Biosecurity High priority exotic pest threat

High priority exotic pest threat

ANGULAR LEAF SCORCH AND ROTBRENNER

Angular leaf scorch, found in in North America, and rotbrenner found in Europe (particularly France and Germany), are caused by two related types of Pseudopezicula fungus.

Particular grapevine cultivars vary greatly in their susceptibility to the diseases, and the amount of damage they cause varies from season to season. With prolonged rains the fungi can cause severe crop losses. Both species can overwinter in dead leaves on the ground, producing spores in early spring that infect the new season’s growth, attacking leaves, flowers and fruit stalks.

Signs and symptoms

Symptoms of both angular leaf scorch and rotbrenner are predominantly seen on leaves. Lesions first appear as faint, yellowing spots which enlarge, changing from yellow to reddish-brown before the tissue eventually dies. Lesions are typically confined by the major veins and the edge of the leaf and may be several centimetres wide. On white-fruited cultivars the lesions are initially yellow. On red and blackfruited cultivars lesions are typically bright red to reddish-brown. Late season infections may look like freckled spots. Infected leaves often fall from the vine prematurely. Both pathogens may attack flowers before or during bloom, causing them to rot and dry out. Only the fruit stalks (pedicels) are attacked, not the bunch stem (rachis). In severe cases, the berries are destroyed, leaving the rachis of the cluster bearing only a few individual berries or none at all.

Protecting your vineyard

Both angular leaf scorch and rotbrenner could spread to Australia in infected cuttings. Once in a vineyard, they are spread through water and airborne spores. To protect your vineyard against Pseudopezicula fungi: - Source high health status plant material (preferably certified) only from reliable and accredited suppliers. - Check your vineyard frequently for the presence of new pests and investigate any sick grapevines for unusual symptoms. - Make sure you are familiar with common grapevine pests so you can tell if you see something different. - Keep records of anything unusual. - Ensure all staff and visitors adhere to on-farm biosecurity and hygiene practices.v

If you notice anything unusual in your vineyard call the Exotic Plant Pest Hotline 1800 084 881.

This series from Plant Health Australia, the national coordinator of the government-industry partnership for plant biosecurity in Australia, features exotic pests that would survive, spread and establish in Australian vineyards should they get through border quarantine controls. Growers should be familiar with their appearance and symptoms so that they can distinguish them from the pests that they normally encounter.

Left: Angular leaf scorch on grapevine leaf, changing from yellow to brown as the tissue gradually dies. Image: M. Sosnowski, South Australian Research and Development Institute Right:Rotbrenner infected tissue changes from yellow to reddish-brown before the tissue eventually dies. Image: Agroscope ACW, Werner Siegfried