Weed Biological Control Pamphlet
September 2008
BIOLOGICAL CONTROL OF BONESEED: BONESEED LEAF
BUCKLE MITE
Background
Boneseed, Chrysanthemoides monilifera ssp.
monilifera, is native to South Africa and has become
a significant environmental weed in Tasmania (Fig.
1), through its ability to invade native vegetation and
compete with the native flora. Native fauna may
also be affected by the loss of available habitat and
food sources. Boneseed, which is also a significant
fire hazard, is widely distributed around the north
and east coastal regions of the state. It has not
reached the limits of its distribution in Tasmania and
has the potential to invade extensive areas of the
coastline.
mass rearing and field release program is now being
conducted in Tasmania in an effort to permanently
establish this agent at selected sites that will not be
subjected to other control methods. These sites will
be used as nursery sites to enable collection and
transfer of colonies to new release sites.
Description
The boneseed leaf buckle mite, Aceria sp., belongs
to a family of mites known as the Eriophyidae.
Eriophyids are specialised plant-feeding mites,
characterised by being very small (even by mite
standards) and are visible only under high
magnification. The boneseed leaf buckle mite is
approximately 0.15 mm long and 0.05 mm wide with
an elongated worm-like body (Fig. 2). The mite has
four legs whereas most other mites have eight legs.
Figure 1. Infestation of boneseed, south-eastern
Tasmania (Photo: R. Holloway, TIA).
Because of its weed status, boneseed has been
approved as a target for biological control and a
number of agents that attack boneseed in South
Africa have been tested for their suitability and
safety to release in Australia. Four foliage feeding
biological control agents have been released in
Tasmania since 1991. Intermittent releases of the
black boneseed beetle, Chrysolina scotti, were made
between 1991 and 1993 and again between 1995 and
1996. The painted boneseed beetle, Chrysolina sp.
B, was released during 1995, the boneseed tip moth,
Comostolopsis germana, between 1993 and 1997
and the boneseed leaf roller moth, Tortrix sp.,
between 2000 and 2001. Despite repeated and often
large releases none of these agents established.
Natural enemies are suspected as a key factor in
preventing their establishment.
Originally from South Africa, the boneseed leaf
buckle mite, Aceria sp., was first released in
Tasmania in spring 2008. This followed tests by the
Department of Primary Industry, Victoria, which
showed that the species attacks only boneseed. A
Figure 2.
Scanning electron micrograph of
boneseed leaf buckle mite (Photo: Charnie Chamer,
ARC Plant Protection Research Institute, Pretoria,
South Africa and Alan Hall, University of Pretoria,
South Africa).
Life cycle
The leaf buckle mite passes through four
development stages consisting of egg, larva, nymph
and adult. Adults may live for several weeks.
Females may lay one or more eggs daily and
unfertilised eggs are likely to give rise to male
offspring only. The duration of the life cycle is
unknown but is temperature dependant and likely to
be comparable to that of other eriophyid mites i.e.
15-20 days in summer and longer in winter.
Impact
Eriophyid mites have piercing and sucking
mouthparts that are used to extract cell contents. All
eriophyid mites feed on plants and some induce
distorted growth such as galls which are localised
growth reactions of the host plant to mite attack.
The boneseed leaf buckle mite induces the formation
of specialised galls called erinea (pl.) or erinaeum
(singular).
Erinea consist of the abnormal
development of leaf hairs associated with a distorted
area on the leaf (Figs. 3 & 4). Production of erinea is
closely linked to plant growth; they are initiated by
the boneseed leaf buckle mite feeding on embryonic
leaves at the shoot tip. As the young leaf grows, a
colony of mites develops within each erinaeum.
Erinea are present on infested plants throughout the
year and new ones develop during boneseed growth
flushes. Erinea provide protection from predators
and weather extremes, a plentiful food supply and an
environment suitable for breeding. One to a few
erinea may develop randomly over the leaf surface.
It is not possible to forecast the impact of boneseed
leaf buckle mite on boneseed in Australia. Impact
assessments at field sites will be determined when
the mites have become well established. However,
it is expected that damage caused by the mite will
contribute to a significant reduction in boneseed
vigour. In South Africa, heavily infested boneseed
plants are unthrifty and appear to have lower growth
rates and reproductive outputs than uninfested plants.
Leaves may become severely distorted and plants
may become stunted due to a reduction of
photosynthetic tissue. Sometimes lateral buds are
each converted to a small erineum from which new
branch development is prevented.
Integrated control
It is important to remember that biological control
is a long-term process that will not, by itself,
eradicate boneseed. However, it is hoped that the
impact of biological agents in combination with
conventional methods could significantly reduce
plant vigour making boneseed easier to control as
part an overall integrated management plan. For
instance, if agents become established in areas where
large-scale clearance work is to be conducted, it may
be possible to retain some infested plants so that any
boneseed regrowth is recolonised by the agents.
Acknowledgments
Figure 3. Distorted leaf growth on boneseed leaves
caused by formation of erinea (Photo: R. Holloway,
TIA).
Department of Primary Industries, Frankston,
Victoria, supplied starter cultures of the boneseed
leaf buckle to TIA. Information on the biology of the
mite was provided by Jamie Davies and Tom Morley
(DPI Victoria). Funding of the boneseed leaf buckle
mite biological control program has been provided
by the Commonwealth Government through the
Defeating the Weeds Menace and Caring For Our
Country programs.
Further information
For further information on this project contact:
John Ireson
Tasmanian Institute of Agriculture,
13 St. John’s Avenue, New Town, 7008.
Phone: (03) 6233 6821; Fax: (03) 62782716
Email: [email protected]
Figure 4. Abnormal development of leaf hairs
caused by the leaf buckle mite (Photo: W.
Chatterton, TIA).