Development of the root-knot nematode as affected by temperature

does not appear. First page follows. Introduction It is well known that invertebrate animals are dependent on the temperature of the environment for their vital activities. In the case of the root-knot nematode, Heterodera marioni (Cornu), this is a factor which must be considered in every phase of biological study. Since it has a direct influence on the rate of metabolism, it is obvious that it must also have an important bearing on problems to which it has not heretofore been applied, such as rate of travel through soil, rate of killing by chemicals, and rate of starvation in fallow fields, as well as on the amount of infestation and the damage done to crops, which have been investigated by (Godfrey (1926)) and by (L. H. Jones (1932)). Temperature is not, however, the only factor influencing the rate of development of this nematode. (Godfrey and Oliveira (1932)) grew cowpea and pineapple plants side by side in the greenhouse. Yet under identical conditions, development to egg-laying took 35 days in pineapple and only 19 days in cowpea. (Baunacke (1922)) has analyzed the effect of temperature on the sugar-beet nematode. His thesis is that the larva, which may normally survive in the soil for months without feeding, depends on a food reserve which it has stored up from the egg. When the soil is cool the larvae are fairly inactive, and the reserve will be used slowly. With higher temperatures, motion and also sense perception are accelerated, so that the larvae should be able to find host plants before the food reserves become exhausted. For the sugar-beet nematode he gives the optimum temperature as 25° C, with a maximum activity at 28°. This increased activity is an escape reaction, which should in nature assist the migration of the larva to a host root or to a cooler environment. If prolonged, it causes death by exhaustion as an indirect result of the high temperature.