Control of San Jose Scale With Lubricating Oil. 13 



chance of injury to trees, however, prevented a few growers, espe- 

 cially orchardists who had light infestations of the scale, from using 

 this material. 



Observations w.ere made in many orchards following the general 

 use of this oil spray during the dormant season, but no injury to the 

 wood or the fruit buds could be detected. In some instances growers 

 sprayed several tanks of material in which some free oil was present, 

 due to hard water, but even in those cases no signs of injury could 

 be found. Trees ranging in age from 1 year up received the dormant 

 treatment with 2 per cent oil emulsion, yet there was no indication 

 of damage to trees of any age. The only trees sprayed with heavier 

 dosages of oil than 2 per cent were those in some of the experi- 

 mental plats. One plat received an application with an emulsion 

 containing 8 per cent of oil. Trees in the heavy dosage plats of the 

 expei'imental spraying had a normal foliage and set a good crop of 

 fruit. 



Lubricating-oil emulsion in tlie summer sprays causea ouming in 

 some orchards at various times, but no very severe cases of injury 

 were noted. When burning occurred it was doubtless produced by 

 excessively hot weather. An emulsion containing 3 per cent of oil 

 was used during very hot sunny weather in one orchard, and rather 

 severe injury resulted to fruit and foliage on some trees. The injury 

 in this orchard was " spotted," being noted in patches here and there. 

 Injury on the fruit showed in the form of small dark spots, slightly 

 sunken. Apparently the hot sun evaporates the water in the emul- 

 sion so quicMy that tiny spots of oil are sometimes left scattered on 

 the fruit and foliage. Three months after this one bad case of injury 

 was noticed it was rather difficult to find any outward signs of 

 injury. Close observation revealed slight stunting of growth and 

 size of fruit on some trees. No case of injury has been observed on 

 fruit sprayed with a 2 per cent emulsion during the sunmier. Some 

 growers used a 2 per cent emulsion in several summer sprays without 

 any injury. 



In instances where burning resulted during the summer sprays, 

 the damage was no more severe than would be caused by summer- 

 strength lime-sulphur solution applied during hot weather. Any 

 one contemplating the use of lubricating-oil emulsion for a summer 

 spray should take care to avoid using it when the temperature is 

 above 90° F. Some growers avoided injury from summer sprays by 

 making the application during the cool part of the day, during the 

 morning and late afternoon. Unless scale infestation is very bad, 

 oil emulsion should not be used in the summer sprays, especially 

 since only a partial control of scale can be obtained at that time. 



METHOD OF PREPARATION. 



Lubricating-oil emulsion, made by the boiled process, is prepared 

 as follows : 



Formula for stock emulsion. 



Red engine oil gallon_ 1 



Water do ^ 



Potash fish-oil soap pound 1 



The oil, water, and soap are placed in a tank and heated until 

 the contents come to a boil. Just before boiling a brown scum ap- 



