Chemistry and biology of novel amine fungicides: Attempts to improve the antifungal activity of fenpropimorph

In spite of considerable efforts by many workers, there has been a lack of progress in the area of amine fungicides since fenpropimorph. Random synthesis of a large variety of different amine compounds, as well as intelligent structural modification of the lead structure fenpropimorph (well over 15 000 amines have been screened at BASF alone) have not led to a new market product so far. Further work has been focused on the reported mode of action of fenpropimorph, notably on the inhibition of the sterol Δ¹⁴-reductase. Although some doubt has to be cast on the hypothesis that fenpropimorph behaves as a sterol mimic, the concept of ‘high energy intermediate’ inhibitors has been employed successfully. Rational drug design of azasterol mimics has led to a number of very potent inhibitors of the sterol Δ¹⁴-reductase which also displayed high fungicidal activity in the greenhouse. Although many of these compounds are more powerful reductase inhibitors than fenpropimorph, under field conditions none showed significant advantages over this established fungicide. Most likely, fenpropimorph already exhibits the maximum fungicidal activity which can be attained by blocking the sterol Δ¹⁴-reductase. This would mean that, with the development of the ‘second generation’ amine fungicide fenpropimorph, this class of compounds has already virtually been optimized.     

Effects of 2-chloroethylphosphonic acid (Ethrel) on gooseberries

Solutions of 2-chloroethylphosphonic acid (Ethrel) up to 480 parts/million concentration were applied as foliar sprays to gooseberries (cv. Careless). Harvesting consisted of shaking the bushes by hand and collecting the dropped fruit. With increasing CEPA level pre-harvest fruit abscission increased and amount of fruit finally left on the bushes decreased. Splitting the application had the effect of reducing pre-harvest abscission. Berry size and total yield were not significantly affected by any of the treatments. Taste-panels did not detect any off-flavours in treated fruit. At hard green fruit stage, analyses for shear value, colour, acidity and soluble solids did not show any marked treatment effects. At ripe fruit stage, softening, yellowing and decrease in acidity were significantly greater for the 480 parts/million CEPA level than for the other treatments. There were no signs of phytotoxic or carry-over effects due to CEPA.