6 



Js^EMATODE GALLWOBM ON POTATOES, ETC., IN NEVADA. 



roots aiid bore their way into the plant tissues by means of a spear- 

 like structure, wliich is protruded from the mouth. They feed upon 

 the cell sap of the host plants. 



After fertihzation takes place the females begin reproduction by 

 forming eggs within the body. These eggs are laid at the rate of 

 from 10 to 15 a day, and it is estimated that one female may lay as 

 many as 500 eggs. After completing the egg-laying process the female 



dies, the male having died 



fertilizing 



the 



Fig. 3— Potato infected with the gallworm. This shows 

 the rough character of the surface, which indicates the 

 presence of these worms. The knobs, or warts, are often 

 much more strongly developed than in the above. Gall- 

 worms in seed potatoes are particularly dangerous, for if 

 infected potatoes are used for seed the land wll l)e inocu- 

 lated. If infected potatoes are used as food, the refuse 

 parts should be cooked or destroyed. Otherwise they 

 may spread the disease. (After F. B. Headley.) 



soon after 

 female. 



The worm lives from one 

 season to the next, either in 

 the egg stage or in the larval 

 stage within tlie host plant. 

 The life of the individual 

 worm is short (only a few 

 weeks), when temperature 

 and moisture conditions are 

 such as to favor growth.' 

 It is possible, therefore, to 

 greatly reduce the numbers, 

 if not to exterminate the 

 worm entirely, by keeping 

 the infested land free from 

 plants upon which the worm 

 can feed. 



SOURCES OF INFESTATION. 



The gallworm discussed in 

 this paper is one of a large 

 number of species of nema- 

 tode worms. This particu- 

 lar species occurs very gen- 

 erally throughout the southern United States. In many sections it 

 is found in such large numbers as to be a serious pest to many crop 

 plants, such as the peacli, the fig, cowpeas, cotton, and many vege- 

 tables. It may be transported from place to place on any of these 

 plants which it infests or in soil from infested fields. Probably the 

 most common method of transporting the worm is through tlie ship- 

 ment of nursery stock and of pota toes. The distribution of the worm 



. Additional information concerning the life history of this parasite, with a list of susceptible Plants and 

 details of experiments in controlling the nematode in the southeastern United States may be found m 

 Bulletin 217 of the Bureau of Plant Industry, entitled "Root-Knot and Its Control, by T).. Ernst A- 

 Bessey, issued November 21, 1911. 

 rCir. 01] 



