Population dynamics and host preference of a major pest, Scirpophaga incertulas Walker (Pyralidae: Lepidoptera)
Souren Dutta, Nayan Roy
In this modern era with increasing human population there is a need to increase rice production per unit of land through sustainable management strategies. The stage-specifc life table study of this notorious rice pest, Scirpophaga incertulas, also known as yellow stem borer (YSB), will be useful for their sustainable ecological management in the field. It helps to understand their population dynamics for safer and ecofriendly management of the pest. The life table study of S. incertulas on rice (Oryza sativa [R]) and non rice [NR] weed (Echinochloa colona) showed four distinct stages with five larval instars and represent similar pattern of development with significant variations (P< 0.001). The gross reproductive rate (GRR) and net reproductive rate (R0) on R was significantly higher than NR weed which ultimately influence the fecundity. The rm, λ, Tc and DT of S. incertulas on R plant was significantly higher than NR weed. These differences in the demographic parameters are due to the variation in their nutritional quality of respective kind of host plants. So, for first step management of the notorious insect pest, S. incertulas, is very essential to weed the NR areas which ultimately would reduce the population size of the pest in the field condition. Their further management strategies may include different ecofriendly control measures guided by their population parameters. At this point population dynamics based ecofriendly approaches would obviously help in the conservation of natural enemies which would bring down the pest load below economic threshold (ET) and eventually lower broad spectrum pesticides use which generally brings pest resurgence and pest resistant problems. There may be few limitations in the methodical scientific study but this particular population dynamics based study somehow has triple- E (Environmental, Ecological and Economical) sustainability for any kind of pest management in near future.