APPLE POWDERY MILDEW AND ITS CONTROL. 11 
spring and summer spraying, intended to prevent foliage and twig 
infection and to kill out any mildew that had become established. 
WINTER SPRAYING. 
The experiments in dormant spraying were conducted through two 
winters. About 16 different materials were used, some of which were 
tested on several plats and in various strengths. Among the mix- 
tures used were Bordeaux mixture, lime-sulphur solution, various 
soluble sulphids, copper sulphate, sulphuric acid (alone and in com- 
bination with copper sulphate and iron sulphate), and various soluble 
copper salts. The results showed that the plats which received the 
various dormant sprayings were just as badly attacked by mildew 
the following spring as those which were not sprayed. 
FOLIAGE SPRAYING. 
While the investigations in winter spraying were in progress, it 
became evident that the dormant or winter spores played a very 
unimportant part in establishing the first infections the following 
spring. It was seen that on each tree great numbers of mildewed 
twigs developed from dormant-bud infections, and that on these dis- 
eased twigs summer spores were produced in quantities and served 
to infect the healthy foliage as it came out. 
The work of winter spraying for the direct control of the mildew 
was, therefore, dropped, though it was taken up again later from a 
different standpoint. Attention was given to finding a suitable fun- 
gicide for foliage spraying and a practical method of reducing to a 
minimum the number of dormant-bud infections. 
About 125 different materials have been tested for foliage spraying, 
and many of them have been used in several different strengths. Ex- 
periments with the more promising ones have been repeated through 
several seasons, and the investigations have been in progress six years. 
For the purposes of this bulletin it will not be necessary to give a 
detailed account of the experimental work, but a brief statement of 
some of the results will not be out of place. It will be remembered 
that these remarks apply particularly to the Pajaro Valley, though 
for the most part they will probably hold true for other sections 
as well. | 
Copper compounds in general can not be used, on account of the 
leaf burning and fruit injury which they cause. Bordeaux mixture 
gives very poor control of apple powdery mildew. Copper acetate 
and copper oxychlorid give fair control of the mildew, but they can 
not be used repeatedly on account of their fruit and foliage injuring 
properties. Dilute lme-sulphur solution and solutions of the soluble 
sulphids in general, such as potassium and sodium sulphid, can not 
