ABSTRACT
Injury to plants through frost is mainly due to certain bacteria on the surface of leaves. Development of techniques for quantitative and qualitative measurement of ice nucleation-active (INA) bacteria has gone a long way to investigate the bacteria responsible for plant damage. The major benefit of this technique is that it gives reliable and repeatable quantitative assessment of ice nuclei contributed by bacteria in almost all situations. Plants treated with streptomycin had about the same total bacterial population as the untreated controls, but had substantially lower numbers of INA bacteria. Treatment with cupric hydroxide also decreased the numbers of INA bacteria as effectively as did treatment with streptomycin and also caused about a tenfold decrease in the total population of bacteria compared to the untreated controls. The effectiveness of selected non-INA bacteria to exclude INA bacteria during subsequent challenge inoculations increased with increasing relative population size of the antagonistic bacteria.
