DISEASES OF CULTIVATED PLANTS 579 



Dodders in General. The dodders, or love-vines, are parasitic 

 flowering plants closely related to the morning glories, or bind weeds. 

 There are several species occurring in this state besides the one which 

 attacks clover. Most of these grow on weeds, particularly in moist 

 bottom lands, and do no damage to the farmers' crops. These plants 

 are peculiar in that they are parasitic in habit, depending on the 

 plants upon which they grow for their food, instead of elaborating it 

 for themselves from the soil-moisture and air, as plants possessing 

 green color are able to do. Dodders are destitute of this green color, 

 called chlorophyll, and so have not the power of elaborating food for 

 themselves. The plant consists of a yellow stem which is practically 

 leafless. 



Methods of Eradication. When occurring in small areas, the 

 following methods of eradication may be practiced : 



1. Cut and rake to the center, the infested plants in the spots, 

 and burn. Cut the clover one yard in all directions outside of the 

 apparently infested area, to be sure that no branches are missed. 

 For complete eradication this cut area should be hoed to a depth of 

 3 inches for about three weeks. This allows the scattered seed to 

 germinate and die. If the spots are cut early before the seeds are 

 ripe, this cultivation is unnecessary. 



2. Sprinkle infested spots with a 10 per cent solution of sul- 

 phate of iron, or potassium or copper. This is best applied to the 

 stubble after the spots have been cut and burned. 



If the dodder covers large areas so that the above suggestions 

 are impracticable, the following may be practicable : 



1. Close grazing with sheep or cattle for some time. 



2. Rotation with crops which involve cultivation for two or 

 more seasons. 



Dodder may be introduced through baled hay and the seeds 

 spread through manure. Thus hay infested with dodder should 

 never be used, as it may be spread in this way to all parts of the 

 farm. 



Seed Inspection. The best method of keeping dodder off the 

 farm is to prevent its introduction by rigid seed inspection. Dodder 

 is usually introduced through impure seed. It is probable that 

 great numbers of cases where dodder appeared recently were directly 

 traceable to the use of impure seed. The seed of clover dodder are 

 smaller than red clover seed, and by close screening may be sepa- 

 rated. (Del. E. S. B. 83.) 



CORN DISEASES. 



The Blight of Corn. This disease first seemed to be almost en- 

 tirely confined to late planted corn, that which was planted as a 

 second crop. The disease is caused by a parasitic fungus, Helmin- 

 thosporium inconspicuum, which makes its appearance on the leaves 

 as a greenish mold visible in mass to the naked eye. This growth is 

 found on discolored, elongated spots, their width being often lim- 

 ited by the veins of the leaf. This is no new trouble, but appears 

 to have done more than the usual amount of injury in Delaware 

 during the past season. The blight causes on corn leaves long dead 



