Agricultural Gazette. 



I shall consider the last of these methods first. 



1. Trapping. — It consists in actually capturing the worms and then killing 

 them by hand or by machinery. How to capture a foe numbering millions 

 and doubly masked by being invisible and being hidden away underground 

 might well seem a puzzling question. How it was answered constitutes one 

 of the interesting passages in the history of applied science. The gall-worm of 

 the sugar-beet had long been known to be one of the worst pests of that 

 crop. " Various investigations were made and various remedies tried by those 

 interested in the sugar-beet industry, but to little purpose. Year by year the 

 pest grew wor.se, — more and more land had annually to be abandoned by the 

 beet grower. At this point the pliilosophical faculty of the University at 

 Leipzig oilered a prize for the best investigation of the cause of the 

 Eiibenmiidigkeit. The prize was awarded to Struboll for an investigation 

 whose results are detailed on page 170, under the head of T. scJiachtii. 



Professor Kiihn, making Strubell's investigations the basis of his reasoning, 

 now devised a plan for trapping the larv». Noting that, according to 

 Strubell's investigations, the larvtc on entering the young beet plant became 

 mature in about live or six weeks, he predicted that if the plants were pulled 

 at the end of four weelcs, the worms in them would die without producing a 

 new brood. It will be seen that Professor Kiihn's plan was based on a 

 careful perusal of the life-history of the Tylenchus. If the plant should be 

 allowed to remain five weeks before being pulled, the worms would, it is 

 true, be lulled, but not so the rggs which in five tveeks the females would 

 have produced. These eggs would ultimately hatch and the pest continue. 

 But after precisely four weeks, even the oldest worms in the roots would 

 not yet have produced eggs, and, being at that time motionless sacs, in- 

 capable of boring their way out, must perish from starvation if the host- 

 plant should suddenly die. In other words, Kiihn proposed to make trapa 

 of the young plants, and naturally chose such plants as are loved best by the 

 worms. Sugar-beet was selected as the plant likelv to entrap tlie greatest 

 numbers. 



The result of the experiments based upon Kiihn's plans was a brilliant one. 

 A piece of ground, so badly infested as to be useless to the sugar-beet grower, 

 was sown with sugar-beet. After four weeks the plants were pulled, and 

 another lot of seed sown. The experiment was repeated a third time, if 

 necessai-y, and it was then found that the post was controlled. The time 

 occupied was about three months. Tlie plants whose roots were used as 

 traps could be turned to account as fodder or fertilizer, so that the twelve 

 weeks were not a dead loss. In Kiihn's first experiments the plants were 

 pulled by hand. That operation was expensive, and led to a trial of ploughing 

 up the trap-roots, and this plan was found to answer almost equally well. 



It is beforehand to be supposed that tlie Australian T. arenarius may be 

 trapped in the same way as T. schachtii, but the time required for its develop- 

 ment is not yet accurately known. As Consulting Pathologist to the 

 Agricultural Department, it is understood that only my spare time is avail- 

 able, and that has latterly been so -very meagre that since fir.st giving atten- 

 tion lo this matter, one month since, I have found but three days in which 

 to make it the subject of investigations. In consequence, I have no data for 

 giving the precise length of time required for the larvio to mature in roots. 

 The most I can say is that it is probably less than that required by the sugar- 

 beet gall-worm. Consequently, in any trial of Kiihn's remedy in dealing 

 with T. arenarius, it will be best, in the present state of our knowledge, to 

 keep well within his limits and allow (say) three weeks before ploughing up 



