Overview
Erwinia amylovora is a Gram-negative bacterium and the cause of fire blight, one of the most feared bacterial diseases of apple, pear and other rosaceous plants. Native to North America, it has spread across many production regions and can move rapidly through an orchard in a single warm, wet season.
Symptoms
Blossoms and shoots suddenly wilt, blacken and take on a characteristic 'shepherd's crook' bend, as though scorched by fire. Cankers form on branches and can girdle and kill whole limbs or trees; a bacterial ooze is often visible in humid conditions.
How it spreads
Warm temperatures during bloom combined with rain, dew or high humidity create high-risk conditions. Pollinating insects, rain and wind carry the bacterium to blossoms, its main point of entry.
The control challenge
In several regions fire blight has been managed with the antibiotic streptomycin — and the emergence of streptomycin-resistant strains is a well-documented example of how disease control can drive antimicrobial resistance (AMR). This makes non-antibiotic, resistance-aware alternatives especially valuable.
Fire blight is a further bacterial category of interest for phage-based research. Bacteriophages are a natural, antibiotic-free way to target bacteria and are being explored internationally as an alternative to streptomycin. For Exacta this represents a research area of interest, not a commercially available product.