Vol. 51—1997 - NorthEastern Weed Science Society

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SIT~ PREPARATION WITH GRANULAR HEXAZINONE
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INCREASES STEM VOLUME OF
BAREROOT BLACK SPRUCE SEEDI..INGS
Phillip E. Reynolds' and Michael 1. Roden'
ABSTRACT
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Granular (P~ONONE lOG and 5G) and liquid (VELPAR L) hexazinone (l to 4 kg
ai/ha) were applied to a northern New Brunswick clearcut to reduce raspberry competition.
Treatment, using sJPdder-mounted herbicide application equipment, occurred in May and
September 1986, '-'lith planting of 2+2, bareroot, black spruce seedlings in June of 1986 and
1987. Seedling survival and growth were measured yearly for 5 growing seasons after
planting. By August 1991, hexazinone formulation did not affect raspberry control, seedling
survival, or growth, Raspberry cover for 3 treatments remained less than that for controls.
Survival of seedlings planted approximately 1 month after spring treatment was less than
controls, but seedling stem volume was greater than that of control seedlings for most
treatments. Survival and stem volume of seedlings planted 1 yr after spring treatment or 9
months after fall tteatment were greater than that of control seedlings for most treatments.
Best survival and frowth occurred for seedlings planted 1 yr after spring treatment. Fifthyear
stem volume Iwas best correlated (~ = 0.58 and 0.72 for spring and fall treatments,
respectively) with Iraspberry height, decreasing as raspberry height increased. We conclude
that the use of thel PRONONE lOG formulation offers operational advantages over the liquid
formulation. i
INTRODUCTION
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Red rasPbtfrry [Rubus idaeus L. var. strigosus (Michx.) Maxim.] is often the major
competitor threattiDing the establishment of spruce plantations in eastern Canada and in
northeastern Maiqe (12). Presently, few herbicides effective in controlling raspberry
competition are r~gistered for forestry use in Canada. Glyphosate (VISION), a conifer release
herbicide, is the nrimary herbicide used to reduce raspberry competition (3). Two site
preparation herbi~ide products that also provide effective raspberry control are registered for
silvicultural use i Canada. They include the liquid (VELPAR L) and granular (PRONONE)
formulations of h xazinone. Depending upon application rate, a typical aircraft can treat up
to 7 times more *ea per load with PRONONE than with VELPAR L in a water carrier (3).
Therefore, if both formulations perform equally, the use of PRONONE offers a significant
operational adva1tage that should result in considerable cost savings.
This wor~ reports raspberry control through 6 growing seasons after hexazinone site
preparation and $rvival and growth of black spruce fPicea mariana (Mill.) B.S.P.] seedlings
through 5 growiryg seasons after planting. Evaluations of PRONONE and VELPAR L efficacy
1. Canadian Forbst Service, 1219 Queen St. E., Sault Ste. Marie, Ontario P6A 5M7.
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