Willow Sawfly Management Trials - Weeds Australia

28Table 9: Willow Tree Defoliation at Monitoring Sites in 2009/10 SeasonExtent of Tree DefoliationSite Willow Taxa Jan 10 Mar 10 Apr 10Baranduda Black 0% - 1 0%Beechworth Grey 0% - 0%Everton Black 70% 5% -Crack 95% 70% 70%Golden 100% 40% -Purple 5% 20% -Happy Valley Crack 1% - 5% 70% 90%Healesville Crack 0% 0% 0%Kergunyah S. x rubens 60% 50% 90%Kiewa Crack 0% 0% 0%Weeping 0% 0% 0%Leneva Crack 0% 0% 0%Pussy 0% 0% 0%Weeping 0% 0% 0%Tarago S. x rubens 0% 0% 0%1 Defoliation for some sites/taxa were not assessed at every monitoring point throughout the season2.3.3 Grey Sallow Defoliation at Happy ValleyAlthough low levels of willow sawfly have been present on grey sallow (S. cinerea) plants at theBeechworth Camp Ground site since the 2006/07 season (Ede et al. 2007), there has been noincrease in willow sawfly numbers over time at this site and no defoliation.At Happy Valley there are two grey sallow plants downstream of the monitoring site. InDecember, 5 minute counts were undertaken on these plants which found 36 larvae. Most of thelarvae were very small, but there were also appreciable numbers of fresh eggs, and one adult wasobserved at this time.By the time of the January assessment, these grey sallow plants had been defoliated by willowsawfly. Defoliation levels across the two plants were 60% - 80% and 107 larvae were foundduring a 5 minute count. In March, the defoliation of the two grey sallow plants was similar tothat seen in January, at 70% - 80%, but increased in April with one plant being >95% defoliated.This is the first recorded occurrence of willow sawfly defoliation of grey sallow in Australia.2.3.4 Extent of Tree DeathOverall between 2008/09 and 2009/10 there had been a slight decrease in the amount of livematerial on trees at Kiewa (Table 10). All trees at this site exhibited some level of small branch