Willow Sawfly Management Trials - Weeds Australia

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10Table 2: Survival of Tube-Stock Planted at Three Trial Sites in Winter 2008Site and Species Common Name Survival atApril 2009Survival atApril 2010Happy ValleyEucalyptus camaldulensis river red gum 80% 68%Acacia dealbata silver wattle 89% 75%Acacia melanoxylon blackwood 94% 94%Callistemon sieberi river bottlebrush 96% 89%Melicytus dentatus tree violet 73% 53%Kunzea ericoides burgan 94% 81%Overall Survival: 88% 78%Kiewa RiverEucalyptus camaldulensis river red gum 100% 100%Acacia dealbata silver wattle 98% 96%Acacia melanoxylon blackwood 93% 93%Callistemon sieberi river bottlebrush 100% 98%Melicytus dentatus tree violet 93% 86%Bursaria spinosa sweet bursaria 95% 86%Overall Survival: 97% 94%Campaspe RiverEucalyptus ovata swamp gum 89% 83%Eucalyptus viminalis manna gum 87% 71%Acacia dealbata silver wattle 77% 57%Acacia melanoxylon blackwood 90% 85%Acacia retinodes wirilda 96% 79%Carex appressa tall sedge 56% 56%Overall Survival: 84% 73%1.3.3 Plant Growth (Tube-stock)1.3.3.1 Happy Valley SiteThose plants which were closest to the river were flooded on one or two occasions in spring andearly summer 2009, indicating that the site was not moisture limited early in the season.Plants at this site had been severely affected by browsing in the 2008/09 season and averageplant heights had not increased for any species except blackwood (Ede et al. 2009). Browsingdamage was evident again in 2009/10, although it appeared to be occurring at a lower intensity.<strong>Weeds</strong> had grown up in the plots around the plants and in some cases, these weeds may haveprovided some protection against browsing, particularly the thistles.Despite this browsing, average plant heights did increase through the 2009/10 season (Table 3) asregrowth from browsed stems grew more strongly. For all species, average heights increased by
50% - 100% between December 2009 and April 2010. As a result of this growth in the latter partof the season, all species recorded an overall increase in average plant height from plantingwhich ranged from 24% for river red gum through to 456% for blackwood (Table 3).One river red gum plant grew very strongly at this site, and by April 2010 was 2.5 m tall. Thisplant was protected from browsing by a fallen branch which surrounded it on all sides. Thegrowth of this individual does indicate that strong plant growth would be possible at this site inthe absence of browsing pressure. Removing this individual from the dataset results in an averageplant height for the remaining river red gums of 57.7 cm in April 2010, which is only slightlytaller than the average height of this species at planting (54.5 cm), indicating that this species hasbeen severely affected by the browsing pressure.A small number of plants, including other river red gums, acacias and a river bottlebrush, weremore than 1 m tall when measured in April 2010, but the tallest of these, a silver wattle at 1.53 mtall, was almost one metre shorter than the protected river red gum.In addition to browsing, future plant growth at this site is likely to be limited by herbicidedamage observed in April 2010. Information from the land-owner indicated that spraying hadoccurred in the period just prior to trial monitoring, but that every effort was made to avoid theplants in the trial. It is likely that some plants will recover as damage was not severe on all plants,but others may not survive.111.3.3.2 Kiewa River SiteAt the Kiewa River site, plants continued to grow strongly in the 2009/10 season with severalriver red gum and silver wattle trees reaching more than 3 m in height by the end of the season.The tallest tree, a silver wattle, was estimated to be 5.5 m tall in April 2010. Because the heightsof the tallest trees were not able to be accurately measured, the height data included only theshorter trees which decreased the average heights presented in Table 3 for these two species. Forthe remaining four species, heights increased 3-5 fold between planting and April 2010.River red gum, silver wattle and blackwood were all significantly taller than river bottlebrush,tree violet and sweet bursaria at this site in December 2009 (Table ii, Appendix 1).As a substitute measure of growth, assessments of dbh were made on the larger trees inDecember 2009 and then again in April 2010. For river red gum the average dbh increased from1.5 cm to 2.5 cm over that period, while for the silver wattle trees the average dbh increased from2.4 cm to 3.4 cm.Most plants at this site were healthy when measured, although some insect damage was evidenton a limited number of individuals. Some plants were also affected by weed competition, beingovergrown by grasses, thistles and other herbaceous weeds, with some particularly affected bybindweed (Convolvulus spp.).A limited amount of natural regeneration occurred in two plots at the site, with one self-sownacacia and four eucalypt seedlings observed. In April 2010, these plants ranged in height from1.3 – 2.9 m.
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 and 12: At the Happy Valley and Campaspe Ri
Page 13 and 14: Planting and sowing were undertaken
Page 15: 91.3 Results1.3.1 Willow Sawfly Pop
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

Willow Sawfly Management Trials - Weeds Australia

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