Tests were carried out to compare Phytophthora cryptogea and P. drechsleri. As the results showed that the two species are very similar morphologically, as well as with regard to growth at different temperatures and in the presence of malachite green, it is suggested that they should be considered as one species. Phytophthora cryptogea Pethybridge & Lafferty as the older name has priority over P. drechsleri Tucker.

The abundance of Pythium propagules and frequency of 11 Pythium species were estimated in 16 soil plots in South Australian forest nurseries, in one ornamental nursery. and in one pine forest. A soil-plating technique Was utilized and a medium developed which was highly selective for these species and allowed their identification directly on the plates. The number of Pythium propagules in a unit volume of soil varied greatly. being lowest (24 per cubic centimetre) in the forest and highest (226 per cubic centimetre) in an alkaline loamy nursery soil. Loams had significantly more Pythium propagules than sandy soils. The immediately previous usage and soil amendments usually made no great difference to the total number of Pythium propagules. It is concluded that the abundance of pathogenic Pythium spp. in these nurseries is not the main factor governing the great variation found in the disease incidence of conifer seedlings. P. irregulare Buisman was frequent in all plots except the forest, and P. mamillatum Meurs in most sandy nurseries. The frequencies of P. ultimum Trow, P. paroecandrum Drechsler, P. rostratum Butler, P. iwayamai Ito, P. oligandrum Drechsler, P. acanthicum Drechsler, and P. echinulatum Matthews varied inconsistently between the plots. A new species, coded as P. col, was rare but occurred in eight plots. Another new species (P. dis) occurred only in one plot but frequently in this. This was a nursery freshly established on grassland pasture which differed from the others also in the frequencies of several other species.

A survey was carried out during the winter of 1971 to determine whether Phytophthora and Pythium spp. are present in South Australian pine plantations. Phytophthora cryptogea was frequently isolated from Kuitpo forest reserve in the Adelaide hills, but Phytophthora cinnamomi was isolated from only one tree in a pine seed orchard.

A grapevine decline that causes considerable loss in grape production in South Australia was studied over a 2-year period. Isolations from soil and roots yielded various Pythium spp., mainly P. ultitnum, P. irregulare, and P. aphanidermatum. Five Pythium spp. were pathogenic to young grapevines in a glasshouse test. In thc field, however, disease incidence was not correlated with numbers of Pythium propagules in soil. Other soil fungi and root-feeding nematodes are also present, and it is suggested that the grapevine decline should be considered as a disease complex.

Live hyphae of 13 different fungi lysed faster (from 2 to 7 days) in a fertile garden soil than in an impoverished wheat-field soil (from 3 to 12 days). Also, rate of lysis was more rapid in wet than in dry soil. Two types of lysis occurred: disappearance of protoplasm and cell wall concurrently, a feature of wet soil; and loss of protoplasm leaving an empty cell wall, as seen in dry soil.