Alternaria leaf blight of parsley

Alternaria leaf blight of parsley is caused by the fungus Alternaria petroselini and commonly infects parsley overseas.

Alternaria leaf blight was first found in Australia on parsley crops in Queensland and Victoria in 2005. In Queensland, it caused significant damage to a single crop following extensive wet, humid weather.

In Victoria, the disease has been found only on one property, where it caused minor damage.

Symptoms of leaf blight

The disease is also known as leaf spot or scorch and can cause dark spots on leaves that may lead to leaf and petiole death (Figure 1).

Root and crown infections can cause damping-off of seedlings and chlorosis and collapse of older plants. Outside of Australia the disease typically occurs during or following wet winter weather.

Spread of leaf blight

The disease is seed-borne, so planting of infested seed causes the disease to spread to new production areas.

Controlling leaf blight

Infected seeds

Since infested seed spreads the disease, control is primarily through planting high quality, pathogen-tested seed.

Using fungicides

Fungicides may also assist in managing the disease – ask your chemical adviser for state regulations on approved products.

Information on fungicides is available from your local nursery, cropping consultants, chemical resellers and the pesticide manufacturer.

For information on currently registered and or permitted chemicals, check the Australian Pesticide and Veterinary Medicine Authority (APVMA) website and always consult the label and Safety Data Sheet before using any chemical product.

Rotating crops

As the disease can also be soil-borne, rotation to non-umbelliferous crops for a period of two to four years is necessary to reduce carryover of the fungus to new parsley crops.

Current situation in Victoria

Alternaria leaf blight is unlikely to become a major issue for Victorian parsley producers except following heavy irrigation in hot weather.