74 INSF.CTS INJUiaoUS TO STAPLE CROPS. 



- Spraying Ditches. — Prof. Morgan states that '^upon 

 river plantations many open ditches are indispensable, and 

 when rains are sufficient to keep tlieni filled or partly filled 

 with water they serve a most excellent purpose in the 

 destruction of the young grasshoppers." 



" The experience of spraying ditch-banks soon developed 

 the method of damming water in the ditches and covering 

 the surface with coal-oil or kerosene emulsion. Before 

 and after rains the ditches were dammed and the water 



Fig. 48.— The Price Oil-pan or Hopperdozer. (After Riley. ) 

 covered Avith a 12 per cent coal-oil emulsion. The young 

 grasshoj^pers were then driven into the ditches, with the 

 result that very few, if any, escaped. In this way a single 

 application of oil would last several days, as many millions 

 may easily float upon the water of a ditch not more than 

 two feet wide. Unless the grasshoppers are scattered too 

 far from the ditch-banks no difficulty is experienced in 

 getting them to move in the directiun of the oiled water 

 on account of the ' homing' instinct.'' 



