Control of fire blight in pears by in-situ flamation of blighted shoots and blossoms

Naturally infected shoots or blossoms with the fire blight pathogen, Erwinia amylovora, developed on limbs (3-6 cm in diameter) of Spadona' pear trees in commercial orchards were burned for a few seconds with the aid of a propane flame-torch, including the surrounding tissue of the infected sites. Before and after burning, segments of bark tissue were aseptically removed from the infected organ and from various distances below and above it on the limb, and at various week intervals afterwards. Samples were ground in phosphate buffer and E. amylovora was detected by plating on CCT and confirmed by PCR. Results showed that burning was highly efficient in eliminating E. amylovora in infected organs. In most cases (>90%) E. amylovora was reduced from 106-107 to 0 cfu per cm² tissue. More importantly, burning prevented the spread of the bacteria from the infected organs to the main limb. In one out of ten samples, a very low level of the bacterium was detected at 10 cm below and above the infection site. Similar findings were obtained on artificially inoculated 6-years-old pear trees grown in containers under insect-proof net. We have observed no damage to tree viability and vitality as yet as a result of this treatment. Results indicate that burning the infected organs (before internal spread of E. amylovora to the main limbs occurs) can provide a safe and rapid measure to control fire blight. Further study is needed to prove if this technique can prevent the pruning of the main limbs.