BIOLOGICAL CONTROL OF CHILO PARTELLUS USING EGG PARASITOID TRICHOGRAMMA CHILONIS AND BACILLUS THURINGIENSIS

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1 Indian J. Agric. Res., 40 (3) : , 2006 BIOLOGICAL CONTROL OF CHILO PARTELLUS USING EGG PARASITOID TRICHOGRAMMA CHILONIS AND BACILLUS THURINGIENSIS S.K. Jalali and S.P. Singh Project Directorate of Biological Control, Post Bag No. 2491, H.A. Farm Post, Bellary Road, Bangalore , Karnataka, India ABSTRACT The results of the trial showed that the parasitism rates by Trichogramma chilonis on Chilo partellus eggs on fodder maize were up to 75.2 and 62.6% in 1 st and 90.4 and 78.4% in 2 nd generation egg laying in three and five days interval parasitoids releases plots. Stem tunnelling by larvae was 1.8 and 2.4 cm in three, five days interval released plots compared to 7 cm per infested plant in untreated control plots. The combined application of T. chilonis and Bt resulted in significantly less pest infestation and stem tunnelling compared to individual treatments. Considering cost factor, releases of T. chilonis at 5 days interval 3 times in 1 st and 2 times in 2 nd generation of the pest is the best treatment for effective control. INTRODUCTION Stem borer, Chilo partellus (Swinhoe) is most important and destructive pest of maize and sorghum is widespread in Asia and Africa. If heavy infestation occurs in young plants stage, the crop has to be re-sown (Fletcher and Ghosh, 1920). If plants are attacked at a more mature stage, the damage is less devastating. However, the loss can still be per cent of the potential yield (Starks, 1969; Warui and Kuria, 1983; Jalali and Singh, 2002). Conventionally this pest is mainly suppressed by use of hazardous chemical pesticides. Biological control program would allay safety concerns related to insecticides. Amongst various natural enemies, trichogrammatids are most widely used biological control agents in the world. Trichogramma spp. have been released world over in different dosages for control of European corn borer, Ostrinia nubilalis (Hubner) in Europe (Hassan et al., 1986), in USA (Losey et al., 1995) and in China against Asiatic corn borer, O. furnacalis (Guenee) (Zhang, 1986). Smith (1996) observed that native species of natural enemies is always most fit and adapted to local agro-climaitc conditions and ecosystem. Jalali (2000) reported Trichogramma chilonis Ishii (maize ecosystem adapted strain) and B. thuringiensis as most promising biological control agents for test against C. partellus. In the present study, this strain and Bacillus thuringiensis Berliner alone and in combination were used to develop biological control strategy for C. partellus. Most of the broad-spectrum pesticides can not be integrated with parasitoid as they were extremely toxic to Trichogramma spp. (Jalali and Singh, 1993), but B. thuringiensis can be integrated since it is found to be fully compatible with Trichogramma spp. (Jalali, 2000). In contrast to earlier studies where only level of parasitism was considered, in the present study impact of treatments on pest infestation, larval population reduction, stem tunnelling and yield data was also recorded to prove the potential of biological control programme. MATERIAL AND METHODS Field trial was carried out during kharif (monsoon) season in Bangalore, which is main cropping and pest activity season. The crop was raised in the third week of July. After one week of germination, virgin female in modified Delta traps were kept for the monitoring of the pest as advocated by Jalali and Singh (2001). The treatments were imposed after first moth trap in the pheromone traps. The

2 Vol. 40, No. 3, plot size was 6 x 4 m and each treatment was replicated 5 times. The treatments were: Sr. No. Treatment details Short form T 1 Release of T. chilonis (maize 00,000/ha with 3 days interval Tc 8R five times during first generation and three times during second generation to cover entire egg laying period T 2 Release of T. chilonis (maize 100,000/ha with 5 days interval Tc 5R three times during first generation and two times during second generation to cover entire egg laying period T 3 Release of T. chilonis (maize 100,000/ha with 3 days interval Tc 8R and Bt 2S five times during first generation and three times during second generation to cover entire egg laying period and spraying of Bacillus thuringiensis (Dipel 8L) one week after peak egg deposition, one spray in each litre/ha T 4 Release of T. chilonis (maize 100,000/ha with 5 days interval Tc 5R and Bt 2S three times during first generation and two times during second generation to cover entire egg laying period and spraying of B. thuringiensis (Dipel 8L) one week after peak egg deposition, one spray in each litre/ha T 5 Spraying of B. thuringiensis (Dipel 8L) one week after peak egg deposition, Bt 2S once in each litre/ha T 6 Spraying of B. thuringiensis (Dipel 8L) twice in each generation, Bt 4S one week after peak egg deposition and second spray with the gap of one litre/ha T 7 Untreated control U T C Each treatment was separated by 50 m row for local control. Trichogramma chilonis was released as parasitized card just before their emergence, i.e. on 8 th day after parasitisation. Each card was cut and stapled on the lower side of the 1 st leaf and bits were stapled at a distance of 5m, thus in each plot parasitized card bits were stapled at five places. Bacillus thuringiensis was sprayed one week after egg laying when larvae were in 1 st and 2 nd instar stage inside the whorl. The sprays were directed in the whorls only. The observations on per cent infestation, per cent egg parasitism, reduction in larval population, number of larvae per infested plant, stem tunnelling and the yield data was recorded. Egg parasitism was recorded by placing laboratory reared C. partellus egg card. In each plot, one egg card containing about 50 eggs was kept and collected back 24h after exposure in the field. Thus for each treatment 5 cards were placed on each observation date. The egg card was placed one day after release of parasitoids. In first generation, egg parasitism was recorded three times after 1 st, 3 rd and 5 th release, while during the second-generation egg parasitism was recorded two times, after 1 st and 3 rd releases. The per cent reduction in larval population was recorded by collecting 5 infested plants from each untreated plot. Thus, 25 plants were collected from untreated control for each treatment. All plants were brought to the laboratory and were methodically examined for presence of larvae. Similarly, in all treatments, five infested plants were collected from each plots, thus 25 plants were collected and number of larvae were counted. Per cent reduction was calculated based on larvae obtained in untreated plants and treated plants. The larval population was recorded at the end of each generation and at harvest in T. chilonis released plots and during each generation after one week of spraying of B. thuringiensis and at harvest. The per cent infestation was recorded

3 186 INDIAN JOURNAL OF AGRICULTURAL RESEARCH during 1 st, 2 nd generations and at harvest by selecting 25 infested plants randomly in each replication, thus 125 plants were observed in each generation and per cent infestation was derived. Number of larvae per infested plants was observed by collecting 5 infested plants from each treated and untreated plots. Thus, 25 plants were collected from treated and untreated plots. All plants were brought to the laboratory and were methodically examined for presence of larvae. The data on stem tunnelling was also recorded by cut opening five plants in each plot and measuring tunnelled portion at harvest determined for each treatment. At harvest, yield was recorded in each treatment plot and was converted to hectare basis. The experimental design was randomised block design and two-way analysis of variance (ANOVA) was carried out for egg parasitism, per cent larval population reduction; per cent infestation and no. of larvae per infested plant and one-way ANOVA was carried out for data on stem tunnelling and yield. The percentage data was transformed by arcsine transformation before analysing the data. RESULTS AND DISCUSSION Parasitism rates (on the placed egg masses) in fodder maize plants was and % after first release in plots where T. chilonis was released at Tc 8R and Tc 5R compared to UTC where 7.8% parasitism was recorded. The parasitism was significantly higher in plots where parasitoids were released at Tc 8R and it rose to 75.2% compared to 62.6% in Tc 5R released plots. However, in both plots parasitism differed significantly with untreated control (Table 1). Parasitoids releases during 2 nd generation egg laying resulted in parasitism rates increasing up to 90.4 and 78.4% in three and five days interval parasitoids releases. Parasitoids could survive on eggs laid by moths emerging between two main generations and parasitoids could colonise in released plots. In UTC, however, maximum parasitism obtained was 16.8%. The results of the study confirmed the effectiveness of predicting the flight activity period for the management of stem borer in the field. In the present study, % parasitism obtained in plots where T. chilonis was released 500,000 and 800,000/ha/season was higher than those reported for European corn borer in USA (Kanour and Burbutis, 1984), in Europe (Hassan et al., 1986; Raynaud and Crouzet, 1985). Releases of Trichogramma with 3 or 5 days interval seems most appropriate based on parasitoid longevity, which is 5 days. In all previous studies parasitoids were released at 7 or 10 days interval and eggs may escape parasitism if released with longer gap. Therefore, in the present study parasitism obtained was higher. In parasitoids released plots, larval population reduction was significantly higher in first generation compared to second generation or at harvest. Our results agrees with prediction of Kanour and Burbutis (1984) that parasitism rate of above 80.0 per cent would be necessary for economical control of corn borer as yield in plots with >80.0 per cent parasitism resulted in 61.1 to 72.1% more yield than control. One or two sprays of Bacillus thuringiensis in each generation did not enhance larval mortality greatly. The sprays were more effective during first generation of the pest compared to second generation. The larval population result indicated that B. thuringiensis did not persist for long in the field and at harvest, mortality declined in all treatment plots (Table 2). Percent infestation differed significantly between treatments at harvest and in both treatments it varied significantly with UTC (SEM = 1.4, CD = 4.0, P = 0.05). The combined application Tc 8R + Bt 2S or Tc 5R + Bt 2S resulted in significantly less pest infestation (6.3 and 8.0%) compared to Tc 8R and Tc 5R plots or Bt 2S or Bt 4S

4 Vol. 40, No. 3, Table 1. Egg parasitism of Chilo partellus by Trichogramma chilonis in various treatments Treatments Per cent egg parasitism (during) B factor mean 1 st generation (after release) 2 nd generation (after release) 1 st 3 rd 5 th 1 st 3 rd Tc 8R (40.7) (52.2) (60.9) (68.9) (71.6) (58.9) a Tc 5R (31.4) (43.5) (52.4) (61.0) (62.1) (50.1) b Tc 8R and Bt 2S (41.2) (52.5) (62.1) (71.2) (72.4) (59.3) Tc 5R and Bt 2S (30.5) (44.1) (52.2) (61.3) (63.2) (50.1) U T C (16.2) (19.7) (22.3) (24.5) (24.1) (21.3) c A factor mean (32.8) (43.0) (49.3) (56.1) (57.1) For A factor For B factor For A x B S E M CD at 5% Values followed by the same letter in the same column are not significantly different (at 5% CD); Figures in the parenthesis are arcsine transformed values; A factor = observation after release; B factor = treatments; A x B = interaction. Tc - T. 1.0 lakhs/release; R - Release; Bt - Bacillus thuriengiensis litres/spray; S - Spray. Table 2. Per cent Chilo partellus larval population reduction after treatment Treatments Per cent larval population reduction (during) B factor mean 1 st 2 nd At harvest Tc 8R (71.9) (68.5) (54.7) (65.2) Tc 5R (71.3) (68.2) (54.1) (64.5) Tc 8R and Bt 2S (72.3) (68.1) (54.4) (63.9) Tc 5R and Bt 2S (71.6) (68.9) (53.4) (63.9) Bt 2S (74.4) (67.6) (54.3) (65.4) Bt 4S (76.3) (72.7) (56.1) (68.4) A factor mean (73.0) (68.5) (54.8) For A factor For B factor For A x B S E M CD at 5% 2.9 N S N S Values followed by the same letter in the same column are not significantly different (at 5% CD); Figures in the parenthesis are arcsine transformed values; A factor = generations; B factor = treatments; A x B = interaction. Tc - T. 1.0 lakhs/release; R - Release, Bt - Bacillus thuriengiensis litres/spray; S - Spray.

5 188 INDIAN JOURNAL OF AGRICULTURAL RESEARCH Table 3. Chilo partellus infestation and larval stem tunnelling and yield in various treatments Treatments Per cent infestation (during generation) B factor mean Stem tunnelling (cm) at harvest 1 st 2 nd At harvest Tc 8R (25.4) (23.4) (19.4) (22.7) Tc 5R (29.1) (25.1) (23.1) (25.8) Tc 8R and Bt 2S (14.6) (14.6) (14.2) (14.6) Tc 5R and Bt 2S (15.3) (17.1) (16.5) (16.3) Bt 2S (20.0) (17.6) (21.4) (19.7) Bt 4S (16.5) (16.2) (21.2) (17.9) U T C (37.6) (43.5) (51.2) (44.1) A factor mean (22.7) (22.5) (23.9) For A factor For B factor For A x B S E M CDat 5% N S Values followed by the same letter in the same column are not significantly different (LSD, P = 0.05); Figures in the parenthesis are arcsine transformed values; A factor = generations; B factor = treatments; A x B = interaction. Tc - T. 1.0 lakhs/release; R - Release; Bt - Bacillus thuriengiensis litres/spray; S - Spray. Table 4. Yield, cost and per cent benefit of various treatments Treatments Yield Treatment cost/ Net return/ Per cent benefit (q/ha) ha (Rs.) ha (Rs.) over control Tc 8R Tc 5R Tc 8R and Bt 2S Tc 5R and Bt 2S Bt 2S Bt 4S U T C S E M 17.1 F value 14.3 CV% 9.4 CD at 5% 49.9 (SEM = 0.8, CD = 2.3, P = 0.05) (Table 3). Similarly stem tunnelling by larvae was significantly less (1.40 and 1.60 cm/infested plant) in Tc 8R + Bt 2S or Tc 5R + Bt 2S treatments. In general stem tunnelling by larvae in all treatment plot was significantly less than UTC plots (7.0 cm/infested plant) (Table 3). The commercial product of B. thuringiensis (Dipel 8L) was selected based on initial laboratory evaluation and net house trial (Jalali, 2000). In the present study, two applications did not reduce infestation significantly. Sprays of B. thuringiensis were found effective immediately after sprays against neonates.

6 McWhorter et al. (1972) earlier reported nonsignificant difference between 1 and 2 sprays of B. thuringiensis, however, multiple applications have shown to be effective (Lynch et al., 1980). Brownbridge (1991) reported that if B. thuringiensis sprays were directed at seedling stage of maize against neonate larvae, no significant plant damage would occur as larvae die within 48 hours in the field. Effectiveness of B. thuringiensis product (Dipel) was demonstrated in maize field in Romania, grain yield was highest in this product comparing other products and untreated control though application of B. thuringiensis was found inferior to diazinon (Galani et al., 1980). Vol. 40, No. 3, Highest yield of q/ha, per cent benefit over control (72.1%) and net return was recorded in plot that received Tc 8R + Bt 2S, however, yield was at par in all treatments but significantly higher than UTC (Table 4). The cost of treatment in plots receiving Tc 8R + Bt 2S or Tc 5R + Bt 2S was almost three and five times more than plots receiving Tc 5R and Tc 8R. Though there was increase in the yield in combined treatment but it was not significantly different from plots receiving T. chilonis alone. Therefore, considering cost factor, releases of Tc 5R is the best treatment for effective suppression of C. partellus on fodder maize during main cropping season of kharif (monsoon). REFERENCES Brownbridge, M. (1991). Insect Sci. Applic., 12: Fletcher, T.B. and Ghosh, C.C. (1920). Rept. Proc. 3rd. Entom. Meeting, Pusa (Feb.), Calcutta, 1920: Galani, G. et al. (1980). Analele Inst. Cerce. Pen. Prot. Plante., 16: Hassan, S.A. et al. (1986). J. Appl. Ent., 101: Jalali, S.K. (2000). Ph.D. Thesis, Mysore University, Mysore, India, 271 pp. Jalali, S.K. and Singh, S.P. (1993). Biocontrol Sci. Technol., 3: Jalali, S.K. and Singh, S.P. (2002). Entomon, 27: Kanour Jr., W.W. and Burbutis, P.P. (1984). J. Econ. Entomol., 77: Losey, J.E. et al. (1995). Environ. Entomol., 24: Lynch, R.E. et al. (1980). J. Econ. Ent., 73: 4-7. MeWhorter, G.M. et al. (1972). J. Econ. Ent., 65: Raynaud, B. and Crouzet, B (1985). Phytoma No. 366, Smith, S.M. (1996). Ann. Review Entomol., 41: Starks, K.J. (1969). East African Agriculture and Forestry Research Organization, Serere Research Station, Uganda (Mimeo). Wurai, C.M. and Kuria, J.N. (1983). Insect Sci. Applic., 4: Zhang, Z.L. (1986). Colloques-de-1 INRA, No. 43,