lo March. 19 ro.] The 0)iton Eel -worm. 163 



THE OXIOX EEL-W OKM. 



Experiments for the Eradication of — 

 With a Short Description of its Life History and Habits. 



ir. Laidlaii-, B.Sc, Micro-Biologist ; and C . A. Price. Microscopist. 



It is only within recent \ear.s that special attention has been directed 

 to the systematic study of the Nematoda or thread worms parasitic on 

 plants, as distinguished from those affecting animals, though various 

 experiments were made manv years ago bv the Department of Agriculture 

 for the eradication of eel -worms affecting the onion crops in the Drvsdale 

 district. 



In the year i8qo. Dr. X. A. Cobb, in the Agricultural Gazette of New 

 South Wales, called aitLmtion to the fact that an eel-worm, know-n to 

 science as Tylenclius devastatrix, was believed to exist in Australia. This 

 was confirmed bv an article from the pen of Mr. A. X. Pearson, who at 

 that time was Agricultural Chemist for Victoria. 



At the instance of the late Mr. Levien. M.L.A., a prominent onion- 

 grower, Mr. Pearson visited the Drysdale district for the purpose of 

 ascertaining the cause of a disease affecting the onions. He discovered 

 in the diseased onions a minute eel -worm. He says : — 



The ground at present is in a deplorable state. It is not surprising that this 

 should be so. In almost all cases where crops are grown year after year on the 

 same land, without rest or change, such a condition of things arises, but besides 

 this continuous onion growing the ground is not cleared of the diseased onions 

 which are allowed to reniain bearing the eggs or spores to the next season. 



For many years jirexious to this date, this land had been continuouslv 

 cropped with onions, owing to its suitabilitv for their culture. Mr. Pearson 

 arrived at the conclusion that the only remedy for the state of things 

 then existing was an entire change in the svstem of agriculture, the aboli- 

 tion for a time of the onion crop from the district and the establishment of 

 suitable rotations. He exjjerimented with a number of chemicals, including 

 chloride of lime, gas lime, dilute solutions of mercuric chloride and dilute 

 arsenical solutions. He also burned straw and brushwood on the surfare 

 of the soil, without any or onlv slight beneficial effects. 



Dr. Cobb applied to Mr. Pearson for specimens of the diseased onions, 

 which were forw^arded and on which he contributed a report to the Agricul- 

 tural Gazette in 1891. After a minute description of the aratomy of the 

 eel -worm (which he rc-cognised to be Tylenchus devastatrix), and the 

 various agencies bv whirh it is spread, he suggested the following 

 remedies : — 



1. To destrov all affected jilants. 



2. To remove all weeds that might afford the worms a subsistence. 



3. Removal of the first three inches of the surface soil. 



4. Deep and thorough ploughing which turns the soil exactly bottom side up. 



5. The promotion of a ra[)id growth of the plants cultivated. 



6. Sowing the infested Inml thicklv with rye, and reaping it while voung. 



7. Injection of carbon bisulphide into the soil, the iniections to be shallow 

 and numerous. 



8. A good svstem of drainage. 



In the year 189 1. various chemicals were tried by Mr. D. McAlpine, 

 Vegetable Pathologist, for the eradication of the onion eel-worm. The 



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