460 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 12 



A PRELIMINARY NOTE CONCERNING A SERIOUS NEMA- 

 TODE DISEASE OF RED CLOVER IN THE 

 NORTHWESTERN STATES 



By Ralph H. Smith, Associate Enloniologist, University of Idaho, Moscow, Idaho 



Soon after taking up work in Idaho in May, 1918, the writer was 

 asked to examine several fields of red clover in which the greater per- 

 centage of plants had either died or showed evidence of being badly 

 diseased. The symptoms of the disease at this time were something 

 like those of the stem rot of red clover that is caused by the fungus, 

 Sderotinia trifoliorum Erks. The widespread destructiveness of the 

 malady during the autumn and early winter led to a careful investi- 

 gation of the cause, with the result that the well known stem and bulb 

 nematode of Europe, Tylenchus dipsaci Kiihn, was found to be the 

 primary pathogenic organism. No trace of any fungous parasite was 

 found. Determination of the species was made by Dr. N. A. Cobb of 

 the Bureau of Plant Industry. 



Information that has been obtained from farmers indicates that 

 this disease of red clover has been present in southern Idaho for several 

 years and that it is rapidly increasing in its destructiveness. During 

 the spring of 1919 several hundred acres of red clover had to be plowed 

 up while a large percentage of the fields left were quite badly affected. 

 The known distribution of the disease is limited chiefly to the irrigated 

 sections of eastern Washington and Oregon, southern Idaho, and 

 northern Utah. 



The causal organism, Tylenchus dipsaci Kiihn (syn. devasiatrix Kiihn) 

 has been a well known destructive nematode of Europe since 1851 

 when, according to L. Reh,^ it was described by Julius Kiihn. It is 

 remarkably polyphagous, having upwards of one hundred known spe- 

 cies of host plants. In Europe it is a pest of clover, alfalfa, oats, rye, 

 wheat, buckwheat, hops, beans, potatoes, onions, certain grasses, 

 various ornamental plants, and numerous weeds. In England it is a 

 leading cause of the malady long known as " clover sickness. " During 

 the past ten years it has become an important pest of different crops in 

 New Zealand, Australia, and Cape Good Hope. 



The occurrence of T. dipsaci in North America was first reported by 

 Dr. E. A. Bessy who found it damaging a field of rye at Edgerton, 

 Kansas, in the summer of 1907.^ It was next discovered in the sum- 

 mer of 1913 at Belhngham, Washington, where it was the cause of a 

 disease of hyacinths.^ In 1915 Professor A, L. Lovett found it injuring 

 red clover at Redmond, Oregon.'* During the summer of 1916 Doctors 

 N. A. Cobb and L. P. Byars of the Bureau of Plant Industry prepared 



