Location: Crop Improvement and Protection Research
2023 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
This report documents progress on project 0500-00007-121-000D, which started in October 2020, titled "Minor Use Pesticide Testing on Vegetables and Sugar Crops."
Interregional Research Project #4 (IR-4) field trials are being conducted on projects during fiscal year (FY) 2023 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 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 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 when combined with laboratory data, are used to establish a pesticide tolerance on minor crops.
A squash field trial was conducted with the fungicide inpyrfluxam to control powdery mildew, which causes squash leaves to die prematurely, and reduces fruit quality and yield. Two foliar applications of inpyrfluxam were made at a fourteen day interval and the squash was harvested the next day. Powdery mildew on squash has developed full resistance to several chemistries limiting options for control; therefore, additional fungicides are critical for growers.
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 lettuce roots from Pythium wilt. The first application was made at thinning and the second application 30 days later.
Root vegetables, including carrots, radishes and turnips, were grown in the field to test two fungicides. Thiophanate methyl was tested for control of Rhizoctonia fungal disease on carrots and white leaf spot (Mycosphaerella capsellae) on radishes. Two foliar applications were made at a seven day interval 10 days prior to harvest. The fungicide cyazofamid was applied for club root control on turnip roots with the first application at planting followed by five foliar sprays.
There is a need for more effective nematicides on radishes so fluazaindolizine was applied for root knot and root lesion nematode control. One in-furrow directed spray was made during planting of the radishes.
Two strawberry projects were undertaken to study the magnitude of the residues from the fungicides cymoxanil and GF-4031. Cymoxanil is needed to reduce selection of resistance to the fungicide mefenoxam, which is currently used to manage Phytopthora crown rot and Phytopthora leather rot on strawberries. Five foliar applications of cymoxanil were made at five day intervals, with the last application made on the day of harvest. GF-4031 is an effective protective fungicide to help manage powdery mildew on strawberries and must be applied prior to visible symptom development on the plants. Three foliar sprays were made at intervals of seven days and the crop was harvested one day after the last application.
Accomplishments
1. Minor use pesticide residue tests. Specialty crop growers benefit by having effective pest management tools that enable them to produce high quality food crops. Ten field trials were conducted by ARS researchers on vegetables and strawberries in Salinas, California, during fiscal year 2023 with various fungicides and one nematicide. Vegetable crops included squash, lettuce, carrots, radishes and turnips. Fungal diseases on these crops can decrease 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.
