INJURIOUS INSECTS. 



89 



perhaps what is known as knapsack spray pump is as convenient 



as any general purpose ma- 

 chine. Where potatoes are 

 grown on a large scale some 

 special spray pump that can be 

 geared to the wheels of a wag- 

 on may often be the best to 

 use. Where insecticides are 

 used in powder form it is a 

 good plan to scatter them on 

 the plants through a coarse lin- 

 en bag or fine wire cloth. When 

 such material needs to be eject- 

 ed with force, a fan or bellows 

 may be used. It is always best 

 to use poisons in a liquid form 

 when practicable since it is the 

 most economical and effective 

 method of applying them. No 

 insecticide should ever be used 

 in a large way, until it has 

 been tried on a small scale to 

 see what its effect vdll be on 

 the crop to be treated, since 

 plants may be more susceptible 

 at one time than at another to 

 applications of this nature. 



COMMON GARDEN INSECTS AND METHODS OP 

 DESTROYING THEM. 

 The Colorado Potato Beetle (Doryphora decemlineata.) — 

 The Colorado potato beetle is so common and so well known by 

 every farmer and gardener in this country that it needs no 

 description here. It came originally from the Rocky Mountain 

 region v\^here it fed on the native sandbur (Solanum rostratum) 

 which is closely allied to the potato, but when this insect came to 

 know the cultivated potato it preferred it to its original food 

 and has since become a very dangerous pest to this vegetable. 

 The orange ..olored eggs, varying in number from a dozen to 

 fifty, are generally laid on the under side of the pota^to leaf. 



T'igure 34. — Colorado potato bee- 

 tle in all stages. 



