Colorado potato beetle herbivory on cultivated potato is a significant issue for producers at all scales, from home gardeners to commercial producers. Depending on the extent of damage, Colorado potato beetle feeding can reduce yields below total loss thresholds. Controlling this annual pest can be accomplished with a diverse set of cultural, mechanical or chemical pest management techniques. However, for large scale production systems, insecticides remain the primary control tactic. To date many studies have experimentally demonstrated effective non-chemical management strategies for Colorado potato at smaller scales. In this study, we chose to improve and extend current cultural control strategies to growers at larger scales. Our objectives were two-fold, first, to predict potato beetle colonization intensity with landscape components surrounding potato fields. Results were integrated into current scouting practices to incorporate pest biology into the decision making process. Second, we transitioned effective physical control tactics (trench barriers) to test non-chemical management of potato beetle at the field scale. Though these objectives were conducted at a large scale (fields > 80 acres) all results are transferable to smaller production systems where non-chemical management strategies are critical pest management components. This project integrated improved scouting techniques to inform the placement of inexpensive cultural control tactics (e.g. trenches) thereby reducing beetle populations in the field. Adoption of research-based cultural control strategies could lessen insecticide reliance for management of Colorado potato beetle, and in doing so, limit impacts to non-target organisms, reduce grower input costs, and improving sustainability of potato production systems.
For more than one hundred years Colorado potato beetle (Leptinotarsa decemlineata) management has relied heavily on chemical management of control (Casagrande 1987, Alyokhin 2009). Although successful control of this pest can be accomplished with pesticides, a high propensity for insecticide resistance development requires a diversified set of pest management strategies for control. Numerous studies have previously explored mechanical (Misener et al. 1993, Boiteau et al. 1994, Boiteau and Osborn 1999) and cultural (Weber and Ferro 1993, Weber et al. 1994, Hoy et al. 1996, Sexson and Wyman 2005) management strategies for Colorado potato beetle. Experimental findings were often logistically difficult to deploy beyond experimental scales. The objective of this project is to model how landscape features surrounding potato systems contribute to the colonization dynamics of CPB overwintering emergence and use this model to selectively scout and accurately deploy preventative cultural management tools to locations were landscape attributes are associated with intense early season CPB emergence and colonization. Completion of the outlined objectives will initiate the development and implementation of a more profitable, ecologically sound and sustainable industry. Research outcomes will further ongoing efforts to produce biologically-based, sustainable IRM and IPM tools for Midwestern potato producers and our proposed studies compliment several of the core goals of the NCR-SARE program by promoting site-specific integrated farming systems and enhancing environmental quality through a reduction of insecticide inputs.
1) Validate spatially explicit colonization models to improve targeted, strategic scouting activities
2) Evaluate spatially targeted beetle trenches as a physical barrier for early season CPB colonization.
Six cooperating growers were identified in 2008 at the Wisconsin Potato and Vegetable Grower’s Meeting in Stevens Point, Wisconsin. Farmers were asked to identify fields scheduled to be potato in 2010 and 16 fields were randomly selected from the selected field set. Field boundaries were digitized into a Geographic Information System (ArcGIS 9.2) and field edges. Edges were then split into 16 equidistant sample points based on edge length.
Locations of potato in the previous season were identified using the 2007 USDA National Agricultural Statistics Service – Cropland Data Layer in ArcGIS. Previous potato locations within 1500 meters of randomly selected 2010 fields were identified and digitized. Previous potato fields were then buffered at a distance of 200m to identify candidate overwintering locations of Colorado potato beetle.
200m buffers were intersected with an standardized land use data layer produced from the Portage, Waushara, and Adams County land use layers. Information was distilled into a 24 land class scheme. Habitat classifications were consistent with those established by the NRI-Managed Ecosystems Project. Land classes contained within the buffers will be visually validated with the assistance of NAIP ortho-rectified aerial photography (National Agriculture Imagery Program 2008). A layer intersect process for each buffer zone will quantify acreage of all land classes within its boundary. The resulting data set produced will be comprised of information quantifying landscape features surrounding sample fields. Insect numbers were described based upon landscape colonization models produced from the 2008 growing season (Huseth et al. in press). Counts were conducted for four weeks in June until the pupation of first generation CPB.
Deployment of trenches in 2010 and 2011 occurred on commercial acreages demonstrating significant beetle pressure in past seasons. Participating growers will be asked to identify anticipated 2010 & 2011 potato acreages. A Model 90 (Mechanical Transplanter Inc., Holland, MI) mulch layer was modified in 2009 to create 12 inch deep plastic lined trench in a single pass. The trencher was used again in 2011 to create beetle trenches. Each sampling location received a paired treatment of 200 foot trenches, one of standard black plastic and another of yellow plastic mulch (Transworld Plastic Films Inc., Rochelle, IL). Each trench will be subdivided into five 20 foot sampling intervals. Beetles falling into sampling areas were restricted with Plexiglas fences on either end of the sample space. Trapped beetles were counted and removed weekly during the month of June 2010 & 2011. Data was analyzed using an ANOVA and Tukey’s HSD pair wise comparisons.
Rotation distance and habitat diversity surrounding previous potato had limited ability to describe potato beetle abundance at the field scale. Using data generated for objective 1, we determined that colonization of potato fields in the current season were linked to incidence/abundance of previous potato in some but not all seasons. Furthermore, simultaneously measuring contribution from all possible previous potato fields within 1,500m represented a more comprehensive descriptive approach than previously used to quantify Colorado potato beetle abundance in Wisconsin potato fields. Variables generated using an inverse distance weighting approach described the greatest amount of potato beetle count variability for all distance metrics generated (Huseth et al. in press).
Several habitats common to the Central Sands potato producing region in Wisconsin were identified for each data set. Habitats commonly surrounding previous potato were extracted with buffering techniques in ArcGIS. Landscapes were further subdivided into classes which have been reported as areas that Colorado potato beetle preferentially overwinters. These specific habitats were regressed against potato beetle numbers in current potato. Seven models were generated to explore the relationship between the landscape and non-crop habitats. The best fitting models only described between 27-28% of count variability. No specific habitat described a greater proportion of Colorado potato beetle counts and the combination of all selected habitats preformed similarly to independent habitats (Huseth et al. in press).
We did find that local landscapes containing grassland or grassland-like habitats correlated negatively with potato beetle counts in both analysis years. The mechanism contributing to this reduction in beetle numbers is unknown.
Trench experiments were established in 2010 and 2011. Treatments consisted of either yellow or black plastic trenches paired with yellow or black shields (to prevent irrigation water from filling trenches. Under high insect pressure we did not see any significant differences among treatment catches or in colonization of the crop behind the trenches. Objective 2 did, however, demonstrate temporary conversion ability of common plastic layers for deployment of Colorado potato beetle trenches. To do this we used common farm tillage implement components to modify a Mechanical Transplanter model 90 for single pass trench deployment. Development of an implement to easily place trenches along potato crops will be extremely useful to smaller scale organic producers where Colorado potato beetle management is an exceptional challenge annually.
Educational & Outreach Activities
Huseth, A. S., K. E. Frost, D. L. Knuteson, J. A. Wyman, and R. L.
Groves. 2012. Effects of landscape composition and rotation distance on Colorado potato beetle (Coleoptera: Leptinotarsa decemlineata) abundance in cultivated potato. Environ. Entomol.
(accepted for publication)
Huseth, A. and R. L. Groves. 2009. “Overwintering Habitats of the Colorado Potato Beetle in Wisconsin’s Central Sands Production Area.” In Proceedings of the Wisconsin Potato and Vegetable Growers Association, Grower Education Conference. February 3-4, Stevens Point, Wisconsin.
Huseth, A. S., K. E. Frost, and R. L. Groves. 2012. Effects of local landscape composition on Colorado potato beetle (Leptinotarsa decemlineata) colonization of commercial potato in Wisconsin. Entomology Society of America National Meeting, November 11 – 14, Knoxville, Tennessee.
Huseth, A. S. and R. L. Groves. 2010. Overwintering biology and extended diapause in Colorado potato
beetle. Wisconsin Potato and Vegetable Growers Association Annual Potato Meeting Research Presentation, February 3-4, Stevens Point, Wisconsin.
Huseth, A. S. and R. L. Groves. 2009. Spatial colonization patterns of Colorado potato beetle in potato: relating land use patterns and population dynamics. Entomology Society of America National Meeting, December 13 – 16, Indianapolis, Indiana.
Huseth, A. S. and R. L. Groves. 2009. Overwintering habitats of the Colorado potato (Leptinotarsa decemlineata) beetle in Wisconsin’s Central Sands production area. North Central Branch – Entomology Society of America Meeting, March 15-17, St. Louis, Missouri.
Impacts of this project are forthcoming. Recent publication of findings from Objective 1 suggest cultural control tactics using previous potato distance may not adequately describe Colorado potato beetle colonization risk. Results are expected to generate preliminary information for a more robust exploration of potato rotation and overwintering habitat selection in potato dominated agroecosystems. Furthermore, findings suggest annual variation in colonization intensity may not be as uniform as previously thought; focusing on interannual variability may prove critical for contemporary description of colonization dynamics under ever increasing environmental change. A better understanding of underlying mechanisms influencing Colorado potato beetle colonization success and magnitude will become more important as grower pest management decisions are influenced by increasing input costs for potato production.
Currently, we have no information on economic impact resulting from the objectives outlined in this project. Outlined objectives were basic and exploratory research into progressive IPM for Colorado potato beetle in Wisconsin. We hope tangible reductions in grower costs will result from future research utilizing findings outlined here.
In Wisconsin, potato producers often rotate potato over time and space to manage Colorado potato beetle infestations. Distance thresholds determined by previous research seem to adequately reduce populations in most years but it is often difficult for smaller producers to rotate over required distances which reduces adoption. At the 2013 Wisconsin Potato and Vegetable Growers Association Annual Potato Meeting we will present our findings from Objectives 1 and 2 in the hope of gaining independent grower adoptions for some of these alternative potato beetle management practices. To date, we know of no commercial scale growers adopting plastic lined trenches. Improvement of deployment technology may improve adoption by smaller growers who currently install trenches by hand. With further refinement of Objectives 1 and 2 we anticipate future grower adoption at various scales of potato production.
Areas needing additional study
Determination of what, if any, habitats within the potato agroecosystem support Colorado potato beetle populations would be an exceptional advancement towards more sustainable management of this key insect pest. Currently, few studies have been able to directly associate potato beetle abundance with specific habitat components in the environment. Improvement of this relationship would improve success of Objectives 1 and 2. Future research by these participants hopes to better understand this pest’s interaction with local landscapes. Long-term outcomes of future findings will be integrated into current rotation management, physical control tactics (e.g. trenches, trap crops) and scouting recommendations.
Boiteau, G., & Osborn, W. P. L. (1999). Comparison of plastic-lined trenches and extruded plastic traps for controlling Leptinotarsa decemlineata (Coleoptera: Chrysomelidae). Canadian Entomologist, 131(4), 567-572.
Boiteau, G., Pelletier, Y., Misener, G. C., &; Bernard, G. (1994). Development and evaluation of a plastic trench barrier for protection of potato from walking adult Colorado potato beetles (Coleoptera: Chrysomelidae). Journal of Economic Entomology, 87(5), 1325-1331.
Hoy, C. W., Wyman, J. A., Vaughn, T. T., East, D. A., & Kaufman, P. (1996). Food, ground cover, and Colorado potato beetle (Coleoptera: Chrysomelidae) dispersal in late summer. Journal of Economic Entomology, 89(4), 963-969.
Misener, G. C., Boiteau, G., & Mcmillan, L. P. (1993). A plastic-lining trenching device for the control of Colorado potato beetle – beetle excluder. American Potato Journal, 70(12), 903-908.
Sexson, D. L., & Wyman, J. A. (2005). Effect of crop rotation distance on populations of Colorado potato beetle (Coleoptera: Chrysomelidae): Development of Area-wide Colorado potato beetle pest management strategies. Journal of Economic Entomology, 98(3), 716-724.
Weber, D. C., Ferro, D. N., Buonaccorsi, J., & Hazzard, R. V. (1994). Disrupting spring colonization of Colorado potato beetle to non-rotated potato fields. Entomologia Experimentalis Et Applicata, 73(1), 39-50.