CHESTNUT BLIGHT IN MICHIGAN 13 
flask-shaped structures which are buried beneath the surface and which 
contain the spores known as ascospores. These spores are shot out directly 
into. the air from the mouths of these fruiting structures. 
The type of spores which ooze out in the spore-horns are released from 
their gelatinous matrix when the tendrils or horns become soaked with 
water in the form of dew or rain. They can be spread by rain splashings, 
by birds, and by crawling and flying insects. Since these pycnidiospores 
from the spore-horns are viable and able to germinate after considerable 
periods of time, days or even months, they constitute active spreading agen- 
cies of the fungus. The ascospores which are largely borne away from the 
diseased area by air currents are also able to disseminate the fungus to 
considerable distances. Man and other agencies may also bring about the 
spread of the fungus. 
As both types of spores seem to be equally effective in producing infection 
and as the enormous numbers of both spore types produced are so readily 
disseminated, it has been impossible to eradicate the chestnut blight from 
other States, and it will be impossible to eradicate it from Michigan. The 
blight usually appears as it has in Michigan ahead of the general infection. 
In such instances it is usually assumed that the sticky spores of the fungus 
have been carried on the feet of birds. 
This organism, being strictly a wound parasite, is unable to invade the 
tree tissue except through openings previously made in the bark, such as 
by splits, cuts, or abrasions where the bark has been broken. Once having 
entered the tissues of the tree the fungus grows with great rapidity and kills 
the tree. Branches or entire trees are killed by the girdling effect produced 
by the mycelium, which causes the formation of a cankered area which 
eventually encircles the twig, branch, or bole. 
Previous Attempts at Control or Eradication of Chestnut Blight 
Early in the period of invasion of the blight in the eastern forests of 
the United States it was apparent that the fungus threatened to kill the 
chestnut throughout the entire commercial range of this species. Realizing 
the significance of this pest, attempts were made to check the rapid spread 
of the pest. The strenuous efforts made to completely eradicate and burn 
the diseased trees in the known infected areas failed to yield the desired 
results. 
In the endeavor to stamp out advance infection, the diseased chestnut 
in local or spot-infected areas were destroyed, but this method, too, failed to 
prevent the spread of the blight. Removal of the chestnut in the spot-in- 
fection areas did however cause a very pronounced delay in the spread of 
the blight. Some hope was expressed that possibly the elimination of 
chestnut from areas surrounding the infected regions might be helpful, but 
it became evident that the establishment of such immune zones was not 
an effective method for control. Many other control measures, such as the 
cutting out of cankers on individual trees, spraying, the injection of chemical 
compounds into the trees were attempted. Soil treatment was also advocated 
as a possible means of stimulating growth of the tree and thereby increasing 
its resistance to the fungus. In addition to the above-mentioned control 
measures, the establishment of quarantines against transportation. of diseased 
stock was immediately put into effect in hopes that such quarantines would 
