PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
Potato leafeating ladbirds
An example of a leafeating beetle
Scientific name
Potato ladybirds (Epilachna spp., Coccinellidae).
Host range
Mainly cucurbits, eg
Vegetables, eg all cucurbits especially
rockmelon also cucumber, marrow, pumpkin,
zucchini, related vine plants; bean, potato, tomato.
Weeds, eg nightshades (Solanum spp.), false
castor oil and paddymelon.
Description & damage
Both adults and larvae chew leaves.
Adult beetles are oval, strongly convex in
outline and about 6 mm long with chewing
mouthparts. They are mainly yellow-orange with
26 or 28 black spots, they fly well but do not fly
readily and are rather sluggish. Larvae, when
fully grown are yellow-green, and 6 mm long and
covered with long, black branching spines which
give them a ‘burry’ appearance.
Leaves. Adults feed on leaf uppersurfaces,
often starting at the margin while the larvae
generally feed on leaf undersurfaces. Leaves are
initially skeletonized but adults may also chew
holes right through leaving only the veins.
Severely skeletonized leaves wither, plants look
scorched. Young crops may be severely injured.
Fruit. Young fruits, eg cucurbits, may have parts
of their skin eaten. Injury reduces yield.
Diagnostics.
Do not confuse potato ladybirds with:
– Pumpkin beetles which have a limited host
range and 2 large spots on each wing cover.
– Common spotted ladybirds (Harmonia
conformis) which have only 18 spots are
beneficial and feed on aphids, scales and other
small insects.
– Other beneficial ladybirds which have fewer
spots or various patterns on their wing covers.
Do not confuse larvae with larvae of
beneficial ladybirds which are not ‘burry’.
List of suppliers www.goodbugs.org.au/
Damage by adults and larvae is distinctive, ie
skeletonisation.
Fig. 72. Leafeating ladybirds (Epilachna spp). Left: Typical skeletonization caused by leafeating ladybirds and
their larva. PhotoCIT, Canberra (P.W.Unger). Centre: Spiny larva and adult. Extreme right: Pumpkin beetle. All about 6 mm long.
Larvae of beneficial ladybirds
Fig. 73. Predatory ladybirds and their larvae feed on aphids, scales, mites and other insects.
Left: Common spotted ladybird (Harmonia conformis). Centre: Transverse ladybird (Coccinella
transversalis). Right: Larva of beneficial ladybirds. All about 5-7 mm long. PhotoCIT, Canberra (P.W.Unger).
104 Insects and allied pests - Coleoptera (beetles, weevils)