Acibenzolar-S-methyl is associated with yield reduction when used for managing bacterial wilt (Erwinia tracheiphila) in cantaloupe

Bacterial wilt, caused by Erwinia tracheiphila (Smith), can result in serious yield loss of cantaloupe in the Midwest United States. Although neonicotinoid insecticides are an effective means of managing the cucumber beetles that vector E. tracheiphila, this management regime may cause toxicity to pollinators. An alternative method of managing this disease is to use products that induce resistance. Over four years, we have compared disease severity of bacterial wilt, cucumber beetle numbers, feeding damage and yield as influenced by products purported to induce Systemic Acquired Resistance (SAR) or Induced Systemic Resistance (ISR). Acibenzolar-S-methyl (Actigard (R)) effectively lowered disease severity of bacterial wilt in years when disease pressure was moderate or high. Actigard (R) was also associated with lower levels of cucumber beetle feeding in some years. However, when disease pressure was low, Actigard (R) at some rates and timings, caused yield loss. The other products, Regalia (R) and Serenade Max (R), are purported to elicit ISR and did not consistently lower disease levels or influence beetle feeding in the current study. The standard insecticide regime, imidacloprid used as a drench at planting and permethrin applications at weeks 3-6, was the most consistent method of lowering beetle feeding and thus managing bacterial wilt. Since Actigard (R) could be associated with yield loss, its use for the management of bacterial wilt in cantaloupe cannot be recommended.