Reducing the incidence of disease in sunflower crops
Disease outbreaks in any crop occur when a pathogen comes in contact with a susceptible host and the environmental conditions favour the development and spread of the disease. To minimise the risk of disease in sunflowers, choose hybrids that have some resistance to common diseases in the area, plant within the range of optimal dates and follow the recommendations for irrigation, plant density, crop nutrition and drainage.
Healthy plants are generally better able to withstand more disease pressure than plants that are already under stress.
Common diseases of sunflower
Some diseases that affect sunflower plants display very similar visual symptoms, making field identification of the cause difficult. For example, Phoma, Phomopsis and Tobacco Streak Virus (TSV) all exhibit as brown or black streaks or lesions on the plant stems.
Be prepared to seek advice and to send plant samples to a plant pathologist for diagnosis.
Currently, the dominant diseases in sunflowers are:
Powdery mildew (Golovinomyces cichoracearum)
Sclerotinia rot (Sclerotinia sclerotiorum, S. minor)
Sclerotinium base rot and crown rot (Sclerotium rolfsii)
Rhizopus head rot (Rhizopus spp.)
Phomopsis stem canker (Diaporthe spp.)
Phoma black stem (Phoma spp.)
Tobacco streak disease (Tobacco Streak Virus, TSV)
Other diseases that may cause management problems in some areas or seasons include:
Rust (Pucinnia helianthi)
White blister (Albugo trogopogonis)
Charcoal stem rot (Macrophomina phaseolina)
Botrytis head rot or grey mould (Botrytis cinerea)
Verticillium wilt (Verticillium dahliae)
Septoria leaf spot (Septoria helianthi)
Integrated disease management
Disease management in sunflower relies heavily on cultural controls and a good understanding of the pathogens of all crops grown in the crop rotation.
The key elements of an IDM are to:
Monitor and diagnose—this may require sending samples to a plant pathology laboratory.
Follow the ‘Come Clean, Go Clean’ on-farm hygiene guidelines.
Control alternative hosts and manage crop residues to reduce inoculum.
Follow best practice crop management for plant population, nutrition, row spacing and weed control.
Choose hybrids with the best available disease resistance profile and suited to the growing region and farming system.
Apply fungicide treatment for powdery mildew if necessary.
Control insects to reduce crop damage and disease entry points.
Manage irrigation to minimise disease risk.
Sunflower as a disease break crop
Sunflowers provide an effective disease break for several key pathogens present in Australian cropping systems.
They are resistant to both species of root lesion nematodes and do not host the pathogens that cause fusarium crown rot in wheat, fusarium stalk rot in sorghum or ascochyta blight in chickpea.