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Efficacy Assessment Starting in May each year, candidate spray blocks are monitored for evidence of needle mining and budmining to evaluate budworm abundance and assess the synchrony of populations with bud flush. In 2012, very high levels of both needle and budmining were observed throughout the Thompson Okanagan project area. There were often multiple larvae per shoot observed ranging from 2 nd instar to 5 th instar in the same 3-bud cluster. Given this observation, it was decided that significant larval assessments were needed pre- and post-spray to evaluate spray efficacy and follow the natural mortality of the budworm population. Thompson Okanagan Region A total of 270 trees, 185 in sprayed areas and 85 in untreated control areas, were sampled for budworm larvae pre- and post-spray (Table 6). Many spray blocks did not have comparable unsprayed areas nearby (e.g. similar elevation, insect density, development stage), therefore fewer unsprayed control areas were sampled. Pre-spray sampling was normally conducted on the day prior to treatment, with the exception of a few control areas, where pre-spray sampling occurred on the day of treatment. The density of larvae at the pre-spray sample time ranged from 36 to 348 larvae per m 2 foliage with an average of 211 larvae per m 2 foliage. Insect density was very high at all sites treated in 2012. Generally after spraying, the larval density was quickly and significantly reduced (Figure 3; Table 7). The four geographic areas highlighted in Figure 3 show a dramatic reduction in budworm numbers by the first post-spray sampling time within the spray blocks compared to unsprayed areas. There is always a natural reduction in density as the larvae mature, but one of the measurements of treatment efficacy is the rapid decrease in larval numbers afforded by B.t.k. application (Figures 3 and 4). Table 6. Number of trees sampled to assess western spruce budworm populations in control and treatment areas showing date of pre-spray sampling. Number of Trees Pre-spray District Location Treated Control sampling date Okanagan Glenrosa 15 15 June 19 Okanagan Sheep Creek 15 15 June 21 Okanagan McKinney 15 15 June 21, 22 Okanagan Orofino 15 N/A June 22 Okanagan Carmi 15 N/A June 20 Thompson Rivers Duffy 15 15 June 30 Cascades Swakum 10 N/A June 26 Cascades Kirby 10 10 June 26 Cascades Tolman 15 15 June 28 Cascades Sackum-1 15 N/A June 29 Cascades Sackum-2 15 N/A June 29 Cascades Pimainus-1 15 N/A June 28 Cascades Pimainus-2 15 N/A June 28 Total # Trees 185 85 Ministry of Forests, Lands and Natural Resource Operations, Kamloops, B.C. 48
Abbott’s corrected mortality compares the mortality caused by the B.t.k. (percent mortality) to the natural mortality observed in untreated control areas (Table 7). Percent mortality and Abbott’s corrected mortality are calculated as follows: % Mortality = (pre-spray density of live insects) - (post-spray density of live insects) x 100 (pre-spray density of live insects) Abbott’s corrected mortality (%) = (treated % mortality) - (untreated % mortality) x 100 100 - (untreated % mortality) This calculation ranged from 37% at the 1 st post-spray assessment in the Sheep Creek area to over 88% in the Duffy Lake area. Both the Sackum and Pimainus areas had very high budworm numbers at the time of spray but by the 2 nd post-spray assessment, Sackum had 84% larval mortality and Pimainus had over 98% larval mortality (Table 7). Populations in the Tolman spray block decreased so drastically after spray compared to the control that no 2 nd post-spray sample was taken (Figure 3). The majority of larvae were 3 rd instar with a good complement of 4 th instar on the Tolman spray block when treated. The lower elevation control site had an equal distribution of 3 rd , 4 th and 5 th instars (Figure 5). The graph in Figure 5 clearly shows the development shift in the Tolman control site to predominantly 4 th instar and 5 th instar larvae by the 1 st post-spray assessment coupled with the drastic population decline in the spray block. Due to the extended cool, wet weather in May through June 2012 larval development was slow but the very high larval numbers caused significant feeding damage to buds and new foliage before the majority of the population reached 4 th instar. At the pre-spray sampling time 81% of insects sprayed were 3 rd or 4 th instars with over 50% still 3 rd instar (Figure 6). By mid-July when the 2 nd post-spray sample was conducted in most locations approximately 64% of budworm were 5 th or 6 th instars (Figure 6). If spraying had been delayed to allow for the insects to develop further (typically peak 4 th instar larvae are targeted) then the defoliation in blocks would have been unacceptable. Clockwise from above: Snakeflies (Raphidiidae), coneworms (Dioryctria pseudotsugella), and sawflies (Neodiprion) are commonly encountered when conducting larval sampling. Ministry of Forests, Lands and Natural Resource Operations, Kamloops, B.C. 49
Page 1 and 2: 2012 Overview of Forest Health Cond
Page 3 and 4: In t r o d u c t I o n This report
Page 5 and 6: Table 2 continued. Area summaries f
Page 7 and 8: So u t h e r n In t e r I o r ov e
Page 9 and 10: Attack in young lodgepole pine stan
Page 11 and 12: A total of 116,012 hectares of high
Page 13 and 14: we S t e r n he M l o c k lo o P e
Page 15 and 16: BI r c h le a f MI n e r, fe n u s
Page 17 and 18: th o M P S o n ok a n a g a n re g
Page 19 and 20: Aspen decline syndrome became more
Page 21 and 22: Defoliators Western spruce budworm
Page 23 and 24: Defoliators Western spruce budworm
Page 25 and 26: Conifer Defoliators Western spruce
Page 27 and 28: A Douglas-fir Drought-Decline Compl
Page 29 and 30: Bo u n d a rY tSa Bark Beetles Moun
Page 31 and 32: cr a n B r o o k tSa Bark Beetles M
Page 33 and 34: go l d e n tSa Bark Beetles Mountai
Page 35 and 36: ca r I B o o re g I o n Su M M a r
Page 37 and 38: Douglas-fir beetle continued to be
Page 39 and 40: Defoliators As expected, western sp
Page 41 and 42: Thompson Okanagan Region The Thomps
Page 43 and 44: Table 2. List of western spruce bud
Page 45 and 46: Hiller spraying B.t.k. on budworm b
Page 47: Kootenay Boundary Region A total of
Page 51 and 52: Figure 5. Density and distribution
Page 53 and 54: 2012 Population Monitoring - Result
Page 55 and 56: Above: Lucy Stad receiving budworm
Page 57 and 58: One of the cancelled spray areas in
Page 59 and 60: In the Thompson-Okanagan Region, we
Page 61 and 62: Figure 9. Average number of western
Page 63 and 64: There is an ongoing study to calibr
Page 65 and 66: Larval density ± SEa b Percent mor
Page 67 and 68: Table 19. Total number of larvae pe
Page 69 and 70: Table 21. Average number of Douglas
Page 71 and 72: This stand has records of defoliati
Page 73 and 74: References Garbutt, R. 1992. Wester
Page 75 and 76: Be a r IM Pa c t S o n gr o w t h o
Page 77 and 78: To better understand the progressio

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