Vol. 15—1961 - NorthEastern Weed Science Society

176.
Perennial weeds, tncludil10 :;rasses, bindweed, dandelion, plantain,
carrot and New England aster were numerous in plots rototilled in 1959 but
not in 1960.
None of the weeds common to both control and treated plots showed
evidence of residual Simazine or Atrazine beyond large and Vigorous plants
of dandelion. These were often darker green than normal. This C0101' may
be more nearly the result of release from competition than a specific
effect of the herbicide.
Residual action of Simazine or Atrazine did not appear to be severe
enough to eliminate plant growth or re-invasion of treated plots by annual
and perennial veeds ,
In other tests re-invasion of treated areas by quackgrase has, been
retaJ:ded for a year or more. Evergreen nursery crops such as Taxus; arborvitae
and juniper, treated as established plan~s navo continued to grow
wi thout obvious or prolonged injury follo'Winl;; use of Simazine and Atrazine
in amounts or 5 to 10 pounds of active ingredient per acre. The combination
or the herbicide and cultivation technique lIlE\Ywell be adequate for
practical purposes of control for quack-grass end some other perennial weeds
in plantings of established evergreen trees and shrubs. Other practical
uses would be cleaning up rough,hod prior to planting ground covers wllere it
is desirable to have two or more years of minimum weed growth for maximurr.
rate of establis~lLlent of clumps or potted planting units of ground cover.
Renovation of wee~ stands of roses, peonies and other ornamentals is Q
thirti possibility. Ti1e continued effectiveness of control from the combination
of herbicide and cultivation is important as a means of.' reducing
t.le surface movement, of.' herbicide on slopes due to rain or meltinG snov,