Fungitoxic and phytotoxic effect of some surface‐active agents applied for the control of apple powdery mildew

Abstract

SUMMARYMixtures of methyl esters of fatty acids (‘Off‐Shoot O’) and mixtures of fatty alcohols (‘Off‐Shoot T’), applied during the late autumn (November), eradicated apple powdery mildew (caused by Podosphaera leucotricha) from infected buds. Applications in the spring at bud‐burst were less effective.The autumn sprays caused little damage to the cultivars Bramley's Seedling, Cox's Orange Pippin and Golden Delicious but on Worcester Pearmain 50% of the buds were killed by a 5% Off‐Shoot O spray. The bud‐burst sprays were damaging and reduced yield on the Cox and Bramley trees.A 5% a.i. mixture of nonanol/lissapol applied to a range of commercial cultivars was effective in eradicating powdery mildew but was more phytotoxic than the Off‐Shoot compounds. Spraying Cox trees later in the winter failed to reduce the damage.Eradication of the overwintering stage of the disease resulted in low spore concentrations during the following spring and early summer, enabling some economies to be made in the summer mildew fungicide programme.

Growth Response of Trichoderma Species to Organic Solvents

“…[3] Although some of alkanols are utilized in cosmetics (2-hexanol, 1-octanol, 3-octanol) they possess unpleasant odor, moreover, the homologues with short carbon chain exert significant toxic effect to vertebrates. Their growth regulatory effects are exploited in plant cultivation: [4] the 1-nonylalcohol elongates the dormancy of potato tubers [5] as well as retards the formation of powdery mildew disease syndrome on apple leaves, [6] while the 1-decylalcohol was recommended against pests of tobacco. [7] Nevertheless, despite of rapid deterioration in the environment [8] the toxicity limits range of their use.…”

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

“…Tween 20 is a mild thinning agent of apples (Harley, Moon and Regeimbal 1957); Ultrawet PR51 increases carrot yields (Seymour 1957). Certain surfactants are phytotoxic to apples (Burchill et al 1979), sugarcane (Singh and Orsenigo 1984) and to the roots ot ryegrass, tall fescue, Kentucky bluegrass and creeping bent grass (Endo et al 1969).…”

“…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).…”

“…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). Other adverse effects include increased fungal decay of Anjou Pear when Ortho X-77 is added to certain fungicides (Spotts 1984); changes in the bacterial population of soils where surfactants are applied (Hislop and Barnaby 1977); absence of earthworms in upper soil layers where didecyl dimethyl ammonium bromide (DDAB) is applied (Hislop and Barnaby 1977) and induced ethylene production and necrotic lesions when some of the Triton X-series of surfactants are applied to leaves of cowpea and sour cherry (Lownds and Bukovac 1983).…”