In the Chico area, almond orchards need frost protection—on the average—six nights a year, two years out of three, with one or two of those nights needing 2F or 3F of protection. Late frosts—in April—generally occur only once in eight years. This year there were about one third more frosty nights than usual, and several of those nights occurred in April. This made it possible to conduct a good series of wind machine tests both when the trees were relatively bare and when they had considerable foliage.

Data, from which the effectiveness of the large, dual gasoline engine wind machines—Good speed orchard near Durham—was determined, were obtained by D. E. Kester, D. S. Brown, and W. P. Pierce, University of California, Davis.

W alter Stile, almond grower; the Frost Master Co.; Harry Hanson, U. S. Weather Bureau; and Ralph Parks, Extension Agricultural Engineer; Henry Euerett, Farm Advisor, Butte County; C. E. Barbee and E. L. Tippie, of the University of California, co-operated in the studies reported here.

The above article is the seventh annual report of progress in the study of wind machines in orchards published in California Agriculture.