CONTROL OF DISEASES IN NEW ZEALAND BROAD BEAN SEED PRODUCTION CROPS

New Zealand grows broad bean crops specifically for seed production, and these crops are prone to attack by a range of diseases. The most severe disease in recent years has been the seed-borne disease leaf and pod spot, caused by Ascochyta fabae. Seed-borne inoculum is the major means of introduction of the disease to crops and because of the splash dispersed nature of the spores produced by this pathogen, spread of disease is limited to short distances within an infected crop. Trial results indicated that the elimination of seed-borne inoculum by the selection of healthy seed lines and seed treatment with fungicides, was the first step in a disease control programme. Foliar sprays, especially of chlorothalonil, were shown to be effective in reducing seed infection and in some cases increasing yields.

The other major diseases were rust and chocolate spot, caused by Uromyces viciae - fabae and Botrytis fabae respectively. These may be controlled to some extent by foliar sprays, and it is possible to integrate their control with an intensive control programme for A. fabae.