Impact of physical characteristics of some mineral and plant oils on efficacy against selected pests

Abstract

Mineral oils have been historically favoured over plant oils for insect pest control in horticultural crops because of their greater efficacy. Recently the increased pressure for environmentally sustainable pest management strategies has renewed interest in the use of plant oils and also in the reasons for differences in efficacy between plant and mineral oils. Efficacy of canola and mineral oils were compared for two modes of action: asphyxia in control of Saissetia oleae on olives and as an oviposition deterrent in control of Phyllocnistis citrella on lemons. On olives both canola and mineral oil treatments significantly reduced the number of black scale in comparison to the control but mineral oil reduced the number of black scale significantly more than canola oil. When oils were applied to lemons as a preventative spray, concentrations of canola oil above 0.5% significantly reduced the number of P. citrella mines per leaf compared to the control and there were no significant differences between any concentration above 0.5% canola oil and 0.5% mineral oil. Canola oil applied at a concentration of 0.5% was significantly less effective than mineral oil applied at the same concentration. Efficacy of canola oil was found to be lower than that of mineral oil in all experiments, but the higher efficacy of mineral oil was more pronounced in suffocation of S. oleae than in deterrence of P. citrella oviposition. Our results indicate that even though canola oil has very different molecular structures than mineral oils the resulting physical characteristics of canola oil, primarily high boiling point and viscosity, may contribute to their lower efficacy against arthropod pests. However, low phytotoxicity of canola oil indicates that the chemical structure of molecules contained in canola oil had much more influence on processes on the plant surface than the physical characteristics of the oil.

Green peach aphid [Myzus persicae (Sulzer) (Hemiptera: Aphididae)] control using Brassicaceae ethyl ester oil sprays

“…At least a portion of the confusion is caused by the differing chemical and physical characteristics of the oils, and the relationship of these differences to pesticidal activity (Agnello ; Nicetic et al. ). For example, whether the oils are dominated by aliphatic, aromatic, saturated or unsaturated hydrocarbons will impact such variables as oil volatility and viscosity, which in turn control the mode of action.…”

“…; Nicetic et al. ). Historically, insecticidal plant‐oil sprays have been more expensive than comparable mineral‐oil spray formulations (Ebbon ).…”

“…; Nicetic et al. ), many published reports provide few specific details about the oils tested. Information on oil chemistry is important in establishing a link between oil chemistry and observed results, proposing mechanisms responsible for observed activity and comparing current results with past and future research findings.…”

“…In contrast to petroleum, plant oils are a renewable resource that can be utilized in a sustainable way. Studies have shown that emulsions of non-aromatic plant oils applied as sprays are effective in controlling a range of plant pests (Sams and Deyton 2002;Marcic et al 2009;Nicetic et al 2011). Historically, insecticidal plant-oil sprays have been more expensive than comparable mineral-oil spray formulations (Ebbon 2002).…”

“…As soybean-based oil sprays dominate the market (Sams and Deyton 2002), there is a need to compare the insecticidal efficacy of Brassicaceae ethyl esters with ethylated soybean oil. Although it has been shown that both the chemical characteristics of raw and processed oils influence arthropod control and phytotoxicity (Agnello 2002;Taverner 2002;Ouyang et al 2010;Nicetic et al 2011), many published reports provide few specific details about the oils tested. Information on oil chemistry is important in establishing a link between oil chemistry and observed results, proposing mechanisms responsible for observed activity and comparing current results with past and future research findings.…”