EXPERIMENT STATION WORK WITH INSECTICIDES. 265 



THE PLUM CTJRCTJLIO. 



The plum ciirciilio has been shown to bo an important enemy of 

 apples by reason of the " sting " which it causes in fruit. This mat- 

 ter became so serious in Missouri " that the station felt called upon to 

 investigate it. It was not only determined that the plum curculio 

 was the cause of the damage, but successful remedies were worked 

 out. There appeared to be three methods of procedure which can be 

 followed in diminishing the injury from this insect upon apples. 

 The trees may be sprayed with arsenate of lead before the blossoms 

 open, after the blossoms fall, and three or four more times at inter- 

 vals of ten days. Spraying with this arsenical appeared to prevent 

 about 60 per cent of the damage. It was also found that consider- 

 able importance attaches to the careful collection and destruction of 

 windfalls, since the larvje remain in fallen apples for about one week. 

 This method, if conscientiouslv carried out, will in itself nearlv con- 

 trol the plum curculio. Some advantage is also found in plowing 

 the orchard shallow and harrowing it thoroughly about the middle of 

 July, following this treatment by further harrowing about August 1 

 and 15. In practice it is best to combine all these methods, and when 

 this is done it was shown that the plum curculio could be prevented 

 from doing serious damage to apples. In Illinois '' the same prob- 

 lem was attacked and the same remedies found to be effective. 

 Spraying with arsenicals caused a saving of from 27 to 54 per cent of 

 the picked fruit which was liable to puncture by curculio. Under 

 favorable conditions it was stated that from 20 to 40 per cent of fruit 

 liable to injury may be saved by five applications, and this is con- 

 sidered a profitable procedure. Experiments made at the Illinois 

 Station demonstrated conclusively that the destruction of small ap- 

 ples and windfalls is of great importance. The cultivation also 

 proved beneficial. This method of attack was aimed at all three 

 stages of the insect, but particularly the pupa?. Both larva) and 

 pupa? are delicate and extremely sensitive to exposure to light and 

 air. Short exposures to suidight are fatal to both forms of the pest, 

 and the insect is also attacked by predaceous insects and birds. Su- 

 perficial tillage for a period of thirty days or longer from July 10 is 

 tlierefore recommended. 



THE APPLE APHIS. 



The apple aphis {Aphia porni) causes more or less injury to apple 

 trees wherever this fruit is grown. In Idaho ' it was found that the 

 eggs could be destroyed in wintci- by s|)raying with various contact 

 in.secticides, among which crude oil, kerosene, kerosene emulsion, 



"Missouri St;i. I'.iil. <;i. ''Tllinctis St.i. I'.iil. 98. 



<• Malio St:i. Util. 10. 



