Publication | Open Access
Effect of Constant and Variable Temperatures on Biological Parameters of Rice Brown Planthopper, Nilaparvata lugens (Stal)
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2005
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BotanyInsect ConservationEntomologyTropical Insect ScienceVariable TemperaturesAdult Life SpanPublic HealthBiological ParametersPlant-insect InteractionRice Brown PlanthopperPest ManagementBiologyTerrestrial ArthropodBph MultiplicationNatural SciencesEvolutionary BiologyCrop ProtectionBrown PlanthopperPest ControlEcophysiologyPopulation Development
The effect of six constant temeperatures (10°C, 15°C, 20°C, 25°C, 30°C and 35°C) and two relative humidities (70% and 90%) on the biological parameters of brown planthopper (BPH) viz., the duration of egg and nymphal instars, adult longevity, fecundity, % survival of nymphs, as well as proportion of macropterous and brachypterous and females was studied with the aid of environmental chamber. The egg period was reduced from 14.18 days at 15°C to 6.32 days at 30°C; nymphal period was lowered from 29.16 days at 15°C to 11.88 days at 30°C while adult life span was 19.6 days at 15°C, 30 days at 20°C and 11 days at 30°C. The fecundity was lower (88 to 94) at 15 and 20°C compared to 194 to 217 at 25°C and 30°C. The proportion of brachypterous forms was higher at 15, 20 and 25°C (85 to 95%) compared to 30°C(72%). An increase of RH from 70% to 90% reduced egg period from 10.41 to 9.38 days an increased adult life span from 12 to 16.4 days. The results on the effect of variable temperatures on BPH suggested that variable temperatures (represented by their means) are more favourable for BPH multiplication than the corresponding constant temperatures. Adult life span of all the forms and sexes was uniform under each of the environmental condition. The threshold temperature for egg and nymphal development were 8.4 and 8.24°C respectively. However, the day degree requirement for egg and nymphal development varied considerably at different constant and variable temperature conditions. Day degree requirement for egg development at different constant and variable temperatures was 93.5 to 172.8 and 172 to 232 while for nymphal development corresponding figures were 197.5 to 258.7 and 300 to 427 respectively. It is concluded that temperatures ranging from 25 to 30°C and 70 to 90% RH are favourable for multiplication of BPH and the insect cannot tolerate > 35°C of constant temperature and >47°C of variable temperature during 24 hours period. BPH cannot survive and multiply at 10°C or below under tropical conditions.