DISSEMINATION OF BACTERIA ANTAGONISTIC TO ERWINIA-AMYLOVORA BY HONEY-BEES

Foraging honey bees (Apis mellifera) were tested for ability to disseminate bacteria antagonistic to Erwinia amylovora to apple and pear flowers in commercial orchards. The bacteria, Pseudomonas fluorescens and E. herbicola, previously known to provide biological control of fire blight, were placed on apple or cattail pollen at populations of 10(9) and 10(8) bacteria per gram, respectively. There was no significant decline in viable bacteria on either pollen over 3 wk at 4 C. These bacteria-treated pollens were placed in pollen inserts in the entrances of beehives. Honey bees emerging from these hives through bacteria-pollen mixtures acquired an average of 10(5) and 10(4) cfu per bee of P. fluorescens and E. herbicola, respectively. E. herbicola was detected on 92% of the apple flowers in a 2.6-ha orchard 2 days after the start of one study. In a pear orchard, 72% of the flowers within 7.6 m of the hive were colonized with P. fluorescens (average population of 10(2) Cfu per flower) 8 days after the start of the study. Our study showed that bees can be efficient vectors of antagonistic bacteria for biological control of fire blight; disease control could not be evaluated because of frost and absence of disease in the test orchards.