Mites - Agricultural Entomology - page 263

(Plate 16f); the mites also cause reddening of
tissue, and severely infested plants may be
stunted. Most damage is caused in dry seasons.
The mites also attack a wide range of grasses but,
unlike several closely related grass-feeding
mites (including grass & cereal mite, Siteroptes
graminum, p. 264), not cocksfoot. Colonies de-
velop within the upper section of leaf sheaths
during the spring and summer, and their pres-
ence is usually noticeable from June onwards.
Adult females are elongate (0.25 x 0.13 mm),
pale brown and translucent, with thin hindlegs.
Males are stouter-bodied, with robust hindlegs,
and their hind femora are distinctively flanged
(Fig. 342b). There are several generations in a
season.

Fig. 342 Hindleg of male Steneotarsonemus: (a) bulb
scale mite, S. laticeps; (b) oat spiral mite, S. spirifex.

Tarsonemus myceliophagus Hussey
Mushroom mite

but then increasing in the following spring with
the onset of warmer weather. Damage in the
field is likely to be seen only if the winter has
been unusually mild. As the bulbs develop, infes-
tations sometimes spread upwards onto the
emerged leaves and flower stalks, but conditions
on exposed tissue are generally unfavourable for
mite development.

This species is an important pest of mushrooms,
the relatively sluggish, barrel-shaped mites feed-
ing on mushroom hyphae. Mite damage appears
to encourage secondary breakdown of tissue,
and this results in a reddish-brown discoloration
around the base of the stipes; if the basal hyphae
are severed, the developing stipes may also
become loosened. The mites are also vectors of
'die back' virus. Development of the mite from
egg to adult is favoured by spawning tempera-
tures, requiring only 8 days at 24°C but taking
about 12 days during the cooler cropping period.
The mites are often particularly numerous if in-
festations develop during or soon after spawn-
ing. The adult mites are 0.2 mm long, pale brown,
translucent and shiny; the hindlegs of males
are robust, terminating in a strong claw, but
lack a distinctive flange (cf. cyclamen mite,
Phytonemus pallidus, p. 260). Mushroom mites
are often preyed upon by long-legged mushroom
mites, Linopodes spp. (family Penthaleidae), es-
pecially L. motatorius (L.). These very active
predators (once thought to be damaging to
mushrooms) are whitish in appearance, with
very long, antenna-like front legs.

DESCRIPTION
Adult female 0.2 mm long, pale brown and trans-
lucent; hindlegs thin and each bearing a terminal,
whip-like seta; gnathosoma broader than long,
cf. cyclamen mite, Phytonemus pallidus (p. 260).
Adult male similar in appearance to female but
smaller; hindlegs robust, unflanged and each with
a strong claw (Fig. 342a). Egg relatively large,
oval, whitish and translucent. Larva whitish
and 6-legged.

Steneotarsonemus spirifex (Marchal)
Oat spiral mite

This species is a minor pest of cereals, especially
late-maturing oats. Inflorescences fail to emerge
fully from mite-infested shoots, the rachis be-
coming spiralled and bearing blind spikelets