MeloidsJ 



there was a quantity of larvae already to hatch but in which the larvae 

 had not really emerged. As soon as she put it in water, they began to 

 hatch. My material was greenhouse groxim in moist soil subject to daily 

 vfatering, and there was no accumulation of larvae to hatch. I thjjik 

 one will get accumulation of larvae in dry weather and a fresh attack 

 of the roots sometimes following rain. 



Of course, moisture is not the only factor that influences hatching. 

 There are also oxygen and teiiiporature . I have been wondering who knows 

 of any Information on the effect of temperature on hatching, because I 

 cannot find any. Therefore, I am going to pass over temperature. I 

 cannot say much about oxygen, except that I am interested in a little 

 more information about it. 



I do know that when hatching larvae for experimental work, one picks 

 the egg masses off the roots, puts them in a Syracuse dish or Petri 

 dish in a very thin film of water, and keeps them in a moist chamber. 

 They practically all hatch in a week. If they are not picked off the 

 roots, they do not hatch. One can cut off the roots with the egg masses 

 intact, put them in the same Petri dishes, and in a week's time may get 

 practically no hatch. I have assumed that that was an oxygen relation- 

 ship, in that when the eggs are dislodged from the roots, they are 

 exposed from the backside, and the resulting hatching would be due to 

 the dissolved oxygen in the water. We are considerably interested in 

 this in ELorida, because we are interested in flooding as a possible 

 means of controlling root-knot. We know that a summer flood is effec- 

 tive, and it has occurred to us that these oxygen relationships might 

 have some importance in understsinding the factors that influence the 

 efficacy of such a procedure. 



In the older literature, one can read that after the larvae hatch, there 

 are two things that can happen. One is that the larvae may migrate or 

 move slightly to one side in the root tissues in which they were pro- 

 duced. That is, they may remain in the same root and there become estab- 

 lished, or they may escape into the soil and seek new roots. After work- 

 ing for a year or so at Beltsville using the tomato almost exclusively 

 as an experimental host plant, I came to the conclusion that there was 

 no reinfection of the s^e plant. The larvae escaped into the soil. I 

 sectioned and studied the stained sections of many roots of various ages, 

 and I never saw any evidence that larvae ever re-established themselves 

 in the same root, I began to doubt that it ever happened. 



Not long ago some Caladium tubers came to our laboratory in Florida in 

 connection with some experimental work which is not pertinent to this 

 discussion. We examined them, and we found that they were infected 

 quite heavily with root-knot. We found numerous females with the acccsn- 

 panying eggs distrubuted throughout the tissues of the tubers. Some 

 were quite ^deeply embeded, some were fairly near the surface. There was 

 no particular pattern of distribution, so far as we could see. We took 

 about a dozen of those tubers and potted them in nematode-free, treated 

 soil and grew them for about ten weeks or three months. Then we brought 



