SUMMARY. 73 



(3) The life cycle of this nematode, from egg to egg, may take place 

 in four weeks, or longer, depending upon the temperature of the soil. 

 The larval stage is that in which entry into the host takes place. 

 It then becomes motionless and soon enlarges and undergoes a sort 

 of metamorphosis, the males eventually recovering the original 

 worm sha])e, wliile the females become pear or flask shaped and very 

 much enlarged in their transverse dimensions. Each female lays 

 500 or more eggs. The winter is passed probably most frequently 

 in the larval stage in the soil, but in the case of galls on perennial 

 roots the nematodes may overwinter in these in a more advanced 

 stage, even as practically mature and perhaj)s already fertilized 

 females. 



(4) For the rapid multiplication of the root-knot nematode the 

 following conditions are necessary: (a) A certain degree of warmth 

 of the soil. Thus, in southern Florida this nematode is active the 

 year round, m part of South Carolina the active season is from 

 April 20 or May 1 to the middle or end of October, while farther 

 north the period is still shorter. (6) Loose-textured soil. Only 

 sandy or at least light soil is favorable to its spread, (c) Moisture. 

 The drying out of the soil is frequently fatal to the nematode and in 

 any case prevents it from doing any harm. Apparently the moister 

 the soil as long as it is well supplied with air, the more favorable it 

 is to the nematode's develo})ment. However, wet soil, i. e., soil in 

 which the air spaces are filled with water, is at length fatal to the 

 nematode, (d) Food supply. The larvae are able to exist in the soil 

 for more than one year, but apparently not for two years, without 

 the presence of living plants into which to enter. They are apparently 

 unable to develop beyond the larval stage unless they enter a suitable 

 host plant. 



(5) The nematode is distributed in several ways: (a) The 

 larva) move through the soil by their own motion, but the distance 

 traversed thus is probably not more than 6 feet or so a season. 

 (6) They are carried from field to field in the earth clinging to imple- 

 ments, the hoofs of animals, the shoes of laborers, wagon wheels, etc. 

 (c) They are conveyed in the soil that is washed from one field to 

 another by heavy rains, a very common mode of distribution of this 

 pest, (d) It is possible that heavy winds may carry larvae or eggs with 

 the soil blown from one field to another, but probably most would be so 

 dried out in the ])rocess that this is not much to be feared, (e) They 

 are introduced into new i)laces in the roots or in the tlirt adhering to 

 the roots of nursery stock, in rooted cuttings, potted plants, etc., 

 especially those of the peach, grape, fig, mulberry, potato, ginseng, 

 etc.; also in the dirt in which some seeds are packed. (/) They are 



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