Pests associated with two brassicaceous oilseeds and a cover crop mix under evaluation as fallow replacements in dryland production systems of the northern Great Plains

Authors: Rand, Tatyana; Allen, Brett; Campbell, Joshua; Jabro, Jalal - Jay; Rana Dangi, Sadikshya

Submitted to: The Canadian Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/16/2022
Publication Date: 6/3/2022
Citation: Rand, T.A., Allen, B.L., Campbell, J.W., Jabro, J.D., Rana Dangi, S. 2022. Pests associated with two brassicaceous oilseeds and a cover crop mix under evaluation as fallow replacements in dryland production systems of the northern Great Plains. The Canadian Entomologist. 154(1). Article e27. https://doi.org/10.4039/tce.2022.14.
DOI: https://doi.org/10.4039/tce.2022.14

Interpretive Summary: Identifying the dominant pests associated with novel crops being considered in diversification efforts is important information to forecast impacts on their production, and determine whether they are likely sources of pests moving over onto cash crops in a region. We surveyed insect pest communities in two bioenergy crops (carinata or camelina) and a 10-species forage/cover crop being trialed as fallow replacement crops for dryland productions systems of the Northern Plains. Crucifer flea beetles, the most important pests of canola in the region, were the dominant pests associated with carinata and the cover crop mix while the pest complex associated with camelina was dominated by generalist lygus bugs. Crucifer flea beetle densities were 200-1000 times greater in carinata relative to camelina. The results suggest that crucifer flea beetles have the potential to be serious pests of carinata, while camelina is both less likely to be attacked by, and/or serve as a reservoir of, these important pests of canola. Thus, camelina could be a good fit to replace fallow and increase crop diversity in regions with high canola acreage and a history of flea beetle problems.

Technical Abstract: Identifying pests associated with novel crops is important to forecast potential impacts on their production, and determine if they could be reservoirs of pests moving over onto cash crops. We carried out pest surveys in a study assessing the potential of diversifying a traditional spring wheat-fallow rotation system, by replacing the fallow phase with either bioenergy crops, carinata (Brassica carinata A.; Brassicaceae) or camelina (Camelina sativa L.; Brassicaceae), or a cover crop mix. Insect pests were sampled in each of the three crops over two years to: (1) inventory the dominant pests associated with each, and (2) assess whether they could be reservoirs of pests of canola (Brassica napus L.; Brassicaceae) an economically important crop in the region. Crucifer flea beetles, Phyllotreta cruciferae Goeze (Coleoptera: Chrysomelidae), the most important pests of canola, dominated the pest complex associated with carinata and the cover crop mix, comprising >70% of the insects sampled. In contrast, the pest complex associated with camelina was dominated (40% -91% across years) by generalist Lygus spp. (Heteroptera: Miridae). Crucifer flea beetle densities were 200-1000 times greater in carinata than camelina, suggesting that they could be serious pests of carinata, while camelina is both less likely to be attacked by, and/or serve as a reservoir of, these important pests of canola. Future work assessing feeding damage and population build-up of pests in these crops will be needed to determine impacts on their production, and the extent to which they may be reservoirs of canola pests over broader spatial scales.