280 



Eradication of Dodder. 



[JULY, 



cup disease (Leaflet No. 209) ; gooseberry bushes from St. Ives 

 (Hunts) were affected with white root-rot (Leaflet No. 64) ; 

 potatoes from Bala with stem-rot (Bacillus phytophthorus) , 

 described in Leaflet No. 117 ; tulip bulbs and leaves from 

 Penryn (Cornwall) and East Grinstead with the tulip mould, 

 Sclerotinia parasitica, Massee, (Leaflet No. 127 deals with 

 Sclerotium disease) ; and onions from Somersham (Hunts) 

 with Sclerotium disease. 



Spraying with a solution of sulphate of iron is a means of 

 destroying dodder on clover, which has proved successful in 



Germany. Dr. Hiltner, Director of the 

 Eradication of Munich Agricultural Botanical Institute, 

 Dodder. reports (Prak. Blatter fur Pfianzenbau, 



April, 1908) that in 1906 a plot was sown 

 with red clover seed containing 2,000 seeds of dodder (Cuscuta 

 arvensis, an American species) in 100 grammes (3 J oz.). The 

 dodder developed luxuriantly and infested the whole crop. In 

 August it was sprayed with an 18 per cent, solution of sulphate 

 of iron, with the result that the clover had so black an appear- 

 ance that one might have thought it was ruined. After a short 

 while, however, it sprouted again, and grew at least as well as 

 the portion which was left unsprayed. The latter was ultimately 

 still more checked in its growth by the spreading dodder. The 

 dodder entirely disappeared from the sprayed plot, though it 

 afterwards made its appearance to a small extent in consequence 

 of fresh infection from the adjacent plot. 



In a similar experiment in 1905 the solution was applied in 

 two strengths, 15 and 18 per cent. In this case, however, 

 the clover did not recover after the application of the stronger 

 solution, and although experience in the destruction of charlock 

 shows that clover is generally able to withstand spraying with 

 iron sulphate, Dr. Hiltner thinks it unnecessary to exceed a 

 strength of 15 per cent. The same treatment is applicable to the 

 destruction of the common clover dodder (Cuscuta Trifolii). 

 The spraying must be done with a sprayer, so that the liquid 

 falls with some force on the ground, and reaches the threads 

 of dodder which are attached to the stalks of the clover beneath 

 the surface. An application with a watering-can did not prove 

 successful. 



