88 Habits of the Tomato Moth 



practicable should be trapped ; (iii) the moths should be trapped through- 

 out the season; (iv) pupae should be destroyed; (v) certain unnecessary- 

 conditions favourable to the insect should be avoided. These will be 

 discussed in turn. 



(i) Spraying. 



Substances which are stomach poisons to the larvae should be used 

 for this. They remain effective for a long time on plants protected from 

 the rain, and are more certain than contact poisons. Suspensions of 

 arsenate of lead paste, with a composition covered by a guarantee from 

 the makers, should be used on young plants. It does not harm the 

 foliage or prevent the setting of the fruit, and is a very stable substance. 

 Paris green, though an effective poison for the larvae, is liable to damage 

 the plants. Vegetable poisons, such as hellebore and nicotine, are costly 

 for wholesale spraying. The sample of lead arsenate paste used in these 

 experiments was guaranteed by the makers to contain 20 per cent, of 

 arsenic pentoxide (As 2 5 ). 



As the arsenate is very heavy it sinks rapidly out of suspension 

 unless very thoroughly agitated. It is liable to leave the machine at 

 the correct strength at first. After a few rows have been sprayed it 

 becomes too weak to be effective. Finally when the machine is nearly 

 empty it becomes wastefully strong. The only kind of agitation that is 

 quite efficient is constant shaking, and as this is difficult when the spray 

 is being applied, some substance should be added to the water which 

 will hold the substance up throughout the operation. A convenient and 

 effective material to use is saponin, and it is economical as very little 

 is necessary. It should be added to the water at the rate of 2 ounces 

 in 100 gallons, or a small half-teaspoonful in 2 gallons. The paste 

 should be mixed with a little of this solution and the thin cream obtained 

 should be added to the bulk. Little agitation is then necessary to keep 

 the suspension even until the machine is empty, and the spray will run 

 in an even film which completely covers the foliage. 



As an alternative to saponin the following spreader could be used. 

 Slake 2 ounces of calcium oxide and suspend it in half-a-pint of water: 

 work one ounce of casein into a cream and suspend it in a second half-a- 

 pint of water: add one-third of this mixture to each 2 gallons of spray. 

 This is approximately one pound of casein to 100 gallons of water. The 

 spreader has been tested on a large scale at the rate of \, 1 and 2 lbs. 

 of casein respectively to 100 gallons. The second concentration is an 

 effective spreader but it is more costly in use than saponin at present 



