DDT Preparations to Control Certain Scale Insects On Citrus

Publisher Website
Google Scholar
Abstract
Field expts. were made to determine the long-term effectiveness of DDT added to light medium spray oil and to kerosene in the control of the California red scale, Aonidiella aurantii, and the yellow scale, A. citrina. Technical DDT was dissolved in the petroleum at 2 conc.; 4.7 wt. % and 9.4 wt. %. Counts were made of the number of scales per fruit before treatment and the number of scales per fruit at the time the results of the expts. were checked. 40 fruits were examined on each of 10 trees in each plot. If the population of red scale 4-14 months after treatment in the plots sprayed with regular spray oil at 1.75% conc. be designated as 100, the following figures represent the relative populations of red scale after treatment in the DDT-petroleum-sprayed plots: 1.75% spray oil plus 4.7% DDT, 65; 1.75% spray oil plus 9.4% DDT, 53; 3% kerosene plus 4.7% DDT, 173; 3% kerosene plus 9.4% DDT, 37; 3% kerosene plus 9.4% DDT with 2 treatments, 13. DDT added to spray oil decreased the effectiveness of the oil against yellow scale. The DDT-kerosene sprays were also relatively ineffective against yellow scale when compared to their performance against red scale. In 2 out of 14 orchards the DDT caused a small amt. of leaf chlorosis, which later disappeared. In contrast with the regular oil spray, the DDT-kerosene sprays did not reduce the quality of oranges nor did they accentuate the malady known as "water spot.".

This publication has 5 references indexed in Scilit: