THE CODLING MOTH IN MASSACHUSETTS 65 



Lead arsenate does not dissolve in ■water but remains as tiny particles sus- 

 pended in the liquid. When the spray on the trees collects in large drops, 

 these particles settle to the bottom, and upon drying leave many areas on 

 the fruit and leaves which have no coating of poison. To avoid this, mater- 

 ials are added which spread the poison over the fruit in a thin film. Soap 

 and glue are very effective spreaders, but at present calcium caseinate is the 

 most practical material for this purpose. The use of a spreader enables the 

 operator to cover tiie fruit more completely and prevents much of the blotcii- 

 ing on red fruit which results from overspraying. 



Calcium caseinate materially delays the undesirable chemical reaction which 

 may result when lead arsenate and lime-sulfur are combined, and altogether 

 its use is justified. (See discussion of spray injury, p. 71.). 



Nicotine sulfate has been tested many times as a spray to kill codling 

 moth eggs and in some cases it improved the control. It is an expensive 

 treatment, however, and is now discarded as uneconomical. In the last two 

 years, weak solutions of lubricating oil emulsions have been used experi- 

 mentally with some success to kill the eggs and small larvae. Oil sprays 

 are natural spreaders and, when used alone, leave no arsenic residue on tiie 

 fruit at harvest time. The degree of control which they give, however, and 

 the possibility of injury to the trees and fruit by summer apjilications of 

 oil have not yet been satisfactorily determined. 



Su(i(/estio7is for Spraying Apples to Control the Codling Moth. 



In spraying pay particular attention to the fruit. It must be hit by spray 

 on at least two sides in order to cover it completely. If combating scab, 

 plant lice and other leaf-attacking pests at the same time, the foliage must 

 also be thorouglily covered. Too much spray is sometimes as harmful as 

 too little, and excessive dripping should be avoided. The best coating is 

 applied wlicn a line misty spray just reaches the fruit. Mist nozzles regulate 

 the tjnpe of spray very well but the spray gim must be frequently adjusted 

 by the handle regulator to give the best results (see Plate II), especially 

 when no spreader is used. Do not use spray gims when the wind is blow- 

 ing. Thoronghness in spraying is most important. Every apple should 

 be completely covered regardless of other factors. About five gallons of 

 .'jpray are necessary to cover the average fifteen-year old apple tree, but 

 the amount varies with the size and crop of each tree. 



When to Spray Apples to Control the Codling Moth. 



Careful timing of sprays is often the key to succes.sful control of tiie 

 codling moth, and other work should net be allowed to interfere with it. 

 The proper time to apply tiie calyx spray depends entirely on the develop- 

 ment of the tree, while the post-calyx sprays are timed in accordance with 

 the development of the insect. The rate of growth of both trees and insects 

 varies from j'ear to year, and the exact date or period to apply post-calyx 

 sprays cannot be accurately predicted in advance. In the following spray 

 schedule the time to spray, as indicated by the detailed studies of the 

 codling moth, is determined approximately for the typical year, with the 

 .suggestion that fruit growers secure each season all available information 

 concerning the seasonal development of pests to help them time the sprays 

 more effectively. 



