Tomato fruit borer, Helicoverpa armigera Hubner is a cosmopolitan, polyphagous pest, distributed widely in Indian subcontinent (Sing et al.

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1 Incidence and abundance of tomato fruit borer, Helicoverpa armigera (Hubner) in relation to the time of cultivation in the northern parts of West Bengal, India Kaushik Chakraborty*, Revadi Santosh and A. K. Chakravarthy *Department of Zoology, Alipurduar College, Alipurduar, Jalpaiguri West Bengal, India Department of Agricultural Entomology, University of Agricultural Sciences, GKVK, Bangalore , India * Incidence and abundance of tomato fruit borer, Helicoverpa armigera (Hubner) is dependent on both the climatic parameters and the growth stage of the tomato crop. Time fitted tomato cultivation as a part of modern IPM is thus found indispensible to minimize H. armigera menace in the northern parts of West Bengal, India where tomato is grown on commercial scale. In order to suppress H. armigera induced damage, field experiment for three consecutive years ( ) under four alternative time schedule (early, middle, late and very late) was carried out in pesticide untreated field of tomato cultivar Pusa ruby at Raiganj, Uttar Dinajpur, West Bengal. Maximum (24.43 individuals/ 5 plants) and minimum (13.92 individuals/ 5 plants) pest incidence was noted when transplantation was done at 12 and 7 standard meteorological weeks (SMWs) respectively. The extent of damage by larval population was comparatively higher as the plantation date advances. Early transplantation was thus found economically prudent to avoid fruit borer menace. Variable impact of the climatic factors on the borer incidence was accordingly also noted to generate a time fitted cultivation schedule. Tomato fruit borer, Helicoverpa armigera Hubner is a cosmopolitan, polyphagous pest, distributed widely in Indian subcontinent (Sing et al., 1990, Fenemore, 1990). Apart from tomato, H. armigera is reported to infest cotton, maize, chickpea, pigeon-pea, sorghum, sunflower, soyabean and groundnut (Fitt, 1989). Larvae affect almost all the aerial parts of the tomato plant from the early growth till to the fruit maturation stage ( Lal et al., 1996, Tripathy et al., 1999). Loss incurred to growing tomato crop is insurmountable and may extend up to per cent in Punjab (Sing et al., 1990); per cent in Bangalore (Khaderkhan et al., 1997) and per cent in Madhya Pradesh (Ganguly et al., 1998). Severe infestation causes necrosis to the leaf chlorophillus tissue, suppresses tomato flowers to bloom and makes the mature fruit unfit to consume (Jallow et al. 2001). In Jalpaiguri, Bengal considerable losses to tomato due to this pest have been reported (Chaudhuri, 2000). Due to the absence of suitable scientific protocol, tomato is commercially grown in northern parts of Bengal by conventional cultivation practices without any specific time schedule. Among the northern parts, the district Uttar Dinajpur offers a congenial environment for tomato cultivation. Farmers do follow irregular planting dates disregarding the incidence of borer population. Time fitted transplantation with the selection of resistant varieties as a part of modern integrated pest management (IPM) package can thus minimize fruit borer menace. 91

2 Experimental layout: Incidence and abundance of H. armigera larvae was recorded in four timeslots of cultivation and was assessed in consideration of standard meteorological weeks (SMWs). Field study was conducted by RBD in in pesticide untreated field of tomato cultivar Pusa ruby at Raiganj [ 25 o 57 N 27 o N 88 o o 54 E], Uttar Dinajpur, West Bengal. Transplantation was done with 25-days old seedlings at 50x65 cm seedling spacing; and in a succession of 15-days intervals and in four separate plots on 44 SMW (early), 46 SMW (middle), 48SMW (late) and 50 SMW (very late), respectively. Incidence of borer larvae was recorded from 5 randomly selected plants from vegetative growth stage till to the fruit maturation and the average was worked out. Extent of damage was recorded 75-days after transplantation, in terms of the number of fruits bearing larval puncture points. There were three replications for each of the experiment years. Larval counts were correlated with climatic factors as maximum temperature (Tmax), minimum temperature (Tmin), temperature gradient (Tgr), maximum humidity (RHmax), minimum humidity (RHmin), humidity gradient (RHgr), sunshine hour (Shr), rainfall (Rfall) and rainy days (Rdays). Incidence of borer population in relation to time of cultivation (Table 1 and Fig 1): Initially the number of borer larvae was low during transplantation. Borer larvae attained the maximum at midvegetative stage. In early sown crop, infestation was initiated at 7 SMW and attained maximum damage of per cent at about 13 SMW. In middle sown crop, infestation was initiated at 9 SMW and maximized at 16 SMW scoring the highest level of damage of per cent. In late sown crop, the larval number was noticed from the beginning of crop establishment (at 11 SMW) which reached the maximum damage of per cent at 16 SMW. In very late sown crop, fruit boring started from 13 SMW and gradually increased attaining the maximum of per cent at 16 SMW. The average incidence was significantly highest in very late sown crop (17 per cent) and the lowest in early sown (7.65 per cent) crop. The middle and late sown crop witnessed 8.74 per cent and 9.91 per cent attack, respectively. In consideration of overall dynamics, extremely low population at early growth stage of tomato plant increased very rapidly and forms the first peak. In a single crop cycle two larval peaks were noted. The first one was found at about SMW. This was followed by sharp fall of the larval population. The next peak of comparatively lower larval incidence but of consistent in nature was generated at about SMW. However, after the second peak substantial number of larval population was found in the field. The population then subsumed gradually as the crop matures. Extent of fruit damage by H.armigera was in average per cent, per cent, per cent and per cent when transplantation was done at 44 SMW (early), 46 SMW (middle), 48SMW (late) and 50 SMW (very late) respectively. Grossly, in consideration of all the time schedule of cultivation, the maximum damage period of fruit borer incidence was initiated at about 13 SMW and continued up to 19 SMW, covering the maximum growth stages of the tomato plant. The plant protection schedule should be fitted accordingly. Incidence of fruit borer was more or less consistent with time showing definite pattern in all the years. However, irrespective of time slots of cultivation, 92

3 high level of borer infestation was noted from 14 to 17 SMW. Theoretically, the period of borer infestation was longer in early sown tomato crop followed by middle sown and late sown crop and the least being noted in very late sown crop. The duration of borer infestation was related to the duration of crop pest interactive time more precisely at fruit stage of the crop. The crop duration vis-à-vis fruiting stage was comparatively longer when early sowing date was adopted, offering congenial situation for maximum period of plat-pest interaction. But when an early plantation was done, the existing climatic parameter has a suppressive function on larval growth and hence the extent of damage was low. So the overall result was low larval numbers and incidence with least range of fruit damage. Incidence of borer larvae in relation to climatic parameters (Table 2): Correlation value between important weather parameters and the incidence of borer population on crop planted at different times varied considerably. Except in early sown crop, maximum temperature (Tmax), minimum temperature (Tmin) and temperature gradient (Tgr) showed significant positive relation with borer larval population on all the planting dates. However, average temperature (Tavg) imparted significant positive effect on all the planting dates. Effect of maximum relative humidity (RHmax) was negative in early and middle sown crops but for late and very late crops it was positive. Except early sown crop where it was negative, the effect of average relative humidity (RHavg) was positive for all other plantation periods. Further, apart from middle sown crop the overall effect of average relative humidity (RHavg) was significant. Irrespective of the planting date effects of sunshine hours (Shr), rainfall (Rfall) and number of rainy days (Rdays) were negative at 5% level of significance. The incidence of fruit borer is governed by both the fruiting stage of the crop and the time of plantation. Fruit damage was the lowest in early sown crop (2.01 per cent) and gradually increased and reached the highest level in very late sown crop (24.43 per cent) during late sown. Temperature has grossly imparted positive effect on borer larval numbers. Late sowing and transplantation is discouraged as ambient temperature gradually increases and has adverse effect on tomato plant growth including fruit maturation. Impact of other climatic factors has definite effect throughout the cultivation time. Chaudhuri (2000) forms Cooch Behar, West Bengal have reported very high loss of tomato due to borer infestation. But in the present study the extent of loss is comparatively moderate. Present observations are supported by Sing (1984) who has also noted that fruit borers lay eggs on buds and flowers of tomato and subsequently attack on developing fruits. All these activities were influenced by climatic factors. Walker and Cameron (1990) have noted high fruit borer population ranging from 6 to 10 SMW. Lal et al. (1996) have also observed maximum borer infestation at the end of March in each year. Minimum yield gain was registered by Sharma et al. (1997) when transplantation was done at 28 th March and 12 th April, respectively. In Haryana, maximum borer infestation was reported to occur in May (Kalra, 1992) which partially corroborates to the present study. H. armigera infestation was comparatively low in early planted tomato. Borer infestation increased as planting was delayed by 15 days. 93

4 CONCLUSION The incidence of larval populatoin of tomato fruit borer, H. armigera was recorded across all the stages of the crop in four specific time slots. Results showed that the population reached the peak during the fruiting stage of the crop resulting in the higher fruit damage. The number comes down as the cropping age reaches the terminal stage. Grossly the damaging potentiality of larval population begins from 9 SMW and continues to 17 SMW, there is a positive correlation between the larval number and number of weeks after transplation. Later the population comes down in a similar fashion. From this observation is found that the incidence and abundance of tomato fruit borer, H. armigera (Hubner) is dependent on both the climatic parameters and the growth stage of the tomato crop. Time fitted transplantation of tomato seedlings at early months as a part of modern IPM is thus found indispensible to minimize H. armigera menace in the northern parts of West Bengal, India. REFERENCES Casimero, V., Tsukuda, R., Nakasuji, F. and Fujisaki, K., 2000, Effect of larval diets on the survival and development of larvae in the cotton bollworm, Helicoverpa armigera Hübner (Lepidoptera: Noctuidae). Applied Entomology and Zoology, 35: Chaudhuri, N., 2000, Insect pest constrains of tomato (Lycopersicon esculentum Mill.) and their management under terai region of West Bengal. Ph.D thesis submitted to the University of North Bengal. Raja Rammohanpur, Darjeeling West Bengal. Fenemore, P. G. and Thanee, N., 1990, Oviposition preference and larval food quality in Helicoverpa armigera. Symp. Biol. Hung. 39: Fitt, G.P., 1989, The ecology of Heliothis in relation to agro ecosystems. Annual Review of Entomol., 34: Ganguly, R. N. and Dubey, V. K., 1998, Management of tomato fruit borer Helicoverpa armigera Hubner in Chhattishgarh of Madhya Pradesh. Insect Environment, 4(1): 25 Jallow, M. F. A., Matsumura, M. and Suzuki, Y., 2001, Oviposition preference and reproductive performance of Japanese Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae). Applied Entomology and Zoology 36: Kalra,V. K.,1992., Heliothis armigera Hubner on tomato incidence and extent of damage-a note. Haryana. Journal of Hotricultural Sciences 21(3-4): Khaderkhan, H., Natarajan, M.S. and Nagaraja, G. N., Economics of IPM in tomato, I st Nat. Symp. On pest management in Horticultural crops: Environmental implications and thrusts, October 15-17, Bangalore. 8 Lal, O.P. and Lal, S. K., Failure of control measures against 94

5 Heliothis armigera (Hubner) infesting tomato in heavy pesticidal application areas in Delhi and satellite towns in western Uttar Pradesh and Haryana (India). Journal Entomological Research, 20(4): Sharma, D. K., Sharma, I. M. and Sharma, J. P., 1997, Effect of different dates of planting on fruit yield and losses caused by fruit borer and different diseases in tomato (Lycopersicon esculentum Mill.) Cv. Roma. Indian Journal Hill Farming,10 (1-2): Sing, D. and Narang, D. D., 1990, Control of tomato fruit borer Heliothis armigera Hubner with synthetic pyrethroids. Indian Journal of Entomology, 52(4): Sing, H.,1984, Household and kitchen garden pests- principal and practices. Kalyani publishers. India.pp Tripathy, M. K., Kumar, R. and Singh, H. N., 1999, Host range and population dynamics of Helicoverpa armigera Hübn. in eastern Uttar Pradesh. Journal of Applied Zoological Research 10: Walker, G. P. and Cameron, P. J., 1990, Pheromone trapping and field scouting for tomato fruit worm in tomatoes and sweet corn. Proceeding of the forty-third New Zealand Weed and pest Control Conference.pp

6 Table 1: Per cent bored tomato fruits due to H. armigera in relation to the time of sowing SMW Incidence of bored fruits (%) in relation to sowing periods Early (44 SMW) Middle (46 SMW) Late (48 SMW) Very late (50 SMW) (1.63) # (2.26) (2.78) 6.78(2.70) (2.57) 7.45(2.82) (3.20) 9.12(3.10) 7.67(2.86) (3.70) 10.12(3.26) 8.45(2.93) (3.76) 9.72(3.20) 7.56(2.84) 8.56(3.01) (3.46) 11.45(3.46) 13.34(3.72) 9.21(3.12) (3.17) 17.56(4.25) 21.11(4.65) 10.11(3.26) (2.78) 18.45(4.35) 13.05(3.68) 24.43(4.99) (2.62) 13.11(3.69) 13.52(3.74) 13.92(3.79) (1.58) 10.42(3.30) 9.67(3.19) 9.51(3.16) (2.68) 8.91(3.07) 8.45(2.99) (1.57) 7.56(2.84) 7.85(2.89) (2.63) 7.35(2.80) (1.58) 7.25(2.78) (2.59) (2.26) (-): No crop period # Figures in the parentheses are square root transformed values Table 2: Correlation coefficient of borer larval numbers with climatic factors Climatic parameters Correlation in consideration of time of sowing early (44SMW) middle (46 SMW) late (48 SMW) very late (50 SMW) Maximum temperature (Tmax) * 0.655* 0.788* 0.871* Minimum temperature (Tmin) * 0.721* 0.821* 0.932* Temperature gradient (Tgr) * 0.734* 0.821* Average temperature (Tavg) 0.713* 0.742* 0.812* 0.911* Maximum humidity(rhmax) * * 0.722* 0.873* Minimum humidity (RHmin) * 0.756* 0.832* Humidity gradient (RHgr) * * * Average humidity (RHavg) * * 0.851* Sunshine hours / day(shr) -0566* * -0663* Rainfall (Rfall) -0611* * -0732* -0811* Rainy days (Rdays) -0602* -0710* -0621* -0507* *Significant at 5% level 96

7 Fig.1: Incidence of fruit borer population in relation to standard meteorological weeks (SMWs) in consideration of all the time slots of cultivation in average [MS received: ; MS accepted: ] 97