PLANT DISEASES. 79 



green manuring. Experiments in 192 1 indicated that a similar 

 though less effective result is obtained by the use of old hay and 

 spent hops. 



A Bacterial Disease of Rhubarb. — Research has recently been 

 carried out into a disease which causes serious losses to growers 

 of early rhubarb. This is a considerable industry in the north 

 of England, round the industrial centres. The rhubarb is grown 

 in fields for three or four years, and is then taken up and placed 

 in forcing sheds in the autumn, providing a supply of early rhubarb 

 from the following December to March, which is sent to the 

 main Enghsh markets and to the Continent. Of late years 

 serious losses have been caused by a disease which causes the 

 crown of the rhubarb to break away from the roots, thus spoiling 

 the latter for further growth. The disease is extremely infectious 

 and is responsible for losses amounting to many thousands of 

 pounds yearly. Research into the nature of the disease was 

 commenced about two years ago, and it was found to be caused 

 by a baciUus. The bacillus belongs to a group of organisms 

 found in sewage, and the widespread nature of the disease is 

 very probably due to the fact that night soil and sewage have 

 been largely used for manure by the rhubarb growers. Field 

 trials have been carried out and various antiseptics applied to 

 the soil, with the result that it was found possible to reduce the 

 disease by 75 per cent, by the use, for example, "of bleaching 

 powder or ammonia. A further series of antiseptics is being 

 tried this year in the hope of discovering one which shall be 

 cheap, easily applied and still more effective. 



East Mailing Research Station, Kent. 

 Test of Fungicides on Apple Trees. — A series of experiments 

 for the control of scab and other fungi on apple trees was begun 

 in the spring of 19 19 and continued through 1920 and 192 1, 

 the object being to test the comparative value of various fungi- 

 cides, their fungicidal power, and the extent of the injury they 

 cause to the foliage and fruit of certain varieties of apples. A 

 number of fungicides were tested : — Lime sulphur, alone, and 

 in mixture with other materials ; " Bordeaux-mixture " of two 

 different formulae ; and ammonium polysulphide with soft soap. 

 Comparisons were obtained of the value of lime-sulphur and 

 Bordeaux ; lime sulphur alone and in mixture with lead-arsenate 

 and saponin; lime-sulphur and ammonium polysulphide; and 

 the two Bordeaux formulae. The work was done with the 

 advice and assistance of the Advisory Mycologist at Wye College. 

 On account of various limitations in the experiment, the results 



