238 VEGETABLE FOES AND DISEASES 



many years we have used a mixture of air-slaked lime 

 and soot in equal parts by measure as soon as the young 

 Onions were well up and again at thinning time, at the 

 rate of a peck per rod, and not been troubled with 

 mildew. Spraying with a solution of potassium 

 sulphide, one ounce to two and a half gallons of 

 water, will also check the spread of the disease. Pre- 

 vention, however, rather than cure should be the aim 

 of the cultivators. 



THE ILLUSTRATIONS REPRESENT ONION MILDEW. 



A, plant of Onion affected with Onion Mildew : a, diseased 

 patches ; b, portions of leaves destroyed and fallen back ; c, 

 bulb not affected ; </, " thick " or long neck, one-third natural 

 . size. B, Onion Mildew (Peronospora schleideni) : e f 

 conidiophore bearing conidia or summer spores ; f y stoma of 

 Onion leaf, x 230. C, mature and free conidia or summer 

 spores, one germinating : g, germ-tube, x 200. D, resting 

 spore, or Oospore. x 300. 



PEA THRIPS (Thrips pisivora). 



The Pea Thrips was first figured and described 

 by Professor Westwood in the Gardeners' Chronicle, 

 1 4th August, 1880, page 206, and it is recorded that 

 in July of that year the Pea crops in the neighbour- 

 hood of Oxford were seriously injured by the pest. 

 Prior to that time, and since, the Pea crops have 

 suffered more or less in hot and dry seasons from 

 attacks of Thrips, particularly on dry soils and in 

 warm situations; especially in 1893, an d in 1896 



