“Severity Factors in Fusarium Wilt of Cotton” aimed to investigate the factors that affect the

severity of Fusarium wilt, and by doing so enable the development of more effective

integrated disease management (IDM) strategies. The three year project resulted in several

important outcomes with direct consequences for the industry.

Outcome 1. Cool, wet early season conditions are the single biggest factor influencing the

severity of Fusarium wilt.

Disease observed in the crop late in the season is the result of infection early in the season,

say within the first 8 weeks after sowing. Therefore, when early season conditions are

conducive to infection, disease severity will be increased. High rainfall and cool temperatures

provide the most conducive conditions for infection of plants by the pathogen. When spring

rainfall is high (say >200mm before December 31), disease severity will be high. A

prolonged period of water-logging later in the season may also induce the appearance of

external symptoms (eg. wilting, yellowing, plant death).

Therefore, the best way to reduce the impact of cool, wet early season conditions is to avoid

them by planting later (say mid-October or later). This strategy enabled us to reduce disease

severity in two out of three years. Benefits from delayed sowing are reduced when diseaseconducive

conditions are prolonged and cannot be avoided. We recommend delayed sowing

as a “best bet” strategy for minimising the impact of Fusarium wilt.

Outcome 2. Fusarium is carried in large numbers on floating trash during irrigations.

We measured over 160 million colony forming units of Fusarium oxysporum per kg of

floating trash during irrigation. Floating trash is the primary means of transport of the

Fusarium wilt fungus around the farm during irrigations. Therefore it is important to 1) stop

trash from leaving the field by using a trash-retaining drop box, and/or remove trash from

channels using trash racks. The process of passaging irrigation water back through a storage

dam or settling pond also aids in removing most of the pathogen from the water.

Outcome 3. Remove stubble, or retain slashed stubble on the surface for a month or longer

before incorporation.

Fusarium wilt will be less severe where stubble from previous crops has been raked and burnt

or slashed and retained on the surface for a month or longer prior to incorporation. These

practices are highly recommended for growers with Fusarium wilt.

Other Outcomes

• Glyphosate (RoundupTM etc) and Roundup ReadyTM technologies do NOT increase

the severity of Fusarium wilt.

• Stress from heavy boll loads does NOT increase the severity of Fusarium wilt.

• There is NO interaction between black root rot and Fusarium wilt.

• Nematodes are NOT a problem in Australian cotton.