INSECTICIDE INDUCED RESURGENCE OF RICE BROWN PLANTHOPPER, Nilaparvata lugens (Stal) (Hemiptera:Delphacidae) AND MANAGEMENT WITH CERTAIN INSECTICIDES
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Date
2019
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Acharya N G Ranga Agricultural University, Guntur
Abstract
Indiscriminate use of insecticides is leading to resurgence of insect pests in various crops. Rice brown planthopper management has become very difficult due to its ability to develop resurgence to different insecticides regularly used by the farmers. Keeping this in view studies were initiated to find out the insecticides causing resurgence and their effect on biology of brown planthopper and also reasons for resurgence. Studies were also conducted to find out the effective insecticide rotations for management of BPH during kharif and rabi 2017-18.
Information generated on insecticide usage pattern adopted by the rice growers revealed that calendar based sprays irrespective of pest and disease incidence, use of non-recommended synthetic pyrethroids for controlling insect pests, application of insecticides at higher doses than the recommended level, mixing more than one pesticide (cock tails) to control insect pests and diseases simultaneously and defective spraying etc. are some of the practices followed by the rice growers contributing to the resurgence of brown planthopper infesting rice. Brown planthopper had two peaks with first peak during 41st SMW (i. e., second week of October 2016) followed by second peak during 43rd SMW (i. e., fourth week of October 2016) during kharif 2016. During rabi 2016-17, the activity of BPH was found initially low during 7th SMW (February 12-18) and gradually increased during successive standard weeks (8th-14th SMW) and reached the highest number during 14th SMW (i.e., first week of April). The incidence of WBPH attained peak initially during 38th SMW (September 17-23) and later during third week of October (42nd SMW) during kharif 2016, while in rabi 2016-17 first WBPH was noticed during 7th SMW (February 12-18) and population increased gradually during successive weeks and attained peak number during 13th SMW (March 26-April 1).
Brown planthopper had significant negative relationship with morning relative humidity of current week and sunshine hours of two weeks earlier but positive correlation with evening relative humidity two weeks earlier in kharif 2016. Maximum and minimum temperatures (current week, one week and two weeks
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earlier) and evening relative humidity two weeks earlier in rabi had significantly positive impact on population of BPH. White backed planthopper had significant negative relation with morning relative humidity of current week during kharif 2016. None of the abiotic factors has showed significant relationship with activity of WBPH during rabi 2016-17.
Field population of both BPH and WBPH had a positive relationship with light trap catches of planthoppers. The field populations of BPH and WBPH are in the proportion of 69.00 per cent and 31.00 per cent, respectively during kharif 2016 and 98.00 per cent and 2.00 per cent, respectively during rabi 2016-17.
Among fourteen insecticides screened in field during kharif and rabi 2016-17 for induction of resurgence in BPH, seven insecticides viz., chlorpyriphos, profenophos, deltamethrin, cypermethrin, bifenthrin, lambda cyhalothrin and imidacloprid significantly increased the population of N. lugens over untreated check and consequently resulted in higher resurgence, whereas the remaining i.e., acephate, monocrotophos, cartap hydrochloride, fipronil, chlorantraniliprole, buprofezin and pymetrozine can be used judiciously, with periodic monitoring for development of resistance and induction of resurgence.
The resurgence inducing mechanism of seven identified insecticides was studied in detail in green house experiments. The results revealed that out of seven insecticides applied at two doses (half of the recommended field dose and recommended field dose), four insecticides viz., cypermethrin, deltamethrin, bifenthrin and lambda cyhalothrin significantly enhanced the reproductive rate (153.67 to 227.67 nymphs / 2 females) of N. lugens and consequently resulted in higher resurgence ratio (1.17 to 1.74 folds). Increase in feeding index (144.33 mm2 to 496.00 mm2 honey dew area), growth index (6.35 % to 7.11 %) and sex ratio in favour of females (1.39 to 1.84 females per 1 male) were the additional factors contributing to the resurgence in the population of the brown planthopper caused by the application of synthetic pyrethroids. While chlorpyriphos, profenophos and imidacloprid resulted in brown planthopper resurgence through changes in the nutritional quality of the host plant that may favour the phytophagus herbivores as indicated by the increased feeding indices (135.33 mm2 to 326.33 mm2 honey dew area).
The results obtained from both field and green house experiments in the present investigation revealed that insecticide induced resurgence in the populations of brown planthopper is due to the direct stimulatory effect on the reproductive potential of the insect, indirect effect through favourable changes in the nutritional quality of rice plant and selective destruction of natural enemies.
Field experiments carried out during kharif and rabi 2017-18 revealed that fipronil (1000 ml ha-1) followed by pymetrozine (300 g ha-1), buprofezin (800 ml ha-1) followed by pymetrozine (300 g ha-1) and acephate (750 g ha-1) followed by pymetrozine (300 g ha-1) were the most effective insecticide rotations in the management of brown planthopper and recorded higher grain yields. With regard to cost benefit ratio, insecticide rotations, acephate (750 g ha-1) followed by pymetrozine (300 g ha-1) and fipronil (1000 g ha-1) followed by pymetrozine (300 g ha-1) had the highest cost benefit ratio of 1: 6.01 and 1: 6.03, respectively. Buprofezin (800 ml ha-1) followed by pymetrozine (300 g ha-1) and fipronil (1000 ml ha-1) followed by dinotefuran (250 g ha-1) are the next best rotations with cost benefit ratioof 1: 5.87 and 1: 5.07, respectively.
Description
D5935
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