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Identifying
characteristics-
Fungus Gnats-Adults
are slender with comparatively long legs and antenna. They are
grayish-black and about 2.5 mm long. Wings are clear with “Y” shaped
veins. They are weak fliers and often are found walking on soil surface.
The larval form, a maggot, has a shiny black head capsule and white body.
Mature larvae are about 5.5 mm long.
Shore Flies-
Adults are small 2mm, black flies. The adults have reddish eyes and gray
wings with clear spots. They are rapid fliers. Antenna are short; this is
a good way to distinguish them from fungus gnats (who have long antenna).
The larva has 2 spiracles (tail like projection) on the rear of its body.
The mature maggot is about 2.6 mm long.
Biology-
Fungus Gnats-
Adults and larvae usually inhabit moist, shady areas. Adults live about 1
week and the female can deposit 100 to 150 eggs in this time. The eggs
are laid in strings of 3 to 40 on soil surface. In greenhouse conditions,
the eggs hatch within 4 days of being laid. The larvae feed on root hairs
in the upper cm of media then work their way up into the plant stem. The
maggot will also feed on organic matter. After feeding for approximately
14 days, the maggot will pupate. The pupal case is made of silk and soil
debris. In about 3.5 days an adult will emerge.
Shore Flies-
Adults are commonly found in areas with algae deposits. Females deposit
eggs on soil surface. The eggs hatch in 2-3 days and the maggots begin to
feed on bacteria, yeasts, and diatoms found in the top surface of potting
mixes. The larvae mature in 3 to 6 days and then pupate. An adult will
immerge in 4 to 5 days and continue to feed on diatoms. They tend to stay
close to breeding sites.
Plant
injury symptoms-
Fungus Gnats-
Damage is first visible when plant health declines from maggots feeding on
plant tissue. Adults flying around are aesthetically not appealing.
Shore Flies- These flies do
not feed on any ornamental plant, but their excrement left on foliage is
unsightly. Adults flying around are undesirable.
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