Submitted to: Environmental Entomology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/4/2013
Publication Date: 10/15/2013
Citation: Cao, T.T., Lou, Y.G., Backus, E.A., Cheng, J.A. 2013. Feeding-induced interactions between Nilaparvata lugens and Laodelphax striatellus: effects on feeding behavior and honeydew excretion. Environmental Entomology. 42:987-997. Interpretive Summary: Brown planthopper (BPH), Nilaparvata lugens, and small brown planthopper (SBPH), Laodelphax striatellus, are two of the most important insect pests on rice in Asia. Piercing-sucking feeding by these insects causes direct injury to rice plants, as well as transmits lethal plant pathogens. Rice breeders have spent many years developing varieties of rice that are resistant to these planthoppers, but recently the pests have adapted to overcome previously resistant rice. In addition, climate change is now causing greater seasonal overlap in the prevalence of these species, so that both co-occur during late summer and early autumn more often than before, causing increased rice damage. The present study used Electrical Penetration Graph (EPG) monitoring to study feeding of these two insects on rice plants that had previously been fed upon (without EPG) by the same or opposite planthopper species. Results showed that many measures of feeding were enhanced when SBPH fed on rice that had previously been fed upon by BPH; however, the reverse was not true. Therefore, facilitation of feeding was asymmetrical. These results explain how late-season damage from SBPH is probably made more severe by early-season BPH feeding in the same rice paddies. It also demonstrates why future feeding studies should incorporate effects from both species, rather than individually testing each species alone. It is expected that these findings will help aid development of the next generation of rice resistant to planthopper feeding.
Technical Abstract: Using Electrical Penetration Graph (EPG), salivary flange, and honeydew measurement, this study was conducted to investigate the effects of prior-feeding-induced intra- and inter-specific interactions on subsequent feeding behavior and excretion of rice planthoppers. Feeding of brown planthopper (BPH), Nilaparvata lugens, was compared with small brown planthopper (SBPH), Laodelphax striatellus, on two different rice varieties. Results showed that many measures of feeding behavior were affected by feeding-induced intra- and inter-specific interactions. For example, both BPH and SBPH made fewer salivary flanges on rice plants that had previously been fed upon by either the same (con-) species or the opposite (hetero-) species, compared with relevant control plants. However, when feeding-induced effects from con- vs. hetero-species were compared within each species, only SBPH showed significant differences. SBPH made fewer salivary flanges on plants previously fed upon by BPH, but not other SBPH. In addition, pathway activities and durations from 1st probe to 1st sustained phloem ingestion were shorter, while duration of phloem ingestion was longer on plants previously fed upon by BPH, compared with both control plants and plants with feeding-induced con-specific effects. Honeydew weights of SBPH also were increased from feeding-induced con-specific effects. The previous findings resemble those of planthoppers feeding on preferred host plants. Thus, all results indicate indirect, asymmetrical improvement, or facilitation, of the feeding behavior of SBPH from BPH-feeding-induced effects, on both rice varieties. These findings are consistent with previously documented asymmetrical effects on performance, demonstrating more benefits to SBPH from BPH feeding than the reverse. Change of nutrients and induced allelochemistry in host plant probably underlies these facilitative effects.