Willow Sawfly Management Trials - Weeds Australia

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6season. This ensured that some trees were defoliated for the duration of the trial, regardless of thewillow sawfly activity.Artificial tree defoliation was achieved by stem injection, with the selected trees treated inDecember 2007 and left in situ throughout the trial. At the Happy Valley and Campaspe Riversites, eight trees were stem-injected while at the Kiewa River site, four trees were stem-injected(Table 1). The remaining trees were not treated.For the Happy Valley site, which had very low willow sawfly populations, it was anticipated thatthe stem-injected trees would lose their foliage while the non-injected trees would maintain fullcanopy cover throughout each growing season.At those sites with high willow sawfly populations, little difference was expected in canopycover between stem-injected trees compared with non-injected trees, as it was expected that alltrees would be defoliated for an extended period, particularly through the latter part of thegrowing season.1.2.5 Re-establishment of Native SpeciesPlots were established under the trees by determining the area of shade cast by the trees in themiddle of the day under high light conditions, when they had full canopy cover, prior to steminjection. The size of the plots was limited to the area under the canopy of each individual tree,with pairs of trees spaced far enough apart to minimise overlap of shade.Each plot was treated with herbicide in late autumn or early winter 2008, with additional weedspraying undertaken approximately two weeks prior to planting. No additional spraying wasundertaken at the sites, but some hand-removal of weeds occurred after planting. Those plotsselected for direct-sowing were cleared of all existing vegetation (both live and dead matter) andsurface soil by scraping with a rake-hoe, to provide an ideal seed-bed.The species selected for planting and sowing were locally indigenous riparian species. At theHappy Valley and Kiewa River sites, the six species used were a mixture of trees and shrubs,while at the Campaspe River site the sedge Carex appressa was also planted (Table 2). The seedmix used in the direct seeding was composed of the same species as the tube-stock at HappyValley, but additional species were included in the seed mix sown at Campaspe River.Tube-stock were hand-planted at spacing of 1.6 m x 1.6 m. The number of plants per plot rangedfrom 11 – 33, depending on plot size. The allocation of plant species to planting positions withinthe plots was haphazard, with the exception of the sedge at Campaspe River which was alwaysplanted at the riverside edge of the plot. All plants were watered-in and protected with a treeguard after planting. Plants at all sites were watered again on one or two occasions in springand/or mid-summer, depending on the patterns of local rainfall.Hand broadcasting was used to sow the seeds. Seeds of Acacia species were broadcast in the firstpass over a plot. The plots were then lightly raked and the remaining species were sown in asecond pass. The Acacia seeds had been pre-treated with heat prior to sowing.
Planting and sowing were undertaken at the Happy Valley and Kiewa River sites on 11-12 thAugust 2008 and at the Campaspe River site on the 24 th September 2008.71.2.6 MonitoringPlant heights were measured at the time of planting and again in December 2008, April 2009,December 2009 and April 2010, for all species except C. appressa, for which survival and healthwere recorded. At the Kiewa River site, some trees had grown to such an extent that it wasdifficult to measure plant heights during the second season. Measurement of the diameter atbreast height (dbh) was made on those trees in December 2009, as well as height measures, withdbh only measured in April 2010.The direct-seeded plots were assessed at the same time by undertaking thorough searches in six,1 m 2 quadrats which were randomly placed within each plot. The number of seedlings found inthe quadrats, and their heights, were recorded. The heights of seedlings which were foundelsewhere in the plots were also measured.The extent of tree defoliation and willow sawfly population levels were also assessed at duringeach site visit.On one occasion some months after planting, the light environment of each planting position forthe tube-stock was determined by measuring PAR (Photosynthetically Active Radiation). Thesemeasurements were made around midday on a clear, sunny day which had a day-length as closeas was feasible to the longest day (mid-December to early-January).Light measurements were also made in the direct-seeded plots on the same day, to give anestimate of the light environment across those plots. Light levels were assessed at six positions ineach plot, three of these positions were spaced evenly along the riverside edge of the plot, andthree were spaced evenly along the landward edge of the plot.A line quantum sensor (Apogee Instruments Inc.) calculated Photosynthetic Photon Flux Densityfrom 10 PAR sensors measuring over a 70 cm length. The output from the ten sensors wasintegrated to give a single reading. This instrument recorded the number of photons in the 400 –700 nm range of the spectrum in units of µmol photons per metre 2 per second. The range of theinstrument was 0 – 2,000 µmol m -2 s -1 .The PAR measurements for each position in both the planted and direct-seeded plots wereconverted to percentage of full light available at the time of measurement by dividing the data byPAR measurements taken in the open within the same time period. This standardisation allowedfor comparison of the data between plots and between sites, as it accounted for variations inavailable light at the time of measurement.1.2.7 Data AnalysisAnalysis of Variance (ANOVA) (GenStat 12.0, 2009; VSN International Ltd.) was used toanalyse data. A one way ANOVA was used to test for the effect of willow tree treatment on plantsurvival at each site, across all species.
Page 5 and 6: Table of ContentsSection 1: Managem
Page 7 and 8: 1Section 1: Management Trials1.1 In
Page 9 and 10: willows limit the light which is av
Page 11: At the Happy Valley and Campaspe Ri
Page 15 and 16: 91.3 Results1.3.1 Willow Sawfly Pop
Page 17 and 18: 50% - 100% between December 2009 an
Page 19 and 20: The tallest plants at this site in
Page 22 and 23: 161.3.6 Direct Seeding1.3.6.1 Happy
Page 24 and 25: 18Key Points: Willow trees were def
Page 26 and 27: 20B) BrowsingAt both Happy Valley a
Page 28 and 29: 22Plant growth is limited under the
Page 30 and 31: 24Section 2: Monitoring Willow Sawf
Page 32 and 33: 262.3 Results2.3.1 Willow Sawfly Po
Page 34 and 35: 28Table 9: Willow Tree Defoliation
Page 36 and 37: 30Key Points: Willow sawfly populat
Page 38 and 39: 32Section 3: Willow Sawfly Across A
Page 40 and 41: 343.2 Western AustraliaThe first re
Page 42 and 43: 36Appendix 1: Details of Statistica

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