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Field Tests with Oil Sprays for the Prevention of Aphid-spread Viruses in Peppers. G. Loebenstein, Head, Virus Laboratory, The Volcani Institute of Agricultural Research, Bet Dagan, Israel; Miriam Alper(2), and S. Levy(3). (2)(3)Research Assistant, and Technician, respectively, Virus Laboratory, The Volcani Institute of Agricultural Research, Bet Dagan, Israel. Phytopathology 60:212-215. Accepted for publication 29 August 1969. DOI: 10.1094/Phyto-60-212.

Oil emulsions applied from emergence in the nursery were highly effective against aphid-borne cucumber mosaic virus and potato virus Y on peppers. Air-blast sprayings at concentrations of 1-2% were given in the nursery every 3-7 days, and in the field at weekly intervals with a concentration of 2.5%. In 2 consecutive years, oil sprayings suppressed virus incidence almost completely in autumn nurseries during periods with high aphid populations. In control plots planted from unsprayed nurseries, infection rates reached 50-60% as soon as 9 to 11 weeks after transplanting. Early infection in the nursery caused a complete failure of the crop, whereas protection afforded by oil sprays resulted in normally developed plants with high yields of 5,000-6,000 kg/1,000 m². Oil sprays similarly protected the nursery and young transplants of spring-grown peppers, increasing development and yields of the plants. Oil sprays were less effective against late infections of mature plants. Although infection was delayed, the increases in yields were small. For practical purposes, it seems sufficient to protect the nurseries or young transplants during the season of intense virus dissemination, and to discontinue spraying in the field.