Landscape effects on flea beetles in the Canadian PrairiesT. F. S. Guimarães*, T. Nagalingam, J. Otani, H. A. Cárcamo, T. Wist, J. Gavloski and A. Costamagna

1. Lamb, R. J., and Turnock, W. J. 1982. Economics of insecticidal control of flea beetles (Coleoptera: Chrysomelidae) attacking rape in Canada. Canadian Entomologist, 114: 827-840. 2. Dosdall, L. M., and Mason, P. G. 2010. Key pests and parasitoids of oilseed rape or canola in North America and the importance of parasitoids in integrated management. In

Biocontrol-based integrated management of oilseed rape pests. Edited by Williams, I. H. Springer Netherlands. Pp. 167-213.3. Gardiner, M. M., Landis, D. A., Gratton, C., DiFonzo, C. D., O’neal, M., Chacon, J. M., Wayo, M. T., Schmidt, N. P., Mueller, E. E., and Heimpel, G. E. 2009. Landscape diversity

enhances biological control of an introduced crop pest in the north-central USA. Ecological Applications, 19: 143–154.4. R Development Core Team. 2011. R: A language and environment for statistical computing. Foundation for Statistical Computing. Retrieved from http://www.R-project.org,

Vienna.5. Costamagna, A. C., Venables, W. N., and Schellhorn, N. A. 2015. Landscape-scale pest suppression is mediated by timing of predator arrival. Ecological Applications, 25: 1114–

1130.

References

From May to August 2015, 10 fields were sampled in Manitoba, Alberta and Saskatchewan (Fig. 2a). Data from additional fields in 2015 and 2016 is still being processed. Fields were selected to represent a gradient of landscape complexity3. Flea beetles were sampled by using yellow sticky cards among five sampling points in each field (Fig. 2b).

Landscape maps were constructed based on basic templates from Google Maps within a 2-km radius from the focal point of the sampling field using ARC GIS 103 (Fig. 3).

Methods

o Canola had no significant association with flea beetle abundance in any of the models.

o Natural vegetation may provide overwintering habitats for flea beetles.

o Increase habitat diversity may interfere with flea beetle movement to colonize canola fields and/or increase the abundance of natural enemies.

o It is unclear why wheat is associated with flea beetle abundance.

o Stripped flea beetles seem to respond differently to landscape characteristics than crucifer flea beetle.

o More data is needed to corroborate the initial trends found for striped flea beetles.

Conclusions

IntroductionFlea beetles are considering a major pest of canola in the Prairie Provinces of Canada, and causing a yearly loss of 300 million1,2.

The main species of flea beetles in Canada are crucifer flea beetle (Phyllotreta cruciferae, Fig. 1a) and striped flea beetle (P. striolata, Fig. 1b). The most severe damage is caused by defoliating the crop when the canola is between the cotyledon and the two leaves stage (Fig. 1b).

Past studies have indicated that increasing habitat diversity is associated to suppression of pest populations3.

However, there have been no previous studies showing how landscape complexity influences interactions between canola and flea beetles.

The primary goal of this research is to quantify the effects of landscape composition on flea beetles in the Prairie Provinces of Canada.

Fig. 3 Digital map from Manitoba by ARC GIS 10.

Fig. 1 (a) A mating pair of crucifer flea beetles (b) defoliation damage caused in the cotyledon stage of canola

Photo: Syngenta

Fig. 2 (a) Canola sites sampled in 2015 in the Prairies, and (b) sampling points with sticky cards

Acknowledgements– Dr. Barb

Sharanowski– Canola growers – Department of

Entomology– Lab and field

assistants

The percent coverage of each landscape category were as follows: other crops 32.9%, canola 31.0%, wheat 19.2%, semi-natural vegetation 8.6%, natural vegetation 6.7%, water 0.5%, and urban areas 1.1%.

For crucifer flea beetle, the best model fitted indicates a positive associationbetween crucifer flea beetle abundance and urban areas (Fig. 4).

Another model with similar support from the data indicates that crucifer flea beetle abundance has positive association with natural vegetation and wheat, and negative association with habitat diversity (Table 2, Fig. 5).

Models for striped flea beetle were not significant . The model with most support suggest negative association with natural vegetation and a positive association with habitat diversity (Table 2, Fig. 6).

Results and DiscussionAll data analyses were done using R4. Multiple regression models were calculated in order to identify landscape variables (Table 1) that best predict flea beetle abundance in canola crops5.

Table 1. Different cover-types combined into seven independent variables.

Models were selected based on Aikake’sInformation Criterion adjusted by sample size(AICc), and the lowest value represents the best model.

For crucifer flea beetles, models with AIC differences (Δi) < 3 are presented.

Methods

*Email: silvagtf@myumanitoba.ca

NV SNV Canola Other crops Urban area Water Wheat

Natural Vegetation

Border grass Canola Alfalfa Oats Building Water Wheat

Riparian Grass Corn Peas Urban area Stream Winter wheat

Shrubland Garden Barley Soybeans Road Durum

Pasture Flax Summer fallow Bare ground

Hemp Canary grass

Mustard

Fig. 5. Landscape effects on crucifer flea beetle.

Fig 4. Landscape effects on crucifer flea beetle.

Part

ial r

esid

uals

(CFB

)

Results

Part

ial r

esid

uals

(CFB

)Pa

rtia

l res

idua

ls (C

FB)

Part

ial r

esid

uals

(CFB

)

Fig. 6. Landscape effects on striped flea beetle.

Part

ial r

esid

uals

(SFB

)Pa

rtia

l res

idua

ls (S

FB)

Table 2. Summary of flea beetle models at 2km radius in the Canadian Prairie Provinces.

Model AICc ∆i df Adj. r² F p-value

Crucifer Flea Beetle

I** + Urban* 12.48 0.00 8 0.39 6.695 0.032

I + NV* + Wheat** - Simpson (*) 14.93 2.45 6 0.77 10.890 0.008

Striped Flea Beetle

- I – NV (*) + Simpson 1.55 -- 7 0.22 2.285 0.172

Notes: Intercept (I), natural vegetation (NV); Aikake’s Information Criterion (AICc), AIC difference (∆i), degrees of freedom (df), Adjusted r-square (Adj. r²). Models in bold represent the best model for each species

a b

a b

Simpson

Simpson

Wheat

Natural Vegetation

Natural Vegetation