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Integrated Pest Management for the Raspberry Beetle, Byturus unicolor (Say), Using Life Stage Prediction and Cultural Management in Red Raspberry Production

Project Coordinator

Craig MacConnell
Washington State University
Office of Grant and Research Development
Room 423 Neill Hall
PO Box 643140
Pullman WA 99164-3140
509-335-9661
509-335-1676 (fax)
ogrd@wsu.edu

Executive Summary

Northwest Washington produces 65% of the nation's red raspberries and is a major producer for the world market. Two thirds of growers use non-IPM strategies for managing the raspberry fruitworm (Byturus unicolor (Say)), a key insect harvest contaminant. Current practices involve a calendar based diazinon treatment prior to bringing pollinators into the field. New tools are required by the red raspberry industry to help reduce reliance on diazinon and eliminating unnecessary pesticide applications for B. unicolor. Alternatives to diazinon that can be applied when bees are foraging are currently being tested.

The objectives of this study are: 1) develop a temperature model for predicting life stages of Byturus unicolor, and 2) determine the efficacy of alternative cultural and biological control methods of B. unicolor.

Descriptions of the life stages of this pest and approximate dates of each life stage are available from earlier research (Baker et al, 1947); however, the timing of each stage can vary greatly between years depending on climate. The prediction of beetle emergence from the soil and the peak occurrence of adult beetle population in the field through soil and air temperature data will allow growers to more accurately predict the best date to monitor and treat for B. unicolor.

Possible alternative control methods of B. unicolor (Say) are currently unavailable for growers. Suggestions from Baker et al, 1947, indicate that tilling the soil while the pest is in the soil at the larval and pupal stage may cause a reduction in endemic populations of the pest, although raspberry production systems have changed significantly since that publication date. The use of entomopathic nematodes such as Heterorhabditis marelatus has not been tested on the control of B. unicolor and may reduce populations of the larvae in the soil.

Objectives

  1. To correlate soil and air temperature with significant biological events of the raspberry beetle, Byturus unicolor (Say) in red raspberry production areas of Washington State
  2. To evaluate non-pesticide control methods of B. unicolor (Say) in red raspberry including soil disruption at the pupal stage and the use of entomopathic nematodes.

Justification

The raspberry fruitworm, Byturus unicolor (Say), is a key fruit contaminant pest in red raspberry production in Whatcom County, Washington. Currently, two out of three growers use non-IPM, calendar-based diazinon application to prevent contamination of this pest. The United States Environmental Protection Agency, under the Food Quality Protection Act of 1996, has sought to reduce risks associated with organophosphates, such as diazinon through higher restrictions and cancellations. The red raspberry industry needs to reduce reliance on diazinon and eliminate unnecessary and ineffective pesticide applications for B. unicolor.

  1. The establishment of temperature cue thresholds or triggers of life stages of B. unicolor will aid growers to effectively predict and time treatments to their fields for managing this contaminant pest. Current research is seeking an alternative to diazinon that can be applied while bees are foraging. With a more pollinator-friendly alternative and a predictive model for peak flight, growers will be able to make an application of pesticide at the time of peak beetle flight, thus increasing the efficacy of the treatment.
  2. The use of cultural and biological control measures may be viable for growers in controlling B. unicolor. Currently, the only available control method for B. unicolor is a diazinon treatment prior to bringing pollinators into the field. By learning the life cycle of the pest, control may be obtained through disruption of certain life stages. Disrupting the soil, by tilling following harvest and again in early autumn when delicate pupae are present may reduce endemic populations of the pest. The application of entomopathic nematodes such as Heterorhabditis marelatus in late summer may be effective in reducing the number of larvae in the soil. These alternative cultural and biological control measures for B. unicolor may be used as alternatives to diazinon that also would qualify under organic standards. Conventional growers may also select dates of tilling in late summer and autumn to correspond with the occurrence of pupae in soils to reduce the number of B. unicolor overwintering in their soil.

Literature Review

Whatcom County, Washington State is a major producer of red raspberry (Rubus ideaus) with over 7500 acres farmed in 2000. One significant pest of this crop is the raspberry fruit-worm, Byturus unicolor (Say), (Menzies, 1999).

Byturus unicolor (Say) is a member of the family Byturidae with common hosts of cultivated red raspberry (Rubus ideaus), thimbleberry (Rubus parvivlorus), blackcap raspberry (Rubus leucodermis), blackberry (Rubus discolor), and salmonberry (Rubus spectabilis) (Baker et al, 1947). As a product contaminant pest, the larvae are present in the receptacle of the red raspberry fruit, and will often fall off with the fruit during mechanical harvest.

The life stages of B. unicolor (Say) include eggs present on Rubus flowers and buds, three stages of larva present in ripening fruit and pupa present in soil. Adults over winter in the soil and emerge to oviposit on developing flowers in the spring. Little is known about the relationship between temperature, development and the life stages of the raspberry fruit-worm. Baker et al, 1947, found that adult beetle emergence began in mid March to early April with adult feeding on leaves beginning in mid to late April. Larval drop was found to be from early July through September and pupae were found in soil from August to October (Baker et al, 1947). Work has not been done to determine temperature cues or thresholds for predicting timing of adult emergence and other life stages. Adult beetles appear to emerge from the soil at a time dependent on soil temperature (Current study, MacConnell et al). Beetles were first detected feeding on leaves on May 7, 2003, and three weeks earlier (April 14) in 2004. The soil temperatures on these dates were similar, with the soil warming earlier in the year in 2004.

A white non-UV reflective sticky trap has been used to attract adult beetles in flight (Woodford et al, 2000, MacConnell and Murray, current study). Visual cues are used by adult beetles in locating flowers for oviposition and the sticky traps mimic the appearance of the flower to the adult beetle (Woodford et al, 2000). These traps (RebellJ Bianco from Swiss Federal Research Station) have been used successfully in Scotland and in Whatcom County, Washington for monitoring of the occurrence of the B. unicolor (Say) in red raspberry fields (Woodford et. Al, 2000; MacConnell et. Al, 2004). This trap is uniquely effective in attracting adult beetles in flight and can be used to estimate occurrence of beetles in fields. MacConnell et al, current study, found that traps with non-UV reflected properties were more effective from other white trap designs.

Baker et al, (1947) tested cultural and chemical control methods of Byturus unicolor from 1931 to 1941. The pupa in the soil was found to be very delicate; the pupal cells were easily broken and the pupae killed when the soil was disrupted under the canes following harvest and again approximately one month later (Baker et al, 1947). Natural enemies of B. unicolor (Say) were observed in Western Washington, but were found to have little effect on the control of the pest (Baker et al, 1947). Insecticides that were trialed are no longer registered for use in this crop.

Approach and Methods

Objective 1: Relationship between temperature and B. unicolor life stages:

Tasks A through D will be performed in 2005 and 2006 to increase the amount of knowledge of temperature effects on the development of B. unicolor (Say).

Task A: Determine temperature for emergence of adults from soil.

Adult beetles will be field collected from October to December 2004 and maintained in potted raspberry containers. In the first year of the study separate groups of beetles will be placed in five distinct soil temperature regimes ranging from 38 to 58 degrees F. Each chamber will be monitored three times per week for beetle emergence. In the second year of the study, the temperature range will be adjusted to more accurately determine the temperature cue needed for adult beetle emergence and flight.

Task B: Determine soil temperature required for beetle emergence in the field.

Hobo temperature loggers will be placed in raspberry fields known to house raspberry beetle populations. Soil temperature probes placed at 3", 6", 9" and 12" and air temperature probes will be used to measure climate activity. RebellJ Bianco sticky traps will be placed at several sites throughout the field and at varying heights in the red raspberry canopy. Traps will be monitored three times per week starting in early March to determine date of first beetle flight. The temperature required for adult beetle emergence in the field will be compared to that temperature found when beetles were encouraged to emerge in the lab.

These traps will be monitored weekly throughout the season to determine soil and air temperature corresponding to beetle emergence from the soil and peak flight.

Task C: Determine oviposition date corresponding to air and soil temperature

Each week following first beetle flight, 100 raspberry flower buds will be taken from the field and inspected for the occurrence of eggs. The range of time of egg occurrence will be determined.

Task D: Determining timing of larval drop and pupa occurrence in soil

Starting in mid-June, soil will be collected bi-weekly from four sites throughout the field. Soil from four depths (3", 6", 9", 12") will be collected at each location and will be examined for occurrence and distribution of larvae and pupa. Soil will be sifted through soil sieves to aid in finding the larvae and pupae. The occurrence of pupa in the soil is expected to begin in late July to early August.

Objective 2: Testing cultural and biological control of Byturus unicolor.

Task E: Determining the efficacy of soil disruption below canes on control of B. unicolor

When the presence of pupa in the soil is evident, soil will be disturbed as close to the cane as possible in selected portions of the field. A randomized complete block design will be used to evaluate the beetle population differences between non-treated areas and areas where soil has been disrupted. The RebellJ Bianco trap will be monitored at sites through the blocks in the year before and the year after the soil disruption occurs to determine if a treatment effect occurs.

Task F: Determining the efficacy of entomopathic nematodes on control of B. unicolor.

Larvae will be taken from the fruit in July and August. Larvae and pupae will be taken from the soil in August and September. These larvae and / or pupae will be counted and placed in a container with field soil. Using a complete randomized block design, each container will house one of the various treatments of a drench of entomopathic nematodes, such as Heterorhabditis marelatus, or water as a control. The number of live and killed larvae and / or pupa will be counted following the treatment to determine efficacy in control using this method. Data will be analyzed with analysis of variance (ANOVA) and mean separations to determine any significant differences between treatments. Trials will be repeated both years.

Impact Assessment

Many red raspberry growers in Whatcom County use a diazinon treatment for raspberry fruitworm control. Little is known about the life cycle and timing of life stages of this pest. Through previous work, we have found how to monitor for the occurrence of this pest using a white, non-UV reflective sticky trap (the RebellJ Bianco trap). In this research, we will develop a model predicting the timing of adult beetle emergence, adult peak flight, and larval stages using soil and air temperature data. This model may be incorporated into the Agweathernet.com website as a tool that growers can use in predicting when monitoring devices should be placed in the field and when pesticide (or non-pesticide) treatments will be most effective.

Upon compiling results, we will disseminate information through existing forums, such as the raspberry listserve, newsletters, fact sheets, WSU Whatcom County Internet site (http://whatcom.wsu.edu), annual workshops, regular breakfast meetings and updates to the raspberry IPM manual (http://whatcom.wsu.edu/ag/comhort/nooksack/ipmweb/Toc.htm). Growers will be surveyed for testimonials and changes in attitudes and practices twice per year of the project. Impacts will be measured through evaluative indicators that growers have increased their knowledge and understanding of pest biology and have undergone a change in attitude or actual practice changes.

Two other tools evaluated in this research (the use of soil disruption during the pest=s larval and pupal stages and the use of entomopathic nematodes) may give growers another option to the use of diazinon. Growers will have more options in making decisions on treatment of this pest, thus reducing their dependence on organophosphate pesticides such as diazinon.

Literature Cited

Baker, W.W, S.E. Crumb, B.J Landis, and J. Wilcox. 1947. Biology and Control of the Western Raspberry Fruitworm in Western Washington. The State College of Washington Institute of Agricultural Sciences Agricultural Experiment Stations. Bulletin No. 497.

MacConnell, C.B. and T.A. Murray. Current Research, 2004. Facilitating Development and Adoption of Integrated Pest Management for the Western Raspberry Fruitworm, Byturus unicolor for Red Raspberry Production. Interim report for AFT and EPA Region 10.

Malloch, G., B. Fenton, and M.A. Goodrich. 2001. Phylogeny of raspberry beetles and other Byturidae (Coleoptera). Insect Molecular Biology. 10(3): 281-291.

Menzies, G. 1999. Crop profile for red raspberries in Washington State. http://www.tricity.wsu.edu/~cdaniels/profiles/rsprev.pdf

Woodford, J.A.T., S.C. Gordon, H. Hohn, K. Schmid, T. Tuovinen, and I. Lindqvist. 2000. Monitoring raspberry beetle (Byturus tomentosus) with white sticky traps: the experience from three geographically distinct European areas. Proceedings BCPC Conference-Pests & Diseases 2000: 321-326.

Timetable

January 2005 to March 2005:

February to August 2005:

June to December 2005:

December 2005 through December 2006:

Major Participants

Principal Investigators:

Craig B. MacConnell is a small fruit horticulturalist with the Washington State University Whatcom County Extension. He will participate as a project facilitator and will as a member of the research team in collaborating in project design and analysis.

Todd A. Murray is the IPM program coordinator for the Washington State University Whatcom County Extension. He will be involved with the project set-up, data collection and analysis and will provide expertise in describing the life stages of the pest.

Colleen L. Burrows is a technical assistant at Washington State University Whatcom County Extension. She will participate in project planning, data-collection and analysis. She will oversee project management, and on and off farm trial set-up and data collection.

Washington State University Cooperative Extension
1000 N. Forest Street, Suite 201
Bellingham, WA 98225
Phone: (360) 676-6736
Fax: (360) 738-2458
Email: cbmac@wsu.edu
Email: tamurray@wsu.edu
Email: colleen_burrows@hotmail.com

Farmer Participant:

Robert Van Dyken is the grower / owner of Pangborn Farms, a small fruit farm in Northeast Lynden, Washington. He currently farms 10 acres of organic raspberries as well as 40 acres of conventional raspberries, blueberries, and black currants. Trials performed at this farm include monitoring of the life stages of raspberry fruitworm and disrupting the soil during larval and pupal stages. Raspberry fruitworm will be collected from this field for determining temperature for emergence in the lab and for tests of entomopathic nematodes on the control of B. unicolor.

Budget Table

Funding Request
Budget Category Funding Requested Matching Non-Federal Funds Matching
Federal Funds
First Year Funding
$20,000
0
0
Second Year Funding
$19,816
0
0
Total Funding
$39,816
0
0
Project Duration: January 1, 2005 - December 31,2006

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