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

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

Summary

The objective of this project is to reduce grower dependence on Lorsban (chlorpyrifos) to manage cabbage maggot (CM; Delia radicum). A strategic IPM “toolbox” of management strategies is under development. The plan includes: monitoring (adults, eggs, and damage); predictive degree-day modeling; spatial management (through monitoring and a regional grower-friendly GIS mapping system); fall cultivation; habitat enhancement for natural enemies (e.g. straw mulches); and alternative chemistries and application methods. A grower survey tool is being developed. This tool will be used to evaluate program impacts and grower IPM adoption over time.

Objectives/Performance Targets

1. Evaluate and implement IPM strategies in cruciferous crop production
   Develop a degree-day model for predicting flight in the spring
   ¨ Implement a viable monitoring system (eggs, mid-season, harvest)
   ¨ Identify alternative chemistries and application techniques
   ¨ Evaluate fall cultivation practices to reduce overwintering CM populations
   ¨ Develop a GIS-IPM tool to assist growers in spatial CM management
   2. Define seasonal impact of cabbage root flies
   ¨ Establish a harvest assessment of damage
   ¨ Install “no-spray” plots in growers fields
   3. Inspire grower IPM interest and adoption
   ¨ One-on-one grower interaction in field
   ¨ Development of “the PEST Plan” to assess progress and adoption of IPM practices
   4. Build collaboration between growers, researchers, and extension personnel
   ¨ Transfer technology to VegNet, Ag consultants, other growers
   ¨ Hold grower workshops (GIS workshop, degree-day workshop, monitoring field day)
   ¨ Create a grower monitoring kit

Accomplishments/Milestones

Objective 1. Evaluate and implement IPM strategies in cruciferous crop production
a) Develop a regional degree-day model
b) Implement a viable monitoring system (eggs, mid-season, harvest)

c) Identify alternate chemistries and pesticide application techniques
d) Evaluate fall cultivation strategies
e) Develop a GIS-IPM tool to assist growers in spatial CM management

1a) Develop 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 initial DD model was based on models from other parts of the United States and will be validated for the region based on emergent cage and water trap data as described below. To develop and validate the DD model, adult flight was monitored through the use of emergent cages and water traps.

1) Spring emergence: Pupae were collected from infested fields in November 2002. Two emergent cages were placed in each of 10 locations in the northern valley and 20 pupae were buried in the soil under each cage. Cages were monitored weekly for adult captures through July 7, 2003, after last emergence of adults. Temperature data were collected from Aurora Agrimet Weather Station and degree days were computed according to the following equation: [(MaxTemp + MinTemp)/2 – BaseTemp (4.3°C)] x 1 day. Spring emergence was related to cumulative degree-days.

2) Seasonal adult flight:
a) Five water trap placement studies were initiated in January 2003 to examine differences in adult fly captures from all directions around a field border (e.g. north vs south vs east vs west sides). This data will be used to evaluate the best placement of water traps for quantifying adult flight.
b) Individual water traps were placed in 30 locations (fields) in February 2003 to follow patterns and trends in flight around the valley throughout the year.
c) An OSU Extension regional pest monitoring program, VegNet, adopted our CM monitoring program and monitored adult flight at 8 additional locations throughout the Willamette Valley.

Results:
· 2001-2003 water trap data indicate that there are 3-5 CM flights each year in the northern Willamette Valley; there were at least 4 in 2003.
· The yellow water traps were adequate for monitoring seasonal trends in adult flies, but cannot be used as predictors of infestation in individual fields. More work (data analysis) on trap placement is required to improve the predictive value of water trap monitoring (Appendix-Figure 1).
· The DD model may be a viable strategy for predicting first and last flight. The intermediate flights overlap with the first flight, generating an extended period of risk in the late spring and early summer. Dan Dalthorp and Amy Dreves are analyzing the monitoring data and refining the degree-day model .(Appendix-Figures 2 & 3).
· Preliminary analyses indicate that there is no simple relationship between crop planting date and damage levels. This is due to the fact that 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.
· Can we predict the potential risk of a particular field? Yes, it may be possible through a combination of improved monitoring of adult flies, applying a refined degree-day model, understanding the relative attractiveness of crop developmental stages, and determining how far the field is from an infested field.
· Preliminary data indicate that water traps located on NE field borders collected more flies than those located on SW field borders. This information will be used to improve the efficacy of adult flight monitoring through the use of water traps.

1b. Implement a viable monitoring system (eggs, plant damage)
For sampling methods to be considered viable by growers, they must be reliable and cost effective. We are evaluating egg counts and plant damage assessments for their utility as CM monitoring tools.
1) Egg counts:
The “egg-scrape” technique 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 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.
2) 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:
· There was a positive relationship between cumulative egg counts and crop damage.
· Attractiveness for egg-laying is impacted by crop development. Flies preferentially lay eggs at the base of root crop plants with 5-9 developing leaves. However, flies will lay eggs on older plants if the preferred stage is not available. (Appendix- Figure 4)
· The “M60” is a conservative, reliable, and rapid method for assessing crop damage.

1c. Identify alternate chemistries and pesticide application techniques
1) Use and efficacy of entomopathogenic fungi, Beauveria and Metarhizium. Three laboratory bioassays were conducted in 2003.
2) Efficacy of Lorsban (chlorpyrifos): seed treatments, and application techniques (furrow, over-the-row, and timing). Three on-farm trials with growers’ assistance were conducted in 2003.
3) Examination of alternative chemistries, timing, and application methods. Three trials were conducted in 2003 were conducted at the NWREC Station in Aurora in collaboration with Bob McReynolds.

Results:
· Lorsban 4E remains the most effective pesticide, especially if 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.
· Laboratory bioassays indicate that some strains of fungal biocontrol agents may have efficacy. Teanure, a Metarhizium strain, has shown the most promise thus far, infecting 65-80% of the larvae (Bruck, Dreves, and Snelling 2003 report)
· Fipronil applied in-furrow and Fipronil seed treatments showed the most efficacy as alternatives to Lorsban 4E. Chlorpyrifos- and Spinosad-treated seed also showed efficacy but lost protection at 4 weeks after planting. In-furrow applications were significantly more effective compared to over-the-row applications. Mustang, Calypso, and Neemix treatments showed no efficacy.

1d. Evaluate fall cultivation strategies to reduce overwintering CM populations
We conducted a replicated experiment station trial in 2002-03 trial to evaluate the potential of fall tillage to reduce pupal load and thereby spring emergence. Cages were used to trap adult flies as they emerged from the soil in the spring. The treatments included: 1) untreated (no action was taken; live crop was left in the ground to overwinter); 2) double-disked, and 3) double-disked and deep plowed.
Results:
· There was no significant difference in fly emergence between treatments. However, sample sizes were low and variability was high. Adult emergence was numerically lower in the double-disked/deep plowed treatment, indicating that this treatment may have some efficacy. We are currently working with a grower to design a more effective emergent cage to be used for another on-farm cultivation trial in 2004.

1e. Develop a GIS tool to assist growers in spatial CM management
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. Three years of monitoring data are currently being evaluated with the GIS-IPM tool.
Results:
· 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 (Appendix-Figures 5 and 6)
· 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 CRF’s high mobility, infested farms put their neighbors at risk. We hypothesize that growers can decrease CRF 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. CRF eggs can hatch in as few as three days, and larval penetration of the root occurs immediately 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 that we have developed 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.

Objective 2. Define seasonal impact of cabbage root flies
a) Evaluate harvest damage over time
b) Install “no-spray” plots in growers fields

Harvest damage was assessed through the use of an “M60” as described in 1B above. Ten un-replicated no-spray strips were installed in grower fields throughout the season of 2003. The rest of the field was treated with Lorsban.

Results:
· Preliminary analyses indicate that there is no simple relationship between crop planting date and damage levels. This is due to the fact that 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.
· Long-season root crops can be attacked by 2 or 3 generations of flies, but damage is most severe during the spring (late April and early May) and late fall (late September).
· Damage levels were lower in fields planted in the fall (August). Planting late in the season to avoid high-risk attack from cabbage maggots may be an effective strategy.
· In general, damage levels were similar in no-spray strips when compared to the conventionally managed adjacent field.

Objective 3. Inspire grower IPM interest and adoption
a) One-on-one grower interaction in field
b) Development of “the PEST Plan” to assess progress and adoption of IPM practices

Objective 4. Build collaboration between growers, researchers, and extension personnel
a) Transfer technology to VegNet, Ag consultants, other growers
b) Hold grower workshops (GIS workshop, degree-day workshop, monitoring field day)
c) Create a grower monitoring kit

Accomplishments for Objectives 3 and 4:
A) Held 3 Workshops in 2003 (Appendix-Figure 7)
B) Developed and distributed a grower-friendly CM monitoring kit and trained growers in its use.
CM monitoring kit
C) Created informational laminated cards on monitoring and management. (Appendix-Set of Laminated Cards)
D) Produced two newsletters (Appendix-Newsletter Issues 1 & 2)
E) Developed a MagNet website (http://oregonstate.edu/magnet/)
F) Developed 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) in June 2003 and is currently under revision (Appendix-Figure 8)
G) 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 Objectives 3 and 4:
· Growers call us weekly inquiring about egg levels, damage, and flight, taking an active interest in obtaining this information (Appendix-Digitals, Hard copy pictures, and CD of pictures).
· One grower has designated an employee as a CM scout. We trained him to scout for eggs, assess damage, and record adult flight. He scouts fields and faxes us data each week (Appendix-Figure 9).
· We have documented 4 cases in which cooperating pilot growers have not sprayed a field because we reported low egg numbers in that field.

· One of our cooperating growers is designing an exclusion fence to exclude flies from a field based on research from Canada reported in our summer newsletter. We are working with the Canadian researchers (and we will visit them in February) to adapt the design to a large-scale field plot.

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 CM management. The impact of this project should 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 DD model and behavioral research will be utilized to develop and implement a region wide detection and warning system for cabbage maggots and reduce pesticide use (Lorsban) by better timing pesticide applications to pest incidence and identifying periods that are of low risk.
· Commercially viable monitoring techniques will permit growers to quantify infestation levels, evaluate treatment options, and determine risk levels in individual fields.
· 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. Utlimately, this tool could be used by a regional community of growers to better manage plantings in space and time and thereby minimize pest infestations.
· The “PEST Plan,” a grower IPM practices rating system, measures a grower’s advancement toward ecologically based management rather than chemically intensive pest management. This tool will be used to evaluate the impact of the MagNet program.
· The following products have been produced by the MagNet team and distributed to the pilot growers and workshop attendees: Maggot Mania newsletters (see Appendix), the MagNet website, a monitoring kit (water trap and recording card, hand lens, viewing jar, miniature emergent cage), and 3×4 laminated educational training cards that fit on a key ring. Growers and agricultural professionals in other CM-affected regions could use these products.
· MagNet staff have presented MagNet program results at many grower and scientific meetings (Appendix-Table 1).
· We intend to publish peer-reviewed journal articles on the degree-day model, the GIS-IPM tool, region-wide monitoring strategies, and spatial-temporal management of CM.

References Cited:

Bruck, B, A. J. Dreves, and J. Snelling. 2003. Efficacy of the entomopathogenic fungi, Metarhizium anisopliae and Beauveria bassiana, for the control of the crucifer pest, Delia radicum L.. USDA Preliminary Dec. Report.

Hawkes, C. 1975. Physiological condition of adult cabbage root fly (Erioschia brassicae Bouche) attracted to host-plants. J. Appl. Ecol. 12: 497-506.

Finch S., and G. Skinner. 1973. Distribution of cabbage root flies in brassica crops. Ann. Appl. Biol. 75:1-14.

Finch S., and G. Skinner. 1975. Dispersal of the cabbage root fly. Ann. Appl. Biol. 81: 1-19.

Vernon, R.S., and J.R. Mackenzie. 1998. The effect of exclusion fences on the colonization of rutabagas by cabbage flies (Diptera: Anthomyiidae). Can. Entomol. 130: 153-162.

Collier, R.H., M. Hommes, S. Finch, A.N.E. Birch, E. Brunnel, J. Freuler, and H. Den Ouden. 1988. Induction of diapause in populations of cabbage root fly pupae; relationship between site latitude and critical day length. WPRS/OILB Bull. 1988/XI/I.

Finch. S. 1990. The effectiveness of traps used currently for monitoring populations for the cabbage root fly (Delia radicum). Ann. Appl. Biol 116: 447-454.

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