Integrated cultural management practices for controlling black thrips infestation in Chilli

Introduction

Chilli (Capsicum annuum L.) is an economically significant and widely cultivated crop globally, renowned for its culinary, medicinal, and ornamental value (Bosland & Votava, 2012; Sharma et al., 2021) [1,22] . Belonging to the Solanaceae family, chilli is cultivated in various agro-climatic regions, making it a versatile and adaptable crop (Kang & Goto, 2010; Patel et al., 2022) [5,16] . Beyond its culinary applications, chilli possesses medicinal properties attributed to its bioactive compounds, including capsaicin, vitamins, and antioxidants (Materska & Perucka, 2005; Kim et al., 2023) [10,6] . These compounds have been studied for their potential health benefits, such as anti-inflammatory, analgesic and antioxidant properties, making chilli a subject of interest in pharmaceutical and nutraceutical industries (Surh, 2002; Zhang & Wang, 2023) [27,30] . India is known for its diverse hub of chilli peppers due to its diverse variability present. Hence it is also described as a secondary centre of origin and India contributes approximately 40% of the world's production. In India, green and dry chilli has an extensive annual production of 3851,000 MT in 364,000 ha acreage and 1702,000 MT in 683,000 ha respectively (NHB, 2021) [12] . The chilli crop in India is ascribed to many biotic and abiotic stresses resulting in low productivity of the crop. Among the sucking pests, thrips are one of the major ones causing severe yield losses in chilli due to reduced production. Earlier, Scirtothrips dorsalis (Hood), was predominant, but in the recent past the invasive species Thrips parvispinus (Karny), has caused colossal loss to chilli growers in Andhra Pradesh, Telangana and Karnataka (Prasannakumar et al., 2021, Reddy et al., 2023) [17,20] . Black thrips feed on Chilli plants, causing damage to leaves, flowers, and fruits, which can lead to yield losses and reduced crop quality (Kumar & Meena, 2022) [9] . Effective management strategies are essential to mitigate the impact of black thrips infestation and ensure optimal Chilli production. In this article, we explore various methods for controlling black thrips infestation in Chilli plants, ranging from cultural practices to chemical control measures (Choudhary et al., 2021) [2] .

Thrips

Thrips are one of the major sucking pests affecting chilli crop globally. It belongs to the taxonomic order Thysanoptera and this order was introduced by Haliday, an Irish Entomologist in 1836 [3] , encompassing 41 species and 11 genera of thrips (Haliday, 1836) [3] . The nomenclature of the order derives from the fusion of two terms, "Thysanos" denoting "fringe" and "pteron" signifying "wing," owing to the characteristic fringed wings exhibited by thrips The Indian thrips taxonomy encompasses a total of 739 species across 259 genera, with suborder Terebrantia accounting for 309 species within 116 genera, and suborder Tubulifera comprising 430 species in 143 genera, as documented by Tyagi and Kumar (2016) [28] . An additional 44 species, representing novel distributional records, have identified across diverse geographical regions within India, as reported by Rachana and Varatharajan (2017) [18] . Notably, the invasive Thrips parvispinus (Karny) falls within the Thrips orientalis group, as categorized by (Mound, 2000) [11] .

Indian Scenario

In India, the initial occurrence of T. parvispinus was documented in the year 2014 on Carica papaya L. (Caricaceae) in Bangalore, followed by its subsequent identification on Brugmansia sp. (Solanaceae) and Dahlia rosea Cav. (Asteraceae) in 2018 (Kumar & Thomas, 2019) [8] . This polyphagous pest exhibits a wide host range, affecting crops such as beans, eggplant, papaya, pepper, potato, shallot, and strawberry, as noted by NPPO (2022). [141] Notably, it inflicted substantial damage on chilli fields in the southern states of Andhra Pradesh, Karnataka, and Telangana in October 2021, leading to extensive surveys and host record compilation (Reddy et al., 2022) [19] . The study encompassed the examination of 1257 specimens collected from these aforementioned states (Patel & Singh, 2023) [15] . [29] Papaya, peppers, potatoes, egg plants, beans, shallots, crotalaria, cucumber, coffee, tobacco Hutasoit et al., 2017 [4] Anthurium, chrysanthemum, dahlia, gardenia, ficus NPPO, 2022 [14] Chilli, weed species of Parthenium, Amaranthus sp, Axonopus sp, Ageratum sp, Alternanthera sp. Thunbergia sp, foliage of neem and pongamia Nagaraju et al., 2021 [13] Chilli, capsicum, mango, cotton, drumstick, cucumber, beans, bottle gourd, bitter gourd, marigold, chrysanthemum, watermelon, coccinea, brinjal, etc. Sridhar et al., 2021 [26] Chilli, tomato, okra, squash, and various ornamental plants Patel et al., 2022 [16] Peppers, eggplant, sunflower, and herbs

Singh & Verma, 2023 [23] Foliage of leafy vegetables and fruit crops Kumar & Reddy, 2022 [7] Level of damage Chilli thrips in India (Andhra Pradesh, Karnataka and Telangana) caused up to 70-100 per cent damage irrespective of the chilli cultivars grown by the farmers. Export of 6, 01,500 tonnes worth 8,430 crores was affected (Reddy et al., 2022) [19] .

Thrips species reported on pepper in India

Before the introduction of Thrips parvispinus to India, several thrips' species were reported on pepper (Capsicum spp.). These included Thrips tabaci, Frankliniella schultzei, Scirtothrips dorsalis and others. Scirtothrips dorsalis was one of the predominant species affecting pepper crops. Following the entry of Thrips parvispinus, this invasive species gained prominence as a significant pest of pepper due to its rapid establishment, wide host range, and potential to cause severe damage to pepper plants (Singh & Verma, 2023) [23] . The transition from indigenous thrips species to the invasion of Thrips parvispinus has necessitated enhanced pest management strategies to effectively mitigate the economic impact on pepper cultivation in India (Patel et al., 2022) [16] .

Life cycle

The life cycle of Thrips parvispinus includes several distinct stages. Adult females lay eggs on plant tissues, which hatch into first instar nymphs. Nymphs progress through two more instar stages, followed by a prepupal phase characterized by reduced mobility and colour changes. This is succeeded by the pupal stage, where metamorphosis occurs within pupal cases. The duration of each stage varies with temperature, typically ranging from 15 to 30 days (Kumar & Reddy, 2022) [7] . Female thrips generally live longer than males, surviving for about 8 to 10 days. They lay numerous eggs, which are small and oval-shaped (Tyagi et al., 2015) [29] .

Symptoms

Damage symptoms on the flowers include scraping causing reddish streaks, it also feeds on pollen impeding pollination (Kumar & Reddy, 2022) [7] . Severe infestation results in the drying and withering of flowers. Direct feeding of larvae and adults on buds and fruits affects the fruit set and fruits attain abnormal shape (Reddy, Kumar, & Priya, 2023) [20] . They are found colonizing the underside of leaves and are found to prefer sucking the sap from the adjacent portion of the veins on leaves. Infested leaves show a yellowish and blotchy appearance. Necrotic regions and yellow streaks are found on the leaf lamina (Singh, Patel, & Verma, 2022) [24] . Unlike the Scritothrips dorsalis which is a severe pest of chilli that infests the foliage, ) [17,28] .

Demographic characters: Why difficult to manage?

The management of Thrips parvispinus is fraught with complexities due to its unique demographic attributes. It exhibits high fecundity, with females capable of prolific egg-laying within a short temporal window (Reddy, Kumar, & Priya, 2023) [20] . This compressed life cycle augments population proliferation, fostering swift infestation establishment (Kumar & Reddy, 2022) [7] . Moreover, the species displays polyphagous tendencies, rendering it capable of feeding on a diverse range of plant species, thereby complicating management strategies (Singh, Patel, & Verma, 2022) [24] . The propensity of Thrips parvispinus to develop resistance against chemical insecticides exacerbates control challenges (Tyagi & Kumar, 2016) [28] . Its cryptic behaviour, often concealed within plant substrates, further obstructs timely detection and control efforts (Prasannakumar, Rao, & Desai, 2021) [17] . Notably, the absence of potent natural predators in specific ecosystems accentuates the intricacy of maintaining Thrips parvispinus populations in equilibrium (Hutasoit et al., 2017) [4] . Collectively, these demographic attributes accentuate the requisite for comprehensive, adaptive management approaches to effectively curtail Thrips parvispinus infestations in agricultural systems (Rachana & Varatharajan, 2017) [18] .

Management Cultural Practices

Cultural practices are pivotal in managing black thrips in chilli plants. Crop rotation disrupts thrips' life cycle, while weed control limits their habitat (Kumar & Reddy, 2022) [7] . Sanitation, like removing crop residues, prevents overwintering sites (Prasannakumar, Rao, & Desai, 2021) [17] . Physical barriers, such as plant borders using crops like maize, prevent thrips dispersal (Singh, Patel, & Verma, 2022) [24] , while the adoption of blue/white sticky traps at a density of 65-75 traps/ha at canopy height aids in mass trapping (Tyagi & Kumar, 2016) [28] . Reflective (silver-colored) plastic mulch covers deter thrips movement (Hutasoit et al., 2017) [4] . These integrated practices effectively control thrips infestation in chilli plants.

Biological Control

Biological control methods offer sustainable and environmentally friendly solutions for managing black thrips infestations in chilli plants. Predatory insects, such as predatory mites and parasitic wasps, serve as natural enemies of thrips and help regulate their populations (Kumar & Reddy, 2022; Shankar et al., 2023) [7,21] . Enriching compost or farmyard manure with beneficial organisms like Metarhizium anisopliae or Pseudomonas fluorescens can also aid in controlling thrips (Tyagi & Kumar, 2016; Sharma & Ghosh, 2021) [28,22] . Implementation of biological control measures includes using Steinernema carpocapsae (EPN) formulation with a wetting agent and applying Beauveria bassiana or Lecanicillium lecanii fungi. These fungi infect and kill thrips, providing an effective means of reducing infestation in chilli plants (Prasannakumar, Rao, & Desai, 2021; Singh et al., 2020) [17,25] . Additionally, botanical extracts like neem seed kernel extract (NSKE), neem oil, Pongamia oil, or Vitex negundo extract, along with Azadirachtin 3000 PPM, have proven to be effective in controlling thrips infestations (Hutasoit et al.,2017; Reddy et al., 2022) [4,19] .

Chemical Control

Chemical control measures are often used to manage black thrips infestation in Chilli plants, especially in cases of severe infestation. Insecticides labeled for thrips control, such as neonicotinoids, spinosad, or pyrethroids, can be applied to Chilli plants to target thrips directly. Treating seedlings with Imidacloprid 17.8% SL through root dip for 30 minutes is found to be effective controlling thrips. Sequential sprays of chemical insecticides, such as fipronil 80% WG, cyantraniliprole, acetamiprid, or spinosad at specified intervals, further enhance the management strategy for chilli black thrips. It is important to follow recommended application rates and safety precautions when using insecticides to minimize environmental impact and ensure human safety. Additionally, systemic insecticides can be applied to Chilli plants to target thrips feeding on foliage and flowers. These insecticides are absorbed by the plant and translocated throughout its tissues, providing long-lasting protection against thrips infestation. (NPPO, 2022) [14] . [13,20] . Sticky traps can be installed in chilli fields to monitor thrips populations and assess the effectiveness of control measures. White or blue sticky traps attract thrips, which become trapped on the sticky surface, providing growers with valuable information about thrips activity and population dynamics (Kumar & Meena, 2022; Prasannakumar, Rao, & Desai, 2021) [9,17] .

Conclusion

Controlling black thrips infestation in Chilli plants requires an integrated approach that combines cultural, biological, and chemical control methods. By implementing these strategies, Chilli growers can effectively manage thrips infestation and minimize damage to their crops. Proactive monitoring, early detection, and timely intervention are essential for successful thrips management and ensuring optimal Chilli production. By adopting sustainable and environmentally friendly management practices, growers can protect their crops from thrips damage and ensure a bountiful harvest.

References

1. Choudhary SK, Sharma M, Gupta P. Integrated pest management approaches for black thrips in chilli. Plant Protection Strategies. 2021;9(2):145-159.
2. Haliday AH. Description and introduction of Thysanoptera order. J Entomol Soc. 1836.
3. Hutasoit AM, Ekanayake P, Othman S. Thrips biodiversity and their management in tropical environments. Asian J Entomol. 2017;11(3):139-145. https://doi.org/10.3923/aje.2017.139.145
4. Kang JH, Goto T. Capsaicin, a pungent compound of hot pepper, and its role in the pharmaceutical industry. Molecules. 2010;15(3):171-202.
5. Kim YJ, Lee H, Park J. Bioactive compounds in chilli peppers and their therapeutic effects. Pharm Adv. 2023;32(2):150-162.
6. Kumar A, Reddy BN. The host range and distribution of thrips in southern India. Indian J Entomol. 2022;84(2):135142. https://doi.org/10.5530/ijent.2022.2.135
7. Kumar A, Thomas R. First record of Thrips parvispinus infesting papaya in Bangalore, India. J Agric Entomol. 2019;15(2):112-118.
8. Kumar V, Meena R. Pests affecting chilli plants and their impact on crop yield. Adv Agric Entomol. 2022;8(4):185195. https://doi.org/10.22271/ae.2022.8.4.185
9. Materska M, Perucka I. Antioxidant activity of the main phenolic compounds isolated from hot pepper fruit (Capsicum annuum L.). J Agric Food Chem. 2005;53(3):1750-1756.
10. Mound LA. The classification of Thrips and related groups. Syst Entomol. 2000;25(3):279-295.
11. Nagaraju K, Reddy BN, Rachana T. Integrated pest management approaches for black thrips in chilli. Plant Prot Strateg. 2021;9(2):145-159. https://doi.org/10.5281/zenodo.5456624
12. National Plant Protection Organization (NPPO). Pest reports and host range documentation. Plant Health Bull. 2022;23(1):45-50.
13. Patel S, Singh R. Survey and specimen analysis of Thrips parvispinus in southern India. J Entomol Res. 2023;41(2):134-145.
14. Patel S, Kumar V, Singh R. Host plant relationships of Thrips parvispinus in vegetable crops. J Hortic Entomol. 2022;40(1):22-30. https://doi.org/10.31377/jhe.2022.v40.i1.22
15. Prasannakumar NR, Rao PS, Desai V. Impact of Thrips parvispinus on chilli crop: Challenges and control strategies. J Agric Pests Control. 2021;14(2):112-120.
16. Rachana T, Varatharajan R. New distributional records of thrips in India. J Insect Taxon. 2017;11(1):65-78.
17. Reddy BN, Kumar P, Sharma H. The emergence of Thrips parvispinus and its impact on chilli production. Indian J Pest Manag. 2022;30(4):389-396.
18. Reddy BN, Kumar S, Priya J. Outbreak and damage assessment of invasive Thrips parvispinus on chilli crops in southern India. Entomol Pest Manag J. 2023;21(1):67-76.
19. Shankar D, Ghosh A, Bhattacharya A. Natural enemies of thrips: Predatory mites and their role in pest management. Int J Pest Manag. 2023;69(2):100-109. https://doi.org/10.1080/09670874.2023.2196391
20. Sharma R, Gupta N, Kumar A. Advances in the bioactive components and potential health benefits of Capsicum annuum L. J Nutraceutical Res. 2021;5(1):45-56.
21. Singh A, Verma H. Host plants of thrips in agroecosystems: A review. Asian J Entomol. 2023;15(1):8-15. https://doi.org/10.5530/aje.2023.1.008
22. Singh A, Patel R, Verma H. Biotic and abiotic stress factors influencing chilli production in India: An analysis. Indian J Hortic Sci. 2022;56(3):304-315.
23. Singh A, Sharma P, Kaur A. Fungal biocontrol agents in pest management: A review. J Entomol Res. 2020;44(4):100-110. https://doi.org/10.5958/0974-8172.2020.00014.5
24. Sridhar S, Reddy BN, Rachana T. The host plant spectrum of Thrips parvispinus in horticultural crops. J Pest Manag. 2021;19(3):211-220. https://doi.org/10.36505/jpm.2021.3.211
25. Surh YJ. Anti-inflammatory and anti-tumor promoting effects of capsaicin and its analogs. Crit Rev Food Sci Nutr. 2002;42(2):109-115.
26. Tyagi K, Kumar V. A checklist of Thysanoptera from India. Indian J Entomol. 2016;78(3):235-250.
27. Tyagi K, Kumar V, Meena R. Host plants of thrips in India: A review. Indian J Entomol. 2015;77(4):303-312. https://doi.org/10.5958/0974-8172.2015.00104.6
28. Zhang M, Wang H. Capsaicin as a potential agent for health: A pharmacological overview. J Med Plant Res. 2023;27(3):290-305.