As. Felsot et al., BIOMONITORING WITH SENTINEL PLANTS TO ASSESS EXPOSURE OF NONTARGET CROPS TO ATMOSPHERIC DEPOSITION OF HERBICIDE RESIDUES, Environmental toxicology and chemistry, 15(4), 1996, pp. 452-459
In regions of highly diversified agriculture, herbicides used in one f
ield may not be compatible with crops growing in nearby fields. Injury
to nontarget crops may occur from drift or localized atmospheric tran
sport of herbicide residues. Pea, bean, and corn seedlings have been u
sed as sentinels to detect atmospheric deposition of trace residues. S
eedlings were exposed at various locations throughout south central Wa
shington and exchanged on a weekly basis with a new set of plants. Pla
nts were returned to a lath house and observed over 3 weeks for develo
pment of symptoms indicative of probable exposure to four classes of h
erbicides-sulfonylureas, phenoxyacetates, aminophosphonic acids, and b
ipyridiliniums. The most frequently observed symptoms on sentinel plan
ts were chlorotic spots on the upper leaf surfaces; such symptoms were
created under controlled conditions by exposing plants to aerosols of
the sulfonylurea (SU) herbicide chlorsulfuron. For 3 years, the great
est incidence of probable SU symptoms was detected during April; howev
er, occurrence of symptoms was not correlated with periods of maximum
use of SU herbicides on wheat in the region. The results suggested a g
eneral atmospheric loading of herbicides with occasional deposition, r
ather than point source drift. Further tests are needed to quantitate
the exposures of sentinel plants and determine if chlorotic spots are
associated with adverse physiological effects.