202 THE NURSERY-MANUAL 



should be made soon after the new leaves are pushed forth 

 in the spring. Four or five subsequent applications should be 

 made at intervals of ten to twenty days. 



THE GOOSEBERRY MILDEW. The gooseberry mildew is 

 often very destructive, and it occurs in all parts of America 

 where gooseberries are grown. It is known to affect currant 

 bushes also. The European varieties of gooseberries, such as 

 Smith and Whitesmith, are more susceptible than the American 

 varieties. The Houghton is the most susceptible of the Ameri- 

 can varieties. 



Description. The leaves, the stems and the fruit are 

 attacked. In the nursery the mildew is commonly observed 

 on the tips of the young shoots as white felt-like spots. The 

 mildew spots continue to enlarge and may almost completely 

 cover the tips, extending for some distance down the shoots. 

 If the disease is very severe the new growth is destroyed, and 

 the older wood may be considerably injured. 



Cause. The mildew is caused by the fungus Sphcerotheca 

 mors-uvce. This fungus is similar to the organism causing 

 the mildew on roses and resembles in many respects the mildew 

 of apples. Spores borne in the white patches of fungus my- 

 celium on the shoots are a means of further spreading of the 

 parasite. After midsummer, specialized fruiting bodies (peri- 

 thecia) are produced in the old mycelial patches of mildew on 

 the twigs, and these fruiting bodies carry the fungus over winter. 



Control. Lime-sulfur solution 1 to 40, or a dust mixture 

 of 95 parts sulfur and 5 parts lead arsenate, is effective for 

 the control of this disease. The first treatment should be made 

 early in the season as soon as the mildew appears, and subse- 

 quent applications should be given according to the prevalence 

 of the mildew; if very abundant, three or four sprayings at 

 intervals of eight to twelve days may be necessary to protect 

 the developing shoots. 



