Experiments were conducted in which single cysts and batches of 100 cysts were exposed to the action of potato-root diffusate and the number of larvae liberated at the end of certain intervals of time recorded. Investigation showed that when the hatch at the end of each time interval was expressed as a probit of the total hatch, and plotted against the logarithm of that time, a close approximation to linearity resulted. Statistical analysis confirmed this agreement in the case of single cyst hatching, but disclosed a significant degree of asymmetry in the case of multiple hatching. It was decided that the degree of curvature resulting from this when plotted as a probit line was sufficiently small for it to be ignored.

An experiment was set up to investigate the effect of root diffusates from different varieties of potatoes on natural infestations of cysts in three different soils. A series was included in which no root diffusate at all was used, to obtain an estimate of the degree of spontaneous hatching which occurred. In the absence of diffusate, about 50 per cent, of larvae emerged from the cysts, as compared with 84 per cent, in the case of soils treated with diffusates. Significant differences were detected in the degree of emergence under the action of the different diffusates, that from “Ulster Chieftain” having the greatest effect. Significant differences were also detected between the different soils, larval emergence being lowest in the greensand.

1. “Chlorphenol” and “dichlorphenol”are shown to be highly toxic to eelworms, both in the active and quiescent stages. Comparisons are made between these chemicals and iodine solutions in this respect.

2. Treatments of clover and teazle seed with “chlorphenol” and iodine solutions are described and it is shown that infesting eelworms may be controlled without affecting germination or subsequent growth.

3. The use of “chlorphenol,” with the addition of a wetting agent is recommended for the hot-water treatment of narcissus bulbs, as an additional insurance for the control of the “wool” stage of bulb eelworm.

4. The phytocidal action of “chlorphenol” is discussed and it is shown that such action is not marked.

5. Some preliminary experiments on the use of “chlorphenol” against potato root eelworm are described.