Tab A - Page 15 
determination that the field test, with the specified conditions, presented no 
significant risk to health or the environment. 
In the initial field test, 16 rows of potato plants covering 0.4 acre at 
the Tulelake Research Station will be used In testing. 0.09 acre will be 
sprayed with suspensions (ca. 10 - 10 cells/ml) of genetically engineered 
ice-nucleation-neoative deletion mutants of Pseudomonas syrlnqae pv. syrlroae 
and Erwinia herblcola to test the suitability of the deletion mutants as frost 
damage biocontrol agents. Another 0.09 acre of potato plants will be sprayed 
with the same suspension, followed by application of a suspension of unmodified 
INA* bacteria of the same strains. Parallel experiments on the same plot will 
be conducted with chemically-induced INA mutants. For comparison, another 
0.044 acre of potatoes will be treated with only INA* bacteria, and a similar 
plot will be left untreated as a control (see complete description In Section 
5.3.2). Field tests will be conducted on a continuing basis during the spring 
and fall of the test period, when frost is imminent. Subsequent experiments will 
involve the same strains of bacteria and the same experimental procedures, 
except that tomatoes and beans will also be used as the target crop. 
The bacteria are common plant epiphytes found in substantial numbers on 
above-ground plant surfaces (leaves, twigs, buds, flowers) with seasonal 
fluctuation from undetectable levels up to 10^ cells/gram tissue fresh weight. 
A- causal relationship between frost damage on frost-sensitive crop plants at 
relatively warm subzero temperatures (down to -5° C) has been established 
through experiments showing that the degree of damage, after exposure to low 
temperatures (either in the field or In growth chambers), Is directly related 
to the populations of ice-nucleatlon-actlve (INA*) bacteria present In, or on 
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