i68 ] ournal of Agriculture . \\o March, 1910. 



leaf, place it in a watch glass with a little water, and examine it under 

 the microscope when the young worms can be seen in active movement. 

 It is even possible to detect them bv the aid of a good pocket lens. This 

 method was fo'und to give positive results in all cases wiien affected soil 

 was submitted to examination. 



Samples of soil taken from infested land at a depth of 4, 8, 12, and 

 14 inches, were all submitted to the above method of examination, and 

 in every case with positive results. This shows that deep ploughing which 

 turns the soil exactly bottom side up, the use of a skim coulter tO' remove 

 the upper layer of the soil, the burning of straw or brushwood on the 

 surface, and even the use of chemicals will have little or no effect on 

 land where the soil is liable to crack, as it is in the Drysdale district, thus, 

 allowing the eggs and embryos to be washed by rain storms, or blown bv 

 the wind into the deeper layers of the soil. 



Of all the constituents of the soil, none probably are more likely to be movecf 

 from place to place than minute organisms, such as the eggs and larvae, of 

 nematodes by the action of currents of water on or beneath the surface. It has 

 long been known that drainage has an important bearing on the spread of nema- 

 todes. Wind, animals, in fact anything that moves either in or upon the soil, 

 will act as agents in disseminating the disease. — (Cobb.) 



The Effect of Flooding and of Drying the Soil. 



The experiments showed that, if boxes of soil were completely sub- 

 merged in water for ten days, the nematodes were sufficiently abundant in 

 the .soil to attack plants sown subsequently. When soil dried in the 

 laboratory for six months was moistened and .strips of onion laid on the 

 surface, the eggs present in the soil were hatched within fourteen days, 

 and the young worms were found in great numbers, having been attracted 

 to the food supply on the surface of the soil. 



In any experiments carried out for the eradication of the onion eel- 

 worm, its great vitality and power of resisting desiccation, especially whilst 

 in the egg and embryonic stages of its existence, must always be borne in 

 mind. Onion plants that had been kept in a dried condition for over 

 two years were moistened and, on examination a few hours later, young 

 worms were seen moving freely in the moistened pulp. 



For the purpose of studying the life cycle of the worm, all that is 

 neces.sary is to take a small portion of this pulp, place it in a covered 

 glass dish, adding to it a small quantity of any vegetable tissue, preferably 

 strips of onion leaf, and keeping the culture in a slightly moist condition. 

 If there is too much moisture, development is retarded. I'he same obser- 

 vation holds good if the culture is too dry. The young worms will, in a 

 few hours, be found attacking the new material ; the embryos, which are 

 about one-fourth the adult size, as soon as they are liberated from the 

 eggs, make their way from the old onion pulp to the fresh food supply. 

 In a few days, these worms become sexually mature, conjunction of the 

 sexes takes place, and in a comparatively short time the fecundated 

 females begin depositing their eggs in large numlx-rs. These eggs in their 

 turn are very soon hatched, and the embryos set free to begin a new 

 generation. 



Sterile Soil. 



A quantity of infected soil was placed in an ordinary flower pot and 

 heated in a steam sterilizer for one hour. The temperature of the soil 

 on removal registered 1870 F. After it had cooled, onion seed was sown. 

 It germinated freely and none of the young plants were attacked by the 



