102 WEEDS OF FARM LAND 



of the parasite appear, as by this means large numbers of the 

 latter are killed. The seedlings may also be destroyed by 

 harrowing in March or even later, but this is not usually as 

 effective as dressing with salt. 1 



Eradication on arable land is a matter of greater difficulty. 

 In ordinary rotation courses cereal crops follow one another 

 at intervals of two years or even less, so that there is no time 

 to work the yellow rattle seeds out of the soil before the 

 favoured host plants are again available. When once the 

 cereals are attacked, mechanical methods of eradication can- 

 not be applied, as the parasites are so closely attached to the 

 hosts that forcible removal of the yellow rattle would injure 

 the roots of the crop. Owing to the in frequency of bad attacks 

 of this weed on arable land little is known as to the best 

 method of cleaning the land ; fallowing, coupled with frequent 

 cultivation when the yellow rattle seedlings appear, might do 

 some good. Possibly, too, if the land were grassed over for 

 a time, and grazed by sheep as soon as feed was available, a 

 clearance might be effected after some years. It would be 

 necessary to carry this on long enough to allow most of the 

 seeds to germinate, and then to keep a careful watch when 

 the land was again ploughed up in order to stamp out the 

 pest at its first reappearance. 



RED BARTSIA (Bartsia odontites) (Fig. 31), Nat Order 

 Scrophulariacece. This partial parasite is rarely accused of 

 causing trouble, but as it is undoubtedly parasitic on the roots 

 of wheat it should be carefully watched wherever it is plenti- 

 ful. The roots of bartsia attach themselves to the wheat roots 

 in much the same way as in the case of yellow rattle, and 

 part of the food is abstracted from the cereal. Bartsia is 

 obviously half parasitical on the roots of various other plants, 

 as it is often much more abundant on the paths and headlands 

 than it is among the crops. It is seldom present in great 

 quantity, but, if conditions were specially favourable, it might 

 conceivably do some amount of mischief. 



Eradication. No special measures are taken to eradicate 

 this weed, which is usually kept in hand by the ordinary 

 methods of weed destruction. 



1 " The Eradication of Yellow Rattle " (1916 ?), Agricultural Department, 

 Univ. Coll. of Wales, Aberystwyth. 



