DAYLIGHT FUMIGATION, COST OF APPLICATION 87 



Especially is this true of I^os Angeles, Orange, and 

 San Diego counties, where ordinarily an orchard is 

 fumigated but once a year. In any of these counties 

 from October until March is considered the best time. 

 During this period the scale is young and will yield 

 quite readily to treatment by fumigation. 



' ' As fumigation for red scale seems to be equally 

 effective at all times of the year, in order to incur the 

 least damage to the grower, in the way of knocking off 

 fruit, etc., also to avoid rainy weather and north 

 winds, we have made a practice in Riverside County of 

 doing the greater part of the fumigation between the 

 months of May and December. This period embraces 

 our warmest weather. In this connection I wish to 

 refer to a matter that has evidently escaped the atten- 

 tion of the advocates of daylight fumigation. During 

 our summer months we have periods, sometimes ex- 

 tending over many days, when the mercury will range 

 in the nineties. With a temperature of from 90 to 95 

 degrees we are quite sure that by enclosing a tree 

 under an air-tight tent for the time required for fumi- 

 gation, which is from 40 to 45 minutes, the tempera- 

 ture under the tent would be increased from 25 to 30 

 degrees. Add to this the increased heat caused by 

 generating the chemicals, which would be perhaps 

 10 degrees more, and the resulting temperature would 

 very likely do harm. It is well known that a citrus 

 tree will not stand a temperature of 135 degrees for 

 any length of time without serious results. We know 

 from actual observation that the action of sunlight upon 

 hydrocyanic acid gas has a scalding or burning effect 

 upon foliage. Practically all of the damage ever done 



