Feeding damage by Bagrada hilaris (Hemiptera: Pentatomidae) and impact on growth and chlorophyll content of Brassicaceous plant species

Bagrada hilaris Burmeister is an invasive species native to the old world and is currently threatening commercial vegetable production in the southwestern USA. A series of no-choice experiments were conducted to investigate multiple plant responses in six Brassica crops to feeding by B. hilaris. Varying numbers of adults were caged onto cotyledon, 2-true leaf, and 4-true leaf-stage plants of broccoli, green cabbage, red cabbage, cauliflower, kale, and radish for a 48-h infestation period. Feeding damage on leaf surfaces, total leaf area, and relative chlorophyll content on plants of each crop were measured before and after the 48-h infestation period. In addition, dry weights and total leaf area for the 4-leaf-stage plants were measured at 21 days post-infestation to estimate the residual impacts on older plants. In all crops tested, feeding damage increased with greater numbers of B. hilaris adults caged on cotyledon and 2-leaf-stage plants. Significantly more feeding damage occurred on the upper (younger) two leaves than on the lower (older) two leaves of the 4-true leaf plants for all host plants suggesting that B. hilaris feeds preferentially on newer leaf tissue. Significant reductions in leaf area, relative chlorophyll content, and dry weight in all crops indicated negative impacts on plant growth by B. hilaris. Moreover, cotyledon and 2-leaf plants were more severely impacted by B. hilaris-induced injury than the 4-leaf plants, and kale appeared to be less sensitive to B. hilaris feeding than the other five Brassicaceous hosts.