Silicon (Si) amendment to plants can confer enhanced resistance to herbivores. In the present study, the physiological and cytological mechanisms underlying the enhanced resistance of plants with Si addition were investigated for one of the most destructive rice pests in Asian countries, the rice leaf folder, Cnaphalocrocis medinalis (Guenée). Activities of defense-related enzymes, superoxide dismutase, peroxidase, catalase, phenylalanine ammonia-lyase, and polyphenol oxidase, and concentrations of malondialdehyde and soluble protein in leaves were measured in rice plants with or without leaf folder infestation and with or without Si amendment at 0.32 g Si/kg soil. Silicon amendment significantly reduced leaf folder larval survival. Silicon addition alone did not change activities of defense-related enzymes and malondialdehyde concentration in rice leaves. With leaf folder infestation, activities of the defense-related enzymes increased and malondialdehyde concentration decreased in plants amended with Si. Soluble protein content increased with Si addition when the plants were not infested, but was reduced more in the infested plants with Si amendment than in those without Si addition. Regardless of leaf folder infestation, Si amendment significantly increased leaf Si content through increases in the number and width of silica cells. Our results show that Si addition enhances rice resistance to the leaf folder through priming the feeding stress defense system, reduction in soluble protein content and cell silicification of rice leaves.

Plant viruses are primarily transmitted by insect vectors and virus infection may influence on the vectors’ feeding behaviors. Using an electrical penetration graph, we detected that infection with the Southern rice black-streaked dwarf virus (SRBSDV) in the white-backed planthopper (WBPH) and in rice plants both altered the vector’s feeding behavior. When viruliferous WBPH (carrying SRBSDV) were fed on uninfected plants, they spent more time in salivation and phloem sap ingestion than non-viruliferous insects. In comparison with uninfected plants, infected plants showed an arrestant effect on non-viruliferous WBPH for phloem sap ingestion. Differential feeding behaviors were also detected between the WBPH that inoculated or acquired SRBSDV and those that failed to. The WBPH that inoculated SRBSDV exhibited more probing bouts, salivation events and phloem sap ingestion events and longer salivation than those that failed to. The WBPH that acquired SRBSDV were quicker to reach phloem and spent more time in phloem sap ingestion than those that failed to. These behavior alterations in the vector may have adaptive advantages for SRBSDV transmission and spread success because greater salivation by viruliferous vectors on uninfected hosts will promote virus inoculation, whereas more sap ingestion by non-viruliferous vectors on infected hosts will promote virus acquisition.