Calag Archive

Not available – first paragraph follows: Several times in the past 75 years, California's citrus industry faced catastrophic losses from fruit and tree diseases. In every case, timely research greatly reduced the damage.

Not available – first paragraph follows: University research on insects and mites on citrus began in southern California in 1906 with the appointment of H. J. Quayle to the U.C. Plant Disease Laboratory at Whittier. In 1916 he correctly attributed resistance of black scale and California red scale to fumigation with HCN— one of the first reports of resistance. Quayle moved to Riverside in 1917, and the Division of Entomology of the Citrus Experiment Station was formed in 1918. Professor Quayle's studies on citrus insects and mites and their control brought worldwide recognition.

Not available – first paragraph follows: From the start of the California citrus industry in the 1860s, the pioneer citrus growers of southern California, many of them retired business or professional men from New England or the central states, showed an eagerness to explore every innovative method of production or marketing that might increase profits.

Not available – first paragraph follows: When Howard B. Frost began citrus breeding at the University of California Citrus Experiment Station in 1914, knowledge of crossing relationships in the genus was limited to earlier studies in Florida by the U.S. Department of Agriculture. Frost began a wide series of crosses among edible types, but the numbers of hybrids first obtained were limited by nucellar embryony. This is the phenomenon by which somatic cells of the nucellus (tissue in the ovule but outside the embryo sac) develop into embryos. Since these nucellar embryos develop asexually, with no male cells contributing to their formation, they are usually genetically identical with the seed parent.

Not available – first paragraph follows: Since the Citrus Experiment Station began in 1907, a major concern has been development of more efficient fertilizer practices. Early experiments by CES scientists, primarily in the orchards of cooperating growers, showed that on most, but not all, California soils, citrus trees do not respond to potassium and phosphorus application. Substantial amounts of nitrogen, however, have been required annually to maintain good vigor and yield. Later (after World War I), it was found that animal and green manures could be replaced as nitrogen sources by chemical sources, which, among other advantages, were more efficiently used by the tree and became progressively cheaper per unit of nitrogen.

Studies so far indicate that whiteflies transmit at least three widespread diseases of desert crops.

Where foliar sprays are impractical, the growth regulator chlorflurenol applied by trunk banding can lengthen the pruning cycle.

Measuring the plant's water status instead of soil moisture makes it possible to irrigate according to needs at each growth stage.

Several parasites are being evaluated for possible use in conjunction with compatible insecticides.