Rugose spiraling whitefly, Aleurodicus rugioperculatus Martin (Hemiptera: Aleyrodidae) on coconut: biology and management: A detailed review

Introduction

Coconut (Cocos nucifera L.) is one of the most important plantation crops cultivated in tropical regions, contributing significantly to food security, rural employment and agro-based industries. However, coconut production is constrained by several biotic stresses, among which insect pests play a dominant role. In recent decades, the spiraling whitefly, Aleurodicus rugioperculatus Martin (Hemiptera: Aleyrodidae), has emerged as a serious invasive pest affecting coconut plantations. Originally native to Central America and the Caribbean, it has spread rapidly across Asia, Africa and the Pacific due to globalization and increased plant trade (Waterhouse and Norris, 1987) [28] . In India, the pest has become well established in major coconut-growing states such as Tamil Nadu, Kerala, and Karnataka, where favorable climatic conditions support its proliferation (Mani and Krishnamoorthy, 2002) [13] . The recent invasion of rugose spiraling whitefly, Aleurodicus rugioperculatus, has further aggravated the situation. This species was first reported in India around 2016 and has since caused widespread damage to coconut palms and other host plants (Sundararaj and Selvaraj, 2017) [27] . Compared to A. dispersus, the rugose spiraling whitefly produces more wax and honeydew, leading to severe sooty mold formation and greater reduction in photosynthetic efficiency. The increasing incidence of these pests highlights the need for a comprehensive understanding of their biology and management. RSW infestation on coconut was first described from Central America is believed to be the centre of origin for the pest. RSW is a highly polyphagaous pest with more than 118 hosts belonging to 43 diverse plant families (Martin, 2004) [14] Among the hosts, palms constitute 22%, followed by Bursera simaruba (16%), Calophyllum spp., (10%), avocado (9%), black olive (4%), and mango varieties (3%) (Francis et al., 2016) [8] . RSW has already been identified as a serious threat to the cultivation of coconut palms and other Arecaceae species in Florida (Kumar et al., 2018 and Stocks et al., 2012) [11,25] . Initially, 17 plant species (belonging to 11 families) were recorded as preferred hosts for RSW after the pest reached South Kerala (Shanas et al., 2016) [24] . Subsequently, the incidence of RSW was reported in the states of Kerala, Karnataka, Andhra Pradesh, Assam, Goa, West Bengal, Maharashtra and Gujarat on several crops such as coconut, banana, sapota, corn, oil palm, mango, cashew and many other ornamental plants (Selvaraj et al., 2016, and Selvaraj et al., 2017) [22,27] . The availability of a wide range of host plants, combined with congenial climatic conditions, favored their successful establishment in the areas of invasion. Both the nymphs and adults of RSW directly suck the phloem sap of the leaf and secrete honey dew which encourages the growth of sooty mould on the leaf surface that eventually reduces the photosynthesis in the affected palms. Currently, RSW has become a regular pest of coconut, warranting effective integrated pest management (IPM) strategies

Surveys on spiraling whitefly infestation

Spiraling whitefly, Aleurodicus dispersus Russell, and the more recently invasive rugose spiraling whitefly, Aleurodicus rugioperculatus, have emerged as major pests of coconut ecosystems across tropical regions. Surveys conducted in different parts of Asia have revealed that the infestation levels vary widely depending on climatic conditions, host availability, and management practices. In India, particularly in southern states such as Tamil Nadu and Kerala, the pest has shown rapid establishment and spread since its introduction, with severe outbreaks reported in coconut plantations (Sundararaj and Selvaraj, 2017 and Maruthadurai et al., 2023) [27,15] . Field surveys indicate that spiraling whitefly infestation is characterized by dense colonization on the undersurface of leaves, with eggs laid in spiral patterns and heavy accumulation of waxy secretions. The infestation intensity has been reported to range from moderate to severe, depending on the season and location. For instance, surveys in South Asia have recorded infestation levels exceeding 70% in coconut plantations, with some areas showing neartotal infestation of palms (Moon and Amin, 2023) [17] . Such high infestation levels significantly reduce the photosynthetic capacity of coconut leaves due to the development of sooty mold on honeydew deposits. Roving surveys conducted across different agro-climatic zones have demonstrated that spiraling whitefly populations are influenced by environmental conditions, particularly temperature and humidity. Peak infestation is generally observed during dry seasons when rainfall is low, allowing uninterrupted development of the pest. Conversely, heavy rains can reduce infestation levels by washing off eggs and nymphs (Byrne and Bellows, 1991) [5] . Seasonal incidence studies further reveal that population peaks often coincide with periods of high vegetative growth in coconut palms, providing abundant feeding sites (Boopathi et al., 2015) [4] . Survey-based studies have also highlighted the role of host plant diversity in influencing infestation levels. Coconut plantations surrounded by alternate host plants such as banana, guava, and ornamental species tend to exhibit higher infestation levels due to continuous availability of suitable hosts (Waterhouse and Norris, 1987) [28] . In contrast, monoculture plantations with proper sanitation practices show relatively lower infestation levels. Recent ecological studies have further confirmed that host plant characteristics significantly influence the developmental and reproductive biology of spiraling whitefly, thereby affecting population dynamics (Boopathi, 2021) [4] . Another important aspect revealed through surveys is the distribution of different life stages on coconut leaves. Eggs and early instar nymphs are usually concentrated on the lower surface of young leaves, while later instars and pupae are distributed more evenly across mature leaves. The aggregation behavior of the pest leads to localized hotspots of infestation, which can expand rapidly if not controlled. Studies on population density have shown that the number of individuals per leaflet can vary significantly, indicating uneven distribution within plantations (Arifunnahar et al., 2018) [1] . Survey data have also emphasized the importance of natural enemies in regulating spiraling whitefly populations. Parasitoids such as Encarsia guadeloupae and predators like Chrysoperla spp. and Cryptolaemus montrouzieri are commonly observed in infested coconut ecosystems. However, their effectiveness varies depending on environmental conditions and pesticide use. In areas where natural enemies are conserved, a significant reduction in whitefly populations has been observed (Mani and Krishnamoorthy, 2002) [13] . Field observations further indicate that parasitization rates can exceed 70% under favorable conditions, highlighting the potential of biological control in managing infestations (Selvaraj et al., 2023) [20] . Recent surveys have also focused on the rapid spread and invasive potential of rugose spiraling whitefly. Since its first report in India, the pest has expanded its range across multiple states within a short period, indicating high dispersal ability and adaptability (Maruthadurai et al., 2023) [15] . Climate modeling studies suggest that large areas of India are suitable for its establishment, raising concerns about future outbreaks. Similar patterns of rapid spread have been observed in other countries, emphasizing the global threat posed by this pest. In terms of damage assessment, survey-based studies have reported significant reductions in coconut yield due to spiraling whitefly infestation. The combined effects of sap sucking and sooty mold formation result in reduced photosynthesis, leading to poor nut development and yield loss. In severe cases, prolonged infestation can cause decline in tree health and productivity (Balikai and Pushpalatha, 2018) [1] . Quantitative assessments of yield loss are still limited, but available data suggest substantial economic impact, particularly in smallholder farming systems. Management-oriented surveys have highlighted the effectiveness of integrated pest management (IPM) strategies in reducing infestation levels. The use of biological control agents, particularly parasitoids and entomopathogenic fungi such as Isaria fumosorosea and Simplicillium lanosoniveum, has shown promising results under field conditions (Sujithra et al., 2021) [26] . Surveys also indicate that eco-friendly approaches such as neem oil sprays and mechanical removal of infested leaves can significantly reduce pest populations when implemented at early stages.

Overall, survey studies clearly demonstrate that spiraling whitefly infestation on coconut is influenced by a complex interaction of biological, ecological, and management factors. High infestation levels are associated with favorable climatic conditions, presence of alternate hosts, and lack of effective natural enemy activity. Conversely, adoption of IPM practices and conservation of natural enemies can significantly reduce infestation levels and mitigate damage.

Distribution and Host Range

Spiraling whitefly is highly polyphagous, which greatly enhances its invasive potential and ecological adaptability. It has been reported on more than 200-300 plant species, including economically important crops such as coconut, banana, guava, citrus, mango, sapota, and ornamental plants (Waterhouse and Norris, 1987) [28] . This extensive host range allows the pest to survive throughout the year by shifting between hosts depending on seasonal availability. In India, the pest has shown rapid geographic expansion, particularly in southern states where climatic conditions such as high temperature and humidity favor its development. The presence of alternate host plants in and around coconut plantations acts as a continuous source of infestation, making control measures more complex. Studies have shown that mixed cropping systems and the presence of unmanaged host plants significantly contribute to population buildup (Boopathi et al., 2015) [4] . Thus, landscape-level management is essential to effectively control this pest.

Biology and Life Cycle

The biology of spiraling whitefly is characterized by high reproductive capacity, short generation time and overlapping generations, all of which contribute to its pest status. Adult whiteflies are small, white, moth-like insects covered with waxy secretions that protect them from environmental stress and natural enemies. Females lay eggs in a characteristic spiral pattern on the underside of leaves, which serves as a diagnostic feature for field identification. Eggs hatch within 7-10 days into first instar nymphs, commonly known as crawlers. These crawlers are the only mobile immature stage and actively search for suitable feeding sites. Once settled, they insert their stylets into plant tissues and remain sessile for the rest of their development. The nymphs pass through four instars before entering the pupal stage. The entire life cycle is completed in approximately 25-30 days under optimal conditions, although it may extend under unfavorable environmental conditions (Byrne and Bellows, 1991) [5] . In the case of rugose spiraling whitefly, the developmental period is longer, often ranging from 45 to 60 days, depending on host plant and environmental factors (Selvaraj et al., 2019) [19] . The high fecundity of females, coupled with rapid development and absence of diapause, enables the pest to build up large populations within a short period. Additionally, the waxy covering produced by nymphs provides protection against desiccation and insecticides, making management more difficult.

Nature and Mechanism of Damage

The damage caused by spiraling whitefly is both direct and indirect, with the latter often being more severe. Direct damage occurs due to sap feeding by nymphs and adults, which leads to depletion of plant nutrients. This results in symptoms such as chlorosis, leaf curling, reduced leaf area, and premature leaf drop. Continuous feeding weakens the plant and reduces its overall vigor (David and Ananthakrishnan, 2004) [6] . Indirect damage is primarily associated with the secretion of honeydew, a sugary substance excreted by feeding whiteflies. Honeydew accumulates on leaf surfaces and provides a substrate for the growth of sooty mold fungi. The black coating formed by sooty mold reduces light interception and photosynthetic efficiency, thereby affecting carbohydrate synthesis and plant growth. In coconut palms, this leads to reduced nut set, poor nut development, and ultimately lower yield. Severe infestations may also interfere with transpiration and gas exchange, further stressing the plant (Boopathi et al., 2015) [4] . Recent studies have also indicated that heavy infestations can alter the microenvironment of the leaf surface, promoting secondary infections and reducing the effectiveness of natural enemies. Thus, the overall impact of spiraling whitefly extends beyond simple sap feeding and involves complex physiological and ecological interactions.

Ecology and Population Dynamics

The population dynamics of spiraling whitefly are influenced by several biotic and abiotic factors. Temperature, humidity, and rainfall play a crucial role in determining the rate of development and survival. Warm and humid conditions are highly favorable, whereas heavy rainfall can reduce populations by washing away nymphs and eggs. Seasonal fluctuations are commonly observed, with peak populations occurring during dry periods (Byrne and Bellows, 1991) [5] . Natural enemies also play a significant role in regulating whitefly populations. However, their effectiveness is often reduced by indiscriminate use of insecticides. Studies have shown that ecosystems with high biodiversity tend to have lower whitefly populations due to better natural enemy activity (Mani and Krishnamoorthy, 2002) [13] . Understanding these ecological interactions is essential for developing sustainable management strategies.

Integrated pest management (IPM) in coconut

Management of spiraling whitefly requires a holistic and integrated approach that combines multiple control methods. Cultural practices such as pruning of infested leaves, maintaining proper plant spacing, and avoiding excessive nitrogen fertilization are important preventive measures. These practices reduce the suitability of the environment for pest development and enhance the effectiveness of natural enemies (Balikai and Pushpalatha, 2018) [1] . Mechanical control methods, including spraying water to dislodge nymphs and using sticky traps for monitoring, can help reduce initial infestations. However, these methods are labor-intensive and less effective under heavy infestation. Chemical control should be used judiciously and only when pest populations exceed economic threshold levels. Selective insecticides such as spinosad and emamectin benzoate can be effective but may negatively impact natural enemies if used indiscriminately (Balikai and Pushpalatha, 2018) [1] . Therefore, chemical control should be integrated with biological methods to ensure sustainability. Biological control is considered the cornerstone of spiraling whitefly management. Parasitoids such as Encarsia guadeloupae and Encarsia haitiensis have been successfully used to control whitefly populations by parasitizing nymphal stages (Mani and Krishnamoorthy, 2002) [13] . Predators such as Nephaspis oculata and Chrysoperla spp. feed on eggs and nymphs, significantly reducing pest populations. In addition, entomopathogenic fungi such as Beauveria bassiana and Lecanicillium lecanii have shown promising results in field conditions, particularly under humid environments (Boopathi et al., 2015) [4] . Among the various biocontrol agents, entomopathogenic fungi (EPF) have been found to be successfully developed as mycopesticides in managing piercing-sucking groups of insects including whiteflies. Whiteflies are known to be infected by more than 20 species of entomopathogenic fungi, of which some of the widely studied fungi are Beauveria bassiana (Vuillemin), Akanthomyces lecanii (Zimm.) and Cordyceps fumosorosea (Wize) (Kepler et [10,16,12,7] . EPFs are considered as potent alternatives for whitefly management because of their unique ability to invade the host insects directly by penetrating through the integument without the concern of resistance development (Gao et al., 2017) [9] . Severe infestation of RSW in palm oil resulted in a reduction of 20-25% bunch yield at Andhra Pradesh (Selvaraj et al., 2019) [19] . Likewise, RSW has become a serious predicament for coconut growers, hence efforts were made to identify the indigenous potential biological control associated with the invasive pest. Integrated Pest Management (IPM) is the most effective approach for managing spiraling whitefly in coconut ecosystems. IPM emphasizes regular monitoring, conservation of natural enemies, and minimal use of chemicals. The use of neem-based products, fish oil rosin soap, and biological control agents has been widely recommended as eco-friendly alternatives (Selvaraj et al., 2019) [19] .

Challenges and future prospects

Despite significant progress in understanding and managing spiraling whitefly, several challenges remain. These include rapid spread of invasive species, development of insecticide resistance, climate change, and limited availability of biological control agents. In addition, lack of awareness among farmers and inadequate extension services hinder the adoption of IPM practices (Sundararaj and Selvaraj, 2017) [27] . Future research should focus on developing resistant coconut varieties, improving mass production and distribution of natural enemies and utilizing advanced technologies such as molecular tools for pest monitoring. Strengthening farmer education and extension programs will be crucial for sustainable pest management.

Conclusion

Spiraling whitefly is a major pest of coconut that causes significant economic losses through both direct and indirect damage. Its high reproductive potential, wide host range, and adaptability make it difficult to control. However, integrated pest management strategies that emphasize biological control and ecological sustainability offer a promising solution. Continued research, farmer awareness, and policy support are essential to effectively manage this pest and ensure sustainable coconut production.

References

1. Arifunnahar M, Ferdous Z, Alim MA, Hossain MA. Incidence of spiraling whitefly and associated natural enemies. J Bio-Sci. 2018;24:45-52.
2. Balikai RA, Pushpalatha. Bio-ecology and management of spiraling whitefly. Farming Manag J. 2018;3(1):5665.
3. Boopathi T. Host plant influence on spiraling whitefly distribution. Phytoparasitica. 2021;49(1):1-23.
4. Boopathi T, Karuppuchamy P, Mohankumar S, Kalyanasundaram M. Studies on the biology and management of spiraling whitefly (Aleurodicus dispersus). J Entomol Zool Stud. 2015;3(5):54-59.
5. Byrne DN, Bellows TS. Whitefly biology. Annu Rev Entomol. 1991;36:431-457.
6. David BV, Ananthakrishnan TN. General and applied entomology. 2nd ed. New Delhi: Tata McGraw-Hill Publishing Company Ltd.; 2004.
7. Faria M, Wraight SP. Biological control of Bemisia tabaci with fungi. Crop Prot. 2001;20:767-778.
8. Francis AW, Stocks IC, Smith TR, Boughton AJ, Mannion CM, Osborne LS. Host plants and natural enemies of rugose spiraling whitefly (Hemiptera: Aleyrodidae) in Florida. Fla Entomol. 2016;99:150153.
9. Gao T, Wang Z, Huang Y, Keyhani NO, Huang Z. Lack of resistance development in Bemisia tabaci to Isaria fumosorosea after multiple generations of selection. Sci Rep. 2017;7:427.
10. Kepler RM, Luangsa-Ard JJ, Hywel-Jones NL. A phylogenetically-based nomenclature for Cordycipitaceae (Hypocreales). IMA Fungus. 2017;8:335-353.
11. Kumar V, McKenzie CL, Mannion C, Stocks I, Smith T, Osborne LS. Rugose spiraling whitefly, Aleurodicus rugioperculatus Martin (Hemiptera: Aleyrodidae). EENY578. Gainesville (FL): University of Florida, IFAS Extension; Available from: https://entnemdept.ufl.edu/creatures/orn/Aleurodicus_ru gioperculatus.htm [Accessed 2018 Jan 5].
12. Li SJ, Xue X, Ahmed MZ, Ren SX, Du YZ, Wu JH. Host plants and natural enemies of Bemisia tabaci (Hemiptera: Aleyrodidae) in China. Insect Sci. 2011;18:101-120.
13. Mani M, Krishnamoorthy A. Biological control of spiraling whitefly, Aleurodicus dispersus Russell (Homoptera: Aleyrodidae). Biocontrol News Inf. 2002;23(3):55N-62N.
14. Martin JH. The whiteflies of Belize (Hemiptera: Aleyrodidae): introduction and account of the subfamily Aleurodicinae Quaintance and Baker. Zootaxa. 2004;681:1-119.
15. Maruthadurai R, Das B, Ramesh R. Invasion risk of rugose spiraling whitefly in India. Pest Manag Sci. 2023;79(1):295-305.
16. Mascarin GM, Kobori NN, Quintela ED, Delalibera I. The virulence of entomopathogenic fungi against Bemisia tabaci biotype B (Hemiptera: Aleyrodidae) and their conidial production using solid substrate fermentation. Biol Control. 2013;66:209-218.
17. Moon TT, Amin MR. Infestation of rugose spiraling whitefly on coconut. Ecol J. 2023;5(1):81-90.
18. Singh S, Ramanujam B, Sandhu RK, Poornesha K, Kundu R. Natural occurrence of entomopathogenic International Journal of Advanced Biochemistry Research https://www.biochemjournal.com fungus, Aschersonia aleyrodis on citrus whitefly, Dialeurodes citri (Ashmead) in kinnow mandarin in Punjab, India. J Biol Control. 2021;35(3):181-186.
19. Selvaraj K, Sundararaj R, Venkatesan T. Biology and management of rugose spiraling whitefly (Aleurodicus rugioperculatus) on coconut. J Appl Nat Sci. 2019;11(1):259-263.
20. Selvaraj K, Sundararaj R, Venkatesan T. Parasitoid interaction with whiteflies. Biochem Syst Ecol. 2023;111:104746.
21. Selvaraj K, Gupta A, Venkatesan T, Jalali SK, Ballal CR, Sundararaj R. First record of invasive rugose spiraling whitefly, Aleurodicus rugioperculatus Martin (Hemiptera: Aleyrodidae) along with parasitoids in Karnataka. J Biol Control. 2017;31:74-78.
22. Selvaraj K, Sundararaj R, Venkatesan T, Ballal CR, Jalali SK, Gupta A, et al. Potential natural enemies of the invasive rugose spiraling whitefly, Aleurodicus rugioperculatus Martin in India. J Biol Control. 2016;30:236-239.
23. Selvaraj K, Venkatesan T, Sumalatha BV, Kiran CM. Invasive rugose spiralling whitefly, Aleurodicus rugioperculatus Martin, a serious pest of oil palm Elaeis guineensis in India. J Oil Palm Res. 2019;31:651-656.
24. Shanas S, Job J, Joseph T, Anjukrishnan G. First report of invasive rugose spiraling whitefly, Aleurodicus rugioperculatus Martin (Hemiptera: Aleyrodidae) from the Old World. Entomon. 2016;41:365-368.
25. Stocks I, Hodges G. The rugose spiralling whitefly, Aleurodicus rugioperculatus Martin, a new exotic whitefly in South Florida (Hemiptera: Aleyrodidae). DACS-P-01745. Tallahassee (FL): Florida Department of Agriculture and Consumer Services, Division of Plant Industry; 2012. p. 1-6.
26. Sujithra M, Prathibha HV, Rajkumar M, GuruPirasanna-Pandi G, Senthil-Nathan S, Hegde V, et al. Entomopathogenic potential of Simplicillium lanosoniveum native strain in suppressing invasive whitefly, Aleurodicus rugioperculatus Martin (Hemiptera: Aleyrodidae), infesting coconut. J Fungi. 2021;7(11):964.
27. Sundararaj R, Selvaraj K. Invasion of rugose spiraling whitefly (Aleurodicus rugioperculatus) in India. Curr Sci. 2017;112(8):1723-1725.
28. Waterhouse DF, Norris KR. Biological control: Pacific prospects. Melbourne: Inkata Press; 1987.