Phytophthora Cinnamomi - Phytophthora Cinnamomi in Gardens and Crops

Phytophthora Cinnamomi in Gardens and Crops

Phytophthora dieback affects a large number of common garden species, natives and horticultural crops. This list of susceptible plants includes roses, azaleas and fruit trees. Since there is presently no known cure, once the disease has been introduced into a garden it cannot be easily eradicated, and can become a major problem.

Protocols to prevent the disease from entering gardens include sourcing plants from non-dieback infested areas (not local bushland), using sterilised potting mixes, and using only mulch that has been properly composted. Transplanting established plants from one garden to another can also spread the disease. Propagating from seed and cuttings is less likely to transmit the disease because there is no soil transported with stock.

Many nurseries are accredited under the Nursery Industry Accreditation Scheme Australia (NIASA) and use hygienic practices to prevent Phytophthora dieback from infecting their stock. Hygienic practices prevent the spread of the disease in contaminated potting mix, plant material and water sources. Other preventative measures include raised benches, regular testing for Phytophthora dieback, and the placing of new stock in quarantine.

Plants typically die from Phytophthora dieback at the end of summer when the plants are under the most stress. For this reason Phytophthora dieback can often be confused with symptoms of drought. Phytophthora dieback will affect a range of different susceptible plants, but will not impact on resistant plant species. If the disease is suspected, a likely mode of disease transmission should be identified. The best method to confirm the presence of the disease is testing of soil and/or plant samples by a diagnostic laboratory.

Control of existing Phytophthora infestations includes injecting or spraying plants with phosphite (a fungicide), using well-composted mulch, and using pre-planting techniques such as solarisation or biofumigation. Composted mulch is highly suppressive to Phytophthora dieback and can prevent healthy plants getting infected. It is most important to prevent the spread of infected soil, plants or water. Infested areas can be revegetated or landscaped with resistant plant species which are not affected by the disease.