Abstract

The herbicide 2, 4-D was applied post-emergently in a field where the herbicide was applied for the past 40 years. The treatments included spraying 2, 4-D isooctyl ester (62% EC) at 0, 0.6, 1.2, 2.4 and 3.6 kg/ha. The treatments were arranged in a completely randomized Latin Square Design with five replicates. Soil samples were collected from two field sites: site 1 where the herbicide was historically applied annually and site 2, a nearby field where the herbicide was never applied. Soil samples from each site were placed in pots in the greenhouse. The herbicide was applied post-emergently to weeds from both the sites at rates described above. The results indicated that the following weeds tolerated the highest rate of herbicide application: forked mouse-ear chickweed, Cerastium dicotomum L. cone catchfly, Silene conoidea L. and cow cockle, Vaccaria pyramidata Medik. This is the first report on 2, 4-D-tolerant Caryophyllaceae weed species.