Probing behavior of the brown planthopper, Nilaparvata lugens Stål (Homoptera: Delphacidae) on a non-host barnyard grass, and resistant and susceptible varieties of rice

Abstract

The feeding activity of Nilaparvata lugens (Stål) (Homoptera: Delphacidae) was compared on the barnyard grass, Echinochloa Crus-galli var. oryzicola, which contains an antifeedant, (E)-aconitic acid, and on resistant (bph4) and susceptible rice varieties using an AC electronic monitoring system (EMS). N. lugens made more frequent probes on the barnyard grass and the resistant rice than on the susceptible rice. Mean duration of probes tended to be the shortest and the percentage of probes that consisted of the primarily salivation phase only was the highest on the barnyard grass, followed by the resistant rice. The most distinct difference in N. lugens feeding activities between the barnyard grass and the resistant rice was the frequency of the primarily ingestion phase. On the barnyard grass, the insect was rarely successful in achieving the primarily ingestion phase, indicating that probing was interrupted before the arrival of the stylets at the sieve elements. On the other hand, on the resistant rice the primarily ingestion phase was observed as frequently as it was on the susceptible rice. However, it stopped within 5 min on the resistant rice in most cases. Probing activities were strongly inhibited by 1% (E)-aconitic acid diluted with distilled water. The inhibitory effect was considerably mitigated when diluted with 15% sucrose. These results suggest that on the barnyard grass, interruption of probing activity by (E)-aconitic acid can occur in stylet pathway tissues rather than in ingestion tissues (e.g. the phloem where sucrose is located).