PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
Garden maggots
Scientific name
Minor pests, Order Diptera:
Bibionid fly (Bibio imitator)
Garden Soldier fly (Exaireta spinigera)
Host range
The adults are nectar-feeding and the maggots feed
on decaying organic matter, so are often found in
overwet compost heaps.
Description & damage
Gardeners find the wriggling masses of maggots
repulsive and usually want to get rid of them
immediately!
Bibionid fly. Female flies are about 12 mm
long, the middle of the head is red and the rest
black. The thorax and the base of the wings are
smoky-brown and the abdomen orange. Maggots
(larvae) are legless, dull gray-brown, and about
14 mm long when fully-fed. Their more or less
cylindrical bodies are covered with a number of
protuberances, those near the end of the abdomen
being the longest.
Garden soldier fly. Flies are about 13 mm
long and have a narrow glossy black body. Wings
are black and white, the hind pair being very long.
When at rest the legs are spread out and the wings
folded together down the back. Maggots (larvae)
are about 15 mm long when fully-fed and are dull
brown. Their broad, flattened bodies which
measure about 3 mm across bear a number of fine
hair-like protuberances.
Roots. Where plants are deep rooted, the
loosening of the soil by the maggots has little
effect on them. However, with shallow-rooted
plants some injury may occur due to the drying out
of the loosened soil.
General. The maggots look unsightly but often
do not seem to do much damage to plants. They
mostly indicate less than ideal growing conditions.
Diagnostics. The large size of the maggots,
their unattractive ‘hairiness’ and habit of clustering
together in overwet areas, make them easy to
recognize.
Pest cycle
There is a complete metamorphosis (egg,
larva, pupa and adult) with several generations
each season.
Conditions favouring
Overwet compost, excessive rains, poor drainage,
organic fertilizers.
Management (IPM)
Are you a commercial grower or home gardener?
1.Prepare a plan. There is limited need for an
IPM program in this case .
2. Crop, region. Recognize variations.
3. Identification of pest must be confirmed.
Consult a diagnostic service if necessary (page
xiv). Locate breeding areas and be familiar with
appearance of maggots, their life cycle and
habits.
4. Monitor pest and/or damage and record results
as recommended.
5. Thresholds. Have any aesthetic thresholds
been established? Do you need to calculate your
own threshold?
6. Action. Take appropriate action when any
threshold is reached or when shallow-rooted
plants are affected. Reduce moisture.
7. Evaluation. Review program to see if garden
maggots were controlled and recommend
improvements if necessary.
Control methods
Control of these maggots in the soil or compost is
not usually desirable or necessary.
Cultural methods. Reduce moisture in
compost and provide adequate drainage.
Sanitation. If it is thought they may be
disturbing the roots of shallow rooted plants, their
habit of clustering together makes them easy to
remove.
Fig. 48. Garden soldier fly (Exaireta spinigera).
Left: Adult (fly) about 12 mm long.
Center: Larvae (maggots) about 15 mm long.
‘Overwintering’
Various stages depending on the region.
Spread
By adults flying. Probably also by movement of
compost from place to place.
Insects and allied pests - Diptera (flies) 77