Biology, host range and natural enemies of corn planthopper, Stenocranus pacificus Kirkaldy

Stenocranus pacificus, Kirkaldy (Hemiptera: Fulgoroidea:Delphacidae) is a new pest attacking corn growing areas of Region 12 later of 2003. By first quarter of 2004, almost all the corn areas of Mindanao were devstated expanding, from Region 12 [Central Mindanao, Philippines] to Regions 9, 10, 11, ARMM to Caraga and just August 2006, was observed at Camarines Sur particularly Pili, Buhi, Iriga, Legaspi and other municipalities. This study on biology shows that, aside from being a sucking pest, the honey dew excreted serves as an avenue for the growth of sooty mold, a fungus disease. The female of the species has a white waxy substance in the abdomen, which was absent in the male, more robust, 4.5 to 5 mm in size, the male was slender 4.0 to 4.2 mm in size. The female imbed its egg in the midrib and leaf sheath using its saw like ovipositor. The eggs were inserted singly its posterior and positioned near the entrance holes which was also its exit hole. After oviposition, the female sealed its eggs using the white waxy substance in the abdomen, the male always visible. Number of eggs deposited ranges from one to twenty four per oviposition sites. Incubation period was 12-14 days with four nymphal instars averaging 3-4--4--4, life span of the adult was 7 to 10 days. Number of eggs laid by the female was 180 to 210. Color of nymphs varies from whitish upon emergence to yellow green on second instars and turn to brown in later instars and orange brown adult. Three species of grasses were identified as alternate host namely Roettbella cochinchinensis, Echinochloa colona, Eleusine indica and Sorghum bicolor. Many species of natural enemies were feeding on pests, predators such as coccinellid beetles, different species of spiders, dermapteran, syrphid flies, dragon flies, damselflies, lacewings and egg predator Cyrtorhinus lividipenis, a Strepsipteran and a pathogen Metarhizium anisoplae.