Biosecurity High priority exotic pest threat

High priorty exotic pest threat

BACTERIAL BLIGHT OF GRAPEVINE

Bacterial blight of grapevine is a serious disease that affects commercially important grapevines in South Africa, Europe and Argentina.

It is caused by the Xylophilus ampelinus bacterium which lives in the vascular tissues of infected plants, causing extensive damage to vines and major harvest losses.

Signs and symptoms

Bacterial blight can affect the whole vine, from leaves and flowers to roots. Look for linear reddish-brown streaks that appear and expand upwards on the shoot, then darken, crack and develop into cankers. Shoots subsequently wilt, droop and dry up and young shoots may develop pale yellowish-green spots on the lowest internodes. Discolouration is less common on very young shoots, but the whole shoot dies back.

Stem cross-section reveals tissue browning. Cankers can also appear on the sides of petioles leading to onesided leaf necrosis. Necrotic leaf spots sometimes occur as well as cankers on flower and fruit stalks. Flowers that have not reached maturity turn black and die back, and roots may stunted. Laboratory diagnostics is needed to confirm the absence or presence of bacterial blight.

Protecting your vineyard

Bacterial blight is spread from country to country in infected cuttings. Once in a vineyard, blight infects rows of vines through irrigation and infected pruning tools.

To protect your vineyard against bacterial blight: - 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 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: Parts of the grape bunch may become necrotic and die back. Image: ARC Infruitec-Nietvoorbij, South Africa Middle Top: Symptoms of infection on shoots of grapevine. Image: C.G. Panagopoulos, Agricultural University, Bugwood.org Middle below: Cankers will darken, crack and spread throughout the grapevine stem. Image: ARC Infruitec-Nietvoorbij, South Africa Right: Leaf spot and marginal necrosis on leaves are symptoms of bacterial blight of grapevine. Image: C.G. Panagopoulos, Agricultural University, Bugwood.org