Location: Crop Improvement and Protection Research
2024 Annual Report
Objectives
Objective 1: Conduct laboratory and field tests to provide residue data needed to establish a tolerance on a specific commodity or to support a crop group tolerance.
Approach
Research to support registrations of minor use pesticides. Apply pesticides according to IR-4 protocol guidelines. Obtain performance data, phytotoxicity, yield, and efficacy from treated and untreated field plots. Ship samples to laboratories for residue analyses. Protocols will be employed using appropriate Standard Operating Procedures and conducted under provisions outlined in 40CFR part 160 in accordance with EPA's Laboratory Practice Standards.
Progress Report
Interregional Research Project #4 (IR-4) field trials are being conducted by ARS researchers in Salinas, California, on projects during FY 2024 according to approved protocols developed by IR-4 Project Headquarters. Following local good agricultural practices for agricultural production, field testing is being done on vegetables, herbs and strawberries. Commercially acceptable minor crops are being grown and sprayed according to the protocols with test substances using small plot sprayers that simulate commercial application equipment. Various pesticides are being evaluated in the field test plots on a variety of minor crops. Plants were frequently monitored for phytotoxicity from application treatments and timing of sprays. Plant samples were collected at harvest and stored frozen until shipment to a designated IR-4 analytical laboratory for residue analysis. Field data was submitted to IR-4 Headquarters, and combined with laboratory data, are used to establish a pesticide tolerance on minor crops.
Commercial growers of head and leaf lettuce are looking for effective fungicides to control Pythium wilt, a new emerging disease in the Central Coast region of California. Mefenoxam is currently registered on lettuce for one application, but two applications are being requested. The material was applied to the soil as a band application near the base of the plant then moved into the rootzone of the plant with sufficient water to protect the head lettuce roots from Pythium wilt. The first application was made at thinning and the second one 30 days later.
Powdery mildew is not being effectively controlled on basil with registered fungicides so the fungicide flutianil was tested for control efficacy on this crop. Powdery mildew causes white spots on the leaves which affects the aesthetics and flavor of the basil. Five applications of flutianil were performed at seven day intervals with a 0 day phi (Pre-Harvest Interval). Both fresh and dried samples were collected from the trial.
Another pathogen attacking basil is Fusarium wilt, caused by the fungus Fusarium oxysporum f. sp. Basilicum, which causes the plants to become stunted and wilt when they reach the 8 to 12” growth stage. This is becoming a significant problem in production fields and there are currently very few fungicides registered for control. The fungicide fludioxonil and pydiflumetofem was applied as a soil drench followed by two foliar sprays at seven day intervals with the last application being on the day of harvest. Fresh and dried samples were collected at harvest.
A study was conducted in strawberry to study the magnitude of the residues from the fungicide flutolanil. Fungicides are needed to control black root rot disease, caused by the fungal pathogens Rhizoctonia ssp., Pythium spp. and Fusarium spp. Rhizoctonia is the most important fungal pathogen causing this disease and there are no effective fungicides or fumigation for control. Flutolanil was directed to the base of the plants as a drench application. Two applications were made at 30 days apart and the second application was made 30 days prior to the harvest.
A summer squash field trial was conducted with the herbicide fluazifop-p-butyl to control grasses. Two applications were made at 14 day intervals with a 14 day interval prior to harvest. There was no phytotoxicity observed on the squash plants from the two broadcast applications. This product works well in commercial squash production and would give growers another herbicide type for grass control.
Due to the lack of alternatives that control problematic winter annual weeds in strawberries, the herbicide 2,4-D Choline was evaluated. A hooded sprayer was used to make the spray to the row middles of the plastic mulched beds avoiding contact with the crop. Two sprays were made at 15 day intervals and the second application was made 14 days before harvest. There was no observed phytotoxicity from the sprays. Ryegrass is frequently grown in the row middles over the winter for weed suppression and limits soil, wind, and water erosion from the middles; unlike other registered herbicides, 2,4-D Choline will not kill the ryegrass.
Anherbicide trial was conducted on strawberries with the chemical glufosinate for control of ragweed (Ambrosia artemisiifolia). This weed is rapidly increasing in strawberry fields and there is known resistance to both glyphosate and paraquat herbicides. Glufosinate is highly effective on ragweed. One application was made to the first set of blooms of the season just before fruit formation to the row middles using a shielded sprayer. Contact with the plants was avoided. Residue samples were collected at the first commercial maturity of the crop. There was no phytotoxicity from the spray.
Accomplishments
1. Minor use pesticide residue trials. Specialty crop growers benefit by having effective pest management tools that enable them to produce high quality food crops. Seven field trials were conducted by ARS researchers on vegetables, herbs, and strawberries in Salinas, California, for fiscal year 2024 with various fungicides and herbicides. Fungal diseases on vegetable and herb crops can decrease the quality and yield, and develop resistance to existing fungicides; therefore, testing of new chemistries is important. ARS researchers continued to assist specialty crop growers and other stakeholders by managing and assisting with field research projects through the IR-4 program.