-5- 



This v/as not the case m the trees receiving the milder fungicide. 

 Furthermore, there was little reduction in yield v;here L. S. was 

 used only in the pre-blossora sprays. 



The effect of caustic sprays on photosynthesis is v/ell 

 knovm. Besides reducing leaf area. Lime Sulfur reduces the ef- 

 ficiency of the leaf in the manufacture of starch. Biennial 

 bearing under these conditions can be easily explained. Leaves 

 thus handicapped throughout the season are unable to develop the 

 current season's crop and at the same time set fruit buds for 

 next year. A tree with uninjured leaves, the result of a v^'ettable 

 sulfur program, is able to do both. Large, healthy leaves are 

 able to manufacture the materials necessary for maturing apples 

 of good average size, plus some reserve materials of vital im.- 

 portance in annual proc.uction. 



But why should the trees v/hich received L. S. in the 

 pre-blossom sprays yield almost cs much as those receiving no 

 L. S. at all? This explanation is offered for what it's v/orth: 

 Fruit buds are formed in June for the following year. If injury 

 to the early leaves is severe, fewer fruit buds will probably 

 form. Two L. S, sprays before bloom, however, v/ith no leaf in- 

 jury later, would probabl: permit the formation of enough buds 

 for" a full crop the next year, as heavy a crop in fact, as a 

 tree \:ould normally bear. This sets the stage for annual bear- 

 ing, i^nd since the leaves are permitted to function normally 

 after bloom, under a wettable sulfur progrstra, the current season's 

 crop develops much better than if the leaves were subjected to 

 repeated applications of L. £. during the summer, as was the case 

 in Block y^. Injury in the early spur leaves seems to have more 

 influence on the next year's fruit buds than it does on the cur- 

 rent season's crop. 



Hew Basis for Timing Curculio Spray 



Curculio beetles do little feeding on apples imtil the 

 individual fruits attain a diameter of about 5/16 of an inch, 

 according to the observations of W. D. liThitcomb of the V/altham 

 Field Station. This fact offers a nev/ method of timing the 1st 

 Cover Spray. Ten years ago, growers commonly apiilied this spray 

 a certain nuiaber of days after the Calyx stage. But the results 

 of this practice were variable. More recently growers have been 

 advised to observe temperatures, since the beetles become increas- 

 ingly active as the thermometer rises. And now comes still an- 

 other refinement in the matter of timing. Warm weather, beetle 

 activity and enlarging fruits are interrelated, '.."hen we realize 

 that the surface area of an apple m.ay double in two days of warm 

 v/eather, and that the film of spray material over the surface 

 does not stretch, the necessity of careful timing is apparent. 



In the experiments at \.'althan the interval bet^/een 

 Calyx and the critical stage in curculio control has varied be- 

 tween 3 and 10 days, since 193-4. In only two of the seven years 

 has the interval been as mucli as 3 days. 



