Prevention of Egg-laying 



sprinkled over cabbages when the white butterflies 

 are on the wing will check egg-laying by them. 

 Meanwhile pyridene compounds might be used on 

 any but those soon to be eaten. 



When cabbages or cauhflowers have been planted 

 tarred felt or cardboard discs may be placed round 

 the stem and pressed close to the ground. These 

 do not prevent egg-laying, but do prevent the fly 

 from laying its eggs near to the cabbage stem, and 

 so ensure that the grub dies before it reaches its 

 food plant. 



VI. Prevention or Postponement of Egg-hatching. 

 — ^A coating over eggs may postpone if it does not 

 altogether prevent their hatching until the food 

 plant has grown so much that^the harm the insects 

 will do is greatly diminished. Aphis and PsyUa 

 eggs on fruit trees may be so treated by means of 

 lime washing or sprajHbig with lime-sulphur. 



Spraying with caustic wash or strong paraffin 

 emulsion is an aid to preventing the hatching of 

 the eggs of scale insects, since the shelter the scale 

 provides is often removed by this winter spraying. 



VII. Poisoning or Suffocation of Insects in the 

 Active Stage by Spraying. — The chief ends of sprajdng 

 against insect attack lie in the direction of poisoning 

 bitiag insects by the food they eat, or all insects 

 through their skins, or by suffocating them by 

 covering their breathing pores. 



Where biting insects are alone concerned the 

 121 



