Vol. 51—1997 - NorthEastern Weed Science Society

182
during the st or 2nd growing seasons after treatment demonstrated that both formulations are
effective in controlling raspberry (13, 14). Seedling mortality increased through August 1989
for all trea ents, but was highest for seedlings planted 1 month after spring treatment (l5,
17). The mber of seedlings overtopped by raspberries declined over time, and differences
in overtop ing between treated and control seedlings were generally significant (16). By
August 19 9, most seedlings planted into herbicide treatments were taller than surrounding
raspberries whereas most control seedlings were shorter. Overtopped seedlings generally
exhibited or growth morphology (i.e., tall, skinny and twisted stems), were characterized by
chlorotic 0 numerous brown needles, and frequently suffered extensive needle loss. In 1989,
the health f seedlings taller than surrounding raspberries, was better than that of seedlings
that remai ed overtopped (Reynolds and Roden, unpublished statistical data).
Ob ectives of this study were: (l) to quantify raspberry competition in treated and
control pl rs: (2) to investigate survival and growth of bareroot, black spruce seedlings
planted at ifferent time intervals after spring or fall site preparation with different
formulatio s of hexazinone; and (3) to determine the best time of treatment and hexazinone
formulatio to achieve optimal seedling survival and growth during the establishment phase of
the plantat on.
METHODS
Site and e
erimental desi n
Th clearcut treatment area is located on J.O. Irving, Ltd. property near St. Leonard
(approxi tely 47°17' latitude and 67°43' longitude), in northwest New Brunswick at
approxim tely 240 m elevation. Soils are fine-textured, including loams, silty loams, clay
loams, sil clays, and clays. Mean sand, silt, and clay content of the soils is 29.7, 44.3, and
26.0%, re pectively. The duff layer varies from 3 to 11 em, organic matter from 2.4 to
25.5%, C C from 6.2 to 18.9 meqllOO g, and pH from 3.6 to 4.9. Annual precipitation
averaged 08 em, falling mostly as rain between May and October. Approximately 7, 5, 14,
18, II, a 5 em of rain was received each month, respectively, from May through October
1986. So 1 freezing occurred in early November 1986.
e site was clearcut in the fall of 1984 and mechanically site prepared in the summer
of 1985, sing a 125-ton Letourneau crusher to fell snags and break up residual logging slash.
Prior to bing harvested, the site supported a stand consisting of approximately 45% balsam
fir Abies balsamea (L.) Mill.], 35% black spruce, and 20% hardwoods composed primarily of
aspen P ulus tremuloides Michx.) and a variety of other northern hardwoods. Following
site prep ation, portions of the site not treated with hexazinone, were rapidly revegetated
with a de se cover of raspberries.
A 1 treatments were replicated 4 times on 0.5 ha plots using a completely randomized
layout of treatment plots. No significant differences in soil characteristics (i.e., pH, organic
matter, C C, % sand, % silt, % clay) were observed among treatments. All plots were
separated by 25 m buffers.