PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
Scientific name
The native fig longicorn (Acalolepta vastator),
Family Cerambycidae, Order Coleoptera. This
family belongs to one of the most common
groups of tree-boring insects in Australia. Other
insects also damage trees and shrubs by ‘boring’
into limbs and trunks, and occasionally roots, eg
Order Coleoptera.
Family Cerambycidae (longicorn beetles), eg
Citrus longicorn (Skeletodes tetrops)
Fig longicorn (Acalolepta vastator)
Pittosporum longicorn (Strongylurus thoracicus)
Poinciana longicorn (Agrianome spinicollis)
Family Curculionidae (weevils)
Family Bostrychidae (auger beetles)
Family Buprestidae (jewel beetles)
Family Scolytidae (bark beetles)
Family Platypodidae (ambrosia beetles, pinhole borers)
Order Lepidoptera.
Family Oecophoridae, eg fruit-tree borer (page 96)
Family Cossidae (wood moths)
Family Hepialidae (ghost moths)
Order Hymenoptera.
Family Siricidae (wood wasps, eg sirex wasp)
Host range
Most longicorn beetles only attack branches that
are already dead, or newly felled trees. Species that
attack living trees and shrubs may attack only one
type of plant or only a few different types.
Fig longicorn. Native and cultivated fig (Ficus
spp.), citrus, grapevine, passion vine and wisteria,
red cedar (Toona australis) and other plants.
Description & damage
Adult beetles are about 30 mm long and gray.
They have very long antennae (‘long horned’ or
‘ longicorn’ refers to these antennae). Males have
antennae about 3 times the length of the body. Fig
longicorns have a prominent spine on each side of
the thorax. Adults do very little damage, except
perhaps chewing a few new shoots or young bark.
Adults fly at night, may be attracted to house or
shed lights and may be seen resting by day in the
junction of main branches on infested trees.
Larvae grow up to 40 mm long, are legless,
creamy-white, club-shaped, glossy with a dark
brown head and well developed black jaws.
Compare with jewel beetle larvae which are
more cobra-shaped (page 103).
Pupae are whitish, about 25 mm long and
slightly flattened, broadest across the middle.
Trunks/limbs/roots. Fig longicorn attacks
young healthy citrus trees as well as older trees. It
is more prevalent after pruning especially in limes.
Internal damage is caused by larvae
chewing tunnels in the phloem and cambium
under the bark and may affect the sap flow to
roots and branches. Tunnels may extend up or
down for a metre or more in trunks, limbs and
roots. Tunnels are oval and tightly packed with
frass (sawdust). Branches may die.
Longicorn beetles
Common borers
External symptoms.
– Damage is more noticeable in smooth-barked trees.
Considerable damage may be done before cracking
bark indicates their presence.
– Damage is characterized by oval holes and dead
patches of bark which crack and eventually fall
away leaving the sapwood exposed. Unless
controlled, longicorn beetles can cause excessive
scarring of trees and often death by ringbarking.
– Sometimes larvae may be traced by the formation
of hard lumps along infested branches (frass and
gnawed wood mixed with gum).
– Trees are commonly attacked near the base of the
trunk due to damage from lawnmowers and cars.
– Branches may snap off. On some hosts exudation of
gum is the most obvious symptom.
Secondary damage. Under moist conditions,
longicorn damage may predispose trunks and
major limbs to secondary fungal rots. Injury by
longicorns on mango facilitates entry of
Botryodiplodia theobromae which can grow
beyond damaged tissue. Frequently more
advanced stages of longicorn damage are
associated with attack by other boring insects, eg
auger and bark beetles. However, they are much
smaller insects and produce round or ovoid holes
in the bark from which fine dry powdery sawdust
is extruded.
Diagnostics.
Longicorn tunnels are often difficult to
recognize. With beetle borers evidence of their
presence may be first indicated when droplets
of clear or yellowish gum exudes from the bark.
Oval exit holes of the adult are visible on
trunks or limbs in advanced infestations.
It may be necessary to get expert advice from an
arborist to confirm identity and get advice on
control. If not immediately obvious then
‘sounding’ will indicate the distribution of
damage (Mann, personal correspondence).
See also fruit-tree borer (page 96), termites
(page 178) and wood rot (page 361).
Lucid key www.lucidcentral.com/
Wood Boring Beetles of the World Part I:
Wood Boring Beetle Families.
Fig. 77. Fig longicorn (Acalolepta vastator). Left: Adult
about 30 mm long causes little damage, may feed on new shoots
or young bark. Centre: Larva about 40 mm long feeds internally
just below the bark. Photos NSW Dept of Industry and Investment. Right:
Larval damage by another species to eucalypt, bark removed,
oval tunnels packed with coarse frass. PhotoCIT, Canberra (P.W.Unger).
Insects and allied pests - Coleoptera (beetles, weevils) 111