Although the results given in this report have not been consistent in every respect 
with those given in previous reports, they agree in attributing to sulfur dusts the most 
uniform effectiveness in preventing new infections. The effectiveness of these dusts 
was greatly increased when they were applied in combination with pruning. 
The use of copper and sulfur fungicides on nursery elms stimulates growth and 
especially the rate of diameter enlargement. These fungicides, when they are properly 
applied, also will control foliage diseases. 
RECOMMENDATIONS 
The growing of American elms involves two distinct problems in disease control. 
One is prevention of the leafspot and anthracnose diseases which recur annually and 
injure leaves and new growth more or less severely according to weather. The other is 
prevention and treatment of the group of destructive diseases known as wilts, which 
invade the interior of the tree and eventually result in the death of the tree. 
CONTROL OF LEAF DISEASES.--Since elms are only retarded in growth by the attack of 
leaf diseases, control of those diseases has not generally been attempted. But the 
estimates given in this report, as well as those given in a previous one, indicate that 
considerable increases in growth and sale value can be obtained if spraying or dusting 
programs are followed which bring the leaf diseases under control. 
For this purpose any of the sprays or dusts named herein are effective. Where 
this type of disease constitutes the chief problem, it is necessary to make only 
Summer applications of fungicides. Dormant applications are likely to have little 
direct beneficial effect. It is important that spraying or dusting be done at rela- 
tively frequent intervals, so as to furnish protection continuously to the growing 
shoots and new leaves. 
CONTROL OF WILT DISEASES.~-Several of the treatments reported upon above have 
given control of wilt diseases to the extent of 30 per cent or more in comparison with 
lack of treatment in check groups of trees. These treatments, we believe, have 
practical value and may be used where the control of wilt diseases is the major problem. 
They are as follows: 
1. Summer dusting with Kolodust,.and pruning. 
&. Summer dusting with sulfurs such as flotation sulfur dust and "Mike" sulfur, 
with or without pruning. 
3. Dormant and summer spraying with instant Bordeaux, and pruning. 
4, Summer spraying with "Mike" sulfur, and pruning. 
In general, it appears advisable to rely on sulfur dusts, since they have given the 
most consistent results over a period of years of éxperimental tests. 
The use of sprays for wilt should be avoided, generally, as for some reason most 
of them appear to favor development of greater numbers of wilt infections or, at best, 
give only a small degree of control. An exception is Bordeaux when combined with prun- 
ing, and a possible exception is "Mike" sulfur with or without pruning. Bordeaux 
combined with pruning is likely to be as effective as any of the sulfur dust treatments. 
Although "Mike" sulfur spray seems to have exceptional possibilities, the two years 
through which it has been tested are not sufficient to prove its full value. 
Pruning, although not uniformly dependable as an individual means of disease 
control, is essential if best results are to be obtained from the use of most of the 
effective fungicides. Pruning in connection with disease control, it should be under- 
stood, is more than the usual shaping of the growth habit of the tree. Its purpose is 
to remove completely all infected material, even to the extent of the destruction of an 
entire tree when needful. 18 
