158 FRUIT INSECTS 



Remedial measures. 



Above ground the woolly aphis can be readily controlled by 

 thoroughly drenching the bark, and particularly the woolly 

 colonies of aphids in summer, with a forceful spray of 15 per cent 

 kerosene emulsion. Two applications may be necessary in ex- 

 treme cases. Soap solutions and tobacco decoctions are not so 

 effective as the emulsion. Drench the lower portion of the trunk 

 and let the spray run down on to the crown and roots. It is 

 often practicable to destroy most of the aphids above ground 

 by simply painting the woolly patches with the emulsion or 

 pure kerosene, crude oil, or a miscible oil (1 to 10 parts water). 



It is much more difficult to reach and kill the aphids working 

 underground on the roots. Nurserymen should destroy all 

 badly infested stock where the roots show many of the char- 

 acteristic galls. Orchardists should never accept and plant such 

 trees. Where infestation by this pest is suspected, all stock 

 should be properly fumigated with hydrocyanic-acid-gas, or 

 the whole trees or the roots only may be dipped in the 15 per 

 cent kerosene emulsion mentioned above, or in a nicotine solu- 

 tion. For dipping, the roots should be freed from lumps of dirt, 

 then held in the liquid a minute or two and spread out to dry 

 before being piled in heaps. Hot water (130° to 150° F.) is 

 said to be an effective dip also, but do not use the lime-sulfur 

 wash, as it often injures or kills the trees. If the emulsion is 

 used, it must be thoroughly emulsified, as any free oil might 

 seriously injure the roots. Plant the trees free from the pest, 

 keep them growing thriftily for a few years, and the woolly aphis 

 will be much less liable to seriously infest the orchard. 



A narrow band of some sticky material around the trunks of 

 infested trees will capture many of the aphids often seen wander- 

 ing up and down the trunks, and thus aid materially in prevent- 

 ing the infestation of the roots by those working above ground. 



Experiments in Missouri in 1896 seemed to show that the 

 aphids could be killed and their ravages largely prevented by 



