STEM NEMATODE ON WILD HOSTS. 5 



found in cultivated strawberries in northwestern Oregon or in Wash- 

 ington. 



Quite frequently a large association of plants was found with 

 the Fragaria or Hypochaeris, including the salal (Gaultheria 

 shatton), the brake (Pteris aquilina), a moss, and a large number 

 of small herbaceous flowering plants. All of these plants were care- 

 fully examined without finding any sign of the disease. 



RELATION TO ENVIRONMENT. 



In the case of Fragaria, nearness to the ocean appeared to be a 

 factor which influenced infection. In most cases no diserse was 

 found 100 yards from the shore, even though it was abundant at 

 the edge of vegetation above the beach. Quite frequently this 

 host growing in the sand about the driftwood was affected. Again, 

 frequently the sea side of a sand dune would have affected plants, 

 while those on the land side would be free. Slopes near a rocky 

 promontory upon which the waves dashed at high tide were often 

 heavily infested. This was the case at Seal Rocks, in Lincoln 

 County, at which point wild-strawberry patches quite extensive in 

 area on a bluff 50 feet high were found more than 50 per cent 

 affected with the nematode disease. (PI. Ill, B). At Yaquina 

 Head (PI. Ill, A), where meadow grasses and strawberries pre- 

 dominate, the disease was found in great abundance, especially on 

 the steep north slope of the hill. Over the entire slope from the 

 beach to the summit, probably 500 feet high, diseased plants were 

 found. Plate III, C, shows a view of a typical spot on the hillside 

 where the disease was found. 



A similar condition of a high percentage of diseased plants in 

 strawberry meadows near the shore existed at another promontory 

 known as " Jump-off Joe." Diseased plants occur close to the beach 

 and on the side of the bluff to the very top. None was found, how- 

 ever, back of the edge of the bluff, a distance of 50 feet. 



In many cases it appeared that almost constant high humidity 

 was required to maintain infection and favor the spread of the 

 disease on this host. This was obviously obtained at times by actual 

 salt spray from the ocean and again from the heavy fog that occurs 

 so frequently near the coast. When the photograph reproduced in 

 Plate III, B, was taken, the atmosphere was saturated by a falling- 

 mist that nearly shut the distant rocks from view. 



Nearness to the ocean did not appear to be a factor in the case 

 of Hypochaeris. At Newport, where the plant grew abundantly as 

 a weed in meadows, on lawns, and beside the streets, the disease 

 was found for several hundred yards back into the town. It also 

 occurred some distance from the shore in Tillamook County, Oreg., 

 and near Long Beach, Wash. The presence of the infested Hypo- 

 chaeris plants a considerable distance from the shore led to the search 

 for and discovery of the disease at the inland valley points, where 

 direct influence of ocean moisture could be no factor in infection. 



ORIGIN AND DISSEMINATION OF THE DISEASE. 



The possibility of the infection of the wild-strawberry plants 

 having originated in the cultivated fields was at first considered 



