310 STATE BOARD OP AGRICULTURE. 



NOTES ON MICHIGAN PLANT DISEASES IN lUlG. 



BY G. H. COONS. 



The weatlier of 101 G was peculiar. The months of April, May and 

 June were especiallj^ rainy. All farm operations were badly interfered 

 with. Rains occurred in May and June every two or three days. Even 

 the sandy lands ordinarily enjoying excellent natural drainage showed 

 troubles sucli as are associated with Avater-logged soil. July and 

 August, throughout the state were as dry as the preceding months were 

 wet. An unprecedented drought cut short all crops. In spite of this 

 dry season which effectively checked many plant diseases, some crops 

 suffered great losses. 



The prevalence of such diseases as Black Kot of grapes and Apple 

 Scab, which are considered diseases associated with wet seasons, in a 

 period of drought such as occurred last year, emphasizes the importance 

 of the weather at the time of primary infection. This matter is ex- 

 tremelj'^ imi)ortant in dictating all policies in control of diseases of this 

 character. In May and June the plant diseases which winter on trash 

 from the preceding diseased crop became established and many succes- 

 sive generations of spores greatly augmented the size of foci of the 

 disease as well as established new foci. We may look upon the fungi as 

 thoroughly entrenched as a result of such favorable weather conditions 

 and in spite of the succeeding dry weather they were able during light 

 showers and heavy dews so heavilv to inoculate the tender fruits and 

 leaves as to produce serious disease conditions. 



TREE DISEASES. 



Hprucc: 



Specimens of spruce have been sent to the laboratory covered with 

 unsightly lichen growths. While in no case was definite injury to the 

 trees noticeable the condition made the trees unsightly and to appear as 

 if unthrifty. 



Such complaints on various forest and fruit trees have come from a 

 variety' of sources and usually from localities close to bodies of water. 

 Low areas, poorh^ drained sites, and wet seasons are largely responsible 

 for the conditions favoring lichens. With fruit trees, failure to prune 

 is a common cause. AVhere the conditions warrant, a dormant spray of 

 lime-sulphur and summer sprays as recommended for apple are effective 

 in cleaning up the trunks. These have been successfully used in several 

 instances. 



Gatalpa Leaf S'pot: 



Catalpa leaves were sent to the laboratory from near Adrian and some 

 were collected at Ann Arbor and also at East Lansing showing small 

 circular spots about 5 mm. in diameter. These spots occurred in great 

 nund)ers on llie leaves and gave the trees a very unsightly appearance. 

 Excessive dropping of the leaves did not occur however. This disease 

 had associated witli it PJii/nosficta catalpac and an Alternaria. It is 

 undoubtedlv the same one which GalloAvav described in 1887. (Dept. of 

 Agr. Report, 1887). 



