54 MASS. EXPERIMENT STATION BULLETIN 184. 



points; whereas the shorter, matted pubescence of the bark and bud 

 scales absorbed it readily, and on this account more injury was often 

 caused to those buds just splitting open than to those sUghtly more 

 advanced. 



Efficiency of Lime-sulfur and Nicotine sulfate combined against the 

 Aphids. — Previous tests have shown that nicotine suKate at the dilu- 

 tion 1 to 800 is practically a perfect aphidicide. The addition of Ume- 

 sulfur probably increases its efficiency very Httle, so that the only logical 

 reason for the use of this combination at the delayed dormant period is 

 for the purpose of saving labor by combining two operations — the San 

 Jos6 scale treatment and aphid treatment — in one. Laboratory tests 

 where absolute thoroughness of application by dipping was possible 

 showed this combination to be 100 per cent, effective. The effectiveness 

 of this combination under field conditions would depend mainly on 

 thoroughness of appUcation. 



Action of the Lime-sulfur-nicotine sulfate Combination upon the Aphids. 

 — As already indicated the action of lime-sulfur in killing the aphids 

 appears to be mainly mechanical, — by sticking them to the plant so 

 that in most cases death is probably the result of starvation. The action 

 of the nicotine sulfate in killing the aphids is rather slow, requiring from 

 about half an hour to twenty-four hours or more for different individuals. 

 Immediately after the dipping there was no evidence that the treatment 

 had any effect upon the aphids. In about fifteen minutes, however, 

 considerable restlessness was apparent and inside of half an hour a num- 

 ber of the plant lice had begun to drop from the twigs, some being pre- 

 cipitated rather forcefully as if from strong muscular contraction. These 

 lay strugghng feebly but unable to crawl, gradually becoming dark 

 colored and motionless. Those plant hce that survived the treatment for 

 a number of hours appeared after a few hours to be paralyzed and in- 

 capable of either locomotion or feeding, but were feebly moving their 

 legs and antennae and excreting honey dew in abnonnally large amounts. 

 An examination of the twigs forty-eight hours after treatment showed all 

 the plant lice to be dead. The fact that nicotine sulfate kills rather 

 slowly may account for the occasional reports that this material is in- 

 effective against plant lice. Examination of treated plants shortly after 

 application might readily lead to this conclusion, but if sufficient time is 

 allowed before examination there will be no question as to its effective- 

 ness. 



Foliage Injury by the Lime-sulfur-nicotine-sulfate Combination. — A 

 comparison of the effects from the use of full dormant-season strength 

 lime-sulfur alone and in combination with nicotine sulfate on apple foli- 

 age in various stages of development from the first sphtting of the buds 

 to a development of an inch or more showed no noticeable difference. 

 Even at the latter period of development the amount of foliage injury 

 was not serious. 



