During the autumn of 1926 Woodfin (1926) recorded an outbreak of downy mildew on grape vines from Henderson, Auckland. Berry-Smith (1965) noted that this disease was particularly severe in Auckland and areas north of Auckland where warm moist conditions encouraged growth of the fungus. He suggested regular applications of copper sprays for its control-preferably Bordeaux mixture-but he noted that these sprays could cause hardening and stunting of foliage. It has also been suggested (Anon. 1957a) that regular application of thiram sprays also controls mildew on grapes but does not damage the growth of vines.

Type: Downy Mildews; Description: Sporangiophores emerging from stomata in clusters of up to 20, erect, 300–500 μm long, branching monopodially; branches at right angles, straight, ultimate branchlets short with blunt tips; forming white, downy patches on the lower surfaces of leaves with corresponding pale green patches on the upper surfaces. Sporangia oval, variable in size, 15–35 × 11–19 μm.

Distribution: Auckland.; 1st Record: Woodfin (1926).

Significance: ‘Downy mildew’ can affect all above-ground parts of the grape vine. The disease can be serious in the Auckland area (Dingley 1969).; Host(s): Vitis vinifera.