Anthracnose (Colletotrichum lupini) is a fungal disease spread by infected seed and rain-splash of spores from infected plants. Stubble is not a major source of infection. All lupin species are affected, but generally albus lupin, yellow lupin and WA blue lupin are more susceptible than narrow-leafed lupin. Anthracnose is favoured by warm wet conditions and therefore the greatest risk of disease is in high-medium rainfall areas, particularly the northern agricultural region where blue lupins are abundant.
Anthracnose can infect all above-ground parts of the lupin plant, severe infection can lead to plant death. The most distinctive symptom is bending and twisting of stems with a lesion in the crook of the bend. Stem lesions are usually dark brown with a pale pinkish-orange spore mass within the lesion. The stem can be completely girdled by lesions or so weakened that it breaks. Both the main stem and lateral branches can be affected and close inspection will often show similar symptoms on leaf petioles. Pods develop lesions similar to stems and are often twisted and distorted. Infections at this stage can result in complete loss of pods or production of infected seed. Infected seeds can appear symptomless or can be malformed with discolouration, fungal mycelium or pink spores on the seed surface.
- Resistant varieties are available; these should be used in higher risk environments.
- Seed can be tested for the presence and quantity of anthracnose infection. Use of clean seed is ideal but in some circumstances (for example, resistant varieties or lower rainfall environment) low levels of seed infection can be tolerated.
- Thiram-based seed dressing fungicide will reduce disease transmission from infected seed.
- Blue lupins are a common source of inoculum, if possible blue lupins should be destroyed or separation from susceptible varieties maintained.
- In high disease situations, registered foliar sprays applied at early podding on main stems and first order branches can be used to reduce yield loss.