24 BUI.LETIN 328 



The application of winter-strength hme-sulfur during dor- 

 mancy followed by "Black Leaf 40'' and soap at the green-bud 

 stage just after the lice had hatched seemed very effective, leav- 

 ing only 2 lice to each 100 buds. 



Scalecide when used during dormancy scorched the buds, and 

 when used during the green-bud' stage, after the lice hatched, 

 killed 50 per cent of the buds. In both cases it reduced the 

 number of lice. 



Thus it appears that until uicthods of drstroying the egg dur- 

 ing dorjiiancy arc better developed, the best aphis treatment from 

 the standpoint of labor, safety and cMciency is an application of 

 winter-strengtli lime-sulfur, to zvhich 40 per cent nicotine has 

 been added at the rate of i to ^00 at the green-bud stage. 

 Under this system no winter-strength lime-sulfur or soluble- 

 oil treatment is ordinarily required, and the normal labor of 

 orchard procedure increased only slightly. 



The one question remaining in the writer's mind after the 

 experiment of IQ16 was whether, if the advancement of the 

 trees should compel treatment before hatching, the eggs would 

 not later hatch a damaging brood of lice. The laboratory work 

 of Dr. Peterson in 19 17, already mentioned, indicated that the 

 unhatched eg"gs would be destroyed. Fortunately, there was 

 opportunity to try this out on a field scale. 



AMien the oat aphis appeared on the buds Mr. Barclay sprayed 

 a block of trees with winter-strength lime-sulfur to which "Black 

 Leaf 40" had been added at the rate of i to 500. At the same 

 time an adjacent block was sprayed with Scalecide (i to 15). 

 On the first block practically no aphis appeared thereafter, and 

 trees were almost entirely free from aphis work. On the sec- 

 ond block, although only a few living aphis could be found on 

 the afternoon of the day wdien the spray w-as applied, colonies 

 of the rosy louse appeared later, curled the foliage and did much 

 damage to the fruit. 



No one knows how many apliis per lOO' buds may be left un- 

 hurt and the crop escape injury. As a matter of fact, the num- 

 lier which mav safely be left this year might next year be suffi- 

 cient to produce large damage, so much depends upon the 

 weather and the natural enemies of the lice. The only safe plan 

 to follow is to kill as many of the lice as possible. This means 

 the application of the recomniended treatment with the utmost 

 thoroughness, for neither lice nor eggs will he destroyed unless 

 thev are well coi'crcd. 



Assuming that the best practical)le treatment for aphis, with 

 our ])resent knowledge, is the aiiplicalion of lime-sulfur and 



