Agriculture Reference
In-Depth Information
turn brown and, finally, black. Attacks can also
occur on the developing fruitlets which, in com-
mon with badly affected leaves, may then be-
come distorted and drop prematurely.
Infestations also occur on other members of the
family Rosaceae, including Crataegus, Malus and
Sorbus; mites on such hosts are sometimes af-
forded separate subspecific or specific status.
autumn as young adults depart to take up their
winter quarters.
DESCRIPTION
Adult 0.22 mm long, whitish to pale brownish,
and cigar-shaped; prodorsal shield setae directed
forwards (cf. pear rust mite, Epitrimerus piri, p.
258).
BIOLOGY
Adult mites overwinter beneath the outer scales
of buds and become active in the early spring as
the buds begin to swell. The mites then penetrate
deeper to feed and deposit eggs. Later, they feed
on the underside of expanding or expanded
leaves, forming distinctive blisters. The centre-
most epithelial cells at the base of these blisters
eventually die, so that pocket-like galls are
formed, with an opening on their ventral surface
(Fig. 338). Breeding in these galls continues
throughout the summer, and newly reared mites
regularly escape and migrate to younger tissue,
where they initiate further galling. Galls are
abandoned as they age and become uninhabit-
able, and breeding eventually ceases in the
Eriophyes padi (Nalepa)
Plum leaf gall mite
Eriophyes similis (Nalepa)
Plum pouch-gall mite
These two gall mites are associated with plum.
They also occur on various other kinds of
Primus, especially P. spinosa. Although the galls
of each species are distinct (see below), both
have sometimes been described both as pouch-
shaped, and this has led to misidentification and
confusion. Galls inhabited by Eriophyes padi
are lantern- or finger-shaped (4-5 mm long), and
occur on the upper surface of leaves, especially
towards the centre of the lamina. Galls inhabited
by E. similis are pouch-like (4-5mm long), and
occur in greatest profusion around or towards
the periphery of infested leaves. In plum or-
chards, E. similis (which appears to be the more
abundant species in the British Isles) tends to
be of greater significance, as the mites can also
cause direct damage to the fruits. Affected plums
enlarge more or less normally but their surface
becomes distinctly uneven and develops irregu-
lar, sunken patches; fruits of certain cultivars,
notably Purple Pershore and Yellow Egg, are
especially liable to be attacked.
Phyllocoptes gracilis (Nalepa)
Raspberry leaf & bud mite
Although associated mainly with raspberry, this
widely distributed and often common pest will
also attack blackberry, loganberry and other
kinds of Rubus, including tayberry. On rasp-
berry, the mites cause distortion and the devel-
opment of distinctive yellow blotches on the
Fig. 338 Leaf gall of pear leaf blister mite,
Eriophyes pyri: (a) ventral view; (b) vertical section
(x8).
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