile
Pine aphids (Hemiptera: Adelgidae and Aphididae)
Two species of exotic aphids (order Hemiptera, superfamily Aphidoidea),
Pineus pini (family Adelgidae) and Eulachnus rileyi (family Aphididae), are
important pests of pines in eastern and southern Africa. P. pini, known as the
‘pine woolly aphid’ or ‘pine adelgid’, is a native of Europe and is believed to have
been accidentally introduced to Africa, via Australia, in the 1960s. It spread
rapidly into several countries in eastern and southern Africa, affecting many
species of exotic as well as native pines. There is some confusion on its taxonomy
and it has been referred to in the literature sometimes as P. laevis and confused
with P. boerneri, which is probably of East Asian origin and difficult to
differentiate morphologically from P. pini (CABI, 2005). A pine adelgid identified
as P. laevis has also been recorded in pine plantations at high elevation sites
in Kerala and Tamil Nadu in southern India where it is believed to be an
inadvertent introduction (Singh et al., 1982). E. rileyi, known as pine needle aphid,
is also native to Europe from where it has spread to North America and Africa.
Life history, nature of damage and impact Aphids are sucking insects which
feed on plant sap. Both P. pini and E. rileyi attack a wide range of pines including
P. caribaea, P. kesiya, P. merkusii and P. patula. Infestation causes the needles to turn
yellow and drop prematurely.
Aphids have complicated life histories in northern temperate zones, with
both winged and apterous adults and an alternation of asexual and sexual
generations. In Africa, where they multiply throughout the year, the life cycle
is simpler and reproduction is parthenogenetic, although both winged and
apterous forms are produced. The young P. pini, called ‘crawlers’, insert their
tubular mouthparts into the tissues and suck the sap from the base of the
needles and young bark. They go through several moults and complete the life
cycle within a few weeks. There are many generations per year and there is
considerable overlap between generations. The apterous form of P. pini produces
waxy thread-like secretions which form a woolly covering over its body, giving it
the name ‘woolly aphid’. The apterous P. pini adult is about 1 mm in length
(Murphy et al., 1991). In Kenya population density of P. pini is influenced by
weather, the density being lowest during the rainy period (Mailu et al., 1980).
The adult E. rileyi is about 2.5 mm in length; all stages feed on pine needles, both
young and old (Murphy et al., 1991). E. rileyi is relatively uncommon within its
native geographic range and is not considered to be a pest, but it has acquired
pest status in Africa where it has been introduced (CABI, 2005).
The two invasive pine aphids, together with a third invasive cypress
aphid Cinara cupressi, have caused substantial damage to pines and cypress in