472 STATE BOARD OF AGRICULTURE. 



Leaf-Spot Control on Cherries and Plums. 



EXPERIMENTS WITH CHERRIES. 



Summary of Previous Experiments. Work with cherries was carried on in 

 1919 and was reported in Special Bulletin No. 102. Briefly, the results were as 

 follows. With Montmorency the results were not conclusive because of 

 absence of leaf spot in the untreated trees, but with English Morello the 

 check trees were defoliated by September. Trees sprayed with lime-sulphur 

 held their foliage in good condition until late in September and then the 

 development of leaf -spot was only very slight. Trees dusted with sulphur 

 dust were affected by leaf spot early in August and were badly defoliated by 

 the middle of September. 



EXPERIMENTS IN 1920 AND 1921. 



During the seasons of 1920 and 1921, extensive experiments for the control 

 of leaf-spot were conducted at Traverse City on the Titus Brothers' farm. 

 Two orchards were used in this work. One was Montmorency with trees 

 nine years old at the beginning of the work. The other orchard was English 

 Morello, one-half the trees being nine years old and the other half twenty- 

 one years old at the time the work was begun. These orchards had been 

 dusted entirely for two or three years previous to 1920 and the control of 

 leaf-spot had, in one year in particular, been unsatisfactory. Thorough 

 cultivation is practised in these orchards, which is usually considered impor- 

 tant in the control of leaf-spot if done early so as to cover the old leaves 

 before infection occurs. 



Object of the experiments. This work was carried on in order to get all 

 information possible concerning the comparative value of the following 

 materials : 



1. Lime-sulphur solution. 



2. Bordeaux mixture. 



3. Sulphur dust. 



4. Dehydrated copper sulphate dust. 



Arrangement of the plots. Each orchard was divided into four large plots, 

 one for each material noted, and one small plot which was left untreated as 

 a check. This cheek plot was so located that very little, if any, dust drifted 

 on to it. The plots were essentially the same for both years except that 

 different trees were used each j^ear for the check plots. Each of the dusted 

 plots contained from 80 to 100 trees, the sprayed plots from 40 to 60 trees, 

 and the check plots 8 to 10 trees. 



Materials used. The same materials were used both seasons but at dif- 

 ferent strengths or proportions. The exact formulae for each year are given 

 in table 20. 



