Agriculture Reference
In-Depth Information
Mites
ORDER PROSTIGMATA
Family PHYTOPTIDAE
Phytoptus avellanae
Nalepa
Filbert bud mite
prodorsal shield
with two pairs of dorsal setae
(see Fig. 168a).
Summer deutonymph
flat-
bodied, with just a few, very broad tergites.
This widely distributed mite is generally com-
mon on cob nut, filbert and hazel. The mites
induce the formation of swollen buds ('big
buds'); infestations also cause blind shoots. Any
detrimental effect on the yield of nut-producing
trees is of little or no significance, except in coun-
tries such as Italy, Spain and Turkey where a
large proportion of buds may be galled.
Family ERIOPHYIDAE (gall mites)
Abacarus
hystrix
(Nalepa)
Cereal rust mite
Infestations of this widely distributed mite occur
on various cereals and grasses but are most often
present on ungrazed or uncut Italian rye-grass
and perennial rye-grass, especially the latter. The
pest is a well-known vector of rye-grass mosaic
virus. In North America, it is also implicated in
the spread of Agropyron mosaic virus. When
numerous, the mites cause direct damage and
infested leaves become discoloured. The com-
bined effect of mite feeding and virus infection
results in undersized plants, which lack vigour
and give reduced yields.
BIOLOGY
The mites breed throughout the late summer,
autumn and winter in the buds of host plants.
Infested buds develop into swollen galls, which
become noticeable from September onwards.
The mites also occur in female flowers and male
catkins. In March and April, adult females in-
vade the underside of expanding leaves. Eggs
are then laid and these give rise to active
protonymphs that eventually develop into more
or less sedentary summer deutonymphs, found
mainly alongside the major leaf veins. These
deutonymphs finally moult into adults that in-
vade new terminal buds to initiate the next gen-
eration of 'big-buds'.
BIOLOGY
Adult females overwinter on tender tissue at the
tips of host plants and become active in the
spring. They then invade the upper surface of
the young leaves, and eventually deposit eggs
within the longitudinal grooves between the
veins. Breeding continues throughout the sum-
mer months and populations reach peak num-
bers in late August or early September. Mites
feeding on virus-infected plants pick up the virus
DESCRIPTION
Adult
0.3 mm long, whitish and spindle-shaped,
with numerous narrow tergites and sternites;
