Feeding location affects demography of cabbage aphid on winter canola

Winter canola production in the south-central US is threatened by a complex of different aphid species, including Brevicoryne brassicae (cabbage aphid). Colonizing behavior of these aphids may be affected by intrinsic characteristics of the host plant including nutritional quality, secondary compounds, plant architecture or feeding structure. Understanding plant-insect interactions is important for timely management of aphids in winter canola. The objective of this experimental study was to evaluate how within-plant distribution impacts cabbage aphid demography on different canola plant structures. A stage-structured matrix model was constructed for aphids restricted to either reproductive or vegetative plant tissues of canola. Greenhouse and field studies revealed that the finite rate of increase (λ) was significantly higher (P < 0.05) when cabbage aphid colonies were restricted to reproductive compared to vegetative tissues. Populations with higher λ exhibited shorter generation times (T) and higher reproductive rates (R₀). Prospective analyses showed that there was a nymph skewed stable distribution and elasticity values revealed that λ is most sensitive to future changes in adult stasis (staying in the same stage) and mortality of adults. Retrospective analyses indicated that contributions from growth of certain nymphal stages accounted for nearly all of the variation in λ between the treatments, but adult fecundity was driving population dynamics. In general, feeding location effected cabbage aphid demographics, but implications of aphid location on monitoring for aphid outbreaks or interactions with natural enemies need further investigation.