Impact of changing temperature combinations on the biology and life table parameters of Nilaparvata lugens (Stål) (Hemiptera: Delphacidae)

AbstractNilaparvata lugens(Stål) (Hemiptera: Delphacidae) is one of the major insect pests of paddy crop which significantly reduces the quality and quantity of yield. The biology and life table parameters of this pest were studied at five set of controlled temperature combinations as 23:9, 27:12, 33:19, 36:23 and 39:27°C with 75 ± 5 per cent humidity and 14 h photoperiod under laboratory conditions. Different biological parameters like number of days for development, nymph survival, oviposition rate, adult longevity and reproductive parameters ofN. lugenswere influenced at different temperature combinations. Optimum temperature range lies between 27:12°C and 33:19°C as fecundity (102 ± 8.50, 112 ± 3.75), per cent egg hatchability (86.86 ± 1.21, 87.14 ± 1.99) and viability of fifth nymphal instar (57.4 ± 4.02, 58.20 ± 3.76) (mean ± standard error) respectively, were recorded higher than other temperature combinations. Various life table parameters like net reproductive rate, true generation time, true intrinsic rate of increase, finite rate of increase, doubling time and weekly multiplication rate of the pest also varied significantly among population at different temperature combinations. The net reproductive rate (163.49) and intrinsic rate of increase (0.1993 females female− 1day− 1) were maximum at 33:19°C. Generation time decreases significantly with increase in temperature. The finite rate of increase was 1.1522, 1.2004, 1.2227, 1.1321 and 1.1300 females female-1day-1at with multiplication rate of 2.8201, 3.5926, 4.2501, 2.3833 and 2.3821, respectively, at 23:9, 27:12, 33:19, 36:23 and 39:27°C temperature combinations. The relatively high values of population growth parameters suggest thatN. lugensthrive well at 33:19°C followed by 27:12°C temperature combinations. In the field conditions when the weather conditions tend to move towards this range of temperature combinations during the crop season, the farmers should be more cautious and frequently monitor the paddy crop to assess economic threshold level of BPH for timely remedial measures.