Effects of Postbloom and Summer Oils on Yield, Fruit Size, and Growth of Four Varieties of Oranges, 1970–7412

Abstract

The yields (5-yr avg) after postbloom and summer oil (228.5°C) (DO) were reduced in comparison to (LSO) light summer oil (213°C) and non-oil summer scalecide treatments with ‘Pineapple’ oranges. Summer oil (SO) (228.5°C) was added to the latter treatment with ‘Hamlin’ oranges. Yield reductions were found with the double oil treatments during the 1st yr with ‘Marrs’, Hamlin, and ‘Valencia’ oranges. Yield differences among treatments were more prevalent with Pineapple and Marrs orange trees. Tree growth was greater only in the 5-yr avg with the double oil treatment with Valencia orange trees. Differences in growth increase among treatments were found more with Marrs orange trees in individual years. Yield and growth seemed to be related more to alternate bearing in Marrs oranges than with the treatments. More size 216 Marrs oranges were produced with double oil treatment while smaller fruit were produced with SO and LSO summer oil treatments; larger fruit were associated with lower yields as compared to smaller fruit with higher yields. However, alternate bearing influenced sizes with this variety. Incidences of differences among treatments were less frequent with Pineapple oranges, but less size 250 fruit were produced with the double oil treatment in 3 of 4 years. The double oil application plot trees generally produced more size 216 Hamlin oranges and less sizes 324 and 288 fruit than with other treatments. Likewise, more size 216 Valencial oranges were produced with double oil plot trees while smaller fruit were produced with other treatments, particularly with the SO treatment.