Winning the Fight Against Fusarium

For the Newell family of Boggabilla, Fusarium wilt has been a part of their cotton growing lives for over a decade, since its discovery in the mid 1990’s.

However, changes in management and the evolution of new technologies, has meant that the Fusarium problem no longer has the dire consequences originally envisaged.

Fusarium wilt is caused by the soil borne fungal pathogen fusarium oxysporum vasinfectum, which starves the plant of moisture and nutrients by blocking its vascular system, resulting in wilting symptoms synonymous with the condition.

The Newell’s property ‘Korolea’ was only the second property in NSW where the disease was discovered in the 1995-96 season, and as Rob Newell recalls, those first few years were when the impact was at its worst.

“We had whole rows of crop, and large patches in fields dying in the later part of the season, with a significant yield impact.”

The 2007-08 season has seen some of the most ideal conditions for Fusarium wilt for a number of years: mild, cloudy conditions, in-crop rainfall and subsequent waterlogging.

But despite the obvious incidence of dead individual plants across the ‘Korolea’ crop this year, there is no sign of the large areas of devastation seen in the mid 1990’s.

Much of the credit for the transformation of Fusarium wilt into a manageable problem is due to the considerable research effort that has occurred in the last decade.

Whilst it has not produced the ‘silver bullet’ solution to the disease that many people wanted, it has spawned a number of strategies that have made the problem manageable.

The most recent innovation has been the seed treatment ‘BION’, released commercially in 2007 after an extensive research effort from Cotton Seed Distributors, NSW DPI, and Syngenta, the product’s manufacturer.

BION triggers the plants natural self-defence mechanisms at germination, readying itself for an array of soil pathogens present in the warm, moist soils found at planting time.

In BIOB’s absence, rapid-acting pathogens such as Fusarium can inflict a fatal infection before the plant activates these self-defence mechanisms.

The Newells used BION treated seed on their entire 2007 planted crop, prompted by several seasons of data highlighting the favourable impact of the product, including data from trials hosted on ‘Korolea’ conducted by NSW DPI plant pathologists.

Time of planting was another simple strategy adopted to manage the disease. “Ten years ago, we were planting at the start of October. Since then, research has shown that planting later, increasing the chances of planting into warmer soils, can reduce the incidence of the disease. We now start planting in the last half of October,” Rob Newell said.

It was apparent in the early days of Fusarium wilt research that there was a lot of variability in disease susceptibility in the range of Australian varieties, and the resultant ‘F-Rank’system has provided growers with a good guide on varieties to use in Fusarium situations.

“When the disease was first discovered we grew Sicot 189, the most resistant variety at the time, and since that time, disease resistance has been one of our main considerations in variety selection,” Rob Newell said.

The news is good on the resistance front with CSD releasing the variety Sicot 75 in 2007, which combines the yield of the world-renowned Sicot 71 with an almost doubling of the Fusarium wilt resistance and a fibre quality package exceeding most other varieties.

Whilst Sicot 75 is currently only available as a conventional variety, one containing the popular Bollgard II® and Roundup Ready Flex® traits is due for release in the 2010 planting season according to the CSIRO cotton breeding team and CSD.