Three crop safety studies and two supplemental dose-response evaluations were conducted in 2019 and 2020 to evaluate the crop safety of the Israeli-developed PICKIT decision support system on California processing tomatoes. These studies were conducted at the UC Davis Plant Sciences Field Research Facility near Davis, California . The soil composition at this site was 41% sand, 34% silt, and 25% clay with 2.1% OM, 6.98 pH, and estimated CEC of 18.2 cmolc/kg of soil. The site did not contain broomrape; this protocol focused on crop safety of 1X and 2X rates of herbicides used in the PICKIT system that are not currently registered for use in tomato in the United States. Plots were 12 m long on 1.5 m beds with one plant line in the center of the bed. Cultivar ‘Heinz 1662’ processing tomato transplants were planted at 30.5 cm spacing. Each bed had two 15.9 mm drip lines buried at 30.5 cm with 0.6 L/hr emitters spaced every 30.5 cm; one line ran the full length of the beds and was used for crop irrigation and fertigation, the second line was terminated at the end of each plot and connected to an above-ground manifold system which was used to apply the experimental chemigation herbicide treatments. Plots were arranged in a randomized complete block design with four replications per treatment. In 2019, two experiments were conducted to represent twoplanting dates, April 25 and May 30; a single experiment was conducted in 2020 with an April 22 planting date. Pre-plant incorporated applications of sulfosulfuron were made one day before transplanting on April 24 and May 29, 2019 in the early- and late-planted experiments respectively, and on the day of planting, April 22, 2020 . PPI herbicides were applied using a backpack sprayer and three-nozzle boom delivering 280.5 L/ha with AIXR 11003 nozzles at 28 pounds per square inch .
PPI treatments were mechanically incorporated to 7.6 cm after application, commercial grow racks after which tomatoes were mechanically transplanted with a three-row transplanter on April 25, 2019 , May 30, 2019 , and April 22, 2020. The PICKIT system’s thermal time model is based on growing degree days , with applications at 400, 500, 600, 700, and 800 GDD after transplanting depending on treatment regimes . The PICKIT program has various regimes depending on level of infestation, with each calling for different application types and total number of applications . In 2019, chemigation applications were made through the terminated irrigation line using a 20.8 L/min 12-volt electric pump and 113.5 L tank. Treatments were applied to four plots at once, with a total carrier volume of 96.1 L per treatment resulting in approximately 15.9 L per plot . In 2020, chemigation applications were made using CO2 to inject a chemigation mix into a distribution manifold with valved connections at each plot . Treatments were applied to two replicate plots at once with separate injection ports for replicates 1 and 2 and replicates 3 and 4 to reduce the system volume receiving herbicide treated water. Herbicides were diluted in 11 L of water and this solution was injected into the already-running irrigation system over approximately 15 minutes, followed by 20 minutes ofwater to flush the distribution lines. Foliar imazapic treatments were made on July 16, 2019, August 15, 2019, and June 12, 2020 and approximately 21 days later with a backpack sprayer and two-nozzle boom delivering 280.5 L/ha with AIXR 11005 nozzles at 20 PSI. These applications were made at estimated broomrape emergence and approximately 21 days later, as these studies occurred in uninfested fields. Phytotoxicity was recorded in all three studies and representative plant height was recorded in the 2020 study. All fruit from one-meter square sections of row were harvested on September 4, 2019, September 19, 2019, and September 3, 2020 at commercial maturity and fresh weights were recorded .
Phytotoxicity, height, and yield data were analyzed using a one-way analysis of variance followed by a Tukey-HSD test using the agricolae package in R version 1.2.5033 . Two supplemental crop safety trials were conducted to evaluate increasing rates of foliar applied imazapic, which is not currently registered on processing tomatoes in California. These studies were conducted at the UC Davis Plant Sciences Field Facility near Davis, CA, . Cultivar ‘Heinz 1662’ tomatoes were transplanted on April 22, 2020 in a single plant line on a 1.5 m bed with 30.5 cm spacing. Imazapic was applied late in the growing season to simulate a rescue application in a PICKIT program. Applications were made on July 7, 2020, 73 days after transplant in the first experiment and on July 21, 2020, 87 days after transplant in the second experiment at 280.5 L/ha using a two-nozzle boom with AIXR 11003 nozzles at 28 PSI. Five rates were applied in a dose response style experiment with a 0.25% v/v nonionic surfactant . Applications were made at full fruit set . Each treatment was replicated four times in a single guard row of an existing processing tomato experiment. Visual crop injury ratings were taken 3, 7, and 14 days after treatment . Phytotoxicity means were analyzed using a one-way analysis of variance followed by a Tukey-HSD test using the agricolae package in R version 1.2.5033 .A two-year study was conducted from spring 2019 to fall 2020 to evaluate rotational crop-safety of the Israeli-developed PICKIT decision support system. This field experiment included a 2019 tomato crop treated with PICKIT herbicides followed by a planting of six common rotational crops in 2020. The study was conducted at the UC Davis Department of Plant Sciences Field Research Facility near Davis, California . The site did not contain broomrape; this experiment focused on crop safety of sulfosulfuron, imazapic, and 2X rates of imazamox, imazapyr, and imazethapyr, none of which are currently registered for use in tomato in the United States.
The 2019 tomato main plots were 54.8 m long on 1.5 m beds with one plant line in the center of the bed. Each bed had one 15.9 mm drip line at a depth of 30.5 cm with 0.6 L/hr emitters spaced every 30.5 cm. This drip line was used for crop irrigation and fertigation as well as chemigation of PICKIT treatments. For the 2019 tomato crop, main plots were arranged as whole rows in a randomized complete block design with four replications. PPI applications of sulfosulfuron were made on May 29, 2019 one day before transplanting tomatoes. PPI herbicides were applied using a backpack sprayer and three-nozzle boom delivering 280.5 L/ha with AIXR 11003 nozzles at 28 PSI. PPI treatments were mechanically incorporated to 7.6 cm after application. Tomato cultivar ‘DRI 319’ transplants were planted at a 30.5 cm spacing with a three-row transplanter on May 30, 2019. At each growing degree day target chemigation applications were made through the drip line using a Venturi-style injection system attached to a cone tank over the course of 45 minutes, with treatments applied to four replicate plots at once . A single one-meter square section of each plot was harvested on September 19, 2019 and total weight of all fruit were recorded . Following the tomato harvest in 2019, the tomato crop was destroyed in place with a flail mower. After the crop residue dried, beds were lightly cultivated to reshape beds but minimize soil mixing. The 54.9 m long tomato main plots were split into six 9.1 m subplots for the 2020 rotational crops in a split plot design. The six rotational crops including wheat, corn, safflower, sunflower, beans and melons were randomly assigned to a subplot such that the 2020 experimental design was a randomized split plot with four replications. On November 22, 2019, wheat subplots were planted with a grain drill. Visual wheat injury measurements were recorded during the winter of 2019 and spring of 2020. In mid-April 2020, vertical grow weed all beds were treated with glyphosate to terminate the wheat and control winter weeds in all plots and lightly cultivated to prepare a seedbed. On April 17, 2020, corn , safflower , sunflower , beans , and melons were planted using an Earthway precision garden seeder .
Plant height and fresh weight biomass were recorded nine weeks after planting on June 23, 2020; the experiment was subsequently terminated without being taken to maturity. Height and fresh biomass data were analyzed using a one-way analysis of variance followed by a Tukey-HSD test with the agricolae package in R version 1.2.5033 .A study was conducted in a commercial tomato field in Yolo County, CA, that had been reported as infested with branched broomrape in 2019 and a portion of the crop was destroyed under CDFA quarantine provisions. The infested area was prepared for planting by the grower and used for a 2020 experiment to test the efficacy of the PICKIT protocol on branched broomrape in California tomato systems. The soil composition at this site was 25% sand, 42% silt, and 33% clay with 2.7% OM, 7.2 pH, and estimated CEC of 23.6 . Plots were 30.5 m long on 1.5 m beds with two drip lines: one 22.2 mm drip line buried at 25.4 cm and one 25.4 mm drip line buried at 30.5 cm in the center of the bed. The 22.2 mm drip line was terminated at the ends of each plot serving as the dedicated chemigation line with 0.6 L/hr emitters at 30.5 cm spacing. The 25.4 mm line was used for crop irrigation and fertigation of the entire experimental area. Plots were arranged in a randomized complete block design with four replications. PPI applications of sulfosulfuron were made on March 27, 2020 . Sulfosulfuron was applied using a backpack sprayer and three-nozzle boom delivering 280.5 L/ha with AIXR 11003 nozzles at 28 PSI. PPI treatments were mechanically incorporated to 7.6 cm after application on the same day. In addition to the experimental treatments, the entire plot area was treated with the grower’s preplant incorporated tank mix, which consisted of S-metolachlor , pendimethalin , metribuzin , and diazinon on March 27, 2020. Cultivar ‘BQ271’were mechanically transplanted using a two-row transplanter on March 30, 2020 with two plant lines in each row with plants spaced 30.5 cm apart within and between lines. A routine foliar application of 7.2 g ai/ha rimsulfuron was made by the grower to the entire experimental area after transplanting.Chemigation applications were made using CO2 to inject the chemigation mix into 50.8 mm lay flat hose connected to valved 22.2 mm chemigation lines in each plot . Treatments were applied to two replicate plots at once; plots of the same treatment in replications 1 and 2 and replications 3 and 4 were treated together. Herbicide treatments were mixed in 11 L of solution which was injected into the already-running irrigation system over approximately 15 minutes, followed by 20 minutes of water to flush the lines. Chemigation applications were made according to a modified version of the PICKIT protocol . Foliar imazapic treatments were made with a 2-nozzle backpack sprayer delivering 280.5 L/ha with AIXR 11003 nozzles at 28 PSI. Broomrape scouting was done 3 times weekly for seven weeks, followed by 1 time per week for 3 weeks starting on June 1, 2020. At each rating, individual clusters of shoots were marked with wire construction flags, with different colors representing each week’s emergence . Broomrape shoot clusters were counted and recorded weekly. Total broomrape cluster numbers were analyzed using a one-way analysis of variance followed by a Tukey-HSD test in the agricolae package in R . Broomrape emergence over time was analyzed with a 3-parameter log-logistic function in the drc package in R version 1.2.5033 . Before the trial was terminated and after the final broomrape cluster count, locations of individual clusters marked by flags were recorded with a GPS device . A Trimble Handheld GPS device was placed at each flag, the coordinate was recorded in the FarmWorksMobile application , and the color of the corresponding flag was recorded. This data was entered into ArcGIS online , and a color coordinated map was created .After two field seasons and three studies, crop safety for the imidazolinone and sulfonylurea herbicides utilized in the PICKIT system appears acceptable at both the proposed rate structure and two times the proposed rate structure in California processing tomato. These results confirm the crop safety reported for the PICKIT program in Israel.