PARASITIC PLANTS 261 



a portion of the crop than risk infestation another 

 year. Further, the whole of the area cut over should 

 be covered several inches deep with chaff and burnt 

 over. 



3. It is recommended by Thaer that infested spots 

 be surrounded by a small trench beyond the outermost 

 threads of Dodder, the soil from the trench being used 

 to cover the patch. 



4. A somewhat similar plan is suggested by Frank : 

 covering the patch with a layer 3 inches deep of chaff, 

 tan, or gypsum, with an inch or so of fine soil on the 

 top, the whole being saturated with liquid manure or 

 sprinkled with powdered quicklime in winter. Such 

 a method usually allows the clover to break through 

 the covering, but the Dodder will be unable to do so. 



5. A plan which appears to have been successfully 

 practised l consisted in " removing the surface of the 

 affected spots with a plate-spade and burning the 

 material (earth, Dodder, &c.) mixed with old thatch in 

 the centre of each patch, followed by burning a layer 

 of waste straw on the top of the cleared patches, taking 

 care to put it well round the edge, even sacrificing a 

 portion of the unaffected crop round the edge." The 

 cost for thus treating twenty-five patches three to six 

 paces in diameter on an area of 7 acres was perhaps 

 five shillings. 



6. Should an infestation be very extensive it will 

 probably be best to plough the whole crop under, but 

 this must be done before the seeds ripen, and if possible 

 before they are formed. 



7. As the seeds may lie dormant in the soil for five 

 or six years, a field that has been attacked by Dodder 

 should not again be sown with clover for seven or 

 eight years. 



1 Jour. Bd. Agric., June, 1909, p. 209. 



