See updated article (2017) Herbicide injury symptoms in tomatoes.
Dr. Darren Robinson, Ridgetown Campus – University of Guelph; Janice LeBoeuf, OMAFRA, Ridgetown
Dual does not translocate far in the plant, and injury symptoms occur only in stressed plants in cold, wet weather. If injury does occur, symptoms will include yellowing and curling of the new leaves and petioles.
Tomatoes are particularly susceptible to Treflan/Bonanza/Rival injury on low organic matter soils, or if transplants have been placed too shallow in the soil. Injury symptoms include club roots, stunting and occasionally purpling of leaves.