Biology Reference
In-Depth Information
1125
1124
1124
Broad mite (
Polyphagotarsonemus latus
) damage to
leaves of
Gloxinia
.
1125
Broad mite (
Polyphagotarsonemus latus
) damage to leaf
of
Fatsia
.
1126
1127
1126
Broad mite (
Polyphagotarsonemus latus
) damage to
flowers of
Cyclamen
.
1127
Bulb scale mite (
Steneotarsonemus laticeps
) damage to
bulb of
Narcissus
.
LIFE HISTORY
Bulbs are invaded in August and September. The mites
enter the spaces between the shrinking scales to feed on
the surface of the tissue, particularly around the neck
region. Breeding is continuous whilst conditions remain
suitable, the lifecycle (which includes egg, larval and
quiescent nymphal stages) being completed in about
two weeks at bulb-forcing temperatures. Mite
development is greatly protracted on infested narcissus
bulbs planted out in the autumn, but increases in
response to warmer conditions in the following spring
and early summer. At this stage the mites occur both
within the bulbs and on aerial parts of the plants.
However, by the time of lifting in mid-summer most
will have moved back into the neck region.
DAMAGE
Hippeastrum:
vegetative growth from infested bulbs
becomes spotted, and streaked or scarred with red;
flowers are malformed and may wither.
Narcissus:
infested bulbs lack vigour, producing weakened,
distorted, often sickle-shaped leaves and small,
malformed flowers. Emerging foliage tends to be bright
green, and lacks the normal greyish bloom. Later, the
leaves become streaked with yellow; they are also
scarred, and the leaf edges appear saw-like. Heavy
attacks result in a marked reduction in both crop yield
and flower quality; they also cause early senescence of
foliage and, sometimes, death of bulbs. Bulbs in store
become very dry and, particularly in the neck region,
display brown streaks of dead tissue if sliced across.
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