Invasion and severe outbreak of the lotus lily midge Stenochironomus nelumbus Tok et Kur (Diptera: Chironomidae) in Indian freshwater ecosystems

摘要

This concise report of pest survey on Nelumbo nucifera describes 15 pest species on which 8 attack the leaves. The pest is reported to have attacked only rose-petalled subtropical Nelumbo nucifera and vulnerability of yellow-petalled temperate Nelumbo corniculatus was yet to be noted. Severe outbreak of Stenochironomus nelumbus was observed in Thirunavaya (Kerala, India) lotus fields since December 2005. The outbreak was initially reported by newspapers as extensive leaf-rotting disease. Laboratory examinations have proven the cause of leaf rotting as the mining of subcuticular parenchyma by the newly-hatched grub. Penetrated grub starts aggressive feeding to initiate brownish-black lesions on the upper leaf surface that quickly grow to 1.5-2.0 cm near-round galls with semitransparent cuticular roofing. Single larvae is accommodated in every gall with faecal matter piling in rail on either side. Approximately 10-50 galls are observed on every leaf during the peak season (first week of November to second week of March). Later the gall lesions coalesce together to start complete leaf rotting by the time the adults emerge.