Evaluation of linear and nonlinear models for temperature driven development of Spodoptera litura (Fabricius) on soybean crop

Y.g Prasad Y.G Prasad,G Rekha G Rekha,M Gayathri M Gayathri,G.ramachandra Rao G.Ramachandra Rao,M Prabhakar M Prabhakar,V Sailaja V Sailaja,S Vennila S Vennila

doi:10.54386/jam.v23i2.63

Abstract

 The tobacco caterpillar, Spodoptera litura, a major pest of soybean in India is under surveillance in all soybean growing areas in Maharashtra in order to issue alerts to farmers and prevent economic losses. In this context, two linear models were fitted to developmental data of S. litura life stages reared on soybean at five constant temperatures viz. 15, 20, 25, 30 and 35°C through laboratory experiments. Optimum temperature for development (Topt) and upper temperature threshold (Tmax) were estimated from three nonlinear models by additionally including developmental response at >35°C. Topt estimates for the total immature development were 34.5°C (Lactin-2), 33.7°C (Briere-1) and 33.2°C (Simplified Beta type function) while Tmax estimates were in the range of 38 to 40°C. Application of a thermodynamic non-linear model (Optim SSI) gave estimate ofintrinsic optimum temperature (Tφ) for development of egg (28.3°C), larva (27.5°C) and pupal stage (30.3°C). The phenology model of S. litura on soybean based on estimated developmental threshold temperatures and thermal constants was validated using available field surveillance data to facilitate informed pest management decisions.

Highlights

Spodoptera litura (Lepidoptera: Noctuidae) is an economically important pest on several crops and incidence of the pest often crosses economic threshold level on several field crops including soybean
Bioclimatic parameter estimates from this study were useful in predicting the timing of S. litura on soybean in area-wide pest surveillance and issue of pest management advisories
Evaluation of both linear and nonlinear models and comparison of parameter estimates with other S. litura populations reported on other hosts was helpful in arriving at more precise estimates necessary for practical field application

Summary

Introduction

Spodoptera litura (Lepidoptera: Noctuidae) is an economically important pest on several crops and incidence of the pest often crosses economic threshold level on several field crops including soybean. Outbreak of S. litura on soybean has become a challenge for its management on soybean in India (Prasad et al, 2013).Temperature is a key factor for driving insect development (Pedigo 1989). Most studies on the developmental biology of S. lituraon several hosts analyzed linear response to constant temperatures in the range of 15 to 40°C (Ranga Rao et al, 1989; Qin et al, 2002; Manimanjari et al, 2014; Srinivasa Rao et al, 2014). The estimates of bioclimatic thresholds and constants are useful in phenology modelling and comparative analysis of different geographical populations. Field application of the model makes it possible to issue pest alert advisories to soybean farmers for informed pest management decisions

Methods

Results

Conclusion