Vol. 16—1962 - NorthEastern Weed Science Society

These tests show once aaaiJithe need for ecmplete frills in dormant
season cl:I"emi-"th1nn1ngin Nort.be..-te:rn United states. They also demonstrate
no advantage tor ~.' over esters or 011 alone in dormant
season work.
431
Conifers
In 1957, a preliminary report (2) was made concerning dormant
eeaaon application of und11.~: 2,4-D amine in partial cuts for chem:i..
th1nn:1ng pine plantations. Briefly this report stated:
1.. In red and Scotch piXIe pl.a.Utations, trees 3-5" d.b.h.
received, 2 or 3 cuts per tree.. Each cut received 3-4 mJ..
of chemical.
2. For red pine treated in November and ~ch, the terminal
leader and uppermost whorl of lateral branches died back
the follow1ng June; the whole tree was top-killed by the
end of sUIlllller.
3., For Scotch pine, death of trees was sJ.()wer; edge trees with
large crowns sometimes recovered.
4.: Presence ofa few dead red pine trees ~acent to treated
trees suggested caution in recormnendiqg the new treatment.
!
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Subsequent red pine growth studies have eSt' :blished the probable
reason tor death of untreated·· trees in the plan :tion as a combination
of drought e.nd shallow soil 'which predisposed t weaker trees to suecessful..
bark beetle attack. S1m:iJ.ar bark beetJ.ei damage has been found
on numerous red pines on poor sites in recent y$rs.
In the past five years, applica.tion of UDi~uted 2,4-n amine
in partial cuts has been made in several. plantat\Lons of moderate size
to test the general utility of this method of chemi-thinning. These
treatJ!'StXts are described in Table 2. '
Nearly all trees in these stands were top-klJ.led by the end of
the graw:l.ng season following tfeatment. Exce:ptibns were hemlock, which
was not killed, and sUllllllertreatments of Scotch ~d red pine, which
resulted in slow kill over .most Of .. two growing s.asons. Slow kill
was observed occasiona1]y in treu, with large,c~s and in trees
with fewer than one cut per two inches of di8iJiet'r.