The effectiveness of phosphite for controlling Phytophthora cinnamomi.  G. C. Marks and I. W. Smith.  May 1988.  12pp. (unpubl.)

SUMMARY

The effectiveness of foliar sprays of Foli-R-Fos (dipotassium phosphite) against Phytophthora cinnamomi root and stem infection in some members of the Proteaceae and Myrtaceae was evaluated under both phytotron/glasshouse and field conditions. Its efficacy was compared with Aliette (Fosetyl-Al) in phytotron/glasshouse tests using foliage sprays and root drenches and by following the progress of artificial inoculations with P. cinnamomi.

The results showed that 1000 ppm of phosphite was non-phytotoxic, provided good protection under phytotron/glasshouse conditions highly conducive to disease development and effective field protection when applied early in spring. Phytotron/glasshouse tests showed that Foli-R-Fos was significantly better than Aliette when used as a foliar spray at equivalent rates of phosphite. Foli-R-Fos has better fungistatic effects, markedly slowing or stopping lesion development.

Aliette was shown to be more effective than Foli-R-Fos when used as a soil drench, possibly because the latter was more rapidly inactivated by the soil microflora.

Re-isolations of P. cinnamomi from stem lesions made eight weeks after inoculation showed that neither Aliette nor Foli-R-Fos killed P. cinnamomi within established infections and that their activity was primarily fungistatic.

Also published:

Marks, G.C. and Smith, I.W. (1990)  Control of experimental Phytophthora cinnamomi stem infections of Rhododendron, Leucodendron and Eucalyptus by dimethomorph, fosetyl-Al and metalaxyl.  Aust. J. Exp. Agr. 30: 139-43.