Responses of Grapefruit Trees to Various Spray Oil Fractions1

Abstract

Certain tree responses were investigated as a possible result of four spray oil fractions and a non-oil treatment applied during July 1959–61. Juice analyses showed the October 1 samples of all treatments failed to meet maturity specifications by Texas standards. By late October, maturity was reached only in 1961 in all samples (except the high molecular weight paraffinic oil treatment) and in the 330-molecular-weight paraffinic oil treatment in 1960. By December, all samples met maturity. The soluble solids of the higher molecular weight paraffinic oil treatment were consistently lower in all samples. The higher percent soluble solids was associated with a higher percent acid, in general, and the resulting ratios were about the same. Significantly greater leaf drop was found in the paraffinic oil plots than in the non-oil plots. However, the greater leaf drop with the 330-molecular-weight paraffinic oil occurred only in 1959 and the general leaf drop in any plot was not excessive. Greater leaf drop occurred during the first 2 to 3 weeks after treatment. No significant differences were found in yield, although the plots sprayed with the oil with a molecular weight of 362 yielded ½ box per tree less than that with the next greater plot yield.