THE SEASONAL RESPONSE OF THE POTATO-ROOT EELWORM HETERODERA ROSTOCHIENSIS WOLLEN-WEBER: EMERGENCE OF LARVAE THROUGHOUT THE YEAR FROM CYSTS EXPOSED TO DIFFERENT TEMPERATURE CYCLES

Air dried cysts collected in 1945 were maintained under five different conditions. One lot was maintained at room temperature, and other lots at 23 degrees C. and at about 5 degrees C; of the remaining two lots, one spent 6 months of each year at 23 degrees C. and 6 months at 5 degrees C., while the other was subjected to the opposite treatment. Hatching trials were carried out at I- or 2-month intervals, beginning about a year after the establishment of the regime, and were continued until 1949. Throughout, cysts were stimulated with solutions of the same sample of concentrated hatching solid. Larval emergence was high throughout in cysts from all treatments. Although there was considerable variation in larval emergence there is no evidence of any dormancy period. Significant differences in the level of emergence from cysts on the different treatments are demonstrated, the cysts stored at room temperature showing the highest levels of larval emergence. It is also shown that there are significant differences in the responses in the different hatching trials; however, there is no suggestion that these are of a seasonal nature. Other experiments suggest that many of the eggs in apparently mature cysts do not reach maturity for some months.