Some Factors Influencing the Ovicidal Effectiveness of Saturated Petroleum Oils and Synthetic Isoparaffins1

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Abstract
The ovicidal effectiveness of highly refined narrow boiling range petroleum oils and synthetic isoparaffins was investigated under laboratory conditions against eggs of the oriental fruit moth, Grapholitha molesta (Busck). Test oils included fractions which were naphthenic, paraffinic, and isoparaffinic in character; their molecular weights ranged from 226 to 352 with 50% boiling points (760 mm mercury) from 560° to 688° F. The major objective was to determine the relationship of volatility at approximately 80°F. to ovicidal efficiency. Eggs deposited on a glass surface were treated with dyed oil by a settling tower technique. Oil deposit was spectrophotometrically determined. Rate of volatilization was measured by periodically weighing oil deposits remaining on aluminum foil. Within limits, it was found that an inverse relationship exists between ovicidal efficiency and volatility. Ovicidal efficiency increases as volatility decreases. This relationship indicates that volatility is the factor which influences the ovicidal efficiency of oils falling below a molecular weight “zero” of around 320. Among heavier oils efficiency is affected by molecular configuration, with efficiency increasing as the percentage of the carbon atoms present in the form of chains as against ring structures is increased. This relationship was best demonstrated in comparing isoparaffinic products with petroleum fractions. Pearce & Chapman (1952) have revealed certain basic relationships between ovicidal efficiency and the physical and chemical properties of saturated hydrocarbon oils. With eggs of the European red mite, Panonychus ulmi (Koch), and the oriental fruit moth, Grapholitha molesta (Busck), they established that ovicidal efficiency increases with increasing molecular weight and with the 50% boiling point; also that maximum ovicidal efficiency is attained at a molecular weight of about 320 and a 50% boiling point (760 mm. mercury) of about 670° F. In addition they showed a relationship between molecular configarution and ovicidal efficiency, namely that efficiency increases in proportion to the percentage of carbon atoms that occur in the form of chains as against ring structures. Thus efficiency was found to be a function of paraffinicity.

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