NEMATODE GALLWORM ON POTATOES, ETC., IN NEVADA. 



almost invisible to the naked eye. The mature female is nearly pear 

 shaped, as shown in figure 1 , being less than a luillimeter in length, 

 more often about three-fourths of a milhmeter long, the body cavity 



being occuined b}^ eggs and lar- 

 va'. The male is a slender, thread- 

 like worm, from 1 to 1.5 milh- 



meters in length (see fig. 2) . Tlie 

 development of the female takes 

 place within the underground tis- 

 sues of tlie host plant and its 

 presence in these tissues is indi- 

 cated by enlargements or mal- 

 formations. Figure 3 show^s a 

 potato which is badly infected 

 with gall worms. The skin is 

 roughened and broken in patches. 

 Fig. i.-Femaie of the nema- Not all infected potatoes show 



the same symptoms. Often tlie 

 gallworm is found in potatoes of 

 which the skin is nearly smooth, 

 and in such cases the presence 

 white spots showing approx- ^j ^j^^ ])arasite can be detected 



imately tlio natural size of -i 



only by cutting the potato. In 

 the infected tubers there is usu- 

 alh^ a ring of darkened tissue just 

 under the skin, and a microscop- 

 ical examination of this tissue 

 ^vill reveal the i)resence of the mature females and the region of the worm 



\_ 1 11 1 J.1 showing blind 



young larvae. In figure 4 are showm the larvae and the 

 eggs of the gallworm as seen through the microscope 

 from a preparation made from a diseased potato. 

 One of the eggs seen in figure 4 is shown still further 

 enlarged in figure 5. 



LIFE HISTORY OF THE GALLWORM. 



todo gallworm (JJeterodera 

 radicicola) magnified So di- 

 ameters: a, Mouth; 6, spher- 

 ical sucking bulb; c, c, ova- ' 

 ries, as seen through the 

 body wall; d, anus; e, small 



jitesp 



lately 



these worms. They are 

 usually wliite. It is gener- 

 ally not difficult to isolate 

 them in water by breaking 

 open the galls containing 

 them. (After N. A. Cobb.) 



Fig 2.— The adult 

 male of Helerodera 

 radicicola, or gall- 

 worni: /, Worm 

 in profile view; //, 

 head of the same, 

 more highly mag- 

 nified; ///.middle 



The larvae of the gallworm upon hatching from the 

 egg, which liatching sometimes occurs within the body 

 of the parent, ultimately escaj)e from the liost ])lant 

 and live for a period in the surrounding soil. Tlicse 

 larva;, although verj' active, have but little power of 

 progressive locomotion, and the spread of infection 

 from place to place must depend upon the transporta- 

 tion of infested soil or infected plants. wSoon after emerging from 

 the parcMit and tlic tissn(> of tlie liost plant these larvse'seek other 



[Cir. 01] 



showing 



ends of the sexual 

 organs; IV, pos- 

 terior extremity. 

 The drawings 

 were prepared 

 from stained speci- 

 mens, examined 

 in carbolic-aeid so- 

 lution. 



a, Lips; fi, oesoph- 

 ageal tube; c, medi- 

 an bulb; d, excre- 

 tory pore; f , spear; 

 /, intestine; g, 

 blind ends of tes- 

 ticles; h, testicles; 

 /, spicula; J, rudi- 

 mentary bursa; k, 

 anus, (.\fter N. 

 A. Cobb.) 



