Consecutive field trials were done during summer–fall of 2009,
2010 and 2011 at the University of California Davis Research Farm
facility. During trials conducted during June to September 2009 and
2010 melon seedlings (Cantaloupe cultivar Oro Rico F1 and Honeydew
cultivar Summer Dew HMX4593) were transplanted in two adjacent
field sections (Yolo silt clay loam; class 1 soil). Inoculumwas introduced
via two different systems, furrow irrigation and sub-surface drip
emitters. To mimic contamination of the field using furrow irrigation,
9 beds (150 cm width) were utilized with 18 corresponding furrows.
A total of 36 seedlings per bed were transplanted with an in‐row
spacing of 77 cm. Each half bed corresponded to one block that contained
18 plants of cantaloupe or 18 plants of honeydew, resulting in a total of 18
blocks of replicated-plantings. Honeydew and cantaloupe vines were
established on approximately 2 m (center to center) raised beds with
flanking furrows. When melon plants were at the initial flowering
stage, each furrow was inoculated with 4 porous infusion sachets spaced
approximately 7.5 m apart as described by Gutierrez-Rodriguez et al.
(2012). Infusion sachets were prepared by mixing 3 kg of sand with 1 L
of log 9 CFU/mL of aPTVS177 supplemented with 2% non-fat powder
milk as an organic carrier to reduce desiccation stress, which resulted in
a final concentration of log 7.5 CFU/50 g of sand. After placement of
the inoculated infusion sachets, water was immediately applied with a
gated pipe into furrows to a uniform depth, without wetting or overflow
across the bed surface as is standard industry practice for furrow irrigation
in CA (ANR 7218, 2008). Irrigation was managed throughout the
trial such that plants during primary fruit set were not in direct contact
with contaminated water. Inoculation with porous sachets was repeated
after 24 days from the first inoculation event, as previously described. At
the peak of irrigation, water samples from each flanking furrow were
collected at the mid-point and near the terminal end from the point
of irrigation delivery to determine the final estimated concentration of
aPTVS177 in the water across the field row-length. The population of
applied Salmonella in water (log CFU/mL) was determined by plating
100 μL of water in triplicate on TSARP and enumerating after 24 h of
incubation at 37 °C. In pre-trial tests of the specific research plot
areas, no rifampicin resistant Salmonella spp. were detected by direct
plating or following enrichment of five replicated 100 g samples (data