Which pest management method uses rootstocks with the K84 strain of Agrobacterium radiobacter?

• A. Antibiosis
• B. Host resistance
• C. Augmentation
• D. Chemical control

Answer: (A)

Antibiosis is a biological control mechanism where a living organism suppresses a pest or pathogen by producing inhibitory substances. Rootstocks treated with Agrobacterium radiobacter strain K84 work this way because K84 emits agrocin 84, an antibiotic that specifically inhibits the crown gall pathogen Agrobacterium tumefaciens. By occupying the root environment and releasing this antimicrobial compound, K84 prevents the pathogen from causing tumors on the roots. This is different from relying on plant-generated resistance, chemical pesticides, or simply releasing other beneficial organisms without an antagonistic effect. Therefore, using K84–treated rootstocks is a classic antibiosis-based biological control.