THE HATCHING RESPONSES OF SOME ROOT EELWORMS OF THE GENUS HETERODERA

An account is given of investigations on the hatching responses, under laboratory conditions, of nine species or varieties of Heterodera, namely, the beet, cabbage, clover, Galeopsis, carrot, hop, potato, oat and pea eelworms. In the first seven of these, marked differences occurred in hatching responses from cysts incubated in root leachings from various plants, these differences being virtually diagnostic for the eelworm species concerned. In general, good responses to leachings from host plants occurred, whereas there was little or no response in non-host leachings; but cases of response to non-hosts and of failure to respond to hosts were encountered. Promising results were obtained in the analysis, by bio-assay, of mixtures of some of these eelworm species. No appreciable response occurred from cysts of oat and pea eelworms incubated in host leachings, but there was some evidence that such a response did occur from pea eelworm cysts under field conditions. Curves for rate of hatching of seven species and for hatching in diluted leachings in five species were found to be of the form described by Fenwick for potato eelworm. Results are given of some experiments on the effect of age of plant on potency of the root leachings, and on the loss of potency during storage.