ENTOMOLOGY. 271 



Omitting the transformations and structure of the male and female I 

 will simply mention the duration of a single generation, during which 

 time the numerous transformations take place. The worm passes 

 through all the changes, from the development of eggs through the larval 

 and cystic state until eggs are again developed in about one month. 

 When we consider the number of eggs one female is capable of producing 

 it will be seen that the worms multiply with startling rapidity. 



It has been stated that these nematode worms cannot survive the cold 

 of severe winters. This may be true or not, but with the arrival of warm 

 winters in Minnesota this injurious worm has arrived from more southern 

 climes, and I am afraid it has come to stay. 



In Minnesota it has been found upon the roots of apple and pear trees, 

 as specimens before you show. But the worm is a rather general feeder, 

 and some forty species of plants are already known which are badly in- 

 jured by it. Of cultivated plants the peach, grape, potato, egg-plant, 

 tomato, cotton, okra, some varieties of peas and clover, sun-flower, water- 

 melon, corn, cabbage, turnips, rutabaga, pirsnips, lettuce, salsify, and 

 others are to the taste of this almost omnivorous worm. 



A number of remedies have been suggested, but careful experiments 

 can only show which are of real value. 



Plants which are already diseased can not be saved, as the worms are 

 so well protected by living in the interior of the root that any direct ap- 

 plication of vermicides will injure the plant as much, and more, than the 

 worms. The application of bi-sulphide of carbon, kerosene emulsions, and 

 various arsenical solutions in sufficient quantities to kill the worms, were 

 also fatal to the plants to be protected. Alkaline fertilizers, like hard 

 wood ashes, muriate and sulphate of potash, kainite, etc., produced a hard 

 growth of roots less susceptible to attack. 



The cheapest and best method would be to starve out the worms by a 

 proper rotation of plants, of course selecting such plants for this purpose 

 as are known not to be attacked. But the question arises: What 

 plants shall we select for this purpose? Only a series of trials will enable 

 us to name plants not susceptible to the disease. All species of annual 

 grasses seem to be unaffected. Unclean cultivation is one of the most 

 fruitful sources of the thorough impregnation of the soil with such worms. 

 Plants infested should be removed and burned, and no other plants sus- 

 ceptible to the disease should be allowed upon the same soil, because other 

 wise a sufficient number of worms will always find food enough to remain 

 in the field for a series of years. The greatest care should be exercised in 

 planting new trees or other perennials, as the grape, and no young plants 

 should be obtained from infested soil. Young trees and seedlings are more 

 seriously affected, and the root-galls upon them are usually quite large 

 and easily seen. 



In Germany cultivators of the sugar beets are in the habit of trapping 

 the worms of an allied species. In badly infested soils they grow plants 

 very susceptible to the disease, and then gather the roots before the 

 worms are fully developed. Such "catch plants" are destroyed with their 

 inhabitants. 



So far as I know this nematode worm is as yet not found in many or- 

 chards and nurseries in Minnesota, but it is here, and great pains should 

 be taken to prevent its further spread. 



