Par.'j„'3. A:2 



Life History- 

 Larvae in the soil enter the roots of plants near the root tips and V}es^in 

 to feed on the developing tissues. Here they undergo three moults, break- 

 ing through the outer root tissue at the last one. Females remain attached 

 to the root by the neck. Males leave the larval cuticle and go in search 

 of females. Apparently all of the females of the H. schachtii and H. gflt- 

 tingiana groups deposit some eggs in a jelly-like substance, forming an 

 eg^ mass or "egg sac." However, these species also retain eggs in the body 

 so that by the end of the life of the female, the body is tightly packed 

 vfith eggs. Females of the H. rostochiensis and H. cacti groups do not de- 

 posit any eggs, retaining all in the body. The female finally dies and 

 her cuticle becomes transformed into a cyst filled with eggs. Eggs in the 

 cyst; develop to the first larval stage, then moult once, becoming second 

 stage larvae. Apparently hatching may then take place immediately, or the 

 larvae can remain in the eggs In the cyst indefinitely. 



It has been shown that root excretions of various plants can stimulate 

 hatching. Most work on this subject has been done with H. rostochiensis . 

 l^en cysts of this species are placed in leachings from a growing potato 

 plant the rate of hatching of their eggs is enonnously increased. How- 

 ever, it is seldom that all the eg-'s in a cyst hatch even \inder the most 

 favorable conditions. In the absence of a host plant only a few eggs 

 hatch each year. Hatching after 17 years has been reported in the litera- 

 ture. Probably the maximum time under most conditions is less than half 

 of that. Once hatched, the larvae make their way to a host plant complet- 

 ing the life cycle. 



Because of the limited host range of most of the Heterodera species, it is 

 usually easy to devise crop rotation methods for control. On the other 

 hand, delayed hatching of the eggs means that the rotations must be very 

 long; in heavily infested sugar beet fields, as long as 5 or 6 years must 

 be allowed between beet crops. Since it has been shown that larvae die 

 within 12 to 18 months after hatching if they do not reach a host plant, 

 efforts are being made to analyze the "hatching factor" in root leachings 

 in the hope that it can be synthesized and used in control. Some progress 

 has apparently been made. 



The literature on Heterodera is voluminous, European workers having studied 

 the sugar beet nematodes and other species of this genus since around l06O. 

 A summary to about 1938 will be found in "A Manual of Agricultural Helmin- 

 thology," by I. N. Filipjev and J. H. Schuurmans Stekhoven (19Ul). A later 

 and shorter suini.iary, "The Cyst-forming species of Heterodera ," by Mary T. 

 Franklin, was published by the Commonwealth Agricultural Bureaux, Farnham 

 Royal, Bucks, England, in 1951. "The Golden Nematode of Potatoes," by 

 B. G. Chitwood, (USDA circular No. 875) summarizes information to about 

 1951 on H. rostochiensis in this covmtry. There are several host lists, 

 but because of the confusion as- to identity of species, most are apt to be 

 misleading. Probably the best information on hosts is fovind in reports of 

 experiments by F. G. W. Jones, "Observations on the beet eelworm and other 

 cyst-forming species of Heterodera." (Annals of Applied Biology 37(3): 



