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Table 85
Neodipriotl {ecomei (Fitch). 327
Semi-operational aerial spray trials were conducted on a further four plantations with
a total area of70 ha. Lyophilized NPV-infected larval material was used at 5 x 10' PIBlha
and the emitted volume was 9.4l1ha. Larvae were mainly in the first and second instars,
with a few unhatched egg clusters present, at the time of application. When the final
survey was made 28 days after spraying, mortality ranged from 82 to 99%.
Ground spray trials were conducted by Ontario Ministry of Natural Resources staff in
five districts, and 88 plantations with a total area of 436.8 ha were treated entirely or
partially over a 47-day period. Insect development ranged from first and second instar in
the early treatments to fourth and fifth instar in the later ones (Cunningham & de Groot
unpublished).
Ground spray trials in Quebec in 1980
A mist blower was used to treat 12 red pine plantations when larvae were in the first and
second instars with 90% of the eggs hatched. The dosage was 5 x 10' PIBlha and two
application volumes were tested, 18.7 and 93.6I1ha. Better results were obtained with
the lower volume and 100% mortality was achieved 20 days after spraying. Thirty-five
days after spraying, 97% mortality was reached with the higher volume. Defoliation in
the treated plantations was negligible because of comparatively low larval population
densities (an average of 21 colonieS/25 trees on the high volume application and 8
colonies/l00 trees on the low volume application) combined with the effectiveness of the
treatments (Bordeleau unpublished).
Surveys of plantations aerially sprayed in Ontario in years following the year of application
In order to assess the durability of the virus treatments, surveys have been conducted
annually on all the plantations aerially sprayed experimentally in Ontario, which by 1980
numbered 15 (de Groot et al. 1979, Cunningham & de Groot unpublished). A summary
of these surveys is shown in Table 85. Although not all these plantations remained
Survey of plantations treated with NPV of redheaded pine sawfly, Neodiprion leeontei
(Fitch), in years following the year of application
Number of colonieS/l00 trees
Pre-spray
Year Plot estimate 1977 1978 1979 1980 1981
1976 1 118 0 0 0 0 0
2 176 0 0 0 0 0.75
3 346 0 0 0 0 0
1977 1 163 0 0 0 0.75
2 81 0 0 1.75 0
3 132 0 0 0 0.5
1978 255 0.5 0 0
2 174 2.5 1.25 2.0
1979 1 124 0.25 0
2 77 0 0.25
3 5 0 0
1980 1 52 0
2 173 0
3 225 0
4 25 0