Vol. 15—1961 - NorthEastern Weed Science Society

515.
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Pine, hemlock, and epruce caught directly in the blast of the spray
and wetted to the point of run';'off were temporarily damaged. Needles
quicIdy browned, and the stemso.t: sane leaders and side branches browned
also. These trees were marked for obServation during the next growing
season. Little damage was obaerved at that time. Five softwoods were
recorded as damaged on the 72 'plots' measured. One of these had the terminal
killed. Most damage occurred in tight spots where the operator had to "bull"
his way through tangled underbrush and vines a.nd was more concerned with his
footing than with direction of the spray. Hemlock and spruce a.re more susceptible
to damage than pine. Damage to softwoods as a whole was very light;
none were more than 20% defoliated.
All the sites treated had sufficient hardwood control to release the
softwoods except Area 7, and even here 46% of the broadleaf trees were
severely damaged or killed. The lesser degree of control on Area 7 is
attributable to the size of the material treated. The crown canopy of the
forty-year old stand of pine and hardwoods was 40 to 50 feet above the
ground and for the most part beyond the effective range of the equipnent.
Good hardwood control
was achieved in other stands up to 30 feet in height.
In Area 7 under optimum conditions trees in excess of this height were killed,
but in general 30 feet seems to be the ceiling for satisfactory operation of
back-pack mist blowers currently available. Taller stands should be treated
from the air or with larger blowers. It is noteworthy that in Area 7 a very
high proportion ·(93%)of the tall brush was killed or severely damaged,
because here the mist was confined wi thin the stand under the crown canopy of
the trees overhead. Some of the shorter pines may have prevented penetration
of spray to the taller hardwoods in the overatory. Many of these hardwoods
had the lower branches killed or severely injured by the herbicide.
Reasonably good selectivity can be exercised with shoulder-mounted mist
blowers.. By shutting off the flow of spray, areas of desirable hardwoods as
small as one-tenth acre in size can be reserved in the midst of a large
treated area.. The larger truck or tractor mounted blowers are less selective;
helicopters are still less selective; and fixed-winged airoraft are the least
selective of all.
COST
Ninety-six acres were sprayed with the back-pack mist blowers at a cost
of ~>6.40 per acre using two machines and a three-man crew. The cost per acre
. would increase if a single machine were used.
Table 4. Per Acre Cost of Back-Pack Mist Blower Applications
of 2,l14, ,-os
Item
Cost
1 pound 2, 4, 5-0S acid equivalent (] ~:,45.00 per 5 gal. ... iftl2':"2'5
2*gallons of fuel oil © 20¢ per gal~ .45
labor costs: 3 men ;31;..'60.00 per day 3.23
Machine cost: operation (5¢), depreciation (3B~), maintenance (4~) .47
V 6..40
" 'G~9und application of herbicides by mist blowers to control hardwoods
should extend the use of chemical foliage sprays to areas where aerial
spraying is not possible or desirable.