Arsenic reduced scale-insect infestation on arsenic hyperaccumulator Pteris vittata L.

Arsenic hyperaccumulation by Pteris vittata L. (Chinese brake fern) may serve as a defense mechanism against herbivore attack. This study examined the effects of arsenic exposure (0, 5, 15 and 30 mg kg−1) on scale insect (Saissetia neglecta) infestation of P. vittata. Scale insects were counted as a percentage fallen from the plant to the total number of insects after 1 week of As-treatment. The arsenic concentrations in the fronds ranged from 5.40 to 812 mg kg−1. Greater arsenic concentrations resulted in higher percentage of fallen-scale insects (17.2–55.0%). Lower arsenic concentrations (≤5 mg kg−1) showed significantly lower effect on the population compared to 15–30 mg kg−1 (p < 0.05). Arsenic content in the fallen-scale insects was as high as 194 mg kg−1, which indicated that arsenic has been ingested by the scale insects via plant sap. This study is consistent with the hypothesis that arsenic may help P. vittata defend against herbivore's attack.