io8 PLANT DISEASES 



until the flowers appear. The disease is often very severe 

 in the United States. Professor Trelese has the following 

 note on its prevention : ' The most convenient way of 

 effecting this is by mowing badly rusted beds soon after the 

 fruit is gathered, covering the dry tops with a light coating 



Fig. 18. Sphaerella fragrariae. i, strawberry leaf 

 diseased ; 2, ascus with eight spores from a perithecium 

 of the Sphaerella or ascigerous condition, x 300 ; 

 3, conidia of the Ramularia stage, x 300. 



of straw, or harrowing up the old mulching, and burning 

 them. This may seem harsh treatment for the plants, but 

 it has been resorted to by many berry-growers for the 

 destruction of insects with most satisfactory results ; and 

 every one who has tried burning over a strawberry bed has 



