Polyclonal antibody-based ELISA for triasulfuron

Sulfonylurea herbicides (Levitt 1978) such as triasulfuron (Logran~'), are widely used at very low application rates of 3-40 g/ha to control both broad leaved and grass weeds in cereal crops. Under certain conditions, e.g. alkaline soils and low rainfall, these herbicides can persist long enough to affect the growth of subsequent crops (Beyer et al. 1987). The problem can be particularly serious when broad-leaved crops, such as rapeseed, sunflower, grain legumes or field peas, are sown in rotation with cereals (O'Sullivan 19827 Brewster and Appleby 1983; Foy and Mersie 19847 Peterson and Arnold 1985). This is a major factor limiting the use of high value rotation crops in many areas of the cereal belt in Australia. Growth of a sensitive crop can be severely reduced by triasulfuron levels as low as i00 pg/g in soil. These concentrations are below, or at the very limits of detection of the HPLC and bioassay methods currently being used (Zahnow 1982; Iwanzik and Egli 1989). Enzyme immunoassays have been described for a number of herbicides and pesticides in recent years (Kelley et al. 1985; Jug et al. 1989; Schlaeppi et al. 1989; van Emon et al. 19897 Hall et al. 1990; Schlaeppl et al. 1992) and provide a versatile and sensitlve alternative to traditional methods. Here we describe a sensitive, easy to operate, and inexpensive competitive inhibition ELISA for reliable detection of triasulfuron in soils.