Report on the occurrence of summit disease syndrome in rice brown planthopper, Nilaparvata lugens (Stal) (Delphacidae: Homoptera)

Abstract

Naturally mycosed field population of the Rice Brown Planthopper (BPH), Nilaparvata lugens (Stal) was observed in a farmer’s rice field in Andhra Pradesh. The adult insects exhibited typical Summit Disease Syndrome (SDS), which is considered to be a fungal-mediated behavioural change in the host. The infected insects, fully or partially covered with mycelial growth, were found firmly clinging to the tip of the leaves as solitary ones or in cohorts of 2, 3 or 4. They were immobile, either dead or in moribund state. Such insects, collected from the leaf tips along with live insects from the base of the plants, were examined in the laboratory. The preliminary microscopic observations showed the presence of micro and macroconidia which resembled Fusarium species. The resident Yeast-like symbiotes commonly present in healthy individuals were absent in live adults and nymphs of BPH collected from the infection site. Our present findings have contributed to an important knowledge in the area of insect pathogens and this could dislodge the notion that hyphomycetous fungi do not influence SDS in their hosts. The occurrence of Summit Disease transmissions in BPH suggests that this association must have been highly evolved. These preliminary investigations are likely to arouse interest to look deep in to this host-pathogen relationship. Further research directions are suggested that may shed more light on the subject. This appears to be the first report on Summit disease syndrome in Rice brown planthopper.