WEEDS AND FUNGI 137 



specially destructive in apple orchards. Cankered trees in a 

 forest should be cut out in the thinnings, and great care should 

 be taken not to wound standing trees while felling. With regard 

 to orchards, the Board of Agriculture leaflet No. 56 recom- 

 mends the cutting off of young infected branches. On older 

 branches the diseased part should be cut away, and the cut 

 surface should be protected with a coat of gas tar. Grafts 

 should not be taken from diseased trees. 



Beech seedling mildeiv. Phytophthora omnivora. 



This very destructive fungus attacks chiefly seedlings of 

 beech, but also those of maple, ash, acacia, spruce, and Scotch 

 pine. It may do considerable damage in natural regenera- 

 tions, and may kill off whole beds of seedlings in nurseries. 

 Damp warm years are favourable to the spread of the fungus, 

 which may be carried about by wind and mice, or on the feet 

 of men and horses. Infected seedlings turn black, and die 

 from below upwards, during germination or immediately 

 afterwards. The stem shrivels up and turns brown, and dark 

 spots appear on the cotyledons, or young leaves. It spreads 

 very rapidly. 



The most effective measure against it is to spray the 

 seedlings immediately the disease appears with Bordeaux 

 mixture Two pounds of sulphate of copper dissolved in 

 ten gallons of water, with one pound of freshly burned lime 

 added. All infected plants and dead leaves lying near by 

 should be burnt. Those parts of the nursery where the 

 disease has appeared should be used for transplants for a 

 few years, and seed-beds should be formed in a new place. 



