Dispersal and resource use by the lesser grain borer (LGB, Rhyzopertha dominica) in southern NSW Mark Stevens Principal Research Scientist NSW DPI, Yanco biosecurity built on science Cooperative Research Centre for National Plant Biosecurity
Objectives Quantify dispersal capability of LGB in SE Australian agricultural landscapes. Screen non-grain food sources for their ability to support LGB development. Collect field samples of plants that support LGB development and try and isolate LGB from them. Project duration: Budget:
9½ months $77,764 biosecurity built on science
Dispersal capability I Validation of fluorescent powder marking using double-marked LGB released and recaptured at 100m into propylene glycol. 1. Marked LGB stay marked. 2. No powder transfer to wild beetles in collection containers.
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Dispersal capability II Medium range quantitative dispersal.
Release station Lindgren funnel trap biosecurity built on science
Dispersal capability II Medium range quantitative dispersal. 8 traps at 1,000 m radius positioned by GPS. 10,000 LGB placed in release station (4 batches over 8 days, recovery every 2 days). Traps emptied and pheromone dispensers replaced every 4 days until 14 days after final release. biosecurity built on science
Medium range quantitative dispersal 5,690 LGB actively dispersed from the release station. 3,855 LGB caught in traps, of which 80 were marked.
1.4% recovery of marked LGB at 1,000m Different grid designs make comparisons with overseas studies difficult - but this seems high relative to studies in the USA. Maximum known distance for LGB dispersal from other studies is 3.6 km (3 LGB of ~ 64,000 released).
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Dispersal capability III Short-range quantitative dispersal.
Traps in concentric circles, equally spaced on perimeter, 100 & 200m radii with plans to extend further. Problem – beetles from weekly releases were surviving in the area for too long; marked LGB dispersed and recovered
2000 dispersed recovered
1800
250 200 150
So we changed to three alternating colours of marking powders.
100 50
20 0
0
0 1
2
3
4
5
6
7
week
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Short-range quantitative dispersal. Mean recovery from 8 traps at 200m not much higher than from the same number of traps at 1,000m 3.0
Marking powder effect? Too early to tell.
2.5
% recovery
2.0
1.5
1.0
0.5
0.0 100
distance (m)
200
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Host plant suitability I • • • • •
Wheat, sorghum and maize standards plus three test materials per experiment. 15 g sample size. 10 female & 5 male LGB < 4 days adult age, recovered after 3 weeks. Weekly monitoring and removal from 42 to 77 days, then final count at 105 days. 30oC, 65% RH, 15L:9D.
Why? 1. What is the best standard? 2. Is one standard enough? 3. How long does it take for the first F1 adults to appear on a REALLY POOR host? 4. How much replication is necessary to separate a non-host from a bad one? Not just about immediate answers, but building a better procedure for future work.
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Host plant suitability I Host
Material
Total LGB recovered (SE)
# of replicates producing LGB
Days to first emergence detection (range)
♀ pronotal width (SE), mm
♂ pronotal width (SE), mm
Experiment 1 Wheat
seed
237 (19.9) a
4
42
NM
NM
Sorghum
seed
247 (7.4) a
4
42
NM
NM
Maize
seed
158 (10.6) b
4
42
NM
NM
A.baileyana
seed
4 (1.3) c
3
60 (48 – 77)
NM
NM
A.cultriformis
seed
0
0
-
-
-
B.populneus
seed
0
0
-
-
-
Experiment 2 Wheat
seed
211 (19.4) a
4
44 (42 – 49)
0.792 (0.004) a
0.797 (0.004) a
Sorghum
seed
234 (13.1) a
4
47 (42 – 49)
0.793 (0.004) a
0.799 (0.005) a
Maize
seed
124 (3.2) b
4
47 (42 – 49)
0.768 (0.006) b
0.767 (0.007) b
P.canariensis
fruit
55 (7.2) c
4
66 (63 – 70)
0.741 (0.004) c
0.739 (0.005) c
fruit (rind)
0
0
-
-
-
fruit
0
0
-
-
-
C.sinensis O.europaea
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Host plant suitability I Moderate hosts (40 - 60 LGB /rep.) Canary Island Date Palm fruit, English Oak acorns. Poor hosts: (< 10 LGB / rep.) Cootamundra Wattle, Flinder’s Range Wattle, Capeweed flowers/seeds. Non-hosts: (0 LGB) Citrus, olives, Knifeleaf wattle seeds, Kurrajong seeds. Faster screening protocol: • single grain standard, 3 replicates, 105 days, assessment at end only. • same exposure to parent LGB. • screening of 10 additional materials underway. No native species yet identified as moderate or good hosts. High oil content seems to preclude LGB development.
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Host plant suitability II â&#x20AC;˘ Field-collected plant samples. â&#x20AC;˘ Sieving, incubation at 30oC for 8 weeks, sieving, then Tullgren funnel extraction.
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Recoveries from field collected plant samples
None so far.
Thousands ex Canary Island date palm
One individual ex Canary Island date palm (only 260g DW of material so far extracted)
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Thank you ď&#x201A;§ For more information, please email mark.stevens@dpi.nsw.gov.au ď&#x201A;§ .... or talk to me afterwards ....
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Host plant suitability I
R.dominica adults (mean cumulative)
300 Wheat Sorghum Maize P.canariensis
250
A A
200 150
B 100 C
50 0
40
50
60
70
80
90
100
110
days biosecurity built on science
Pheromone dispenser activity decline r 2= 0.34
'fixed' trap as % of 'renewed'
100
80
60
40
20
0 1
2
3
4
5
6
7
8
9
10
days since establishment biosecurity built on science