24 JAMESTOWN CONGRESS 'OF HORTICULTURE 



profitably treated, but for most staple crops other methods must be 

 employed. 



The process involves numerous special features as applied to differ- 

 ent insects and crops, but the object in all cases is to thoroughly dis- 

 tribute the insecticide over the plants. Spraying low growing plants, 

 as, potatoes and truck crops, is largely mechanical, and requires no 

 comment. In the treatment of orchards, spraying finds its greatest 

 development, and correct spraying is really an art. The thoroughness 

 of the work and consequent results, will depend on the ideas and experi- 

 ence of the man using the nozzle rods. While there is an increasing 

 adoption of spraying among fruit growers, there has not been corre- 

 sponding improvement in regard to thoroughness in the work. Dor- 

 mant tree spraying of deciduous fruits as opposed to applications during 

 the growing season, is well illustrated in the use of lime sulphur wash 

 against the San Jose scale. 



In this case a very strong wash is used, which would be quite 

 unsafe after the foliage has appeared. Its caustic action destroys the 

 San Jose scale, and numerous other insects which may coexist on the 

 trees, such as other scale pests, pear leaf blister mite, eggs of aphids, 

 larvae of the peach moth, etc. The wash is also most useful as a 

 fungicide, and is practically a specific for peach leaf curl. Its increased 

 use in the control of the scale on peaches, has greatly lessened curl leaf, 

 giving the industry a stability it did not previously possess. 



Spraying during the growing season is best illustrated in the case 

 of the apple, and is restricted in the East largely to the use of an 

 arsenical as Paris green or arsenate of lead in Bordeaux mixture, 

 effecting a combination treatment for insects and diseases. A schedule 

 of applications has been determined for various parts of the country, 

 based on an accurate knowledge of the trouble to be controlled, afford- 

 ing almost complete protection from such insects as the codling moth, 

 curculio, green fruit worms, canker worms, and among diseases, the 

 scab, bitter rot, fruit blotch, leaf spot, etc. The spraying of apples is 

 more highly specialized than is the case of other fruits and no crop 

 perhaps shows a greater percentage of benefit. 



In the above remarks liquid sprays entirely have been meant. 

 Rather recently the so-called dust spray has come into more or less 

 of use, especially in portions of the middle west, and considerable 

 difference of opinion has arisen as to the relative merits of the two 

 methods. If effective, dust spraying has much to recommend it as not 

 requiring the use of water and the lightness of the outfit permits its 

 use on steep and hilly ground. 



A less fortunate condition exists in regard to summer spraying of 

 stone fruits, especially the peach. Even neutral arsenical sprays, such 

 as arsenate of lead, are likely to cause serious shot holing and drop- 

 ping of the leaves, and scalding of the fruit, while more caustic arseni- 

 cals, as Paris green, may actually kill the twigs and limbs. The control 

 of the curculio on peach, to which it is a very serious enemy, could 

 readily be accomplished, were a safe arsenical available. At the present 



