Vol. 15—1961 - NorthEastern Weed Science Society

506.
HARJJ.rlOOD CONTROL WITHMIST BLCWERS
by
WillfaillP. HaOC~11"al\(fRObert S.Bond 2
Aerial applicatiOn
tit h8rbicid~.'torelease "conifers has been' eueeesaf'u1
in many ,Parts or,thecotmtry. BothfiJ;ted"!"wing aircraft and helicopters
have been uSed ,in thi~ vOrk~· Va;oious test'$ have, established spray formulations
ot 2,,4-];)and '2,4, ,-T'that are effective agafnSt hardwoods and do
little damage to conif~s if applied d:uring, the PFoper season. Spray mixtures
have 'ranged 'from, one to three ':poundS aoid equivalent (one quart low volatile
propylene glycol butyl .ether' ester:s) per acre 1:nvaJ'1ingamounts ot fuel oil
or water,- or· !U&lc>ll and' water. 'Applioations:have ranged from 21to 7 gal-:
lons of m1x~ "1'aore.'D&mag. to conifers. i~ .insignificant if applications&:t:'fmade,
a.tter' the newgrcswth has hardened cift ln late summer" and
ooncentrations aretlot'stronger"th&n two pounds acid equivalent per acre.
~~.' .: • 'l ' c " ~
'Aerial, applica.1ilOD!·coats range &om 1.-p1J.cation. Application b)" fixed-Wing airoraft on
large area" canbe acoomplished 'tdr, about ':wS.OOperaore. Helioopter application
on ~e areae eosts abOUt ~8'.OO per aCre.
Aerial appl1eattonof" herbteideshas manYadva,ntages of which we are all
aware, but it alaoh.&e' san.e disad,.:ntages; ."nnf't'-is so serious a problem
that aircra·f't a,pliea.tlOft of 2" 4-Dhaa been outlawed entirely, and strict
lirnitatt.onsbave been~placed on ground machines in'sc';'called tfbasard areas"
in California. Helicopter application in still'weather, using low concentration
ot herbicide and large droplet size, reduces the hazard of drift. Invert
emulsions ot 2, 4, S-T whioh make a thiok, creamy spray and reduoe drift are
available for field trials.
Interception of spray b)" the overstory beoomes a problem if the objective
is to control understory hardwoods. Overstory softwoods are not seriously
damaged by the spray, but a dense overs tory prevents good coverage of the
understory. Better foliage penetration is achieved by helicopter application
at slow speed to attain maximumbenetit from rotor prop wash.
Large areas must be treated to make aerial spraying economical" and all
hardwoods regardless of value on a treated area ma)" be killed or damaged.
Smaller areas may be sprayed by helicopter, but the oost per acre of marking
the areas to be sprayed inoreases sharply as the size of the areas decrease.
Other costs also inorease when ntanerous small areas are treated by helioopter.
1 William P. MacConnell" Associate Professor of Forestry, University or
Massachusetts, Amherst, Massachusetts.
2 Robert S. Bond, Instructor of Forestry, university or Massachusetts,
Amherst, Massachusetts.