Eradication of over‐wintering mildew (Podosphaera leucotricha) in apple buds by nitrogen‐containing surfactants

Abstract

The eradicant activities of 24 nitrogen‐containing preparations, comprising primary, secondary or tertiary amines, amine acetates, diamines, amine oxides or quaternary ammonium salts, were assessed in trials with potted dormant apple rootstocks, heavily infected with the powdery mildew fungus Podosphaera leucotricha. The surfactants consisted of mixtures in which C12/C14 or C16/C18 alkyl or alkenyl compounds predominated. Of the amine acetates (at 50g litre−1), only the formulation containing C12/C14 primary amine acctates was considered worthy of further evaluation. Some amine oxides and quaternary ammonium compounds (at 35 g litre−1) were good eradicants and were as effective as ‘PP222’ a (nonylphenol‐ethoxylate mixture) which was included for comparison. All the compounds showing good activity contained one C12/C14 alkyl group whereas C16/C18 compounds, whether saturated or unsaturated, were relatively inactive. In a field trial, C12/C14 (dimethyl) amine oxide, C12/C14bis (2‐hydroxyethyl) amine oxide, and C12/C14 amine acetate (35 g litre−1) greatly reduced the amount of primary mildew on trees that were previously heavily infected, but there were signs that the fruit yield was reduced.

The effect of nonionic surfactants on the endogenous ethylene and chlorophyll content of Poa pratensis leaves infected with Bipolaris sorokiniana

“…Surfactants have also been shown to affect bacteria and fungi both favorably and adversely from and agricultural viewpoint. Certain surfactants control (Evans et al 1970) or eradicate (Hislop and Clifford 1976;Burchill et al 1979;Clifford et al 1981) apple powdery mildew and apple scab (Burchill and Swait 1977). Ortho X-77 however, added to certain fungicides increases fungal decay of Anjou pear (Spotts 1984).…”

“…There is evidence that besides reducing surface tension at interfaces, surfactants are capable of exerting biochemical effects upon living organisms (Parr and Norman 1965). Some favorable effects of surfactants have been reported: Tween 20 enhances apple thinning effectiveness of napthaleneacetic acid (NAA) and is in itself a mild thinning agent (Harley, Moon and Regeimbal 1957); polyvinyl alcohol increases rate of growth and chlorophyll content in peas (Czeczuga, Rejniak and Nowak 1960); Aqua-Gro stimulates shoot growth ot barley (Endo et al 1969); and various surfactants control (Evans et al 1970;Clifford and Hislop 1975) or eradicate apple powdery mildew (Hislop and Clifford 1976;Burchill et al 1979;Clifford et al 1981) and apple scab (Burchill and Swait 1977). Some adverse effects of surfactants include phytotoxicity to apples (Burchill et al 1979), sugarcane (Singh and Orsenigo 1984), and to the roots ot ryegrass, tall fescue, Kentucky bluegrass and creeping bentgrass (Endo et al 1969).…”