Effects of foliar sprays for frost protection in test with young citrus trees

A number OF new chemical sprays were tested for frost protection of young citrus during the winter of 1969-70. Fifteen commercial compounds were sprayed on container-grown grapefruit nursery trees and young lemon trees in the field. Most of the compounds were antitranspirants (film-forming, stomata closing, and reflecting types). Growth inhibitors used were maleic hydrazide (MH), potassium salt of 6-hydroxy-3-(2H)-pyridacinone (KMH), and ethyl hydrogen 1-prophylphosphonate (NIA-10637). Freezing the grapefruit nursery trees in a cold chamber resulted in no significant differences in the amount of cold protection given by any of the sprays. Temperatures in the field where the young lemon trial was located never reached freezing, but there were significant differences in growth response to the different sprays.