Some Properties of Oil Emulsions Influencing Insecticidal Efficiency

Abstract

It is very difficult to isolate any one property of an emulsion and determine separately its action on insects. The physical and chemical properties of the oil, the kind and amount of emulsifying agent, and the stability of the emulsion are all so closely interlocked that one property usually cannot be varied without changing the others. There is good reason for believing that no two emulsions—and, very likely, no two lots of an emulsion made by the same formula—are exactly alike.

A quasi-static model of drop impact

“…When these two conditions are met, we expect A ≈ A (W e). Richard et al 16 found experimentally that A ≈ 2.6 for 1 < W e < 30, while the numerical models of Foote 13 and Gopinath and Koch 14 indicate that for W e < 1, A (W e) ∼ ln 1 W e . The linear spring model of Okumura et al 17 predicts A = 2.31 independent of W e, and thus must become invalid for sufficiently low W e. We expect the coefficient of restitution C R to depend most strongly on Oh, with C R → 0 as Oh → ∞ and C R → 1 as Oh → 0.…”

“…The impact of liquid droplets on solids is important in a variety of industrial and biological processes. Industrial applications include insecticide and pesticide design, [1][2][3] inkjet printing, 4 and fuel injection, as well as the design of airplane, ship, and windmill blades. 5 For many plants and small creatures, the impact and adherence of a raindrop can lead to tissue damage or other deleterious consequences, such as compromised photosynthesis in the case of plants and respiration in the case of insects; thus, the integument of many plants and insects is hydrophobic.…”

The Wetting of Insect Cuticle

“…The wetting of insect cuticle by liquids has received little attention in spite of the fact that the effectiveness of almost all contact insecticides depends upon it. Although a considerable amount of work has been done in the past few years upon the mechanism of wetting and spreading of liquids on solids, Stellwaag (1924), English (1928), Wilcoxon and Hartzell (1931) and O' Kane & others (1932) are the only workers who have studied the wetting of insects.…”

Effect of certain hydrocarbon oils on respiration of foliage and dormant twigs of the apple / by Victor W. Kelley.

“…That a light unsaturated oil affected respiration more than a light saturated one during both periods may indicate a greater chemical effect with light oils, but it can also be explained on a physical basis. According to English (1928), unsaturated emulsions are more stable than saturated. The greater effect of unsaturated oils may be due to their longer persistence in the emulsified condition, in which case their removal by evaporation would be delayed.…”

“…A large number of fruit buds were killed outright and many leaf buds on one-year twigs failed to start growth. English (1928) reported that the lower the volatility and the higher the viscosity of an oil, the more likely it was to cause injury, whether it was saturated or unsaturated. When the residue persisted, which was necessary for insect control, the degree of unsaturation became the most important consideration in plant injury.…”