University of California

Effect of oil spray on California red scale at various stages of development


Walter Ebeling

Author Affiliations

Walter Ebeling was Junior Entomologist in the Citrus Experiment Station.

Publication Information

Hilgardia 10(4):95-125. DOI:10.3733/hilg.v10n04p095. April 1936.

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During several years of field investigation with oil sprays used against the California red scale, Aonidiella aurantii (Mask.), the writer has observed that often some insects may not have received a sufficient amount of oil to cause sudden death and that they may live for two or three weeks after other individuals have been killed. Where the lethal action is thus prolonged, the typical signs of death, such as dryness or discoloration of the body fluids, may not be definitely discernible until six weeks or more after the spray treatment. In many cases examinations of infested citrus groves a month after treatment with oil spray have revealed an unsatisfactory degree of control of the red scale; at the end of six weeks, however, the mortality of the insects was very much higher.

The work of (deOng, Knight, and Chamberlin (1927), p. 372) indicated that the lethal effect of highly refined oil sprays is the result of suffocation of the insect, but (Smith (1932)) has observed that often the oil does not reach the tracheae, and in that case death may be caused by a “prolonged impairment of physiological processes such as might be induced by the presence of oil in the scale covering or in contact with the derm of the insect’s body.” In cases in which the lethal effect is retarded because of incomplete suffocation, the appearance of the insect indicates that it has some oil in its body. Its scale covering is oily, and a certain amount of dust has adhered to the oil film.

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Ebeling W. 1936. Effect of oil spray on California red scale at various stages of development. Hilgardia 10(4):95-125. DOI:10.3733/hilg.v10n04p095
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