Vol. 15—1961 - NorthEastern Weed Science Society

more consistently effective than 5 lbs. AlAwettable powder formulations in
reducing stands of perennial grasses. Hedge bindweed developed in dense
stands in all plots from which turf was reduced by half or more.
The herbicides Simazine and Atrazine applied to turf without rototilling
or mechanically disturbing the soil surface resulted in appreciable reduction
in grass stand. Wettable powder formulations were consistently more
effective immediately following application in 1959 but were less effective
than granular formulations in the year following application, i. e. 1960
compared to 1959. Thus granular fo:rmulations in this test had longer or
gJ:"eater residual effect than wettable powder.
The most effective combination of treatments in the present experiment
is the combination of the herbicide followed at once by rototilling.
175.
Residual action of herbicides
The primary objective of rototilling in 1960 was to provide a seed bed
for test crops. These crops included buckwheat and oats. .'Both species of
the ornamental crops Ligustrum ovaUfolium and Euon;ymusfortunei are sensitive
to Simazine. They were set out bare root for maximumexposure of roots
to residual herbicide. Forsythia intermedia "Spring Glory and Pachysandra
terminalis were also included in fiel! planting.
In OCtober 1950 soil samples were taken and planted to kidney beans in
the greenhouse as a final bioass~ for residual effect of the herbicides
Simazine and Atrazine.
Observations made in early August on discoloration in the seedling
stage of buckwheat and oats or in the young foliage of Eu0D1InUSindicated
clear response only with Simazine at the 10 pound rate of the granular
formulation. Response to Atrazine was found in the 10 pound rate in the
twice rototilled plots for both liquid and granular formulations. Not all
plants of a kind in these plots showed response. Usually less than half of
the plants showed yellowing of seedling leaves only or of new foliage formed
after planting.
Later season results in November indicated less response except with
the Euon;ymus. Mature foliage of oats and buckwheat were normal. The test
plants grew essentially as well as the normal non-yellow controls. Seedling
beans showed no indication of abnOrmal growth in soil samples taken in
October 1960 after herbicide application in July 1959.
Residual action in cla;y loam ma;ybe effective in deterring immediate
regrowth of grasses. Bindweed and Canada thistle, dandelion, and plantain
appeared in 1959 and continued in 1960 unless rototilling was done. In
this case regrowth was reduced in amount or to seedling stage. Residual
action in 1959 or in 1960 was not adequate to prevent. the establishment
of annual grasses and other weeds.