Mites - Pests of Ornamental Trees, Shrubs and Flowers - page 407

mites cause severe galling of infested tissue,
particularly at the shoot tips. Leaves at first become
light green and felt-like, and eventually tinged with red.
Infested plants, including the flowers, are also greatly
deformed. There are several generations annually, and
development from egg to adult takes about three weeks
at a temperature of 18ºC. The mites ( c . 0.20-0.25 mm
long) are pale yellow to whitish, with about 50
abdominal tergites and 70 sternites.

Belgium, England and the Netherlands. The mites are
free-living and cause noticeable bronzing of infested
foliage. Heavy infestations also result in the
development of black lesions on the underside of leaves,
followed by desiccation and premature leaf fall.

Cecidophyopsis malpighianus (Canestrini &
Massalongo)
Bay big bud mite
This little-known Mediterranean species feeds and
breeds in the flower buds of bay laurel ( Laurus nobilis ).
Infested buds swell considerably, and also become
noticeably discoloured and distorted. The worm-like
mites ( c . 0.27 mm long) are whitish or yellowish in
colour, and occur in vast numbers within infested buds.
The pest was originally discovered in Italy, but has since
also been found in certain other countries, including
Belgium, England, the former Yugoslavia and the USA.

JUGLANS

Aceria erinea (Nalepa) ( 1099 )
Walnut leaf erineum mite
A generally abundant mite, responsible for the
formation of erinea on the underside of the leaves of
walnut ( Juglans ). The galls appear as large, reddish-
tinged blisters on the upper surface of the expanded
leaves; the lower surface is coated with a felt-like mass
of whitish hairs, within which the mites breed. Galling
is often extensive on both nursery stock and mature
trees but is of little or no importance. The causal mites
are c . 0.22 mm long and whitish, with a pair of
moderately long, posteriorly directed setae arising from
tubercles on the hind margin of the prodorsal shield.

1099

Aceria tristriatus (Nalepa) ( 1100 )
syn. Eriophyes tristriata (Nalepa)
Walnut leaf gall mite
A locally common pest of walnut ( Juglans ), forming
small (1-2 mm diameter) hard, dark red, pimple-like
galls on the upper surface of leaves, each with a tiny
opening through the lower surface. Galls are often
located alongside the midrib and other major veins.
Heavily infested leaves may be distorted, but there
appears to be little or no impact on tree growth. Adult
females (0.20-0.24 mm long) are pinkish to reddish and
elongate, with a pair of moderately long, posteriorly
directed setae arising from tubercles located on the hind
margin of the prodorsal shield.

1099 Galls of walnut leaf erineum mite ( Aceria erinea ).

1100

LAURUS

Several European species of eriophyid mite attack bay
laurel ( Laurus nobilis ). The following two species are of
particular significance.

Calepitrimerus russoi Di Stefano
Bay rust mite
This brownish-orange, pear-shaped mite (0.15-0.19
mm long) is a pest of bay laurel (Laurus nobilis) in
various parts of central and southern Europe. The pest
has also been found on greenhouse-grown plants in

1100 Galls of walnut leaf gall mite ( Aceria tristriatus ).