NEMATHELMINTHES 91 



Family 2. Anguillulidae.— This immense group consists of 

 small, thread-like nematodes which live in water, mud and soil, 

 and also parasitically in plants and animals. 



Anguillula aceti, the vinegar eel,^ a frequent subject for laboratory- 

 experimentation, lives in vinegar and stale paste. Tylenchus 

 dipsaci {devastatrix) attacks oats, rye, clover, hyacinths, the ear 

 cockle of wheat and about a hundred other plants. Tylenchus 

 tritici attacks oats. Caconema {Heteroderd) radicicola attacks 

 over seven hundred plant species, including tomatoes, cucum- 

 bers, potatoes, turnips, peach trees, lettuce, and most other crops 

 and weeds. In crop rotation it is most important to keep down the 

 weeds. 



Lije History of Caconema radicicola.— The female is pear shaped, 

 and about 1/25 of an inch or about one-half the diameter of the head 

 of an ordinary pin. More than 500 eggs may be produced by one 

 female. Some of these pass out to the exterior, but many remain in 

 the body of the mother to develop, nourished by her remains and 

 by egg yolk. Upon hatching, the larvae seek out roots of many 

 species of hosts and drill into them by means of a protrusible oral 

 spine. The irritation causes a swelling or tubercle, the root-gall or 

 root-knot. The males pass through a larval stage and shed their 

 skins, then travel through the root tissue, as long eelworms, pair 

 with the females and die. Males are 1/12 to i/io of an inch long. 



Experiments showed that Heterodera schachtii, the beet-root 

 nema, will travel thirty feet to a bed of germinating beet seeds. 



In warm climates, such as the southern states and parts of 

 California, soil nematodes may pass through ten generations a year. 

 In colder latitudes, freezing may destroy them. Their ability to 

 encyst themselves preserves many in cases where the soil is porous 

 enough to enable them to burrow deep and then encyst. Warm, 

 moist sandy soils favor these nemas; heavy wet soils are less affected. 



Control. — The best method of removing plant parasitic nemas 

 from the soil seems to be by rotation of crops. A few plants, like 

 some varieties of wheat, millet, peanuts, rye, red-top, forw, cow-peas 

 and soy beans, prove to be only slightly susceptible to Caconema 

 {Heterodera) radicicola. In greenhouse soils, either stearn steriliza- 

 tion or the use of hot water is effective. In the absence of weeds, 

 lure-crops are used in greenhouses to advantage. 



1 Consult G. Zebrowski, 1931, "Anguillula Aceti— A Desirable Nema For Type 

 Study." Science, vol. 74, pp. 390-391, Oct. 16, 1931. 



