6 
The Colorado Experiment Station. 
ALTERNARIA. 
Experiments were undertaken during the season to determine 
the best method of controlling this rot which was thought to be 
damaging* the fruit and foliage of Keiffer pear and Ben 
Davis and Gano apples. Three orchards were selected where 
severe injury was reported during the summer of 1905 and ex¬ 
periments outlined. Inquiries among orchard men led me to be¬ 
lieve that a part of this injury, at least, might be due to spray¬ 
ing, and the experiments were planned with this point in mind. 
In one orchard a block of seventy-five Keiffer pear trees was se¬ 
lected and divided into blocks I, II and III. Block I was sprayed 
with Bordeaux mixture (3-4-50) on April 14th. The buds were 
well started at this time and were out far enough to expose the in¬ 
dividual blossom stems. This block was again sprayed on May 
8th with Bordeaux mixture (2-4-50), with 3 lbs. of arsenate of 
lead added to each fifty gallons of Bordeaux for the first codling 
moth spray. 
Block II was sprayed on May 5th and 8th with Bordeaux 
applied at the same strength and with the same insecticide as used 
in block I, and was again spraved with the same material on lune 
8th. 
Block III was sprayed with arsenate of lead only, during the 
entire season. O11 July 10 th block II was divided, and half was spray¬ 
ed with arsenite of lime while the remainder and all other blocks 
were sprayed with arsenate of lead. A light rain followed and 
black blotches on the fruit were quite noticeable by the first of Au¬ 
gust. All other blocks sprayed with arsenate of lead during the en¬ 
tire season were perfectly clean. This indicates that the injury in 
the part of block II sprayed with arsenite of lime was due to burn¬ 
ing. 
In the second orchard a block of fifty Keiffer pears and a 
block of fifty Gano and Ben Davis apples were selected for experi¬ 
ments. The block of Keiffer pears was divided into two blocks 
and block I was sprayed on May 8th, or just after the blossoms 
had fallen, with Bordeaux mixture (2-4-50) with two and one 
half pounds of arsenate of lead added to each fifty gallons of Bor¬ 
deaux. The brand of arsenate of lead used was of poor manu¬ 
facture, and on May 23rd the check trees making up block II and 
sprayed on May 12th with arsenate of lead only, were found to be 
badly burned,while the foliage and fruit of block I showed no injury. 
The injury on block II was mostly to foliage though some fruits 
were burned, most of which dropped early. Block I was saved 
by the excess of lime in the Bordeaux which combined with the 
free arsenic in the lead. A good grade of lead was used on all 
blocks after this spraying. 
Block I was again sprayed on June 9th with Bordeaux mix- 
