Cinidon-ethyl (Lotus (R)): Studies on the mode of action and selectivity and behaviour in combination with auxin herbicides

The isoindoldione cinidon-ethyl is a new herbicide which selectively contro ls Galium aparine and other dicot weeds in cereals when applied post-emerge nce at a field rate of 50 g a.i. ha(-1). Studies on the mode of action and selectivity of cinidon-ethyl in Galium aparine, Solanum nigrum and on wheat , as a the tolerant crop species showed that the herbicide strongly inhibit ed protoporphyrinogen IX oxidase (Protox), a key enzyme particularly involv ed in the synthesis of chlorophyll. However, protoporphyrin IX accumulates only in the green tissues of the weed species which generates active oxygen in the presence of light. Subsequently, formation of stress ethylene, etha ne evolution from membrane peroxidation and tissue desiccation and complete necrosis within a few days are induced. Radiotracer studies revealed that cinidon-ethyl is effective through contact action in the green tissue of th e weeds. The mechanism of selectivity is based upon a more efficient metabo lism in the crop species. Cinidon-ethyl used in combination with auxin herb icides such as dichlorprop-P (Duplosan(R) DP) improves their systemic actio n synergistically, particularly at low temperature. It is hypothesized that cinidon-ethyl interacts with the auxin partner at the mode of action level which includes in both cases ethylene as a phytohormonal factor.