Laboratory-Estimation of Lower Temperature Threshold and Thermal Constant (DDs) for Development of Spodoptera frugiperda and Spodoptera littoralis (Noctuidae: Lepidoptera) under Varying Temperature Regimes and Host Plants

Document Type : Original Article

Authors

1 Department of Economic Entomology, Faculty of Agriculture, Mansoura University, Egypt

2 Sakha Research Station, Plant Protection Research Institute, Agricultural Research Center, Giza

Abstract

The fall armyworm, Spodoptera frugiperda and the cotton leafworm, Spodoptera littoralis are among the
most important pests attacking several plant species and causing economic losses. Although, polyphagous species
can feed on a wide range of plant species, they may perform more effectively when feeding on just one host plant
species or a limited number of species. In addition, temperature is an important ecological factor among others to
determine the rate of development, survival and other traits. Results revealed that there were significant effects of
host plant, temperature, and their interaction on total developmental times (egg-adult) of both insect species. Maize
seems to be suitable host for development of FAW, and soybean for CLW. The lower temperature thresholds (T0)
for FAW development were 14.74°, 16.05°, and 14.80°C on caster bean, maize, and soybean, respectively, while
they were 9.60°, 8.89°, and 12.93°C for CLW, respectively. The coefficient of determination (R2) was used to
determine the accuracy of the relation between temperature and developmental rates. On all host plants, R2 was
not less than 0.99 for both Spodoptera species which emphasized the powerful of the relation. For either insect
species, there were significant differences between thermal units (DDs) required for complete development of both
species on all host plants, with the highest thermal units were on caster bean (359 DDs for FAW and 579 DDs for
CLW). These theoretical estimates would be valuable in control decision making since it may enable to predict
with population peaks of each species under field conditions.

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