here. - Ministry of Forests, Lands and Natural Resource Operations
here. - Ministry of Forests, Lands and Natural Resource Operations
here. - Ministry of Forests, Lands and Natural Resource Operations
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Abbott’s corrected mortality compares the mortality caused by the B.t.k. (percent mortality) to the natural mortality<br />
observed in untreated control areas (Table 7).<br />
Percent mortality <strong>and</strong> Abbott’s corrected mortality are calculated as follows:<br />
% Mortality = (pre-spray density <strong>of</strong> live insects) - (post-spray density <strong>of</strong> live insects) x 100<br />
(pre-spray density <strong>of</strong> live insects)<br />
Abbott’s corrected mortality (%) = (treated % mortality) - (untreated % mortality) x 100<br />
100 - (untreated % mortality)<br />
This calculation ranged from 37% at the 1 st post-spray assessment in the Sheep Creek area to over 88% in the<br />
Duffy Lake area. Both the Sackum <strong>and</strong> Pimainus areas had very high budworm numbers at the time <strong>of</strong> spray but<br />
by the 2 nd post-spray assessment, Sackum had 84% larval mortality <strong>and</strong> Pimainus had over 98% larval mortality<br />
(Table 7). Populations in the Tolman spray block decreased so drastically after spray compared to the control that<br />
no 2 nd post-spray sample was taken (Figure 3). The majority <strong>of</strong> larvae were 3 rd instar with a good complement <strong>of</strong><br />
4 th instar on the Tolman spray block when treated. The lower elevation control site had an equal distribution <strong>of</strong> 3 rd ,<br />
4 th <strong>and</strong> 5 th instars (Figure 5). The graph in Figure 5 clearly shows the development shift in the Tolman control site<br />
to predominantly 4 th instar <strong>and</strong> 5 th instar larvae by the 1 st post-spray assessment coupled with the drastic population<br />
decline in the spray block. Due to the extended cool, wet weather in May through June 2012 larval development<br />
was slow but the very high larval numbers caused significant feeding damage to buds <strong>and</strong> new foliage before the<br />
majority <strong>of</strong> the population reached 4 th instar. At the pre-spray sampling time 81% <strong>of</strong> insects sprayed were 3 rd or<br />
4 th instars with over 50% still 3 rd instar (Figure 6). By mid-July when the 2 nd post-spray sample was conducted<br />
in most locations approximately 64% <strong>of</strong> budworm were 5 th or 6 th instars (Figure 6). If spraying had been delayed<br />
to allow for the insects to develop further (typically peak 4 th instar larvae are targeted) then the defoliation in<br />
blocks would have been unacceptable.<br />
Clockwise from above:<br />
Snakeflies (Raphidiidae), coneworms (Dioryctria<br />
pseudotsugella), <strong>and</strong> sawflies (Neodiprion) are commonly<br />
encountered when conducting larval sampling.<br />
<strong>Ministry</strong> <strong>of</strong> <strong>Forests</strong>, <strong>L<strong>and</strong>s</strong> <strong>and</strong> <strong>Natural</strong> <strong>Resource</strong> <strong>Operations</strong>, Kamloops, B.C.<br />
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