Tab A - Page 40 
could successfully colonize any plant other than potatoes, tomatoes, or beans 
since the bacterial strain Is adapted best to the target plant and other plants 
are already colonized by other bacteria. If there was colonization by the 
deletion mutants the result would be either conditional protection of the crops 
from frost damage or no effect. The foregoing discussion applies equally to 
non-commercial plants. Moreover, no known bacterial diseases occur In 
conifers, which dominate the forest around Tulelake 8as1n. 
Erwlnia herbicola Is not pathogenic to plants In Northern California. 
Therefore, no plant diseases are expected from application of E. herbicola in 
the proposed field test. Moreover, the same factors limiting colonization or 
spread of _P. _s- syrinaae INA~ mutants would limit the spread of E. herbicola 
INA" mutants. 
5.3.4 Local Epiphytic Bacterial Populations 
P_. s_. syrinqae and Erwlnia herbicola occur naturally in the vicinity of 
the test site. Under California conditions, a large seasonal variation in the 
numbers of epiphytic ice-nucleation-actlve bacteria on both annual and 
perennial plants has been observed. The bacterial populations found on healthy 
pear flowers and leaves are typical of this variation. Populations of 
Ice-nucleation-artlve-bacteria are generally low (less than 100 cells/g fresh 
weight of leaf or bud tissue) on overwintering plant tissues of deciduous 
plants or on emerging cotyledons or leaves of annual plants. However, large 
epiphytic populations of such bacteria (principally P_. syrinqae ) are present on 
emerging flowers and/or leaves of these plants. A 100-fold Increase In 
bacterial populations has occurred on pear during the 2-week period following 
37 
[234] 
