Grafting Reduces Southern Blight on Tomato by 83%

From Clemson Plant Pathologist Tony Keinath.

Southern blight has become more common on tomatoes grown without fumigation throughout the southern United States. A joint project between the University of Georgia and Clemson University looked at grafting as a management option. In the 2021 trial in Charleston, SC, grafting reduced the percentage of diseased plants from 44% on nongrafted ‘Roadster’ to 7% on ‘Roadster’ grafted on ‘Maxifort’ rootstock. Even better, marketable weight was 71% greater on the grafted plants than on the nongrafted. The extra yield was mostly in the extra-large red and pink fruit categories, based on weights of fruits from 8 plants per plot.

Tan and white sclerotia of Southern blight (Athelia rolfsii) develop at the base of tomato plants before falling into the soil, where they will remain until the next susceptible host crop is planted. Photo from Tony Keinath.

For growers unsure about grafting, we also saw that ‘BHN 602’ was somewhat tolerant to southern blight. Although nongrafted ‘BHN 602’ had 33% diseased plants by the end of the season, marketable weight was not significantly lower than on the grafted plants, although there were fewer extra-large fruit. For information about grafted tomatoes, see or Note that grafted plants need to be ordered 60 days before delivery.

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