PEOCEEDIXGS OF THE THIRD ENTOMOLOGICAL MEETING 767 



Suffice it to know that the potatoes are attacked in the field — leaf, stem 

 and tubers alike. In years when the monsoon fails or there are long 

 breaks the cracks m the soil allow the larvse access to the tubers below. 

 The potatoes ia the soil are much less attacked if the rainfall is even 

 and well distributed. Irrigated potatoes escape being attacked in the 

 field on account of the soil receiving regular and timely watering which 

 keeps the soil from cracking. The source of infection may also be from 

 green potatoes which get exposed in the field and so get unwittingly 

 mixed with the sound tubers that go to the store. The moth is known 

 to breed in much the same way as stored grain pests breed in tie granary. 

 The larvse inside the potatoes camiot be killed by any amount of dipping 

 and laboratory experiments show that moths hatch out from such 

 potatoes even by using double the ordinary strength of lead arsenate. 

 Crude-oil emulsion and copper Sulphate are equally ineffective for the 

 purpose. JRepeated trials with crude-oil emulsion in Bombay have 

 resulted in failures. Experiments of dipping in crude-oil emulsion 

 carried out in Bengal have proved the uselessness of this method. The 

 -Central Provinces' experience at Chindwara and Saugor are not reas- 

 suring ; fifty to seventy-five per cent, were found destroyed even al- 

 though the potatoes were carefully selected before storage. Experi- 

 ments by F. Steward, D.Sc, Government Botanist, Western Austraha, 

 show that formalin, mercuric chloride and copper Sulphate have had 

 no effect on the larvse even after six hours of dippmg. The eggs and 

 pupje are more refractory and they are not killed without destroying 

 the germination of the potatoes- also. He is positive when he affirms 

 that the dipping is harmful to the germination if continued suffi- 

 ciently long to kill the live forms of the moth. Dipping in water 

 iilled the larvse by exclusion of air to the galleries in which the larvse 

 live. 



Fumigation by carbon bisulphide was first tried and gave excellent 

 results. It kills the larvse and pupse but has no action against the 

 eggs, unless they are exposed to the fumes for 48 hours or longer. Future 

 generations can be prevented from breeding in the potatoes if they are 

 fumigated before the first generation of moths have had the chance of 

 laying their eggs. Experiments with other compounds which evaporate 

 easily have shown that the fumes of benzine and petrol have a lethal 

 efltect on the larvse and pupse nearly quite as much as carbon-bisulphide. 

 Benzine and carbon-bisulphide have to be discarded on account of their 

 being extremely costly and not easily available except in big cities and 

 towns. Petrol is better on account of its being available even in the 

 nearest taluqa places. During normal times petrol is available at one 

 rupee a gallon and there are no restrictions against its transport. From 



