Sigastus Weevil Pest Information and Management Options

AUSTRALIANmacadamia
SOCIETY LTD
FACT SHEET 12
Sigastus Weevil Pest Information and Management Options
1. What to look for
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Look for nuts on the ground with ‘chew’ marks on them
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Sigastus Weevil lays eggs into nuts of varying size and age (young nutlets up to
shell hardening). Once the eggs are laid the female causes the nut to fall off the
raceme by chewing on the stalk of the nutlet.
The photos illustrate a Sigastus Weevil infected nutlet (Photo 1) and the Sigastus
Weevil Larvae (Photo 2).
Sigastus Weevil feeds on developing nutlets that have not yet reached shell
hardening stage. Nutlets that have reached shell hardening have a greatly
Photo 1 – Typical Sigastus Weevil damage
reduced risk of Sigastus Weevil damage.
2. Why is Sigastus Weevil damage occurring this season?
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Abandoned & untreated orchards are the major source of the
pest
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Long flowering season with range of crop stages
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Sigastus Weevil pupae are killed by sunlight (solarisation). As orchards get older and crowded, less and less sunlight
reaches the orchard floor, hence creating a more suitable environment for the Sigastus Weevil.
Warm winter months
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The 2013 flowering season has been an unusually long one,
Photo 2 – Sigastus pupa shot from within a macadamia nut
stretching over many months (April/May through to September/
October in many regions). This has resulted in a wide range of crop development stages (match head, pea size and full
size) occurring within the same tree at the same time. This has inadvertently provided a food source over a longer
period of time for the Sigastus Weevil, which has led to an increase in the Sigastus Weevil populations.
Dark orchards
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Sigastus Weevil will breed up on abandoned macadamia orchards
and then fly to neighbouring orchards. If you have abandoned
macadamia orchards near your orchard you are at a higher risk of
Sigastus Weevil damage.
Sigastus Weevil lifecycle, like many other insects, is governed by the temperature. The warmer the temperature the
quicker the lifecycle. The 2013 winter temperatures were very mild, resulting in an increase in Sigastus Weevil
populations early in the season.
Native vegetation
o Sigastus Weevil is known to breed on Brush Cherry (Syzgium austral) which is a native rainforest tree, and fig trees
(Fiscus sp). If you have native rainforest and native vegetation within, surrounding or close by to your orchard you are at
a higher risk of Sigastus Weevil damage.
AUSTRALIAN MACADAMIA SOCIETY LTD | FACT SHEET 13 – Sigastus Weevil Pest Information and Management Options
3. What level of damage can occur from Sigastus Weevil?
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Previous research conducted by QDAFF researcher Dr Harry Fay estimated potential crop loss from Sigastus
Weevil to as high as 30%.
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To view this article go to http://era.deedi.qld.gov.au/543/1/Fay_sigastus-sec.pdf
4. Where has Sigastus Weevil been found?
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Reports of Sigastus Weevil damage across all growing regions (QLD and NSW) have been received.
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The highest levels consistently reported are in the Clunes and Eureka regions of the Northern Rivers, NSW.
5. How can Sigastus Weevil be managed?
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Do not rely on chemical control
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Orchard hygiene is critical
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As Sigastus Weevil develops on the fallen nut, it is
VITAL to destroy fallen nut during the season.
Mulching fallen nuts will culturally reduce the
Sigastus Weevil populations.
Sunlight (solarisation)
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Currently we have no registered controls for this pest
for the industry. Please consult with your pest scout
for advice. The most suitable means of managing
Sigastus Weevil is with cultural control options
(Orchard hygiene and solarisation)
Photo 3 – A Sigastus Weevil on a nut in husk with damage on the husk
Sunlight will kill the Sigastus Weevil larvae.
In orchards where sunlight is still reaching the orchard floor, sweeping and mulching of fallen nuts into the centre of the
row (where the sunlight is) is recommended.
In dark crowded orchards it is recommended that the fallen nuts be harvested and exposed to sunlight outside of the
orchard.
Monitor lifecycle
o If you find infected nuts (damaged as seen in photos
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above) it is recommended that growers collect several
nuts and incubate them to track Sigastus Weevil
development over time.
Store the nuts in a plastic container with
flyscreen/gauze or mesh cut into the container
somewhere to allow oxygen into the container and
label the container with the pest and the date.
Store the container in a cool open area that has
ambient temperatures and is not in direct sunlight. It
is important that the container is stored in an area
that is representative of the orchard (cool, dark). Do
not store on the window sill of a closed shed. That will
be a hotter and brighter climate than within your
orchard.
Photo 4 - Incubation container. Note the mesh sides and the information
written on the top of the container.
*The expected development time from egg to adult is 45–60 days. The day the Sigastus Weevil hatches within the
incubation container is an indication of the hatch time within the orchard. This can be used to track and predict the time
that peak Sigastus Weevil damage will occur and allow you to undertake appropriate management methods to reduce
damage in a timely manner.
AUSTRALIAN MACADAMIA SOCIETY LTD | FACT SHEET 13 – Sigastus Weevil Pest Information and Management Options
6. Report Sigastus Weevil damage
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Growers are asked to report Sigastus Weevil damage to the AMS or the NSW DPI. The information we are
seeking is:
i. Your location (region)
ii. Low, medium or high pressure
If you do have Sigastus Weevil damage, please email this information to [email protected]
or [email protected] or [email protected] .
The information gathered this season will help to make an informed assessment of the level of damage
occurring, the economic impact and the need for R&D on managing Sigastus Weevil in the future.
Contact the AMS
Address: 113 Dawson Street, Lismore NSW 2480 Australia
Phone: 1800 262 426 (Australia only) or +61 2 6622 4933 (international)
Email: [email protected] Website: www.australian-macadamias.org/industry
AUSTRALIAN MACADAMIA SOCIETY LTD | FACT SHEET 13 – Sigastus Weevil Pest Information and Management Options