Location: Crop Improvement and Protection Research
2025 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 is the final report for project 0500-00007-121-000D, Minor Use Pesticide Testing on Vegetables and Sugar Crops, which has been replaced by new project 0500-00007-128-000D, Minor Use Pesticide Testing on Vegetables and Sugar Crops. During this time, Interregional Research Project #4 (IR-4) field trials have been conducted on minor crops by ARS researchers in Salinas, California. The objective is to establish new crop pesticide tolerances from specific pesticide use patterns according to protocols developed by IR-4 Project Headquarters. Following good local agriculture practices for commercial production, field testing has been done on vegetables, field crops, herbs and strawberries. Various fungicides, insecticides, herbicides and nematicides have been evaluated in the field on these minor crops.
Each year, commercially acceptable minor crops have been grown and sprayed according to the IR-4 protocols with various test substances using small plot sprayers that simulate commercial application equipment. Various pesticides have been evaluated in field test plots on a variety of minor crops. Plants were frequently monitored for phytotoxicity from application treatments and timing of sprays. Residue samples were collected at harvest and frozen until shipment to a designated IR-4 laboratory for residue analysis. Data collected from the field experiments was submitted to IR-4 Program Headquarters, and when combined with laboratory data, was used to establish pesticide tolerances on these minor crops by the Environmental Protection Agency (EPA).
Over the life of the project, 51 field trials have been conducted by ARS researchers in Salinas, California. These projects involved 41 vegetable, one field crop, four herb and five strawberry trials. Most of the research work has been done with cool season vegetables, which consisted of broccoli, cabbage, table beets, carrots, green onions, radishes, mustard greens, spinach, lettuce (head & leaf), turnip, and swiss chard. Warm season vegetables included dry bulb onions, bell peppers, tomatoes, lima beans and summer squash. Field crops consisted of dry beans. Herbs included trials with basil and stevia. Of these IR-4 field projects assigned, 35 have been fungicide trials, five insecticide trials, 10 herbicide trials and 1 nematicide trial. Testing new chemistries is important to minimize fungicide and insecticide resistance of existing pesticides on minor crops.
The 28 cool season vegetable trials consisted of most of the IR-4 field projects conducted in Salinas, California. Leafy greens included trials with spinach, mustard greens, Swiss chard and lettuce. Spinach is prone to the disease Stemphyllium so additional fungicides are needed to help prevent the development of fungicide resistance. The fungicide mix of difenoconazole & azoxystrobin applied 4 times at 7-day intervals with a 3-day pre-harvest interval (phi) was tested with no observed phytotoxicity. The mustard greens herbicide label for S-metolachlor is a 30 days phi, which is too long due to a growing demand for younger more tender greens, so a 21-day phi was tested with no observed phytotoxicity on the mustard greens. With few herbicides registered for use on Swiss chard, ethofumesate was applied preemergence and post emergence at the 2 to 4 leaf stage, and provided control of broadleaves and grasses.
One leafy green trial was especially important to commercial growers of head and leaf lettuce who 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 were requested by Monterey County farm advisor. 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 thirty 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 ten 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 . Table beets need additional fungicides to control various root rots, as there are limited effective products available, so flutolanil was applied soil directed at planting and a foliar spray 1 day before harvest.
Six cole crop trials were conducted on broccoli and cabbage for control of Alternaria leaf spot, a disease of growing concern to growers nationwide particularly in the Southwestern U.S. and coastal California, because of decreasing efficacy of a narrow number of fungicides available. Florylpicoxamid was tested at 5 foliar applications at 10-14 day intervals with a 1-day phi. Another fungicide, Mefentrifluconazole, was applied with 3 foliar applications at 7-day intervals with a 0-day phi. Neither fungicide caused phytotoxicity on the broccoli or cabbage plants.
Two green onions trials were conducted for control of onion and western flower thrips, which are difficult to control due in large part to insecticide resistance. Testing was done with two insecticides, flonicamid and cyclaniliprole, with no phytotoxicity observed. One green onion trial was conducted with the fungicide florylpicoxamid, which has a new novel mode of action, for controlling two important onion diseases botrytis and Alternaria.
There were 13 warm season vegetable field projects managed over the life of the project. For dry bulb onions, two insecticide trials for control of onion thrips, one insecticide trial for control of seed corn maggots and one fungicide trial for control of botrytis and Alternaria were conducted. One fungicide trial was conducted on bell peppers for control of southern blight. On tomatoes, one herbicide trial and three fungicide trials for control of southern blight were carried out. For lima beans, the herbicide linuron was applied for weed control with no phytotoxicity observed. The summer squash projects consisted of one fungicide trial for control of powdery mildew and two herbicide trials.
One field crop trial was conducted on dry beans with the fungicide cyazofamid for control of cottony leak caused by pythium aphanidermatum. Six foliar sprays were made weekly with a 7-day pre harvest interval (PHI). Phytotoxicity was not observed on the bean plants.
The four herb trials included basil and stevia projects. Basil is highly suspectable of many diseases including downy mildew; fluoxapiprolin was tested, powdery mildew; flutianil was applied, and fusarium; fludiozonil and pydiflumetofen were sprayed on the plants. None of these fungicides caused any phytotoxicity to the basil. Weeds can become problematic to stevia during the winter, linuron herbicide was applied when the plants were dormant, with no plant damage observed. Both fresh and dried residue samples were collected during the following summer.
Strawberry projects consisted of three fungicide trials and two herbicide trials. The fungicides tested were cymoxanil for control of Phytopthora crown rot and Phytophora leather rot, GF-431 for control of powdery mildew and flutolanil for control of black rot disease. The herbicides tested were 2,4-D choline and glufosinate for problematic winter weeds in commercial strawberry production. Both herbicides were applied with a shielded sprayer to avoid contact with the crop and residue samples were collected at the first commercial maturity of the crop. There was no phytotoxicity from these herbicide sprays.
Accomplishments