Insects - Pests of Ornamental Trees, Shrubs and Flowers - page 62

Pentalonia nigronervosa Coquerel ( 118 )
Banana aphid
A tropical and subtropical species, established in
various parts of mainland Europe on hot-house palms
and certain other monocotyledonous hosts. The aphids
are small (1.1-1.8 mm long) and mainly dark brown,
with stout siphunculi. Colonies develop on the
underside of the leaves and are usually attended by ants.

LIFE HISTORY
Although sometimes overwintering in the egg stage on
nectarine and peach trees, this aphid more frequently
survives as adults and nymphs on herbaceous
(secondary) hosts such as outdoor brassicas and
protected lettuce. The aphids breed parthenogenetically
throughout much of the year. They are very restless and
frequently wander over the foodplant, on flower crops
often migrating upwards to invade the buds. Winged
forms are produced in the summer months, and these
readily spread infestations to other hosts. Colonies are
never very populous and reach their maximum
development in July.

Rhopalosiphoninus latysiphon (Davidson)
Bulb & potato aphid
Infestations of this cosmopolitan species occur on plant
roots and on tulip ( Tulipa ) bulbs in store, building up
rapidly during forcing; they also occur on other stored
bulbs, corms and tubers, including Gladiolus . When
developing leaves are attacked they often turn brown
and shrivel at the tips. The aphids (1.4-2.5 mm long) are
plump and dark olive-green, with shiny black and
strongly swollen siphunculi. Unlike Dysaphis tulipae
(p. 60), which also attacks tulip bulbs, this species is
never attended by ants.

DAMAGE
This aphid is a major vector of plant viruses, including
carnation latent virus, chrysanthemum virus B and
various mosaic viruses (e.g. carnation, dahlia and orchid
mosaic virus). Direct feeding is rarely significant,
although the aphids sometimes damage protected crops,
causing distortion of leaves, buds and flowers, and
stunting of terminal shoots. Although populations are
usually small, the mere presence at harvest of aphids on
crops affects marketability and is, therefore,
unacceptable.

Rhopalosiphoninus staphyleae (Koch)
syn. Hyperomyzus tulipaella (Theobald)
Mangold aphid
Colonies of this widespread aphid occur during the
winter on stored bulbs and corms, including Crocus ,
day-lily ( Hemerocallis ) , Hippeastrum, Lilium and tulip
( Tulipa ). Aphids are 1.5-2.4 mm long and mainly olive-
brown, with dark crossbands along the back; the head
and first two antennal segments bear numerous small
spines, and the siphunculi are noticeably swollen.

Myzus ascalonicus Doncaster
Shallot aphid
A widely distributed, virtually cosmopolitan species;
unknown before 1940 but now an often common pest
of herbaceous plants, including ornamentals such as
Gladiolus, Hippeastrum, Lilium and winter cherry
( Solanum capsicastrum ). The aphids breed asexually
throughout the year, and often survive the winter on
stored bulbs and corms, and on various greenhouse
plants. In mild conditions colonies also survive the
winter outdoors. Winged migrants appear in the spring,
and these spread infestations to various herbaceous
summer hosts. Infestations lead to considerable
distortion and malformation of foliage and flower
trusses. Further, when previously infested bulbs and
corms in store are planted out, new shoots are often
weak and noticeably distorted. Apterae (1.1-2.2 mm
long) are light brown, greenish brown or yellowish
brown, shiny and distinctly convex; the head is
emarginate, with slightly convergent prominences, the
siphunculi distinctly swollen towards the tip, and the
cauda bluntly triangular and barely visible from above.

Rhopalosiphum nymphaeae (Linnaeus) ( 119 )
Water-lily aphid
A generally common pest of aquatic plants, especially
water-lilies ( Nymphaea and Nuphar ). Virtually
cosmopolitan. Widely distributed in Europe.

DESCRIPTION
Apterous female: 1.6-2.6 mm long; dark olive-green to
brown, lightly dusted with whitish wax; siphunculi
relatively long and swollen, mainly pale but dark
apically. Alate: 1.6-2.6 mm long; dark brown to shiny
black.