Pests and Diseases
As red spider rarely builds up to epidemic proportions, no control is practised. Black root rot (Phytophthora cactorum), a soil-born fungus, has caused great losses of plants. Resistant varieties are being used as replacement plants. Two minor outbreaks of Verticillium wilt (V. albo-atrum) have been recorded. Quarantine measures prevented the first outbreak spreading and it is hoped that the second one has been also confined. It does not seem necessary to spray hops to control insect pests or diseases.
by Moore Grant Baumgart, B.SC., Horticultural Division, Department of Agriculture, Nelson.