Js. Fletcher et al., POTENTIAL IMPACT OF LOW-LEVELS OF CHLORSULFURON AND OTHER HERBICIDES ON GROWTH AND YIELD OF NONTARGET PLANTS, Environmental toxicology and chemistry, 15(7), 1996, pp. 1189-1196
The influence of low application rates of chlorsulfuron on the growth
and reproduction of four taxonomically diverse plant species (canola,
smartweed, soybean, and sunflower) were examined. Exposures examined r
anged from 1 x 10(-3) to 8 x 10(-3) of the recommended field rates for
cereal crops and were approximately 1,000 times less than the highest
exposure recommended by the U.S. Environmental Protection Agency. Eac
h species received a single application at one of three different stag
es of reproductive development. Effects were determined by measuring t
he height and yield of mature plants. The comparative effects of four
different herbicides (atrazine, chlorsulfuron, glyphosate, and 2,4-D)
were determined in the same manner by exposing each test species to a
single low dose at one of three critical stages of reproductive develo
pment. Chlorsulfuron reduced the yield of all plants tested, with the
amount of reduction depending on the time and rate of application. Mos
t noteworthy was its influence on canola and soybean, in which at crit
ical stages in development, applications of 9.2 x 10(-5) and 1.8 x 10(
-4) kg/ha, respectively, reduced seed yields (dry wt) to 8 and 1% of t
hose of controls without causing a significant change in vegetative gr
owth. These low application rates are within the range of reported her
bicide drift levels and suggest that chlorsulfuron may cause severe re
duction in the yields of some nontarget crops if they are subjected to
exposure at critical stages of development. Application of other herb
icides at comparable rates and stages of plant development had no infl
uence on either canola or soybean.