Alternatives to chlorpyrifos for sugarbeet production in the Imperial Valley of California.

Abstract

This research focusses on identifying less toxic substitutes for chlorpyrifos (Lorsban®) in sugarbeet production in the Imperial Valley.  Chlorpyrifos is a known neurotoxin and affects both humans and other animal and fish species.  It is hazardous to applicators and workers, has been shown to accumulate in the Salton Sea and has been restricted in California. The primary insects affecting stand establishment are diverse flea beetle species, primarily pale stripped flea beetle (Systena blanda) and armyworm species (Spodoptera sp.).  In spring with rising temperatures, army worms and diverse leaf hoppers (Empoasca sp.) can reach pest level.  Low risk strategies for stand establishment emphasize IPM practices including pre-irrigation of fields, dates of planting, and seed treatments.  Complementary field experiments were carried out over the 2020 to 2022 period at UC Desert Research and Extension Center (DREC), integrated with complementary trials in 6 growers’ fields.  Poncho Beta® (clothianidan + cyfluthrin-PB) seed treatments are a reduced toxicity standard common to all station and field experiments.  Data collected include seedling emergence and loss, seedling dry weight at establishment, season-long estimates of insect pest abundance and damage, yield and root quality, and comparative costs of differing treatments.  At the UC DREC, pesticide treatments were compared to untreated controls within pre-irrigated or dry-planted treatments, at two different planting dates (mid-September and mid-October).  Additional soil treatments at planting are compared and include granular, soil-applied chlorpyrifos, Coragen® (chlorantaniliprole), PB seed treatments and PB plus Coragen®.  These plots are split and half include additional post emergence control with Asana® (esfenvalerate), commonly used in growers’ fields.  A randomized block design is used in growers’ fields with different treatment comparisons depending on the grower and year.  Typically, three treatment comparisons were carried out using chlothianidan alone or in combination of without clothianidan.  Strips (plots) 50 to 60 feet wide the length of the field were compared.  The common practice used by each grower was the control in each field.  Yields and pesticide use and costs were tracked for all trials and compared.  The Pesticide Risk Tool (https://pesticiderisk.org/about) was used to compare treatments and risk.  In general, seed treatment with clothianidin, a neonicotinid, was as effective as other pesticide combinations, tended to be less expensive, and rated lower on the pesticide risk scale compared to most other pesticide-use strategies or superior to other pesticides used in the trials.  Results from the trials are reported and discussed.