74 CIRCULAR 2 7 0, U. S. DEPARTMENT OF AGRICULTURE 



RoTENONE 



Rotenone is a derivative of certain tropical plants, such as cube or 

 derris, that is sometimes useful as a contact insecticide. It seems to 

 be particularly effective in controlling some of the red spiders. The 

 manufacturers' directions should be followed in using it. 



Spreaders and Stickers 



Some sprays have a tendency to collect in drops and roll off the fruit 

 or foliage, and some are easily washed off by rains. A number of 

 materials may be added to insecticides to overcome these difficulties. 

 Various soaps have been used as spreaders and are very useful in 

 nicotine sprays; but soaps are incompatible with lime-sulfur solution 

 and should not be used with it. Also, when used with standard lead 

 arsenate they have a tendency to produce free arsenic, which may burn 

 the foliage or fruit; although when used at not over one-third of a 

 pound to 100 gallons this injury does not usually occur. Another 

 spreader that has been used very commonly is a mixture of casein and 

 lime, commonly known as casein spreader or calcium casemate. This 

 is very useful with nicotine or lime-sulfur sprays and in a combination 

 of lead arsenate and lime-sulfur or lead arsenate and oil emulsion. Its 

 use with lead arsenate alone, however, is of doubtful value, as it has a 

 tendency to spread the insecticide too thinly. There are other 

 spreaders containing protein that may not have this disadvantage. 

 Spreaders containing mineral oil are also useful. Fish oil is a very 

 effective sticker for lead arsenate and other poisons, and some fish 

 oils, particularly certain herring and dogfish oils, also tend to spread 

 the insecticide more uniformly. 



SPRAYING SCHEDULES 



In the Pacific Northwest extensive spraying schedules for insect 

 control are required only for pears and apples. Ordinarily other fruit 

 trees should be sprayed while dormant, and at other times only if 

 insects become troublesome, as explained in the sections of this circu- 

 lar dealing with the control of the various insects. Apple and pear 

 trees should also be sprayed while dormant, as a rule, for the control 

 of scale insects, red spiders, and other pests that may be on the trees 

 at that time. Delayed dormant and "pink" sprays may also be 

 necessary, especially if scab or mildew is to be combated. On account 

 of the prevalence of the codling moth, summer spraying of apple and 

 pear trees should follow a definite schedule. Suggested schedules are 

 given in table 3, and the individual grower must determine from 

 his own experience and that of others which schedule to follow. It is 

 not often necessary to apply separate sprays during the summer for 

 other insects, since these may be ordinarily controlled by modifying 

 the schedule for the codling moth. For example, nicotine sulfate 

 and oil emulsion will control a number of other insects, and this com- 



