Spring Ridge grower Dave Brownhill says a FHB outbreak in 1999 prompted them to rethink their cropping rotation. (Photo: GRDC)

THE 1999 winter cropping season is firmly etched in Dave Brownhill’s mind. Not only was it the family’s first experience with the devastating disease Fusarium Head Blight (FHB), it also forced a strategic rethink of their entire cropping program.

Back then, the Brownhills grew durum wheat in rotation with maize under both pivot and flood irrigation on their farm near Spring Ridge in northern New South Wales.

It was a rotation that suited the growing conditions and the farm management program and had traditionally performed well from a gross margin perspective.

However, all that changed with the onset of FHB, forcing the family to replace maize with cotton to avoid a repeat of the 1999 disaster.

“Our problem began when we no-tilled durum directly into corn stubble. The wheat looked magnificent until about late October when the heads began turning pink and white which we had never seen before,” Mr Brownhill said.

“We immediately called NSW DPI (Department of Primary Industries) and soon afterwards it was established that FHB was the cause. We also involved Sydney University, through our private agronomist Greg Giblett, as they had undertaken research on host plants including grass species and sorghum stubble.

“The outbreak was devastating; the disease didn’t just affect the irrigated fields; it affected our entire durum crop that year because the pathogen, Gibberella zeae, spores became airborne and travelled significant distances.

“We knew we had to implement a long term disease management plan and really our only options were to switch to a bread wheat variety and burn corn stubble prior to the wheat plant, or completely avoid growing durum in rotation with corn.

“At the end of the day, we felt that rotation management was the best way to minimise future disease risk and since then we have grown cotton in rotation with durum.”

In contrast to the dry conditions currently affecting large tracts of NSW, the 1999 year was highly conducive to disease development with good rainfall through winter and spring.

Prolonged periods (36-72 hours) of high humidity (>80pc), low evaporation and temperatures from 20 to 30°C during flowering and early grain-fill produce the most favourable conditions for FHB infection. Hence, frequent rainfall events during these growth stages in 1999 were very conducive to FHB development.

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 presence of these toxins can create issues with marketing as they impact product quality for human and stock consumption.

Over the past 20 years, the Grains Research and Development Corporation (GRDC) and its research partners have invested in research and extension to better understand and manage the disease and recommends that growers:

• avoid durum crops in areas with known high prevalence of FHB;
• avoid sowing durum into or adjacent to paddocks that contained maize the previous year;
• avoid sowing durum into wheat, barley and sorghum paddocks;
• plant the least susceptible varieties available (although this can be difficult with durum);
• reduce FHB inoculum levels by rotating with non-grass crops, such as sunflowers, cotton, soybeans, mungbeans, chickpeas, faba beans, canola and field peas;
• vary sowing times and varieties to minimise the risk of the entire crop flowering when weather is favourable for infection
• in high risk situations and if conducive weather conditions for FHB are predicted during flowering, consider a preventative registered fungicide application targeted at the heads. Recommended application strategies (nozzle angle and water rate) need to be employed to maximise efficacy; and
• use clean seed – if contaminated seed must be used, seek further advice. Grain infected with FHB is usually white and, if prolonged wet conditions occurred during grain‐fill, infected grains will take on a pink appearance. However, it should be noted that if any white or pink grains are evident, then the levels of Fusarium infection can be significantly higher than what may be indicated by visual inspection.

Source: GRDC

For more information on FHB and other field crop diseases, visit the GRDC Communities Field Crop Diseases website https://communities.grdc.com.au/field-crop-diseases/