Agriculture Reference
In-Depth Information
sternal spatula
with an angular, distinctly bifid tip
(Fig. 246d).
white.
Larva
up to 4 mm long, creamish-white
and translucent, pointed anteriorly but blunt
posteriorly;
anal segment
with a pair of promi-
nent spiracles and distinct papillae.
Puparium
2.5 mm long, brown;
anterior spiracles
horn-like.
Family PHORIDAE (scuttle flies)
Megaselia halterata
(Wood)
Worthing phorid
Megaselia nigra
(Meigen)
A mushroom scuttle fly
This fly is often a serious pest of cultivated mush-
rooms, although the larvae feed only on fungal
mycelium and do not tunnel into the developing
mushrooms (cf.
Megaselia nigra,
below). Minor
attacks are of little or no significance but heavy
infestations can cause considerable yield loss.
The adult flies are sometimes a nuisance to pick-
ers; they may also inadvertently pick up spores of
Verticillium fungicola
on their bodies, and then
spread them from infected to previously healthy
mushroom beds.
Larvae of this generally abundant species tunnel
within the stipe and cap of wild mushrooms dur-
ing the late summer and autumn. Damage is of-
ten extensive
(Plate 6e)
and may be followed by
bacterial breakdown of the tissue. The larvae
also infest cultivated mushroom crops and, prior
to the introduction of modern cultural methods,
were often serious pests. The females deposit
eggs on the gills of mushrooms or on the casing
but, unlike the previous species, they will
oviposit only in daylight; attacks do not occur,
therefore, in blacked-out mushroom houses or
culture chambers, and this has led to a significant
decline in the importance of this insect. Adults
occur from June to December; they are mainly
black and slightly larger than those of
Megaselia
halterata
(above).
BIOLOGY
Adults occur during the summer and autumn,
and are sometimes very numerous in mushroom
houses, especially close to doors and lights. They
often gather in considerable numbers and make
characteristic jerky runs over the surface of
walls, trays and boxes. In mushroom houses,
most eggs are deposited in the casing material,
close to the tips of the rapidly developing fungal
hyphae, during the short period of mycelial
growth. Under normal casing conditions, the
eggs hatch in about 2 days and the larvae feed for
4-5 days before pupating; adults emerge 7-8
days later. In the lower temperatures associated
with spawn-running rooms, where eggs are also
deposited, development from egg to adult may
take about 2 months. The adult flies often
emerge in vast numbers from dumped mush-
room compost and sometimes invade nearby
dwellings; they may then cause considerable con-
cern to local residents.
Family SYRPHIDAE (hover flies)
Eumerus strigatus
Fallen
A small narcissus fly
Infestations of this generally common species
occur on narcissus and onion bulbs; roots of vari-
ous other crops, including cabbage, carrot, pars-
nip and potato, are also attacked. The larvae
feed gregariously and break down the invaded
tissue into a wet, greyish or blackish mass. The
pest is usually of secondary importance and typi-
cally invades unhealthy or previously damaged
plant material.
DESCRIPTION
Adult
brownish-yellow to reddish-brown, with a
hump-backed appearance;
antennae
short and
inconspicuous, with a distinctly swollen third
segment;
wings
1.5-2.5 mm long, without cross-
veins (see Fig. 96).
Egg
0.5 x 0.2mm, oval,
BIOLOGY
Adult flies occur in the early spring and are at-
tracted to rotting vegetative tissue. Eggs are then
laid, in batches, in suitable situations. The larvae
feed gregariously, hollowing out bulbs, tubers
