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Spotting telltale signs of Fusarium Race 4 in cotton

There are symptoms for the various Fusarium races and all look similar. The only way to confirm Race 4 is through lab analysis. However, here are some telltale signs.

There are symptoms for the various Fusarium races and all look similar. The only way to confirm Race 4 is through lab analysis.

Telltale signs of Race 4 are:

• Blank areas of a cotton field where there are no plants or plants are dying.

• These areas may be small initially, but can expand down the rows and across fields in year two or three, especially if the field has a history of susceptible varieties.

• Surviving plants adjacent to the blank areas will have wilted, splotchy foliar chlorosis and/or necrosis and nearly continuous, dark brown vascular staining in the tap roots

• Race 4 vascular dark brown staining will be most evident on tap root.

• Verticillium wilt symptoms appear later in the season and vascular staining is generally lighter with verticillium, more discontinuous and usually evident in lower stems as well as in root tissue.

Containment practices

• Limit soil movement from infected fields.

• Pressure wash implements, sprinkler pipe, machinery from farms even suspected of having Race 4.

• On known Race 4-infected fields, avoid land planing or other leveling that moves soil and consider reduced, conservation tillage in those fields.

• Restrict irrigation tail water movement off infested fields.

• Limit equipment traffic through Race 4 infested areas of fields.

• Keep gin trash from infested fields off ground.

• Avoid using manure from cattle corrals using gin trash for bedding or cattle fed with cottonseed from known Race 4-infested fields.

• Do not allow seed production from infested fields or even fields next to known infested fields.

Management of Race 4

• Plant only varieties with the highest level of Race 4 resistance. UC/USDA screening tolerant/susceptible variety trials are available at

• Rotation to non-host summer crops or summer fallow will likely reduce inoculums, especially in multi-year rotations.

•Long term weed free fallow may reduce inoculum.

• Soil solarization with fumigants/tarping for one to two months may reduce inoculums.

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