“MagNet”: A Positive Pull Toward Integrated Pest Management in Root Crop Production.

2004 Annual Report for SW02-050

Project Type: Research and Education
Funds awarded in 2002: $134,829.00
Projected End Date: 12/31/2006
Region: Western
State: Oregon
Principal Investigator:
Amy Dreves
Oregon State University; Dept of Horticulture

“MagNet”: A Positive Pull Toward Integrated Pest Management in Root Crop Production.


The objective of this project is to reduce grower dependence on chlorpyrifos use to manage an important pest, the cabbage maggot (CM; Delia radicum L.). A strategic IPM “toolbox” of management strategies is under development.

The IPM plan includes: monitoring (flight, eggs, and damage); degree-day modeling of flight activity; spatial management (through monitoring and a regional grower-friendly GIS mapping system); fall and spring cultivation; row cover and exclusion fence usage, and new alternative chemistries and application methods for control of CM.

A survey tool for growers is being developed. This tool will be used to evaluate program impacts and grower IPM adoption over time.

Objectives/Performance Targets


1. Define seasonal impact of cabbage maggots in western Oregon.

2. Research, evaluate, and implement IPM strategies in cruciferous crop production.

3. Build collaboration between growers, researchers, and extension personnel.

4. Inspire grower IPM interest and adoption of pest management tools for control of the cabbage maggot.

Performance Targets

Objective 1

-Establish a harvest assessment of CM damage
-Install “no-spray” plots in growers fields

Objective 2

-Develop a degree-day model for predicting seasonal flight
-Implement a viable monitoring system (flight, eggs, damage)
-Identify alternative chemistries and application techniques
-Evaluate cultivation practices to reduce overwintering CM populations
-Evaluate the use of row covers for managing CM in root crop production
-Develop a GIS-IPM tool to assist growers in spatial CM management

Objective 3

-Transfer technology to VegNet, Ag consultants, Brassica growers
-Hold workshops (e.g., GIS-IPM tools, degree-day modeling, use of monitoring techniques) and present information at scientific meetings
-Create a grower monitoring kit

Objective 4

-One-on-one grower interaction in field
-Development of “the PEST Plan” to assess progress and grower adoption of IPM practices


Accomplishments for Obj 1.
1) Harvest damage was assessed in the northern Valley region in 2001 through 2004 with the use of a technique termed “M60” as described below.
2) Ten, un-replicated no-spray field plots were installed in grower fields in 2003.
3) Four, replicated no-spray plots were installed in grower fields in 2004. Treated plots were sprayed at 14-day intervals with Lorsban 4E.

Results of Obj 1:
– Preliminary analyses indicate that there is a relationship between crop planting date and damage levels. However, there are many factors other than CM phenology that impact damage, including management practices, landscape factors, a field’s proximity to other infested fields, and crop developmental stage. More analysis will take place in Feb 2005.
– Growing of long-season root crops can be attacked by 2 generations of flies, but damage was most severe during the spring (mid March and early May) and fall (early Sept to mid-October). Above-ground crops including broccoli and cauliflower were most vulnerable during the first 5-6 weeks after transplanting, but little to no yield loss was shown.
– Preliminary analyses indicate that damage levels were lower in fields planted in the summer and fall (August) (data being analyzed).
Planting later in the season (after June 1st) and harvesting before fall flight (Sept 1st) to avoid high-risk attack from cabbage maggots may be an effective strategy.
– In general, damage levels were similar in no-spray plots when compared to the conventionally managed adjacent fields. More replicated studies will be scheduled in 2005.

Accomplishments for Obj 2.

2a. 1) Developed a regional degree-day model. Predicting adult flight through the use of a degree-day (DD) model could help growers to both eliminate sprays and improve the timing of sprays. Our DD model was based on models from other parts of the US (e.g. New York, North Carolina, SW Ontario, Wellesbourne, England). The daily average DD were accumulated using a single sine approximation method and a low and high developmental threshold of 4.3 °C and 30 °C, respectively, beginning January 1st. To develop and validate the DD model, adult flight was monitored through the use of emergent cages and yellow water traps over a 4-year period (2001 through 2004).

i) Spring emergence: a) Overwintering pupae were collected from infested fields located at the NWREC station each fall. Twenty pupae were buried under each emergent cage in commercial fields in the northern Valley. Cages were monitored weekly for adult captures from January 5th through July 1st, after last emergence of adults. b) Temperature data were collected from Aurora Agrimet Weather Station and degree days were computed. Spring emergence was related to cumulative degree-days.

ii) Seasonal adult flight: a) Individual yellow water traps were placed each year in Brassica fields to follow patterns and trends in flight around the northern production region throughout the year. b) An OSU Extension regional pest monitoring program, VegNet, adopted the CM monitoring program and monitored adult flight at 8 additional locations throughout the Willamette Valley in 2002-2003.

iii) Placement of Water Traps: A trap placement study was also initiated to: a) better understand fly movement in the field, and b) optimize the location of traps within a field. The trap placement study was conducted at 5 commercial turnip fields in the northern Willamette Valley.

Results of Obj 2a:
– 2001-2004 water trap data indicate that there are 3-5 CM flights each year in the northern Willamette Valley of western Oregon.
– The DD model may be a viable strategy for predicting spring emergence and the beginning of fall flight. The degree-day accumulation also provides valuable context for interpretation of adult fly population data from yellow water traps. A bimodal spring emergence pattern was observed as noted by other researchers. Early-emerging flies constituted approximately 70% of the spring population, while only about 30% were late-emerging flies. The strategy of trying to plant crops between the early and late spring peak is not likely to be effective as it would be hard to predict and fly pressure is more or less constant throughout the spring season. By the end of spring emergence (approx. June 1s approximately 850 DD), CM flight activity decreased markedly over the summer months. A notable increase in fly activity increased again with DD accumulation of 2138, approximately Sept 1st. (Appendix-Table 1 & 2, Fig. 1). (Paper in review—to be submitted to Journal of Environmental Entomology).
– The yellow water traps were adequate for monitoring seasonal trends in CM adult activity (Appendix- Fig. 2). Abundant rainfall following the onset of emergence may contribute to increased emergence and flight activity. We observed delays of 5 days to 3 weeks between fly emergence (measured by emergence traps) and flight activity (detected by water trap catches) (Appendix- Fig. 3).
– More flies were captured in water traps at the northeast and eastern borders of fields than the southwest field borders. Data indicate that flies migrate upwind to the traps as prevailing winds have been recorded from the southwest. This information will be used to improve the efficacy of adult flight monitoring through the use of water traps (Appendix- Fig. 4).
– More data analysis is required in 2005 to evaluate if water traps can be used as predictors of egg-laying events or level of CM infestation in individual fields.
– Preliminary analyses indicate that there is a linear relationship between crop planting date and damage levels. However, many factors other than CM phenology impact damage, including management practices, landscape factors, a field’s proximity to other infested fields, and crop developmental stage. More data analysis is required to interpret the usefulness of the information for designing a management plan for a grower.
– Can we predict the potential risk of a particular field? Yes, it may be possible through a combination of applying a degree-day model, improved monitoring of adult flies, understanding the relative attractiveness of crop developmental stages, and determining how far the field is from an infested field.

2b. Implement a viable monitoring system (eggs, plant damage)
For sampling methods to be considered viable by growers, they must be practical, reliable, and cost effective. We are evaluating egg count and plant damage assessments for their utility as CM monitoring tools.
i) Egg counts: The “egg-scrape” technique (otherwise known as ES90) was designed to estimate CM egg levels. We scout 4 corner and 2 middle sections representative of each field. In each section, we randomly select 5 “clusters” of 3 plants along a zig-zag pattern extending 40 feet into the field. We inspect the base of plants for maggot eggs at the soil surface within a 1-inch radius from the base of each plant. With a knife, we gently scrape away the top ¼ inch of soil, revealing the eggs under clods and crevices. The proportion of infested plants and average number of eggs per plant is calculated. In 2005, we are designing and testing a “speed-scouting” technique to increase efficiency, but maintain the accuracy of egg level and damage estimates.
ii) Plant damage: We scout 6 sections of the field (as described above), selecting 10 plants along an “M”-shaped transect in each section, termed “M60”. The proportion of damaged roots is calculated.

Results of Obj 2b:
– The “M60” is a conservative and reliable method for assessing crop damage.
– The “ES90” is a bit more tedious and strenuous, but also an accurate technique for measuring egg levels in a field. A ‘speed-scouting’ technique will be further explored in 2005.
– More data analysis (2005) into the relationships between adult flight activity, egg-laying, maggot damage, and environmental conditions is needed before specific management recommendations can be made. However, preliminary work is showing a positive relationship between cumulative egg counts and crop damage in fields.
– Fly attractiveness for egg-laying is impacted by crop development stage. Flies preferentially lay eggs at the base of root crop plants with 5-9 developing leaves (3-4 weeks after planting). However, flies will lay eggs on older plants, if the preferred stage is not available (See 2003 Progress report).

2c. Identify alternate chemistries and pesticide application techniques
i) Laboratory soil bioassays were performed at economic field rates for in-furrow (3.85 x 106 spores/g dry soil) and broadcast (3.85 x 105 spores/g dry soil) applications with 3 entomopathogenic fungal isolates of Metarhizium anisopliae (F52, ATCC62176, and ARSEF5520) and one isolate of Beauveria bassiana (GHA).
ii) The efficacy of Lorsban, Fipronil, and Spinosad as seed treatments and applied in-furrow and over-the-row application techniques was evaluated. Three on-farm trials with growers’ assistance were conducted in 2003 and two were conducted in 2004.
iii) Adult foliar treatments were examined in 2003 and 2004 at the NWREC Station (Aurora, OR) in collaboration with Bob McReynolds, Vegetable Extension Specialist.

Results of Obj 2c:
– Laboratory bioassays indicate that some strains of fungal biocontrol agents have efficacy. Teanure (F52), a Metarhizium strain, performed best killing an average of 85 and 72% of D. radicum larvae at the high and low concentration, respectively. (Appendix- Fig. 5). (Bruck, Snelling, Dreves, and Jaronski 2004, in review).
– Lorsban 4E remains the most effective pesticide with increased protection, especially if treatment is applied in the furrow. However, efficacy is not 100% and is therefore insufficient for these zero-tolerance root crops.
– There may be CM resistance to Lorsban as has been shown previously by Canadian researchers (Zimmerman, Ministry of Agriculture 2004). In 2004, five root crop fields resulted in >80% damage even though 4 applications of Lorsban 4E was applied during the season (Appendix- Table 3). Root damage from CM has only increased each year from 2001 to 2004 (Appendix-Table 4).
– Fipronil (Regent) (applied in-furrow) and Fipronil seed treatments revealed efficacious results as an alternative chemistry (Appendix-Table 5). Chlorpyrifos- (Lorsban 4E), Spinosad- (Entrust), and Fipronil-treated seeds showed promising results for control of CM, but these treatments lost their protection at 4-5 weeks after planting (Appendix- Table 6 & 7). Seed treatments use 88% less insecticide than broadcast applications. In-furrow applications were significantly more effective compared to over-the-row applications. Mustang, Calypso, Neemix, Cruiser, Gaucho, Poncho 600 treatments showed little to no efficacy.
– Maggot pressure is not as evident on short-term (23-30 days) radish production because the insecticide at planting appears to provide adequate protection, if you miss the high- risk egg-laying window.
– Bob McReynolds, OSU Vegetable Extension Specialist at NWREC, is requesting from EPA a Section 18 for fipronil-treated seed and in-furrow application based on our efficacy data. We are also requesting from IR-4 the use of Spinosad and Warrior, an adult foliar, in turnips, radish, and rutabagas.

2d. Evaluate cultivation strategies to reduce overwintering CM populations
i) We evaluated both fall and spring tillage practices to reduce overwintering puparia load and thereby spring emergence. The fall cultivation trial was conducted in 2002-03 located at the NWREC station in Canby, OR. A second trial was carried out in the spring of 2004 on a grower’s field also located in Canby, OR. Emergence cages were used to trap adult flies as they emerged from the soil in the spring. The trial consisted of a randomized block design, replicated 3x with 3 treatments including: 1) untreated (no action was taken; live mature crop was left in the ground over the winter months; 2) double-disked, and 3) double-disked and deep plowed (18”).

Results of Obj 2d:
– Research conducted in the fall of 2002 suggested the double-disking and deep plowing reduced spring emergence of CM in 2003. However, numbers of flies captured under each cage was variable within treatments. Increased numbers of sample cages are necessary to reduce variability.
– A second cultivation trial was conducted during the spring of 2004 and preliminary analysis suggested that field cultivation in the spring reduces CM emergence. There were significant differences in numbers of emerged flies between treatments. The uncultivated treatment had significantly more flies emerge than both cultivation treatments. There was double the number of flies in cages recorded in the untreated plots than in the cultivation cage plots. There were no significant differences in numbers of flies observed between the rototilling and double-disking/deep plowing treatments. (Appendix- Table 8). More research is needed to further test efficacy of cultivation practice as a reliable management strategy.

2e. Evaluate row cover and exclusion fence usage for managing CM .
i) The use of Reemay, a spun polyester row-cover material, was tested as a barrier to cabbage maggot infestations. Four row cover trials were conducted in 2004 on a grower’s root crop fields (turnips and daikon). Each plot consisted of four rows, 100-200 feet long and 80 feet wide. The treatments were either with or without Reemay row covers (applied at 2 weeks after planting), planted in a complete-block design with 4 replicates. At harvest, numbers of roots with cabbage maggot damage was determined. Twenty roots per side (N, S, E; 15 feet adjacent to fence). Means were separated by the Waller-Duncan mean separation test (SAS Institute 1999).
ii) The use of exclusion fences around Brassica fields was evaluated for efficacy in excluding cabbage flies from a turnip crop. The trial’s objective was to define an appropriate fence design for larger scale commercial use and to obtain preliminary data on the efficacy of such a design. Canadian researchers (Vernon and McGregor 1999; Vernon and Mackenzie 1998; Bomford et al. 2000) reported effectiveness of exclusion fences. The trial was not replicated. A fine nylon mesh fence (30’ x 30’) was designed by a local grower in Canby measured 135 cm high with 25-cm overhangs. We examined 60 roots inside and outside the fence, representative throughout the sampling area.

Results of Obj 2e:
The row cover dramatically reduced populations of cabbage maggots, but aphid populations and bacterial soft rot (due to excessive humidity) was increased in some plots. Marketable yields were substantially higher under the row covers quantified in Trial 1. (Appendix- Figure 6). Although row covers are quite expensive, our data suggest that row covers provided economic returns primarily because of an increase in early harvest when the market prices are high, an increase in crop yield, and because row covers can be used several years in a row if care is taken. It is anticipated that fewer sprays would be required using this strategy.
Based on current results from an unreplicated study, reduced numbers of damaged roots were reported in the enclosed turnip plot than the plot in an open area without a fence. Twenty percent of roots were damaged from cabbage maggots outside of the fence and only 1.3% root damage inside of fence. The fence excluded 93% of cabbage flies from entering the host crop. The results were promising and the grower has indicated that he would like to replicate the study in 2005 and is willing to take on the expense.

2f. Develop a GIS tool to assist growers in spatial CM management
i) There are many commercially available GIS software packages, but most of these are expensive, difficult to use, and require a significant time commitment to master. Our approach has been to add GIS capabilities to software programs that growers are already familiar with. A model CM GIS-IPM tool has been developed and is being refined to: 1) serve as a research tool to develop risk assessment criteria and evaluate CM dynamics in time and space, and 2) assist growers in regional spatial CM management. This GIS provides risk analysis, mapping and visualization tools within Microsoft Excel that supplement standard data entry and spreadsheet analyses. Data can also be exported or imported in formats that are compatible with most GIS packages. Four years of monitoring data will be evaluated in 2005 using the GIS-IPM tool.

Results of Obj 2f:
– The application of the GIS-IPM tool is under development (See 2003 Progress report). The GIS-IPM tool will locate and map CM incidence across the region in time and space and relate damage levels to distance from previously infested fields. Fields at risk and the severity of this risk can be identified using many different user-defined risk assignment criteria. Ultimately, a regional community of growers could use this tool to better manage plantings in space and time and thereby minimize pest infestations.
– The program is multifunctional. It has the ability to conduct complex queries that allow researchers to analyze risk factors in detail. At the same time, it acts as a user-friendly program that allows growers to access numerous maps by simply pointing and clicking a mouse.
– The CM is an ideal model for our GIS-IPM tool, as it is mobile (flight distances up to 1 mile). Due to CM’s high mobility, infested farms put their neighbors at risk. We hypothesize that growers can decrease CM infestation levels by using our software to coordinate crop rotations with neighboring growers.
– The shape file-GIS interface also can benefit growers by displaying current monitoring data. Cabbage maggot eggs can hatch in as few as three days, and larval penetration of the root occurs soon thereafter. Therefore, timing of insecticide application is critical. The ability to view current, near real-time monitoring data will assist growers in making treatment decisions. This could also reduce pesticide use, as chemical applications could be made on an as-need basis.
– The software is a research tool that can be used by scientists to create an extension tool. It allows researchers to test for the utility of different methods of calculating a field’s potential risk. Scientists can test their proposed rotation management systems using past data. Once an accurate model has been developed, growers can use the program to monitor insect levels in their fields, calculate potential risk levels, and rotate plantings.

Accomplishments for Objectives 3 and 4:
i) Held 3 grower workshops in 2004 (Appendix- Table 9).
ii) Presented MagNet research at the annual 2004 Entomological Society of America meetings and co-moderated a Maggot Symposium. Title of talk was: Know thy enemy: strategies for the managing the cabbage maggot, Delia radicum L.
iii) Developed, distributed, and trained grower’s staff to use grower-friendly CM monitoring techniques.
iv) Created informational laminated cards on monitoring and management.
v) Produced three newsletters (Appendix- See Spring 2004 Issue #3).
vi)Developed a MagNet web site (http://oregonstate.edu/magnet/).
vii)Developing a grower practice survey, called the ”PEST Plan.” This tool can be used by growers and program staff to evaluate grower practices and IPM adoption over time. The document went through a peer review process (including grower reviewers) and will be tested in spring 2005 (see 2003 progress report).
iix)An OSU Extension regional pest monitoring program adopted our CM monitoring program and monitored adult flight at 8 additional locations throughout the Willamette Valley

Results of Obj 3 and 4:
– Growers called us regularly inquiring about egg levels, damage, and flight levels. They have taken an active interest in obtaining information about CM (Appendix- 11: pictures).
– One grower hired an employee in November 2004 for 18 months who will help in the technical transfer of monitoring techniques, evaluate speed scouting, and test new chemicals and cultivation techniques on the farm.
– We have documented 6 cases in which cooperating pilot growers have not sprayed a field because we reported low egg numbers in that field. Also, 4 fields were harvested early before the next generation of flies appeared based on flight activity. Four fields were also removed in a timely fashion to avoid further development of CM, because of information we provided them.
– One of our cooperating growers designed an exclusion fence, reported in our summer newsletter, to provide a barrier around a field; which has been reported to reduce the number of flies entering a field, thus less damage. We intend to replicate the trial in 2004.

Impacts and Contributions/Outcomes

The primary objectives of the MagNet project are to reduce broad-spectrum pesticide use and expand grower interest in and adoption of IPM tools for cabbage maggot (CM) management. As data analysis has yet to be fully completed on all aspects of the project when this annual report was submitted, assessing impacts and contributions or outcomes is too early. However, we expect the impact to be widespread throughout the Pacific Northwest and the Western United States. In addition, much of the information and tools developed by the project could be utilized in other regions affected by CM. “The PEST Plan” will be a great prototype for measuring impact of IPM programs in other crops with pest problems.

Development of a degree-day (DD) model. The completed DD model and behavioral research for CM will be presented to Pacific Northwest growers in 2005 in hopes to reduce pesticide use (Lorsban) by better timing pesticide applications to pest incidence and identifying periods that are of low risk.

Use of monitoring tools. Commercially viable monitoring techniques will permit growers to quantify infestation levels, evaluate treatment options, and determine risk levels in individual Brassica fields.

Creation of GIS-IPM mapping tool. The development of the GIS-IPM tool for analyzing field pest risk will locate and map CM incidence across the region in time and space and relate damage levels to distance from previously infested fields. Ultimately, this tool could be used by a regional community of growers to better manage plantings in space and time and thereby minimize pest infestations. This tool is being developed with the intention to implement a regionwide detection and warning system for cabbage maggot presence in the northern Willamette Valley.

Measuring IPM Impact.

The “PEST Plan,” a grower IPM practices rating system, will measure a grower’s advancement toward ecologically based management rather than chemically intensive pest management. It is being critiqued and modified for grower use. We intend to implement this tool in 2005 to evaluate the impact of the MagNet program.

Identifying alternative chemistries and improved application product uses. After 4 years of trials researching alternative chemistries, 3 products will be suggested for registration to provide growers with chemical choices to help reduce resistance possibilities.

Education and Training. The following products have been produced by the MagNet team and distributed to the pilot growers and workshop attendees: Maggot Mania newsletters, a MagNet website, a monitoring kit (water trap and recording card, hand lens, viewing jar, miniature emergent cage), and 3×4 inch, laminated educational training cards that fit on a key ring. These cards have also been distributed in SW Canada in spring 2004. Growers and agricultural professionals in other CM-affected regions could benefit from these educational cards as a reference tool and reminder of tool choices.

Professional Meetings. MagNet staff have presented program results at many grower and scientific meetings and have exchanged IPM ideas with other worldwide researchers.

Production of Articles, Newletters, etc. The degree-day model and results on the use of a fungal agent as control for CM have been submitted for review in the Journal of Economic Entomology and Journal of Invertebrate Pathology, respectively. We intend to submit other articles in peer-reviewed journals including regionwide monitoring strategies, the GIS-IPM tool, spatial-temporal management of CM, and the PEST Plan.


Steve Montecucco

Montecucco Farms
4015 N Locust
Canby, OR 97013
Office Phone: 5032636066
Dr. Daniel McGrath

VegNet Coordinator, Extn Chair -Ag. Vegetables
Linn County Extn
PO Box 765
Albany, OR 97321
Office Phone: 5419673871
Jane Snelling

Student in Pest Biology and Management
Oregon State University
Corvallis, OR 97331
Dr. Glenn Fisher

Entomologist-Crops and Soils Department
Oregon State University
Cordley Hall, Room 2053
Corvallis, OR 97331
Office Phone: 5417375502
Dr. Dan Dalthorp

Oregon State University
Statistics Dept.
Corvallis, OR 97331
Office Phone: 5417371988
Bob McReynolds

NWREC Vegetable Specialist
Oregon State University
15210 Miley Rd
Aurora, OR 97002
Office Phone: 503678126425
Mike Iverson

Fresh Marcket Grower
Aurora Farms
13490 Cedarwood Rd
Aurora, OR 97002
Office Phone: 5036782684
Rebeca Siplak

Research Technician
Oregon State University
Dr. Timonthy Righetti

Professor of Horticulture
Oregon State University
4017 Ag and Life Science Bldg
Corvallis, OR 97331
Office Phone: 5417375466
Dr. Denny Bruck

Research Entomologist
USDA-ARS Horticulture Crops Research Laboratory
3420 NW Orchard Ave
Corvallis, OR 97330
Office Phone: 5417384026
Dr. Alexandra Stone

Vegetable Cropping Systems Specialist
Oregon State University
4017 Ag and Life Science Bldg
Corvallis, OR 97331
Office Phone: 5417375461
Shannon Heuberger

Faculty Research Assistant
Oregon State University
4017 Ag and Life Science Bldg
Corvallis, OR 97331
Office Phone: 5417379494
Manfred Schosnig

C&S Farms
1935 NE 20th Ave
Canby, OR 97013
Office Phone: 5032665809