Feeding-induced interactions between Nilaparvata lugens and Laodelphax striatellus (Hemiptera: Delphacidae): effects on feeding behavior and honeydew excretion.

Using electrical penetration graph, salivary flange, and honeydew measurement, this study investigated the effects of feeding-induced intra- and interspecific interactions on feeding behavior and honeydew excretion of brown planthopper (Nilaparvata lugens) compared with small brown planthopper (Laodelphax striatellus). Results showed that many measures of feeding behavior were affected by feeding-induced intra- and interspecific interactions on two different rice varieties. There were significantly fewer salivary flanges for both brown planthopper and small brown planthopper on rice plants with feeding-induced conspecific or heterospecific effects than on relevant control plants. In contrast, only small brown planthopper on rice plants with feeding-induced heterospecific effects had significantly fewer salivary flanges than those with feeding-induced conspecific effects. The mean durations of pathway activities per insect and mean durations from first probe to first sustained phloem ingestion for small brown planthopper were significantly shorter, whereas the mean duration per insect of phloem ingestion was significantly longer, on rice plants with feeding-induced heterospecific effects than those on relevant control plants, as well as rice plants with feeding-induced conspecific effects. Honeydew weights of small brown planthopper were significantly increased by the induced heterospecific effect. Thus, all results indicated indirect, asymmetrical, facilitative effects of induced interspecific interactions on the feeding behavior and honeydew weight for small brown planthopper on both varieties. These findings are consistent with the previously documented asymmetrical effects on performance, with more benefits to small brown planthopper from brown planthopper indirectly. The change of nutrient and induced allelochemistry in host plant probably underlies these facilitative effects.