Agriculture Reference
In-Depth Information
Family PYGMEPHORIDAE
(red pepper mites)
Pygmephorus mesembrinae
Canestrini;
P. sellnicki
Krczal
Red pepper mites
BIOLOGY
Colonies of this unusual mite occur in the shelter
of leaf sheaths or bud scales. The females feed on
plant tissue and on hyphae of the fungus
Fusarium poae,
with which they may form a
symbiotic relationship. The immature stages
(eggs, larvae and nymphs) develop within the
swollen, sac-like body of the female. Adults
eventually merge as the hysterosoma splits
open and the maternal mite dies. There are
several generations in the year, the mites
being most numerous in the late summer and
autumn.
Red pepper mites are frequently abundant in
mushroom beds but are not regarded as harmful
to crops, although their presence often causes
concern. The mites breed within decompos-
ing mushroom composts, where they feed on
the weed mould
Trichoderma; Pygmephorus
sellnicki
is capable of surviving on a wider range
of weed moulds than
P. mesembrinae,
including
Humicola
and
Monilia.
Female red pepper mites
deposit large numbers of eggs, and these hatch
into small 6-legged larvae which develop to
adults through an active 8-legged nymphal and a
quiescent resting stage; the whole cycle is usually
completed in a matter of days. Adults are wedge-
shaped, 0.25 mm long and stout-legged; the legs
and body bear feathery setae. Populations in-
crease extremely rapidly under suitable condi-
tions and, soon after casing, the mites may swarm
over the beds and developing sporophores in
reddish-brown masses; populations then decline
rapidly. The mites do not cause damage to the
sporophores, or reduce cropping, even when
present in considerable numbers.
DESCRIPTION
Adult female
0.19 x 0.07mm, shiny hyaline-
whitish;
hysterosoma
elongate but globular and
up to 3 mm or more in diameter when bloated
with developing young.
Adult male
0.15 mm
long and stout-bodied;
head
very small.
Family EUPODIDAE
Penthaleus major
(Duges)
Red-legged earth mite
This mite is associated mainly with cereals and
grasses but will also attack other plants, includ-
ing vegetable crops. They cause a general silver-
ing of infested foliage and, sometimes, withering
of leaf tips. Damage, which may result in patches
of poor growth, is most evident during the winter
months. Development of the mites is favoured
by cool conditions, and the life-cycle includes a
period of extended summer aestivation in the
egg stage. All stages of the mite occur during the
autumn and winter; unlike summer eggs, winter
eggs hatch in a few weeks. There are two genera-
tions annually. The mites (up to 1 mm long) are
globular but pointed posteriorly and vary in
colour from pale green to red or brownish,
with either green or red legs; characteristically,
the anus occurs on the dorsal surface of the
hysterosoma. Although a well-known pest in
Australia and North America, damage to crops
in Europe is less often reported. The name 'red-
legged earth mite' is also associated with a re-
lated species:
Halotydeus destructor
(Tucker), an
Siteroptes graminum
(Reuter)
Grass & cereal mite
Infestations of this widespread but sporadic and
usually minor pest are sometimes noted on
cereals (including wheat and barley) and
grasses. Affected plants are stunted and their
infloresences fail to emerge properly, becoming
distorted and silvery in appearance (a condition
known as 'silver top'). Attacks are usually
established in association with the fungus
Fusarium poae.
A similar relationship occurs on
glasshouse-grown carnation; this results in rot-
ting and death of the buds (a condition known as
'bud rot' or 'central bud rot'). Such attacks are
infrequent and usually initiated in the autumn
after a period of hot, dry weather.
