Dormant or semidormant treatments often are used to control the various species of aphids that are troublesome to the hardy fruits. They may be applied with the object of killing either the overwintering eggs or the newly hatched aphids on the opening buds. Conventional spray oils are not particularly effective aphicides in either case. In the Pacific Northwest green-tip or delayed-dormant applications of oil are suggested for the control of fruit aphids.

Growers in the East rely on dormant applications of dinitro insecticides to destroy the eggs or on the inclusion of nicotine sulfate or parathion in the delayed-dormant spray. Apparently there is little relationship between paraffinicity and the response of aphid eggs to oil sprays. If anything, the correlation lies between response and the aromatic content of oils. It is well known, for example, that aphid eggs are highly susceptible to such aromatic products as cresylic acid and the tar oils. From this one might conclude that there would be an advantage in using oils of high aromatic content, that is, having low U. R. values. Unfortunately, such oils apparently cannot be depended upon alone to control aphids; furthermore, their use must be restricted to dormant applications.

The older types of summer oils have declined in popularity. Much of this situation can be attributed to their incompatibility with fungicides and other insecticides. Sulfur has long been the stumbling block to the more extensive use of summer oils in the Eastern States. Serious direct foliage burn or delayed leaf drop may result from the use of oil and sulfur on the hardy tree fruits. Similar harmful effects have been noted with DDT and oil combinations.

No very definite specifications have been established for summer spray oils. A product meeting the following specifications should prove satisfactory for use in the East: A narrow-boiling- range product having Saybolt viscosity at 100 F. of 65-70 seconds, a minimum U. R. of 92 percent, and an A. P. I. gravity of 33. Such an oil would be used at a 1-percent concentration to combat summer infestations of mites, the cottony peach scale, and, combined with nicotine sulfate or rotenone, the pear psylla.

The use of oil sprays in the future depends on several considerations.

Most of the objections to them revolve around unfavorable plant responses. If safer oils could be produced, particularly for use on the more sensitive plants, the use of oil should increase. It should be possible to produce safer and more efficient oils synthetic Oils and special fractions of petroleum, for example.

Oils are less toxic than many other insecticidal materials to man. Their relative safety in that respect recommends them for wider use.

Insects have shown a disturbing ability to develop resistance to some insecticides, but so far not to oils. The way oils kill insects and mites, apparently through physical means, merits attention; it may prove to be a valuable quality in the future use of chemical treatments for the control of pests.

P. J. CHAPMAN is professor of entomology, and head of the division of entomology at the New York State Agricultural Experiment Station at Geneva, a unit of Cornell University. A native Of California, he was trained at Stanford University, Oregon State College, and Cornell University. He was granted a doctor's degree from Cornell in 1928. From 1923 to 1928 he engaged in extension activities at Cornell and from 1928 to 1930 served as entomologist of the Virginia Truck Experiment Station at Norfolk.

L. A. RIEHL is an assistant entomologist of the division of entomology at the University of California Citrus Experiment Station at Riverside. He was trained at the University of California at Berkeley and at Iowa State College, which ,granted him a doctor's degree in 1942. From 1942 to 1945 he was employed by the Rockefeller Foundation and served as a consultant on insect-borne diseases to the Surgeon General, United States Army. For those services he was awarded the bronze star and the medal of the United States of America Typhus Commission. From the Egyptian Government he received the Order of the Nile (Chevalier) and the Gambia Eradication Medal.

G. W. PEARCE in 1951 was appointed chief of the chemistry section of the technical development services in the Communicable Disease Center of the United States Public Health Service in Savannah, Ga. From 1930 to 1951 he was a member of the staff of the New York State Agricultural Experiment Station at Geneva. He holds three degrees from Pennsylvania State College. Dr. Pearce has worked on investigations of insecticides and fungicides, especially their analysis and chemistry in relation to their use on fruits.