GROWERS HAVE good reason to be wary of fusarium head blight (FHB) after big outbreaks in northern NSW in 1999 and 2000. Hope for effective management of the blight is now on the horizon through climate risk management combined with cultivar resistance and chemical or biological control.
Low levels of FHB in northern NSW in the wetter-than-average 2001 season provided encouraging news for growers, particularly those who suffered severe crop losses in 1999 and 2000. In those years, exceptionally wet seasons led to serious outbreaks of FHB on the Liverpool Plains and caused a major downgrading in quality and yield losses ranging from 20 to 100 per cent.
FHB is a significant disease in wheat and barley in many areas of the world. The disease can also infect oats, triticale, other small cereal grains and maize.
Prolonged periods (36-72 hours) of moisture, low evaporation and temperatures from 20 to 30°C during flowering and early grain-fill produce the most favourable conditions for infection. Yield and economic losses result from sterility of the flowers, and grain that is shrivelled, lightweight, low quality and prone to containing toxins such as deoxynivalenol.
The limited outbreak of FHB in wheat crops on the Liverpool Plains in 200 I suggests that FHB is a disease of exceptionally wet springs, according to research led by Peter Hayman of the Tamworth Centre for Crop Improvement.
(Growers now worrying about an exceptionally dry winter may want to file this away for future reference, but keep in mind conditions just two years ago - Ed.)
The research, supported by growers and the Federal Government through the GRDC, found that flowering wheat crops experienced the greatest number of rainy days ever recorded during 1999 and the highest recorded rainfall in a 20-day period during 2000. In comparison to 1999 and 2000, the 2001 season was drier and cooler, especially overnight.
Another project supported by the GRDC shows the potential for controlling FHB with cultivar resistance combined with a fungicide or biocontrol agent.
The research found that the most effective control of FHB is likely to be through an integrated approach including:
- selection of more resistant wheat varieties (Bread wheats are generally more resistant than susceptible durum varieties. Of the four wheats tested, Sunvale was the most resistant, followed by Kennedy and Kamilaroi, and Yallaroi was the most susceptible; nine - all 2-row - barley varieties showed low levels of infection compared to durum varieties.)
applying fungicides Tebuconazole or Carbendazim (not yet rcgistered in Australia) once or twice during flowering stage
(Both fungicides were very effective in reducing FHB in all four wheat varieties.)
applying biological control Bacillus spp. as a cheaper but inferior control to the fungicides
(The bacterial treatments reduced FHB infection by up to 86 per cent compared to the control.)
Steven Simpfendorfer of the Tamworth Centre for Crop Improvement is involved in both these FHB projects and recently visited the United States to attend the Fusarium Head Blight Forum and develop collaborative research into the disease.
"While Australia's FHB problems may not be as widespread as in the United States. the 1999 and 2000 seasons showed that we cannot be complacent," Dr Simpfendorfer said.
"When interviewed as part of our research, growers from the worst hit areas of the Liverpool Plains reported that FHB was likely to occur 30 per cent of the time in the future, causing a 50 per cent reduction in yield and a 90 per cent reduction in gross margin," Dr Hayman said.
Although history does not show high levels of infection in 30 per cent of seasons, it is clear that growers are concerned about changed farming systems and general inoculum levels, he added. "Growers would be wise to maintain vigilance on this disease by avoiding high-risk rotations and avoiding sowing susceptible cereal crops like durum wheats into maize residues."
Contact: Dr Steven Simpfendorfer