Efficacy of bio-pesticides and insecticides against sucking insect-pest of okra

Introduction

Okra [Abelmoschus esculentus (L.) Moench] is most popular vegetable crop belongs to the Malvaceae family. In India, it is grown both in summer and rainy seasons. It is generally utilized as a green vegetable with lots of nutrition. Tender fruits of okra are used as vegetable or in culinary preparations as sliced and dried pieces. It is also used for thickening gravies and soups, because of its high mucilage content. In Uttar Pradesh Varanasi, Jaunpur, Gazipur, Chanduli, Gorakhpur, Deoria and Kushinagar are the major okra producing district. These tender okra fruits/capsules are used as vegetable. It is a good source of vitamins (A, B and C), proteins, minerals and an excellent source of iodine, linoleic acid, an essential fatty acid, has also been reported to be present, abundantly in okra seed oil (Saini et al. 2023) [7] . Growers of okra commonly claim productivity losses due to insect infestations. However, its cultivation faces substantial challenges from insect pests, which reduces both yield and quality, posing economic risks to farmers. Among the most damaging pests are sucking insects such as Jassids/Leaf hopper (Amrasca biguttula biguttula), Whiteflies (Bemisia tabaci) and Mealy bug (Phenacoccus solenopsis), alongside the lepidopteran shoot and fruit borer (Earias vittella). Whiteflies cause direct feeding damage and transmit viral diseases, such as yellow vein mosaic virus, with reported yield losses of 17.46 to 54.04% if left uncontrolled in early growth stages. (Mohapatra, 2023) [4] . Sastry and Singh (1974) [8] reported 93.80 percent yield loss caused due to whitefly in okra. Kishnaiah (1980) [2] reported about 40 to 56 percent losses in okra due to leafhopper. There is a reduction of 49.8 and 45.1 percent in height and number of leaves, respectively due to attack of leaf hopper. Mealy bug (Homoptera: Pseudococcidae) are cottony in appearance small oval soft bodied sucking insects. Both nymphs and adults cause damage by sucking the phloem sap from the growing points resulting the infested plants to lose their vitality, remain stunted, leaves turning yellow, dry up and finally death of plants in case of heavy infestation. Excess sap is excreted as honey dew which attracts ants develops sooty mould inhibiting the plants ability to manufacture food. .7% SC @ 0.25 ml 1 -1 , Neem oil 5% @ 5 ml 1 -1 , Fipronil 5% SC @ 1 ml 1 -1 , Dr. Neem @ 5 ml 1 -1 , Imidacloprid 17.8 SL @ 0.5 ml 1 -1 , Neem Rus @ 2 ml 1 -1 and Emamectin benzoate @ 1 ml 1 -1 . Insecticidal sprays were applied when the pest population reached the economic threshold level (ETL). Observations were recorded at 3, 5, 7 and 10 days after spraying (DAS). The population of major sucking insect-pest viz., Whitefly and Jassid recorded per three leaves (Top, middle and Bottom leaves) while Mealy bug per plant form randomly 10 selected plants on each experimental plot. All the observations were recorded with the help of a hand lens (10X). All recommended agronomic practices were followed to raise the crop.

Results and Discussion

Efficacy of bio-pesticides and insecticides against Whitefly (Aleyrodidae: Hemiptera)

The data presented in Table 1 and Figure 1 indicated that the pre-treatment population of Whitefly was uniformly distributed in the experimental plots and did not differ significantly among treatments, ranging from 8.22 to 8.34 per 3 leaves. After application of treatments, all insecticides significantly reduced the pest population compared with the untreated control. At 3 days after spraying (DAS), the lowest population of whitefly (0.96/3 leaves) was recorded in the Imidacloprid 17.8 SL @ 0.5 ml l⁻¹ treated plots, followed by Spinetoram 11.7% SC @ 0.25 ml l⁻¹ (1.33/3 leaves) and Fipronil 5% SC @ 1 ml l⁻¹ (1.80/3 leaves). Emamectin benzoate 5% SG @ 1 ml l⁻¹ (2.37/3 leaves) and Dr. Neem @ 5 ml 1 -1 (3.01/3 leaves) showed moderate effectiveness, whereas the botanical treatments Neem oil 5% @ 5 ml 1 -1 (3.07/3 leaves) and Neem rus @ 2 ml 1 -1 (3.18/3 leaves) were comparatively less effective against whitefly. The highest population was recorded in the untreated control (8.33/3 leaves). A similar tendency was observed at 5, 7 and 10 DAS Imidacloprid 17.8 SL @ 0.5 ml l⁻¹ consistently recorded the lowest pest population (0.67, 0.50 and 0.92 whitefly/3 leaves respectively,) followed by Spinetoram 11.7% SC @ 0.25 ml l⁻¹ (1.04, 0.81 and 1.27 whitefly/3leaves) and Fipronil 5% SC @ 1 ml l⁻¹ (1.45, 1.20 and 1.78 whitefly/3 leaves). Emamectin benzoate 5% SG @ 1 ml l⁻¹ (2.01, 1.74 and 3.34/3 leaves) and Dr. Neem @ 5 ml 1 -1 (2.84, 2.19 and 3.01/3 leaves) showed moderate effectiveness, whereas the botanical treatments Neem oil 5% @ 5 ml 1 -1 (2.89, 2.47 and 3.11/3 leaves) and Neem rus @ 2 ml 1 -1 (2.93, 2.55 and 3.19/3 leaves) remained least effective throughout the observation period against whitefly. The untreated control plots recorded the highest whitefly population (8.67, 9.00 and 9.08/3 leaves, respectively) at all observation intervals. The higher efficacy of Imidacloprid 17.8 SL against whitefly observed in the present study is in agreement with the findings of Kumar and Kumar (2017) revealed that all the treatments were found effective in reducing the population of whitefly. Imidacloprid 17.8SL was the most effective treatment indicating reduction in population of whitefly (1.33/3leaves) followed by Thiamethoxam 25WG. Similar results were also reported by Begum and patil (2016) [1] reported that Imidacloprid 17.8SL was the most effective treatment indicating reduction in population of whiteflies.

Efficacy of bio-pesticides and insecticides against Leafhopper (Cicadellidae: Hemiptera)

The data presented in Table 2 and Figure 1 indicated that the pre-treatment population of Leafhopper (Amrasca biguttula biguttula) was uniformly distributed in the experimental plots and did not differ significantly among treatments, ranging from 6.26 to 6.38 per 3 leaves. After application of treatments, all insecticides significantly reduced the pest population compared with the untreated control. At 3 days after spraying (DAS), the lowest population of leafhopper (1.37/3 leaves) was recorded in the Imidacloprid 17.8 SL @ 0.5 ml l⁻¹ treated plots, followed by Spinetoram 11.7% SC @ 0.25 ml l⁻¹ (1.86/3 leaves) and Fipronil 5% SC @ 1 ml l⁻¹ (2.49/3 leaves). Emamectin benzoate 5% SG @ 1 ml l⁻¹ (3.19/3 leaves) and Dr. Neem @ 5 ml 1 -1 (3.98/3 leaves) showed moderate effectiveness, whereas the botanical treatments Neem oil 5% @ 5 ml 1 -1 (4.09/3 leaves) and Neem rus @ 2 ml 1 -1 (4.19/3 leaves) were comparatively less effective against leafhopper. The highest population was recorded in the control plot (6.34/3 leaves). A similar trend was observed at 5, 7 and 10 DAS Imidacloprid 17.8 SL @ 0.5 ml l⁻¹ consistently recorded the lowest leaf hopper population (0.80, 0.59 and 0.77 leafhopper/3 leaves respectively,) followed by Spinetoram 11.7% SC @ 0.25 ml l⁻¹ (1.41, 0.95 and 1.19 leafhopper/3leaves) and Fipronil 5% SC @ 1 ml l⁻¹ (2.31, 1.45 and 1.66 Leafhopper/3 leaves). Emamectin benzoate 5% SG @ 1 ml l⁻¹ (2.94, 1.95 and 2.15 leafhopper/3 leaves) and Dr. Neem @ 5 ml 1 -1 (3.73, 2.95 and 2.91 leafhopper/3 leaves) showed moderate effectiveness, whereas the botanical treatments Neem oil 5% @ 5 ml 1 -1 (3.80, 3.20 and 3.39/3 leaves) and Neem rus @ 2 ml 1 -1 (3.99, 3.57 and 3.75 leafhopper/3 leaves) remained least effective throughout the observation period against Leafhopper. The untreated control plots recorded the highest leafhopper population (6.42, 6.59 and 6.70/3 leaves, respectively) at all observation intervals. These findings are in accordance with the findings of Kumar and Kumar (2017) [3] revealed that all the treatments were found effective in reducing the population of Leafhopper. Imidacloprid 17.8SL was the most effective treatment indicating reduction in population of leafhopper/jassid (1.26/3leaves) followed by Thiamethoxam 25WG. Also Pawar et al., (2016) [6] reported that, mean population of jassids after three sprays revealed that Imidacloprid was effective and superior, the next best were Thiamethoxam.

Efficacy of bio-pesticides and insecticides against Mealy bug (Pseudococcidae: Hemiptera)

The data presented in Table-3 and Figure-1 indicated that the pre-treatment population of Mealy bug (Phenacoccus solenopsis) was uniformly distributed in the experimental plots and did not differ significantly among treatments, ranging from 3.09 to 3.16 per plant. After application of treatments, all insecticides significantly reduced the mealy bug population compared with the untreated control. At 3 days after spraying (DAS), the lowest population of mealy bug (0.16/plant) was recorded in the Imidacloprid 17.8 SL @ 0.5 ml l⁻¹ treated plots, followed by Spinetoram 11.7% SC @ 0.25 ml l⁻¹ (0.31/plant) and Fipronil 5% SC @ 1 ml l⁻¹ (0.48/plant). Emamectin benzoate 5% SG @ 1 ml l⁻¹ (0.67/plant) and Dr. Neem @ 5 ml 1 -1 (0.94/plant) showed moderate effectiveness, whereas the botanical treatments Neem oil 5% @ 5 ml 1 -1 (1.24/plant) and Neem rus @ 2 ml 1 -1 (1.53/plant) were comparatively less effective against mealy bug. The highest population was recorded in the control plot (3.21/plant). A similar tendency was observed at 5, 7 and 10 day after spray Imidacloprid 17.8 SL @ 0.5 ml l⁻¹ consistently recorded the lowest mealy bug population (0.12, 0.21 and 0.15/plant respectively,) followed by Spinetoram 11.7% SC @ 0.25 ml l⁻¹ (0.22, 0.34 and 0.32/plant) and Fipronil 5% SC @ 1 ml l⁻¹ (0.37, 0.51 and 0.55/plant). Emamectin benzoate 5% SG @ 1 ml l⁻¹ (0.51, 0.71 and 0.84/plant) and Dr. Neem @ 5 ml 1 -1 (0.93, 1.05 and 1.15/plant) showed moderate effectiveness, whereas the botanical treatments Neem oil 5% @ 5 ml 1 -1 (0.70, 1.31 and 1.44/plant) and Neem rus @ 2 ml 1 -1 (0.95, 1.61 and 1.78/plant) remained least effective throughout the observation period against Mealy bug. The untreated control plots recorded the highest mealy bug population (3.27, 3.32 and 3.39/plant, respectively) at all observation intervals. These result collaborate with Nidheesh et al. (2020) [5] recorded that out of the seven insecticides screened against P. solenopsis under laboratory conditions, neonicotinoids such as Thiamethoxam 25% WG @ 0.40 g/l and dinotefuran 20% SG @ 0.25 g/l were found to be most effective in reducing the mealy bug population at recommended and above recommended doses.

Conclusion

The study revealed that all insecticidal treatments significantly reduced the population of sucking insect-pest viz., Whitefly, Leafhopper and Mealy bug in Okra compared to the untreated control. Imidacloprid 17.8 SL @ 0.5 ml l⁻ ¹ was most effective against all major sucking insect pest of okra. These insecticides can be recommended for effective pest management in Okra growing farmers under Eastern Uttar Pradesh conditions.

Acknowledgement

AcknowledgementThe authors gratefully acknowledge the guidance, encouragement and scholarly support provided by Prof. Rajnish Kumar, Professor & Head, Department of Entomology, B.R.D. P.G. College, Deoria, whose insightful suggestions and continuous motivation were instrumental in the successful completion of this research.

References

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