Pheromone-Based Pest Management Can Be Cost-Effective for Walnut Growers

ReSeARCh ARtiCle t Pheromone-based pest management can be cost-effective for walnut growers by Kimberly P. Steinmann, Minghua Zhang, Joseph A. Grant, Carolyn Pickel and Rachael E. Goodhue Many organophosphate and pyrethroid insecticides currently used by California walnut growers have been linked to negative environmental or human health impacts, increasing the probability of use restrictions and phase-outs. We assessed the accept- ability of alternative reduced-risk strategies by comparing their costs to those of pest management programs currently in use among San Joaquin County walnut growers. To do this, we analyzed data from the California Department of Pesticide Regula- tion’s legally mandated Pesticide Use Reports on actual pesticide applications for 3 years, from 2002 to 2004. While many factors other than cost influence growers’ pest management choices, we found that alternative strategies can be cost-competitive with conventional approaches, depending on the pest pressure and savings due to reductions in secondary pest outbreaks. alifornia produces 99% of walnuts nationwide, and this commod- ityC is ranked 14th in the state with an important pests of walnuts include codling moth, walnut husk fly, navel orangeworm, aphids and mites. Alternative, reduced-risk pest control strategies, annual value of $610 million (USDA such as pheromone “puffers” for codling moth (shown), were compared with 2006). The most important walnut pests strategies currently in use by walnut growers in the San Joaquin Valley. that can cause significant economic loss are codling moth (Cydia pomonella) However, many products frequently Food Quality Protection Act (FQPA) of and, in certain areas, walnut husk fly used by walnut growers are being re- 1996. In addition, nine of these 30 active (Rhagoletis completa). Webspinning mites evaluated for reduction or elimination ingredients are currently listed as im- (Tetranychus spp.) and aphids (primarily by regulatory bodies due to adverse pairing California water bodies under Chromaphis juglandicola) can also cause human health or environmental risks. the Clean Water Act of 1972, and more economic damage if not controlled by For example, 22 of the 30 active ingredi- are likely to be listed as water quality natural predators. The current manage- ents used to control walnut arthropod monitoring is extended to additional ment of these pests is based on periodic pests such as codling moth, walnut insecticides and miticides (US EPA 1997, treatments with organophosphates, husk fly, aphids and mites from 2002 2002; CDPR 2005). pyrethroids, growth-regulating insecti- to 2004 could be affected by proposed Because some of these pesticides are cides and miticides. changes stemming from the federal broad spectrum and have long residual http://CaliforniaAgriculture.ucop.edu • JULy–SEPtEMBER 2008 105 activity, they kill beneficial insects as costs of selected alternative strategies to well as the targeted pests. The loss of those of conventional strategies for con- beneficial insects can result in outbreaks trolling key pests of walnuts. of secondary pests such as mites and Conventional strategies and costs aphids, necessitating additional treatments and further increasing the poten- The first step in comparing the eco- tial for negative environmental impacts nomic feasibility of alternative and (Agnello et al. 2003; Prischmann et al. conventional strategies was to define 2005; Zalom et al. 2001). the specific products, use rates and Stemming from impending regu- application costs associated with each latory changes as well as growers’ strategy. To define conventional strate- heightened awareness of environmental gies, we used actual grower data from and worker safety, new technologies the California Department of Pesticide have emerged in the form of alterna- Regulation’s Pesticide Use Reports tive, lower risk products for controlling (PUR), a public database of legally arthropods. These include pheromone mandated pesticide application reports mating disruption, biopesticides and (CDPR 2005). The PUR database offers a growth-regulating insecticides. Mating wealth of information about California disruption works through the inun- growers’ pesticide use, including ac- dation of an orchard with synthetic tive ingredients, amount per acre ap- chemicals designed to mimic phero- plied and number of applications per mones that are released by females to season. This allowed us to compile attract males of a species, thus decreas- comprehensive, detailed and accurate ing the male’s ability to locate a female representations of individual grower’s and successfully mate. Biopesticides pest management strategies based on integrated pest management, along with new technologies such as pheromone are microbial and biochemical controls reported pesticide use in the study area. mating disruption, biopesticides and with microorganisms naturally antago- We analyzed PUR data for walnut or- growth-regulating insecticides, help to nistic toward pests, while insect growth chards in San Joaquin County for 2002 protect farmworkers and the environment. Retired Butte County farm advisor Bill Olson regulators disrupt hormone functions through 2004. San Joaquin County is monitors for codling moth by hanging traps responsible for molting, maturation California’s leading walnut-producing in walnut orchards. and other insect life-cycle processes. county, with just under 32,000 acres of Although varying in their modes of ac- orchards accounting for about 16% of tion, these new, narrow-spectrum alter- the annual walnut crop value statewide natives selectively control pests and are (CASS 2004). From 2002 to 2004, 372 to less disruptive to beneficial insects and 384 San Joaquin County walnut grow- 3 years, depending on whether they mites. Many of these new approaches ers reported pesticide use in the PUR treated for codling moth in a given also reduce the risk that orchard pesti- database (CDPR 2005). year. As a result, there were approxi- cide applications will adversely affect For each of the 3 years studied, we mately 220 pest management strategies wildlife, water quality and human created a subset of the PUR database analyzed each year, with a total of 661 health (US EPA 2006). that included only those growers who strategies over the 3 years combined. Recent studies have documented the appeared to have treated solely for We calculated the costs of conven- effectiveness of certain alternative strat- codling moth, or for codling moth plus tional strategies reported in the PUR egies for controlling codling moth and other pests, based on product choice database using the amounts of product walnut husk fly in walnuts (Coates et al. and timing criteria. Codling moth was applied per acre and their 2003 prices, 2001; Flora et al. 1999; Pickel et al. 2007; the focal pest for defining the proj- and adding a standardized cost for each Van Steenwyk et al. 2005), and growers ect’s PUR subset for analysis, given application in a treatment that covered have begun integrating some of these its economic importance as a walnut fuel, labor and maintenance. We as- approaches into their orchard manage- pest and the promise of pheromone sumed that all pesticide applications ment programs. However, alternative mating disruption as an effective con- were made by a conventional orchard approaches may be more expensive due trol. However, for each grower in the air-blast sprayer. Multiple pesticides to an increased number of applications, subset, the grower’s pest management reported by a grower on the same date higher material costs, a greater time strategy was defined as all of the ar- and same acreage were assumed to be commitment for orchard pest monitor- thropod pest controls used throughout combined into a single “tank mix” ap- ing, and lower numbers of pest species the entire season on all orchards listed plication. All insecticide and miticide controlled per application. Because under a grower’s PUR identification costs were then summed to arrive at growers will not broadly adopt alterna- number. Therefore, the pest manage- a total pest-management strategy cost tive technologies unless they are effec- ment strategies of a single grower per acre for each grower’s conventional tive and economical, we compared the could have been included for 1, 2 or all strategy in each year. 106 CALIFORNIA AGRICULTURE • VOLUME 62, NUMBER 3 Sarah Goldman Smith tABle 1. Average annual conventional pest-management strategy costs of San Joaquin County walnut grower sample Grower Strategies Average chemical class analyzed cost/acre* no. (average/yr.) $ Combination 262 (87) 160 a† Organophosphate 350 (117) 124 b Pyrethroid 49 (16) 73 c All classes 661 (220) 134 * Data pooled over the 3 years (insignificant effect of year on cost). † Means in columns with different letters differ (P < 0.05), least squares mean test with square-root transformation to meet normality and homogeneity of variance assumptions. We compared costs for the entire While many walnut growers are trying out alternative pest-control strategies, the analysis subset of pest management strategies of California Pesticide Use Reports from 2002 to 2004 found that actual adoption rates in the PUR database for a given year, are low. Left to right, Rick enos of Carriere Farms, tom larsen of Suterra, Bill Carriere, as well as divided the subset into three Christine Abbott of Suterra and Glenn County farm advisor Bill Krueger learned about pheromone puffers at Carriere Farms in Glenn County. groups based on the predominant

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