Vol. 16—1962 - NorthEastern Weed Science Society

239
Weed Control and Residual Effects of Simaz1ne and of Atrazine
Applied to Soil Prior to Planting ~$ery Stock
A. M. S. Pridham, Cornell University
Simazine and atrazine have both been used in wettable powder and
granular formulation in two series of tests since J.951in plantings of evergreens
(~ and Thuja) in Cornell nursery areas.
The 1957 series of plants were rototilled and replanted in 1959. Rototilling
has continued throughl961. The originaJ. plan of the plots is no
longer visible from the weed growth or lack of it. 'Evergreen crop gro'l-rth is
normal.
Red l~idney beans were planted. in JUly 1961 in soil that had not been
treated with triazines as well as in the old plot areas. Germination and
growth were similar in both sections of the field, indicating that the soil
was essentially free of triazines in the area of the bean root zone.
A second nursery area was treuted in 1959 to till sod before planting
nursery crops. Simazine and atrazine were applied JUne .21 and 22, 1959 at
two rates, 5 and 10 pounds of active ingredient framlCeach of two formulations
(wettable powder and granular) as well as surfaoe· application and in-­
corporation of the herbicide by rototilling 3-4 inches immediately following
planting.
During the summer of 1959 timothy sod was eliminated from treated plots
except when simazine was used on the· sod surface in granular form without
rototilling. Dandelion was st1muJ.e.ted in she and dark green color. Bindweed
was released but re-invasion by seedling weeds was of minor proportions.
In 1960 half of each 10 x 10 I plot was rototilled and the nursery indicator
plants, Ligustrum oValifolium, EuOnymus fortunei, Pachysandra terminalis
and Forsythia intermedia were planted in the freshly rototilled soil. The
indicator crops oats, buckwheat and later red kidney beans were also planted.
Typical growth response of these test crops to triazines was found only
at the 10 pound level. Not all plants of an indicator group responded within
a plot. Growth of beans was normal in soil samples taken to the greenhouse
in fe.ll 1960 for testing indoors under soil moisture at field capacity from
intermittent misting.
June observations in 1961 indicated very little residual response in
test crops. EuOnymus fortunei foliage in granular simazine plots at 10
pound level showed yellow margins on a few leaves in young growth typicaJ.of
triazine injury in this and other crops including ~ and Taxus.
A single strip was rototilled in June 1961 at right angles to 1959 and
1960 rototilling. Red kidney beans were planted in a single row through each
rototilled strip. Growth and color of the red kidney beans in the untreated
controls and in the triazine plots were very similar. Samples of 10 bean
plants at flowering stage were cut at the soil level and green weight taken