Impact of flood irrigation on defoliator attack in commercial teak plantation

摘要

Teak defoliator, Hyblaea puera Cramer (Lepidopetra: Hyblaeidae) is so serious a pest that it could reduce the current annual increment of its timber volume by 44 per cent. Several methods are employed to manage the pest (Sudheendrakumar, 1986). We observed in a commercial plantation that flood irrigation before the monsoon showers lowered the defoliator incidence. This note highlights the difference in defoliator attack between two irrigation systems in a 16-block commercial teak plantation at Veeravanallur in Tamil Nadu where drip irrigation was the normal practice in all blocks experiencing an acute water stress evident before the onset of North West Monsoon in 1996. Flushing started in drip irrigation blocks only after rainfall. On the other hand, a pocket of trees (around 500) in one of the blocks had received unplanned flood irrigation from a nearby newly sunk open well.