Development and Adoption of Integrated Pest Management for Major Pests of Cabbage Using Indian Mustard as a Trap Crop

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1 57 Development and Adoption of Integrated Pest Management for Major Pests of Cabbage Using Indian Mustard as a Trap Crop K. Srinivasan and P.N. Krishna Moorthy Indian Institute of Horticultural Research, Hessaraghatta Lake Post, Bangalore , India Abstract Use of Indian mustard (Brassica juncea (L.) Czern.) as a trap crop for management of diamondback moth, Plutella xylostella (L.), and leafwebber, Crocidolomia binotalis Zeller, was tried on an experimental farm and farmers fields. Preliminary studies indicated that planting of 15 cabbage rows followed by paired mustard rows to manage both pests was useful. The first mustard row is sown 15 days prior to planting, and the other is sown 25 days after. During our studies the intercropped cabbage was successfully raised during the rainy season without insecticidal application, however two sprays with 0.05% cartap hydrochloride were necessary to control diamondback moth during winter. Control of insects colonizing mustard was achieved with 0.1% dichlorvos sprays starting from 15 days after sowing at either 10- or 15-day intervals depending on population pressure. Later studies, however, indicated that raising of paired mustard rows at either end of 25 cabbage rows is the most promising planting pattern for successful management of both pests. The intercropped cabbages received two sprays with 0.05% cartap hydrochloride to control diamondback moth and spot application with 0.07% endosulfan and 0.1% phosphamidon to control localized infestation of Helicoverpa armigera (Hübner) and aphids, Brevicoryne brassicae L. respectively. Mustard also attracted other cabbage pests viz., Hellula undalis Zeller and the aphid B. brassicae. Several growers have come forward to adopt this technology as a result of the successful on-farm trials and effective publicity. Introduction Cabbage (Brassica oleracea var. capitata L.) is a commercially important cruciferous vegetable and is cultivated in rainy, winter and summer seasons on 10,753 ha in Karnataka State, India (Anon. 1987). Successful cultivation of this crop is hampered due to the incidence of major defoliating caterpillars like the diamondback moth (DBM), Plutella xylostella (L.) (Lepidoptera: Yponomeutidae), and leafwebber, Crocidolomia binotalis Zeller (Lepidoptera: Pyralidae). Cabbage webworm, Hellula undalis Zeller (Lepidoptera: Pyralidae), tomato fruitworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), and aphids, Brevicoryne brassicae L. (Homoptera: Aphididae) also infect the crop in different areas in various seasons (Nagarkatti and Jayanth 1982; Srinivasan and Veeresh 1986). The cabbage growers resort to weekly insecticide applications, and problems arising from widespread use of insecticides are well known. Inadequate control of major pests on cabbage, especially DBM following application of both organophosphorus insecticides and pyrethroids, has recently been reported (Srinivasan 1988). This pest has developed resistance to a wide variety of insecticides in Asia (Chen and Sun 1986; Sun et al. 1986; Kao et al. 1989). It is therefore necessary to develop a rational pest management program to reduce the number of applications of hazardous chemicals. 51 1

2 512 Srinivasan and Krishna Moorthy Cultural practices are considered important to suppress pest populations in integrated pest management programs (Brader 1979). Planting of trap crops is one of the cultural methods used for pest management (Metcalf and Luckman 1975). Indian mustard (Brassica juncea (L.) Czern) was reported to be a host for DBM and C. binotalis (Jayarathnam 1977; Singh and Rawat 1983). Srinivasan and Krishna Moorthy (1991) confirmed the distinct preference for oviposition on mustard by DBM and C. binotalis as compared to cabbage. Their field studies showed that a planting pattern of 15 cabbage rows followed by paired mustard rows (first sown days prior to cabbage and the other sown 25 days after cabbage planting) was the most promising for successful management of both pests. We examined the possibility of maximizing the number of cabbage rows that could be raised with mustard without significant reduction in cabbage yield. Further, the results were also verified in two on-farm trials conducted in traditional cabbage areas around Bangalore. The research leading to development and extent of adoption of technology by the growers is discussed later. Materials and Methods One field experiment at the experiment station, Hessaraghatta, and two on-farm trials in traditional cabbage areas around Bangalore were conducted utilizing mustard as a trap crop. Ridges and furrows were made in each plot with a spacing of 50 cm between ridges, and 30-day cabbage seedlings were planted 50 cm apart along the sides of ridges. Local mustard (bold seeded type used as an oilseed) was used in all experiments to serve as trap crop. Other details are given in Table 1. Results and Discussion Successful use of Indian mustard as a trap crop for management of DBM and C. binotalis on cabbage is on record (Srinivasan and Krishna Moorthy 1991). Continuous presence of mustard foliage should be maintained in order to facilitate oviposition by resident and immigrant moths. This is accomplished by taking up an early sowing (15 days prior to cabbage planting) so that mustard attains a height of about 6-8 cm and provides thick and bushy foliage to help attract early arrivals of both pests. Mustard starts flowering around 40 days after sowing and stops producing new foliage. This results in onset of senescence and leaves become unsuitable for larval feeding. In order to maintain continuous foliage, second sowing is recommended in the adjacent ridge on the 40th day after first sowing (i.e. 25 days after cabbage planting). It is also essential to obtain a reasonable kill of adult moths and larvae sheltered on mustard foliage with a suitable insecticide. Depending on insect pressure, application of 0.1 % dichlorvos at either 10- or 15-day intervals is recommended since this chemical has short residual toxicity. It is believed that quick degradation of dichlorvos after every application might have helped the incoming moths to continuously oviposit on mustard without hindrance. Srinivasan and Krishna Moorthy (1991) also reported that intercropped cabbage could be successfully raised during the rainy season without insecticidal application, whereas two sprays with 0.05 % cartap hydrochloride were necessary during winter. The intercropped cabbages received sprays at the time of primordial appearance (initial head formation stage as evidenced by about 2 cm firm leaf ball) since it is a critical crop stage. Preliminary field studies conducted by Srinivasan and Krishna Moorthy (1991) revealed that 15 cabbage rows can be successfully intercropped with mustard rows to manage both pests. In their study, mustard rows were raised either at the beginning or at the end of cabbage rows. We felt that the number of cabbage rows could be easily doubled if mustard is raised on either end of cabbage. With this in mind, we increased the number of cabbage rows to 25, 30, 35 and 40 and evaluated them with mustard raised at the beginning and at the end of each plot.

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6 516 Srinivasan and Krishna Moorthy Adoption of randomized block design for treatment evaluation of this kind may not be always suitable because mustard rows will interfere with insect attraction within and between blocks. Hence we chose to adopt ah exploded block design for evaluation. In this layout, each intercropped cabbage plot was separated by 20 m fallow to limit interference in attraction of insects between plots by the mustard foliage. During summer 1988, the intercropped cabbages received two sprays of 0.05% cartap hydrochloride at 34 and 39 days after planting (dap) (coinciding with primordial appearance) for the control of DBM. Cartap hydrochloride was chosen in view of its effectiveness against DBM as compared to other insecticides including synthetic pyrethroids (Srinivasan and Krishna Moorthy 1988). The mean larval population of DBM recorded among 25 and 30 intercropped cabbage rows was low as compared to the rest of the planting combinations including the control cabbage. The overall reduction in DBM larvae is attributed to combined effects of planting pattern and insecticide application (Table 2). A negligible larval population of C. binotalis was recorded in all the intercropped cabbages up to 34 dap. However, plots with 35 and 40 cabbage rows supported 0.4 and 0.5 larva/plant, respectively, as compared to 0.1 larva/plant in 25 and 30 cabbage rows at 38 dap. Increased incidence of C. binotalis larvae at 38 dap in 35 and 40 cabbage rows revealed less effectiveness of both planting patterns and application of cartap hydrochloride at 34 dap (Table 3). We also found that mustard had an added potential to attract H. undalis and B. brassicae. A larval population of H. undalis ranging from 0.6 to 0.9/plant and B. brassicae ranging from 13.1 to 18.4/plant was recorded on mustard at 53 and 69 das, respectively, in different planting combinations. Control cabbage recorded 0.8 H. undalis larva and 18.3 B. brassicue/plant at the corresponding observation days of 38 and 54 dap, respectively. There was no incidence of B. brassicae among all the planting patterns of intercropped cabbages up to 54 dap. Low incidence of H. undalis ( larva plant) was observed in 25 and 30 cabbage rows as against /plant for 35 and 40 cabbage rows, at 38 dap (Table 3). Table 2. Population of DBM in different cabbage (figures in parentheses denote corresponding population on mustard). DAP/DAS / Mean DBM larvaelplant on C and M in 25 RC/ 30 RC/ 35 RC/ 40 RC/ C MR MR MR MR alone ( 1.2) 1.1 I.4 (0.8) 0.4 I.8 (1.4) 0. I I.3 (0.5) (0.5) (0.7) 0.3 I.3 LSD (P = 0.05) C = Cabbage; M = mustard; RC = rows cabbage; MR = mustard rows; Observation time 0. I6 DAP = days after cabbage planting; Planting pattern 0. I4 DAS = days after 1 mustard sowing Interaction 0.35

7 IPM of Cabbage Pests 517 Table 3. Population of C. binotalis, H. undalis and B. brassicae in different cabbages (figures in parentheses denote corresponding population on mustard). Planting pattern lnsects/plant days after cabbage planting/days after 1 mustard sowing C. binotalis larvae H. undalis larvae 5. brassicae 34/59 38/53 54/69 Mean 38/53 SD 54 /69 SD 25 RC/MR I (3.5) (1.1) I (0.4) 0. I (0.6) (18.4) 30 RC/MR (5.6) (0.6) (0.3) 0.2 (0.0) (15.4) 35 RC/MR (3.6) (0.8) I (0.2) I (13.1) 40 RC/MR (9.4) (1.2) (0.5) (13.4) C alone Mean Factorial randomized block design comparison for C. binotalis on different DAP. LSD (P = 0.05) Observation time 0.33 Planting pattern 0.49 Interaction 0.85 C = Cabbage; M = mustard; SD = standard deviation; RC = rows cabbage; MR = mustard rows; DAP = days after cabbage planting Spot application of 0.07 % endosulfan was undertaken to control localized infestation of early larval instars of H. armigera among the intercropped cabbages at 53 dap. In 25, 30, 35 and 40 cabbage rows 2, 3.3, 3.6 and 5% plants were damaged respectively, whereas in control cabbage 3.4% had damage. On average, 3.4% of intercropped cabbage (inclusive of all the treatments) harbored colonies of B. brassicae at 65 dap. It was controlled by spot application with 0.1% phosphamidon on that day. Highest marketable yield of 67.5 t/ha was recorded for intercropped cabbage with 25 rows (Table 4). Based on reduction in insect incidence and marketable yield criteria, a planting pattern consisting of 25 cabbage rows with mustard was selected for testing in two on-farm trials. At Singapura, the intercropped cabbage was grown on 1.2 ha receiving two sprays with 0.05% cartap hydrochloride at 23 and 40 dap for the control of DBM larvae. Spot application with 0.07% endosulfan was also undertaken to control localized infestation of H. armigera larvae which damaged 5.3% in intercropped cabbage at 51 dap. Control cabbage recorded 4.9% damage on that day. Consistently low larval populations of DBM eggs and larvae of C. binotalis were recorded on all the observation days among the intercropped cabbage as compared to control cabbage. Intervention of dichlorvos sprays registered a rise and fall of larval populations of both pests on mustard. It supported significantly higher pest population levels as compared to intercropped cabbages on all the observation days (Table 5). All heads were destroyed in the control cabbage while the intercropped cabbage recorded 93.5 % marketable heads. Intercropped cabbage grown on 0.6 ha at Thalagavara was compared with control (untreated check) and weekly sprayed cabbages (grower's practice). Growers have a tendency to mix at least two insecticides belonging to entirely different groups to control DBM. Hence the grower was advised to spray the usual chemicals which he would have chosen in the normal course. The grower had alternated weekly sprays with a mixture of % cypermethrin (Ripcord 10 EC) % carbaryl (Sevin 50 WP) and followed by 0.01 % fenvalerate (Sumicidin 20 EC)

8 518 Srinivasan and Krishna Moorthy Table 4. Marketable yield of cabbage in different management programs (summer 1988). Number of Marketable 'Z' statistic for comparisons of proportions C rows heads (%) Number of C rows with M with M C alone Marketable yield (t/ha) I 49.6 C alone C = Cabbage; M = mustard. 'Z' statistic tabulated value = 2.0 (P = 0.05). Table 5. Population of DBM and C. binotalis recorded in different management programs and its relationship (Singapura). Larvae/ plant Student 't' valueª DAP/DAS M IC C M vs IC IC vs c alone alone DBM 21 /36 39/ I I.8 4.4** 4.8** I.9 4.7* * 9.0** I 6.3** 11.8** C. binotalis Egg mass 10/ ** 6.8* * Larvae 21 / ** 9.8* * 39/ I ' * 7.1** ** I0.7* * ** 25.2** DAP = Days after cabbage planting; DAS = days after I mustard sowing; M = mustard; IC = intercropped cabbage; C = cabbage. a' 'Significant at I % probability level % oxydemeton methyl (Metasystox 25 EC). Ten such sprays were applied at 7-day intervals terminating on the 70th dap, before the crop was harvested at 75 dap. The intercropped cabbage received one spray with 0.05 % cartap hydrochloride (coinciding with primordial appearance) for the control of DBM at 30 dap. Localized infestation of H. armigera and B. brassicae was observed in 6.2 and 3.3% of the plants among intercropped cabbages at 43 and 63 dap, respectively. Spot application of 0.07% endosulfan and 0.1% phosphamidon was undertaken to control H. armigera and B. brassicae, respectively, in the affected plants. While there was no incidence of H. armigera in plots sprayed (weekly), the control cabbage recorded 4.5% damage at 43 dap. Populations of DBM, C. binotalis and B. brassicae recorded in different crops are provided (Table 6). Intercropped cabbages supported the least number of DBM larvae on all observation days. Cabbages sprayed weekly recorded the maximum number of DBM larvae/plant from 29

9 IPM of Cabbage Pests 519 Table 6. Population of DBM and C. binotalis recorded in different management programs and its relationship (Thalagavara). Larvae/plant Student 't' value DAP/DAS M IC C WSC M vs IC IC vs C IC vs c vs WSC alone alone WSC alone DBM 10/ I ' 3.4" " 6.8** 8.0** 0.6 NS 3.0** 14.4" 20.9" 5.1** 5.0** 13.9" 20.7" 3.2** C. binotalis Egg mas 10/25 Larvae 29/44 58/ " " ** 5.1** 4.4" 8.8** 58/ B. brassicae " DAP = Days after cabbage planting; DAS = days after I mustard sowing; M = mustard; IC = intercropped cabbage; C = cabbage. a* 'Significant at I % probability level. dap as compared to the rest of the management programs. There was no incidence of C. binotalis and B. brassicae among the intercropped and cabbage sprayed weekly up to 58 dap. The results obtained in our study amply demonstrate that tank mix sprays lead to increased incidence of DBM. Control, weekly sprayed and intercropped cabbage recorded 0, 20 and 93% marketable heads, respectively, at the Thalagavara on-farm trial. Grower's adoption Based on successful outcome of on-farm trials, the Indian Institute of Horticulture Research conducted an IPM field day at the grower's field in Singapura on 28 January About 250 cabbage growers in and around Bangalore, staff from the Horticulture Department, Government of Karnataka and University of Agricultural Sciences, Bangalore, attended the function. Details of technology in the form of extension literature were distributed to the growers. Wide coverage on the field day was also given by the press. Based on the success of adoption, the extension education unit of University of Agricultural Sciences, Bangalore, has come forward to disseminate the technology by laying out adaptive trials at each taluka (county) of Bangalore district through its extension guides. Such adaptive trials are presently being conducted in selected grower's fields at Chikballapur, Devanahalli, Doddaballapur and Malur talukas at the time of writing. We have also received reports from officers of Horticulture Department, Government of Karnataka, employees of pesticide companies and growers that the technology has already spread to several counties where cabbage is grown in Karnataka State. The extent of adoption, however, is not known. In the neighboring Tamil Nadu State, the Horticulture Department and the Agricultural University have laid out demonstration trials at Ooty (Nilagiris district) and Kanniwadi (Madurai district) where cabbages are grown. Recently we have found that 5 % neem seed kernel extract (NSKE-water extract) spray gives effective control of all pests on cabbage. Our empirical observations in the field also indicate that there is significant increase in the resident natural enemy, Cotesia plutellae Kurdjumov, 5.6**

10 520 Srinivasan and Krishna Moorthy population wherever NSKE is sprayed. Hence NSKE spray is recommended instead of insecticides on the intercropped cabbages. Some growers have reported difficulties in taking up first mustard sowing (15 days prior to cabbage planting) since it involves early land preparation and irrigating the mustard rows. These growers, however, had sown mustard simultaneously with cabbage planting and resorted to an additional round of spray during preheading stages on cabbage to control early pest incidence. Growers often forget to raise the second mustard row at 25 dap, which resulted in additional 2-3 postheading sprays due to increased pest incidence. To overcome the necessity of second sowing, we are looking for a long-duration mustard variety that produces foliage up to 75 das. It has become increasingly difficult to grow cabbages around Bangalore, utilizing only insecticides since none of the presently available insecticides or combinations give adequate control of DBM. Several growers in Karnataka and neighboring Tamil Nadu states have voluntarily come forward to adopt IPM technology using Indian mustard as a trap crop in less than 2 years after it was demonstrated. This is mainly because of its effectiveness and low input requirement (0.5 kg mustard seeds required/ha costing US$0.5). It is hoped that the technology would spread to cabbage areas in other Indian states within a few years. Acknowledgments We wish to record our appreciation to Mr. M.B. Munirathnaiah and Mr. S. Venkateshaiah for rendering assistance in conducting the field experiments. Thanks are also due to Mr. K.L. Sudhakar and Mr. Gowdaiah for taking up on-farm trials at their field. We owe our gratitude to extension education unit, University of Agricultural Sciences, Bangalore, and to several other growers who had taken up adaptive trials and helped in transfer of technology. This is contribution no. 33/90 of the Indian Institute of Horticultural Research. References Anonymous Area under vegetable crops in Karnataka. Department of Horticulture compilation. (Bangalore : Government of Karnataka), 2 p. Brader, L Integrated pest control in the developing world. Ann. Rev. Entomol., 24, Chen, J.S., and Sun, C. N Resistance of diamondback moth (Lepidoptera: Plutellidae) to a combination of fenvalerate and piperonyl butoxide. J. Econ. Entomol., 79, Jayarathnam, K Studies on the population dynamics of the diamondback moth, Plutella xylostella (Linnaeus) (Lepidoptera : Yponomeutidae) and crop loss due to the pest in cabbage. Ph.D. thesis, University of Agricultural Sciences, Bangalore, 215 p. Kao, C.H., Hung, C.F. and Sun, C.N Parathion and methyl parathion resistance in diamondback moth (Lepidoptera : Plutellidae) larvae. J. Econ. Entomol., 82, Metcalf, R.L., and Luckman, W.H Introduction to Insect Pest Management. New York: John Wiley and Sons Inc., 587 p. Nagarkatti, S., and Jayanth, K.P Population dynamics of major insect pests of cabbage and of their natural enemies in Bangalore district (India). In Proceedings of the International Conference on Plant Protection in the Tropics, Malaysian Plant Protection Society, Kuala Lumpur, Malaysia, Singh, O.P., and Rawat, R.R Bionomics of cabbage web-worm, Crocidolomia binotalis Zeller on mustard at Jabalpur. Bull. Entomol., 24, Snedecor, G.W., and Cochran, W.G Statistical Methods. Calcutta: Oxford and IBH Publishing Co., 583 p. Srinivasan, K Changing pest complex in relation to cropping systems - vegetables. National Seminar on Changing pest situation in the current agriculture scenario of India, Indian Agricultural Research Institute, New Delhi, India, Abstract Volume, p. 27.

11 IPM of Cabbage Pests 52 1 Srinivasan, K., and Krishna Moorthy, P.N Pest management in crucifers. In Annual Report, Indian Institute of Horticultural Research, Bangalore, India, p Indian mustard as a trap crop for management of major lepidopterous pests on cabbage. Tropical Pest Mgt., 37, Srinivasan, K., and Veeresh, G.K The development and comparison of visual damage thresholds for the chemical control of Plutella xylostella and Crocidolomia binotalis on cabbage in India. Insect Sci. Applic., 7, Sun, C.N., Wu, T.K., Chen, J.S., and Lee. W.T Insecticide resistance in diamondback moth. In Talekar, N. S., and Griggs, T. D. (ed.) Diamondback Moth Management: Proceedings of the first international workshop, Asian Vegetable Research and Development Center, Shanhua, Taiwan, ROC,