‘Cotton Fusarium Wilt Management’, had a number of objectives to obtain data to improve the management of this disease. The three year project resulted in several important outcomes with direct consequence for the industry.

Outcome 1. Collection of disease incidence data annually has enabled the quantification of the relative performance of disease threats and the effectiveness of response, and the detection of new pathogens and problems.

Planting resistant varieties, delaying planting to avoid cold shock and sowing seed treated with BION have contributed to the reduction in the incidence of Fusarium wilt over the last two seasons compared over eight.

Irrigation water management from Fusarium infested fields is important as use of irrigation water from the tail-drain will increase the incidence of Fusarium wilt.

It is important to manage volunteer cotton as they harbour pests and diseases; carrying them from season to season providing an inoculum source for re-infection of crops.

The identification of a new cotton pathogen in Australia during disease surveys highlights the importance of these surveys. Nematospora coryli is a fungus that causes several serious diseases of cotton including seed rot, internal boll rot (stigmatomycosis) and tight lock. The fungus is the only plant pathogenic yeast and is spread to bolls punctured by insects during feeding. Insect control is the best way to prevent infection, although improved cultivar resistance may be possible.

Outcome 2. The diversity of Fov in cotton growing regions is changing.

Further isolates of the Mungindi strain detected in 2005 were again detected in 2009 from the same field. Pathogenicity tests determined that these isolates were pathogenic on a susceptible cotton host. AFLP analysis determined that the isolates did not belong to VCG 01111 or 01112, but were similar to the original Mungindi strain. An understanding of pathogen diversity is very important when screening germplasm for resistance.

To enhance the diagnostic capabilities of DEEDI staff, training in Amplified Fragment Length Polymorphism PCR has commenced. This technique will be used as a tool to characterise Fusarium oxysporum f. sp. vasinfectum (Fov).Outcome 3. Since the pathogen remains indefinitely in the soil, using rotations as a management tool may be limited; however a maize/sorghum-fallow-cotton rotation looks promising. Growers need to manage residues (and weeds) through fallow periods and use green manure/cover crops with caution where Fusarium is present.

An understanding of the effect of different rotation and residue management on incidence of Fusarium wilt in subsequent cotton crops will provide growers and consultants with greater options and improved decision support packages to manage Fusarium wilt.Outcome 4. Fusarium wilt severity is influenced by the balance of nutrients; however cultivars differing in disease resistance are affected differently in some instances.

Fertiliser recommendations are developed to optimise nutrient uptake and provide the crop with adequate nutrients for normal growth and yield. An understanding of how N, P and K influences Fusarium wilt severity will provide growers with improved decision making tools for the management of this disease.

These early trials in the investigation of N, P and K on disease management highlight the importance of nutrient balance in the soil. This is achieved through knowledge of what is present in the soil and what is being removed, and developing an appropriate nutrient replacement program.

In general, higher disease ratings were observed in plants with lower levels of nutrients applied, particularly low N (0 and 40 kg N/ha), and lower disease ratings tended to have higher N (120, 150 and 250 kg N/ha) and K (100 kg K/ha) applied.