Population dynamics of major lepidopteran insect pests on cabbage (Brassica oleracea var. capitata)

Introduction

The importance of vegetables in human diets is well known among different vegetable cole crops economically important throughout the world. In India, cabbage and cauliflower are two important vegetable crops, grown in different states of the country. In India, it is cultivated in 410.00 thousand ha area with 9869 MT. production and the volume of cabbage production in India is estimated to have an amount of about 9.72 million metric tons. In Uttar Pradesh, the total area of cabbage is 12.2 thousand ha with 348.94 thousand MT. production [1, 2] . Cabbage leaves are low in calories 27 percent, fat 0.1 percent and carbohydrates 4.6 percent also a good source of protein 1.3 percent which contains all essential amino acids Cabbage is an excellent source of minerals such as calcium 39 mg, iron 0.8 mg, magnesium 10 mg, sodium 14.1 mg potassium 114mg and phosphorus 44 mg. It is a rich source of vitamin A 2000 I.U. B1 50 I.U. and C 124 mg/100gm [4] . Insect pests, diseases and weeds are the major constraints limiting agricultural Productivity and growth. It is estimated that herbivorous insects eat about 26 percent of the Potential food Production [6] . Cabbage is attacked by several insect pests due to their succulent nature and year-round availability. More than 27 species of insect pests are reported on cabbage in India(of which 11 belonged to order Lepidoptera, 5 to Orthoptera, 3 each to Heteroptera and Coleoptera, 2 each to Homoptera and Hymenoptera and 1 to Diptera. Among these, fourteen pests have so far been recorded infesting cabbage crops. The insect pests attacking cabbage are diamondback moth (Plutella xylostella Linnaeus), cabbage butterfly (Pieris brassicae Linnaeus), tobacco caterpillar (Spodoptera litura Fabricius), cabbage semi looper (Trichoplusia ni. Hubner), aphid (Brevicoryne brassicae Linnaeus), painted bug (Bagrada cruciferarum Kirkaldy), cabbage leaf webber (Crocidolomia binotalis Zeller), cabbage head borer (Hellula undalis Fabricius), cabbage flea beetle (Phyllotreta cruciferae Goeze) and bihar hairy caterpillar (Spilosoma oblique Walk) are observed commonly on cabbage in different seasons and cause considerable losses. The present studies on population dynamics of major pests of cabbage would give an idea about their peak period of activity and may help develop pest management strategies against them. Indigenous products viz. Neem products are not only effective against crop pests but also ecologically safe and free from residual problems. Neem oil 1 percent water extract of neem leaves 40 percent and neem kernel extract 2 percent have been found effective against bud fly in linseed [3] . and so, attention is now being focused on the use of biopesticides. Beauveria bassiana constitutes an important component to supplement or as an alternative to synthetic chemicals. Keeping these facts in view present study was conducted to evaluate the efficacy of indigenous products and the Entomopathogenic fungus Beauveria bassiana against Plutella xylostella L. under laboratory conditions. While only 1 percent of the global insecticide market is occupied by the two insecticides (bt. based products) and insecticides of plant origin (Pyrethrum and neem-based products) toxicity and development of resistance issues have limited the use of this synthetic insecticide therefore, It is desirable to develop alternative methods for pest management based on biological pesticides, which are safe for both humans and the environment. Considering the above points the present study entitled "Population dynamics of major lepidopteran insect pests of cabbage and management of diamondback moth (Plutella xylostella L.) using different bio-pesticides." was carried out under Bundelkhand region of Jhansi.

Materials and Methods

The Experiment was carried out in an organic research farm at Kargua Ji Institute of Agricultural Sciences, Department of Entomology, Bundelkhand University Jhansi Uttar Pradesh during the Rabi season, 2022-2023. It is situated at 78 o 36 E Longitude and 25 o 47 N Latitude and is about 178.37 m above mean sea level. The climate is subtropical and semi-arid. The preparation of the field was done by a tractor-drawn cultivator followed by two cross-harrowing to pulverize the soil. Finally, the field was levelled with leveler and then channels were prepared according to the layout three replication and net plot size 2.0 x 2.60 m 2 of the experiments. The seedlings were sown on raised nursery beds and transplanted after 29 days in the laid-out field. The variety cabbage golden acare used for seed sowing. Seeds were sown on 10.10.2022 in Rabi season 2022-2023. Transplanting was done in the field at the spacing of 60 cm × 45 cm on 09.11.2022 in Rabi 2022-2023. Protective irrigation was given immediately after transplanting. The observations of major insect pests on cabbage crop were recorded on randomly selected 5 plants, one plot twice in a standard week. Observations on different insects were recorded as follows diamondback moth, aphid, leaf webber, cabbage head borer and ladybird beetle. The observation starts from transplanting and continues till the maturity of the crop. The population of cabbage insect pests was recorded by counting the number of larvae/plant. The population of insects was recorded by counting the number of nymphs and adults per leaf (top, middle and bottom) plant. The data recorded on major insect pests and meteorological parameters were used for statistical analysis. To infer the results of population dynamics was worked out between populations of insect pests.

Method of recording observations:

To study the population dynamics of major lepidopteran insect pests of cabbage (Brassica oleracea var. capitata) the observations of major insect pests on cabbage crop were recorded on 5 plants selected randomly one plot twice in a standard week. Observations on different insects were recorded as follows diamondback moth, aphid, leaf webber, cabbage head borer and ladybird beetle. For DBM (Plutella xylostella L.) pretreatment observation was recorded at the 3 rd , 7 th , and 14 th days after first and second spraying on 5 plants selected randomly. Observation on DBM insects was recorded as follows. The populations of diamondback moth (both larvae as well as adult; alate and apterous) were recorded visually (absolute count.) on leaves, one each from the top, middle and bottom canopy of each tagged plant in the early morning hours. 1.

The diamondback moth, (Plutella xylostella L.):

The observation regarding the larval population of the diamondback moth (DBM) revealed that the population varied from 0.5 to 9.9/plant during 2022-2023. DBM first appeared during the 49 th SMW (3-9 Dec.) with intensity of 0.5/plant. Then the population gradually increased and attained peak during the 4 th SMW (22-28 Jan.) when the maximum temperature, minimum temperature, maximum relative humidity, minimum relative humidity, evaporation, rainfall and wind velocity were 22 °C, 8.2 °C, 94.0%, 62.0%, 1.5 mm, 7.00 mm, and 8.9 Km/hr, respectively. After that, the population decreased up to the 9 th SMW (26 Feb-04 Mar.) at the end of the season. The data on the population dynamics diamondback moth (DBM) is depicted in Fig 1 . Present observations were more or less similar to the results of earlier workers [7] . The larval population of DBM, head borer, leaf webber, cabbage semi looper and tobacco leafeating caterpillar ranged from 1.2 to 5.5, 0.45 to 1.8, 2.0 to 7.0, 0.77 to 1.2 and 1.98 to 3.2, respectively. The infestation of DBM, head borer, leaf webber and cabbage semi-looper was initiated during the 47 th SMW and of tobacco leafeating caterpillar during the 46 th SMW. The peak incidence of DBM, head borer, leaf webber, cabbage semi looper and tobacco leaf-eating caterpillar was observed during 51st, 3 rd , 48 th , 49 th and 49 th SMW, respectively during 2016-17 [5] .

Studies on population dynamics of diamond backmoth, Plutella xylostella (Linnaeus) on cabbage revealed that the pest population of (Plutella xylostella Linnaeus) appeared from the third week of December which gradually increased and attained a peak of 8.9 larvae per plant during fourth week January. It indicated that the pest was more active during January the peak population of DBM (9.9/plant). First fortnight of January.

Cabbage head borer, (Hellula undalis F.):

The observation on larval count of cabbage head borer depicted that the larval population ranged from 2.2 to 5.9/plant during 2022-2023. The activity of cabbage head borer caterpillar initiated during 51st SMW (17-23 Dec.) with gradual increase its population and reach its peak (5.9/plant) 3 rd SMW (15-21 Jan.) when the maximum temperature, minimum temperature, maximum relative humidity, minimum relative humidity, evaporation, rainfall and wind velocity were 26.4 °C 7.0 °C, 90%, 66%, 3.4mm, and 6.9 Km/h, respectively. After that, the larval population decreased up to 9 th (26 Feb-04 Mar.) (0.5/plant). The data on population dynamics of cabbage head borer caterpillar is depicted in Fig 1.

Cabbage leaf Webber, (Crocidolomia binotalis Z.): The observation on the larval count of cabbage leaf webber depicted that the larval population ranged from 0.3 to 4.9/plant during 2022-2023. The incidence of cabbage leaf webber was noticed from the 48 th SMW (26 Nov-02 Dec.)

to the 9 th SMW (26 Feb-04 Mar.). The peak incidence was observed in 1 st SMW when the maximum temperature, minimum temperature, maximum relative humidity, minimum relative humidity, evaporation, rainfall and wind velocity were 20.0 °C, 3.2 °C, 100%, 78%, 0.0mm, 0.00mm, 6.5 Km/hr respectively. After that, the larval population decreased up to the 9 th SMW (26 Feb-04 Mar.) (0.2/plant). The data on population dynamics in cabbage leaf webber is depicted in Fig 1.

Present observations were more or less similar to the results of earlier workers [7] . have reported leaf webber C. binotalis (maximum 3.00 larvae/plant in 2 nd SMW). (Pawar et al.,) have reported leaf webber on mustard revealed that the pest was active from the 3 rd week of November to the 4 th week of December the pest population ranged between 1.10 to 9.0 larvae per plant throughout the season [3] . peak population of leaf webber (3.07/leaf). Second fortnight of January. Present observations were more or less similar to the results of earlier workers [8] . the incidence of ladybird beetle initiated in the second fortnight of December (0.30/leaf) with a gradual increase and attained its peak in the second fortnight of January (2.13/leaf). The population gradually decreased and reached its minimum during the second fortnight of Feb (0.78/leaf).

Conclusion

Based on number of populations per infestation. DBM, Cabbage Head Borer, Cabbage Leaf Webber, Cabbage Aphids and Cabbage Ladybird beetle were recorded as major insect pests in cabbage crop and noticed from 49 th SMW, 51 th SMW, 48 th SMW, 49 th SMW and 49 th SMW or peak level presence 9 th , 3 rd , 1 st , 6 th and 5 th SMW.

Acknowledgement

AcknowledgementsI thank the Department of Entomology, Institute of Agricultural Science Bundelkhand University, Jhansi for providing the resources for the completion of my research work.

References

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