Southern Bacterial Wilt on Marigolds and Dahlias: Resistant Varieties and Slug Management

Disease Identification

Marigolds & dahlias: stop flowering → wilt → brown from bottom up. Roots look fine; stems hollow. Classic Southern bacterial wilt (Ralstonia solanacearum). Hosts: tobacco, tomato, potato, dahlia, geranium, hollyhock, hydrangea, marigold, nasturtium, zinnia.

No Chemical Cure

Control = avoid susceptible plants or grow resistant cultivars.

Resistant Marigold Cultivars

Cupid; Irish Lace; Papaya Crush; Pineapple Crush; Pumpkin Crush; Rusty Red; Sparky; Sparky Mix; Bonanza Yellow; Choice Mix; Copper Canyon; Cupid Mix; Fort Knox; Golden Harmony; Goldie; Gypsy Dancer; Naughty Marietta; Orange Lady; Senator Dirksen; Tangerine Gem.

Cultural Management

• Destroy (burn) diseased plants.
• Plant susceptible cultivars in new soil or soilless media in containers.
• Minimize spread to other hosts (broad host range).

Slug Control (Separate Issue)

• Reduce hiding spots (boards, pots).
• Diatomaceous earth barrier (sharp silica cuts slugs).
• Beer traps (½" stale beer in saucer overnight).
• Commercial slug baits for large infestations.