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Development of a Farm-Wide System for Control of the Beet Armyworm in Sugar Beets Based on Disruption of Premating Pheromone Communication Between Female and Male Moths

Project Coordinator

Ben Goodwin, Executive Manager
California Beet Growers Association
Two West Swain Road
Stockton, CA 95207-4395
209-477-5596
209-477-1610 (fax)

Abstract

Until now, attempts at pheromone-communication disruption of the beet armyworm have not been made because of three serious impediments: strong flight habits of the moths will necessitate disruption of mating over very large areas; the larvae attack a wide variety of crops that are all grown in the same area, so all these crops will have to receive the pheromone treatment; the primary component of the pheromone loses activity rapidly on exposure to air. A technological advance, which addresses these impediments and makes communication disruption of this species possible, is the “puffer”, a timer- activated machine which releases massive amounts of pheromone into the air from pressurized canisters.

Puffers will he placed at great separations in the field, arrayed along 1/4-mile grids, with 4 machines per mile. We will permeate the air over large acreages of sugar beets and neighboring crops with pheromone and maintain the treatment during the entire 180-day season. Prior research will be conducted to fine-tune the amount of synthetic pheromone that must he released to ensure complete disruption of moth communication, and to address technical questions regarding pheromone release. The distance of inflight of mated females into a pheromone-protected block of sugar beets and companion crops will be determined, so future application of the strategy can be based on knowledge of minimum dimensions that treated areas must possess.

Impact assessment will be conducted to determine environmental and pest-control advantages that result from this selective method of beet armyworm control, in comparison to conventional control using broad-spectrum pesticide& Benefits will include less risk of environmental contamination, increased worker safety, greater preservation of beneficial arthropod species, and fewer outbreaks of secondary pest species.

Goals

The goals of Safe Handling of Pesticides for the Home Pesticide User are to reduce the risks for rural and urban home pesticide users, their families, pets, and their environment. These goals will be met by developing, conducting, and evaluating demonstration workshops for rural and urban home pesticide users in cooperation with the CSU Cooperative Extension Service’s Master Gardener program and conducting a pilot assessment of 2,4-dichlorophenoxyacetic acid (2,4-D) exposure in the home environment.

Objectives

  1. Demonstrate the efficacy of a novel system for distributing synthetic pheromone into the air over large acreages of sugar beets and adjoining crops, for disruption of premating pheromone communication among moths of the beet armyworm.
  2. Determine the minimum size acreage of sugar beets (and adjoining crops) that must be treated by the use of this system, to prevent significant numbers of already-mated female moths from entering the pheromone-treated areas from neighboring untreated areas and avoiding the pheromone communication disruption.
  3. Calculate the benefits derived from controlling the beet armyworm by this pheromone-communication-disruption system, including reductions in the use of conventional pesticides, preservation of natural enemies in pheromone-treated fields, and reduction in outbreaks of secondary pests of sugar beets.
  4. Organize outreach activities that will ensure that this emerging technology is understood by and available to sugar beet growers, as well as PCA’s, regulatory personnel, farm advisors, and other affected personnel.

Justification

  1. Sugar beets are one of the top five row crops in California, with the value of production during 1995 totaling about $150 million. Although the industry faces a broad spectrum of insect pests, it is attempting to develop environmentally friendly means for controlling the pests while reducing the use of broad-spectrum insecticides. The beet armyworm is the most important lepidopterous pest of sugar beets in California (and US) sugar beet fields, plus in many other row and field crops. These other row and field crops include cotton, alfalfa, and tomatoes, crops that typically are grown in sugar beet-growing areas, in rotation with sugar beets. The beet arrnyworm has a very wide host range, outbreaks of larval infestation are often very severe and crop threatening, and the adult moths of this noctuid species are strong fliers. Therefore, the need for effective control of the beet armyworm is a community problem that often triggers the simultaneous initiation of broad-spectrum pesticide use on a number of ranches over a wide geographic area. These strong-flight and broad-host-range characteristics, plus the fact that the beet armyworm pheromone loses activity upon prolonged exposure to air have caused investigators to feel that a pheromone-communication-disruption program may not have much potential for control of this pest. However, based on recent technological advances developed by Dr. Shorey and associates (see literature review), it now appears that bringing beet armyworms under effective, environmentally acceptable control through pheromone communication disruption can be accomplished through the use of high- pheromone-output, time-clock-activated machines called “puffers”. It is our intention to demonstrate the feasibility of using these devices to continuously dispense the pheromone of this species over large (up to 9-square-mile blocks) plantings of sugar beets together with neighboring row and field crops during the whole susceptible period (May through October in the San Joaquin Valley), to reduce in-field mating sufficiently to cause damaging larval population levels to he non-economic.
  2. The communication-disruption approach has been said by some to have already shown a generally low potential as a pest management tool. However, we believe that this approach has a high potential for the control of lepidopterous pests and that difficulties encountered in developing the approach are often caused by a lack of fundamental understanding of the behaviors of the insect pests and of the pheromone odor when it is released into the air.
  3. The beet armyworm is often the key to broad-spectrum pesticide use on sugar beets; an ability to reduce the use of those materials has obvious advantages, enabling us to move away from the pesticide treadmill for the beet armyworm, as well as other pests that may flare up in numbers in response to the use of broad-spectrum pesticides on the commodity. Barring difficulties in obtaining federal and state approval for the proposed system, we hope to have it operational within the two growing seasons (1996 and 1997) encompassed by this project, thereby eliminating a major hurdle in sugar beets to the implementation of a reduced-pesticide program for pest control.

Approach and Methods

  1. Prepare education workshop handouts and materials including: (a) workshop materials and handouts; (b) questionnaires to evaluate home users’ knowledge about pesticides; (c) field observational checksheet; (d) demonstration videotape including label information, equipment maintenance, use and selection of personal protective equipment, and handling techniques appropriate for home pesticide users; and (e) separate education module including use of fluorescent dye marker to reinforce training.
  2. Conduct workshops for Master Gardeners’ training, and for home users in cooperation with Master Gardeners’ programs for gardeners in their communities. In 1995, three hundred fifty-two volunteers completed 40 hours of Master Gardener training. Thus, a sufficient number of potential participants is available to make meaningful assessment of the impact of the proposed training. (Power calculations indicate that 225 subjects will be required.)
  3. In suitable workshop locations, reinforce safety for home users and the home environment by using hands-on practice with water, fluorescent marker, ultraviolet light, videotaping of practice sessions, and measurement of the area of fluorescent marker deposits on protective clothing.
  4. Offer interested home users the opportunity to volunteer for a pilot biomonitoring assessment of exposure to 2,4-D for themselves and their families. Sterile containers are delivered to participants’ homes. They and their family members collect urine samples at home during the spring application season. Urine samples are picked up and transported to CSU and analyzed using commercial enzyme-linked immunosorbent assay (ELISA) kits. Biomonitoring participants receive written results of their own analyses.

Literature Review

A number of laboratories throughout the world are actively researching communication disruption as a means for controlling lepidopterous pests (review by Carde & Minks (1995)). Research during 1993 through 1995 by Dr. Shorey and associates in the University of California, Riverside, has been directed toward the beet armyworm on tomatoes. This research was sponsored by the California Tomato Board and the California Tomato Research Institute.

An important finding that emerged from the research and that apparently has not been recognized or capitalized on by most pheromone researchers, is that pheromone evaporators can he placed at great separations in the field (fewer than one evaporator per acre) as long as the pheromone release rate is adjusted high enough to provide the critical concentration needed for communication disruption (Shorey et al. 1996a). This widely separated evaporator concept led Shorey et al.(1996a,b) to develop pheromone-release sources consisting of pressurized canisters filled with pheromone, which is released in relatively massive amounts as puffs (we call these machines “puffers”) at predetermined time intervals through the employment of mechanical switches and time clocks. Each puff, which is estimated by Dr. Shorey to contain about 10,000,000 female equivalents of beet armyworm pheromone, is directed onto a target of cotton cloth, serving as a constant evaporation source.

In early research, using the beet army-worm pheromone released from 40 puffers equally spaced around the peripheries of square 40-acre blocks of tomatoes, the number of male moths captured in traps placed in the centers .of the blocks and baited with virgin female moths of this species were reduced to 0, in comparison to 54 to 100 male moths captured in similar female- baited traps in untreated blocks (Shorey et at 1996a). In these trials, each puffer released 8.8 mg of pheromone components per puff, with the interval between puffs being 30 mm. In further research, during 1995, Shorey et al. (1996h) placed 40 puffers at much greater separations (0.1 mile between puffers) around 640-acre square blocks of tomatoes and cotton. This array of puffers provided a pheromone release rate of 18 mg per acre/d (costing only about $0.05 per acre/day), and complete disruption of premating pheromone communication was achieved.

Communication disruption was again measured by comparing the numbers of male moths of the beet armyworm that located living females used as bait in traps in the centers of the protected blocks, 1/2 mile from the nearest puffers, with the numbers captured in similar traps in untreated blocks. In the same year, a 150-acre block of tomatoes was provided with 117 puffers for eleven weeks, during most of the period of tomato plant growth. The block received 100 mg of pheromone per acre/d. Greater than 99% communication disruption was achieved, measured by the reduction in numbers of male moths captured in female-or lure-baited traps. Beet armyworm egg masses laid by female moths in the treated block were 76% fewer than in the control block; the investigators interpreted that this less-than-complete larval control was probably due to a large flight range of mated beet armyworm female moths, causing them to enter the protected area after mating in adjacent, untreated fields.

The natural pheromone of the beet armyworm consists of 5 chemicals that are simultaneously released into the atmosphere by the female moths (Tumlinson et al. 1990). However, Shorey et al. (1994) found that only one of the chemicals is needed to permeate the atmosphere and prevent male moths from finding females used as bait in traps in the centers of treated areas, even when evaporated into the air in quantities as low as 1 mg per acre/day.

Approach and Methods

1996 research

An aerosol can-filling facility for use in pheromone research has recently been constructed on the grounds of the University of California Kearney Agricultural Center in Parlier, CA. This facility is managed by Dr. Shorey and will be used to custom-fill the cans used in this research. Initially, 16 grams of the primary beet armyworm pheromone component will be dispensed into each of 64 cans, which then will be filled with 234 g of DuPont Product I 34A, a recently developed non-flammable propellant. Each canister will he placed in a time-clock-equipped automatic puffer machine, having a cotton-cloth target in front of the canister orifice, to catch most of the pheromone directed at it in each puff and then to rerelease it into the air by evaporation.

During most of this research, paired comparisons will be made of the communication disruption occurring in puffer-protected vs untreated control blocks. This phase of research is not aimed at whole season protection, but, rather, at determining on a single- night basis whether a given strategy prevents male moths from orienting to females that we use as bait in traps in the middle of treated or untreated blocks. Thus, single nights will constitute replicates, and puffers and controls will be reassigned at random to new blocks for additional replication on subsequent nights. This will allow a number of strategies to he tested over a single season, yielding a best strategy that can he tested on a whole-season basis for control of breeding populations and larval damage during the next year. Strategies tested will include:

  1. 64 Puffers deployed 1/4-mile apart in an 8 x 8- array; thus, the 64 puffers will be placed on the corner of each 40-acre block in.a 4-square-mile (2 x 2 miles) protected area. Each can will release pheromone day and night, providing 5 mg/acre/d.
  2. Puffers deployed as in Strategy I, with pheromone release rate being 10 mg/acre/d.
  3. Puffers deployed as in Strategy I, with pheromone release rate being 20 mg/acre/d.
    Assuming that Strategies I - 3 yield 100% communication disruption, the release rate of pheromone from cans will be decreased in further testing, until 100% disruption is no longer obtained, to determine the limits of the method.
  4. The cotton cloth target has been arbitrarily included as part of the puffer design, based on an intuitive feeling that the target gives a constant release rate of much of the pheromone that it catches in each puff. Puffers with vs without targets will be tested, using a low pheromone release rate that provides less than complete disruption.
  5. The above strategies are based on release of pheromone through the 24-hr day. However, mating among beet armyworm moths occurs at a fairly specific time between midnight and dawn, and pheromone release from puffers during night hours only may give adequate disruption of premating communication. Strategies that will be tested will be:
    1. The 64 puffers running on normal timing (one puff per 0.5 hr, through the 24 hour cycle, using a release rate that gives less than complete disruption of communication.
    2. The puffers operating during night hours only, using the same release rate.
    3. The puffers operating during night hours only, using 2x the above release rate.

    The above experimentation is highly exploratory, and any interesting leads will be followed to find the most effective strategy for puffer operation and deployment.
    Locations of treated and control blocks of crops will be assigned at random, and 4 nightly replicates will be conducted for each paired comparison of protected vs untreated blocks.

1997 research

Large block, whole season crop protection research will be initiated. 5800 acres (9 square miles) of sugar beets and intermingled crops will he provided with 144 puffers deployed on grids 1/4 mile apart in each direction. Puffer strategy will have been perfected through the earlier single-night testing. Control blocks will be maintained at least ten miles from the treated block, in a general upwind direction, and evaluations that are conducted in the treated block will be conducted also in the control blocks.

Provisionally, pheromone release rates will be 5 mg per acre/day, giving 0.9 g per acre/180-day season, for a total of 6kg of material in the 5800-acre block per season.
The efficacy of the treatment will be evaluated in a number of different ways which will yield information about the flight range of mated females and the absolute reduction in infesting larvae at a distance into the block that is beyond that flight range. The flight- range aspect will provide information about the minimal size block that must be treated to provide communication disruption of this species. This type of determination has not previously been made in pheromone communication disruption work. We will sample for adult moths, egg masses, and larvae along transects, with the transects being the two intersecting center lines of the 5800-acre block, from the center of each edge through the middle of the block to the center of the opposing edge.

At regular intervals during the season, we will employ the following types of measurement along these transects:

  1. Numbers of beet armyworm males captured in sticky traps baited with female moths.
  2. Percentage mating by virgin females, tethered on “mating tables” among the foliage.
  3. Numbers of males, virgin females, and mated females captured in battery-powered, photocell-activated ultraviolet light traps placed among the foliage close to the soil surface. We presently have 25 such traps, constructed for this purpose.
  4. Numbers of egg masses per plant laid by female beet armyworm moths.
  5. Numbers of larvae of the beet armyworm found feeding on the foliage.
  6. Occurrence of other pests of sugar beets, including aphids and tetranychid mites, as well as the complex of beneficial arthropods, determined through D-vac sampling.

Similar determinations will he made in four 40-acre blocks situated upwind and subjected to conventional pesticide applications for control of the beet armyworm.

Note on the size of the trial. The 5800-acre trial is purposefully very large to ensure that the center of the block is beyond the normal flight range of mated female moths. This is a major, and a unique aspect of this experimentation. If acreages were smaller, a negative result, with oviposition by beet armyworm females in the centers of the blocks, would be uninterpretable, because female flight ranges might then overwhelm block size.

Impact Assessment and Outreach:

A steering committee of sugar beet growers will be formed from the membership of the California Beet Growers Association. This committee will meet as needed, together with a panel of scientists organized by Dr. Shorey, to assess progress of the research and implications with regard to the objective of producing the highest yielding crop while minimizing the use of broad-spectrum pesticides. Using figures compiled from grower interviews and questionnaires and from California EPA, we will determine the amount and cost of the various pesticides used for sugar beet pest control in conventionally treated areas and compare it to amounts used in our 5800-acre pheromone-treated block and in the conventional comparison blocks.

This comparison will be based only on a single puffer-protected block, but the summarizations will form a basis for a procedure of impact assessment that we will use as the farm-wide pheromone-disruption program is developed into commercial usage during the following years. Also, we will develop a summarization of the pest and beneficial arthropod populations levels found in pheromone-treated blocks of sugar beets vs conventionally treated blocks and will use this in informational and educational releases directed to the general public as well as to growers, packers, federal and state regulatory personnel, extension personnel, and the research community.

Losses of crop due to beet armyworm damage will he determined directly through harvesting 30-foot sections of row in ten different locations in the treated block and each conventionally treated, non-pheromone-protected control block, and directly recording yield and the amount of damage attributable to attack by the pests. Yield and loss data will be scaled up as estimates for these factors on a per-acre basis. These will be converted to cost data, allowing us to assess season-long effectiveness of our pheromone communication-disruption program.

Outreach

Through the public-education resources of our organization, we can send information on the puffer technology to all sugar beet growers in the State of California. We will expand this information dissemination through the public education channels of UC, organizing at least 4 regional meetings of sugar beet growers as test and demonstration plots using the technology are put in place. Some meetings will be held on site at fields provided with puffers, so growers, PCA representatives, and extension and regulatory personnel can be informed with regard to the technology.

Appendix A - Literature Cited

Appendix B - Timetable

  1. Demonstrate the efficacy of a novel system for distributing synthetic pheromone components into the air over large acreages on ranches containing sugar beets and other field and vegetable crops, for disruption of pre-mating pheromone communication of the beet armyworm.
    1. Determination of puffer spacings and release rates needed to provide communication disruption for the beet armyworm moth. Initiate 7/96. Mostly complete 10/96, although unfinished work will be competed in 5-6/97.
    2. Culmination-of-research, education, and demonstration block that will be operated during the summer of 1996 in 5800 acres of sugar beets and companion crops. Start preparations 7/96. Initiate field work 5/97. Complete 10/97.
  2. Determine the minimum size acreage of sugar beets (and adjoining crops) that must be treated by the use of this system, in order to prevent significant numbers of already- mated female moths from entering the pheromone-treated areas from neighboring untreated areas, thus avoiding the pheromone communication disruption. Initiate 5/97. Complete 10/97.
  3. Calculate the benefits derived from controlling the beet armyworm by this pheromone-communication-disruption system, including reductions in the use of conventional pesticides, preservation of natural enemies in pheromone-treated fields, and reduction in outbreaks of secondary pests of sugar beets. Conduct detailed economic analyses. Initiate 1/97. Complete 12/97.
  4. Outreach activities. Already initiated. Complete 12/97.

Appendix C - Major Participants

Project Coordinator

Ben Goodwin, Managing Director
California Beet Growers Association

Grower Steering Committee

As-yet unidentified beet growers will provide crops for the research, education, and demonstration trials, will assist as needed in evaluation procedures, especially at harvest, will provide collaborating PCA expertise, will have direct responsibility in contributing to the preparation of impact assessments, and will assist in other aspects requiring their expertise and experience in sugar beet growing and pest management problems and practices.

Project Director

Dr. Harry H. Shorey, Research Entomologist, Department of Entomology, University of California, Riverside. Headquartered at the University of California Kearney Agricultural Center, 9240 S. Riverbend Ave., Parlier, CA 93648. Telephone 209-891-2578. Fax 209-891-2593. Dr. Shorey, who will be contracted with through channels already established between the Project Coordinator and the University of California, will have primary responsibility for the planning and conduct of the research, education, and demonstration, the procurement of supplies, the enlisting and directing of personnel, who will be hired through his UC channels to participate in this project, as well as the preparation of reports and publications resulting from this project.

Dr. Shorey will enlist and coordinate the assistance of the following University of California scientists, who are all experienced in designing row-crop IPM programs and have agreed to lend their technical, organizational, and instructional expertise to this project:

Project Budget

Project Period: July 1, 1996 - December 31, 1997

Funding Request
Funding Requested Other Funding Total Funding
$39,960
$2,000
$41,960

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