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Washes, (b) Cover Washes, (c) Internal Poison Insecticides, 

 (d) Contact Insecticides. 



(a.) Cleansing Washes, such as a solution of caustic soda, 

 might equally have been dealt with under Indirect Measures 

 as they are used primarily with the idea of killing moss, 

 lichen, &c., which serve as winter quarters for pests. They 

 are only applied in winter as they would burn foliage, and 

 except in badly neglected orchards can generally be replaced 

 by cover washes which also help to destroy moss, lichen, &c. 



(b) Cover Washes, of which plain lime-wash is a typical 

 example, are applied in spring early or late according to 

 the season and kind of fruit tree. They act by covering or 

 sealing up the eggs of pests just at the time they should be 

 hatching, and also by smothering any young insects which 

 may already have hatched. This being the case it is obvious 

 that the more complete the coat of wash applied, the more 

 pests will be killed, and since insect eggs occur more abun- 

 dantly on the twigs than on the larger branches, the sprayers 

 should specially endeavour to cover the twigs properly. 

 Further, in the case of lime, as the wash should dry on 

 and resist rain for some weeks, as thick a fluid as can be 

 forced through the spraying machine should be used. 



(c) Internal Poison Insecticides are insecticides which 

 when eaten cause death but otherwise may be quite harmless, 

 having no effect on the skin or external parts of an insect. 

 In using internal poisons therefore the object is to spray 

 not the pest but the leaves of the tree, whicn under favour- 

 able conditions remain poisonous to pests for a considerable 

 period. 



As it is necessary to cover every leaf and bud with a 

 uniform coating of poison, a nozzle giving the finest spray 

 should be used, and further, the nozzle must be moved 

 from one direction to another fairly rapidly for if leaves 

 receive too much spray, the minute drops run together and 

 collect at the tip of the leaf, with the result that there is 

 too much poison at the tip and too little elsewhere. A" 

 further point is that the liquid should stick to the leaves 

 and not merely collect in globules. Just as plain water will 

 not thoroughly wet a greasy plate, some leaves are so 

 formed that they are not easily wetted. In such cases it 

 is necessary to add to the insecticide some substance such as 

 saponin which enables the liquid to wet the leaf just as 

 the addition of soap to water allows it to wet the greasy 

 plate. 



Finally, in connection with internal poisons, attention 

 should be drawn to the necessity for spraying soon enough. 

 It should be noted (1) that young insects are more easily 

 poisoned than old, and (2) that insects such as caterpillars 

 cause damage very rapidly an orchard green and seemingly 

 not much injured may be completely stripped of leaves n 



