April, '20] 
CROSBY AND PALMER: SPECIAL SPRAY SERVICE 
217 
They should be distributed throughout the county so as to represent 
the different climatic zones and also serve as object lessons to the grow¬ 
ers in different parts of the county. The differences in the seasonal 
development of the trees, owing to topographic and climatic factors, 
is much greater than is usually supposed, even in comparatively small 
areas. In Monroe County, for instance, a difference in the time of 
blossoming of from one to two weeks is not uncommon in orchards 
less than fifteen miles apart, on a gently sloping plain,—due in large 
measure to the retarding influence of the cold waters of Lake Ontario. 
The criterion orchard should be a representative commercial orchard 
consisting of the varieties commonly grown in the locality. It is 
important that the grower should be in sympathy with the work, that 
he be thorough-going and careful, and that he possess a modern and 
efficient spraying equipment. The arrangements for the criterion 
orchards are usually made by the field assistant with the advice and 
assistance of the county agricultural agent. Much of the success of 
the spray service depends on the results obtained in the criterion 
orchards, and too much care cannot be exercised in selecting energetic 
and congenial cooperators. 
While special demonstrations, e. g., tests of insecticides, methods of 
application, etc., are not so important, the rule still holds that the 
better the cooperator, the greater are the chances of the work being 
successful. In all cases the cooperator should agree to follow fully the 
directions of the field assistant and, where it would interfere with 
checking results, to leave at least a part of the crop unthinned. To 
determine the value of applications checks are desirable, but on 
account of the value of the crop it is not practicable to leave many trees 
untreated. Where the intent is to show the value of a seasonal sys¬ 
tem of spraying in comparison with no treatment, untreated trees are 
indispensable and should be selected with care. Where the demonstra¬ 
tion is designed to show the different methods of control or the use of 
different materials, one part of the orchard can be checked against the 
other. In some cases, e. g., pear psylla, checks cannot be left because 
of the danger of reinfestation from the untreated trees. 
During the past season the six assistants we had in the field traveled 
an aggregate of 34,343 miles, making 3,017 visits, and issued 66 cir¬ 
cular letters with a total circulation of 18,207. It is very difficult to 
estimate the financial return to the growers of the counties concerned, 
but there is every reason to believe that the increased value of the crops 
directly resulting from the work would pay several times over the 
entire cost of the undertaking including supervision and overhead. As 
an indication of the growers’ appreciation of the work it may be stated 
that for next year twelve counties have requested to enter into a sim- 
