Natural products as potential herbicide adjuvants: Citric acid esters and quercetin

With the addition of activator adjuvants, herbicides become more effective, whether the adjuvant increases absorption, prevents photodegradation or facilitates wetting. Citric acid esters have been shown to enhance herbicidal activity. Though the mode of action is not yet known, the structure of the citric acid ester is known to be related to their function. The structure-function relationship of citric acid esters, which vary in alkyl chain length, ethylene oxide number and number of chains, was examined. Ethylene oxide number, alkyl chain length and number of chains influenced adjuvant efficacy as well. Nineteen experimental adjuvants were evaluated in the greenhouse with five commercial herbicides on various weed species. Adjuvant efficacy was weed and herbicide specific for both the citric acid esters and the 19 experimental adjuvants.; Two naturally occurring, known UV absorbing compounds, carotenoids and quercetin were studied to determine if they could prevent photodegradation of cyclohexanediones herbicides. The herbicides BAS 620 and clethodim were determined to be photolabile. In addition, the UV absorbing compound quercetin was added to the spray solution, applied to the plants, and irradiated in the UV light chamber for 0, 1, and 3 hrs. When quercetin was added to the spray solution and subjected to UV irradiation, the rate of phototransfonnation of clethodim was decreased.