Influence of weather variables on the host range and population dynamics of guava spiralling whitefly (Aleurodicus dispersus Russell) in Tiruchirappalli district of Tamil Nadu, India

Introduction

Guava (Psidium guajava L.) a member of the Myrtaceae family, is also known as "Poor man's apple" and the "Apple of Tropics". It is one of the most important commercially grown fruit crop in many tropical and subtropical regions worldwide with abundant source of vitamins, minerals, soluble sugars and fibers (Singh, 2011; Khan, 2017; Angulo-Lopez et al., 2021) [23,7,1] . Guava production faces significant threats from various biotic stresses including numerous insect pests such as spiralling whitefly, mealybugs, aphids, thrips, tea mosquito bugs, scale insects, psyllids, fruit flies, hairy caterpillars and leaf weevils (Nair and Visalakshi, 1999; Baradevanal et al., 2018; Picanco et al., 2022) [12,2,15] . Among these pests, the spiralling whitefly-Aleurodicus dispersus Russell (Aleyrodidae; Hemiptera) the second invasive whitefly in India, is a major sucking pest that inflicts substantial damage on guava trees adversely affecting yield and fruit quality (Gupta et al., 2018; Rashid et al., 2003; Reddy et al., 2020; Sampiano and Aceres, 2021) [6,18,20,21] . The spiralling whitefly, Aleurodicus dispersus is native to Central America and was first collected from coconut plantations in Florida-USA in 1957, with its formal description by Russell in 1965. During its description, Russell documented 44 plant species as hosts of the spiralling whitefly from regions including Florida, Central and South America and the Caribbean islands. A. dispersus is notable for having the highest number of host plants among whiteflies with 481 plant species spanning 295 genera and 90 families. In India, it is known to attack 253 plant species, which accounts for 52.5% of its known host plant species (Srinivasa, 2000) [24] . In India, Aleurodicus dispersus was first recorded on cassava in Kerala in 1993 (Palanisami et al., 1995) [13] . It was subsequently reported in the Western Ghats of Kerala and the Kanyakumari district of Tamil Nadu on various hosts (David and Regu, 1995) [4] . The pest was also noted in Maharashtra in 1997 (Sathe, 1999) [22] , Andhra Pradesh in 1998 (Reddy and Chandurkar, 1999) [19] and in Karnataka from Bangalore on guava (Mani and Krishnamoorthy, 2000) [9] . Due to its rapid dispersal, the pest is now widespread throughout Tamil Nadu, emerging as a key pest on numerous cultivated plant species including fruits, plantations, vegetables, field crops and ornamental plants. Some significant cultivated hosts include guava, banana, coconut, mulberry, mango, fig, papaya, cassava, chili, cotton, okra, tomato, eggplant, citrus, avocado, rose, hibiscus, crotons and acalypha. While the literature on the rugose spiralling whitefly Aleurodicus rugioperculatus is sparse, the host range of the spiralling whitefly Aleurodicus dispersus has not been extensively studied in Tamil Nadu. Therefore, the present study aims to explore the host range and population dynamics of Aleurodicus dispersus in the Tiruchirappalli district of Tamil Nadu.

Materials and Methods

An intensive survey was conducted from 2023 to 2024 in Tiruchirappalli district covering the blocks of Andhanallur, Lalgudi, Manikandam, Manapparai, and Thiruverumbur (Figure 1.) to document the various host plants and to assess the damage intensity of Aleurodicus dispersus. Host plants were recorded by randomly surveying plant species along roadsides, household ornamentals, kitchen gardens, field and horticultural crops in both urban and rural areas. The host plants were photodocumented and the samples were collected for preservation. Specimens from heavily infested guava and country almond plants were collected and sent to NBAIR, Bengaluru for species identification and were confirmed as Aleurodicus dispersus. Observations on the damage intensity were recorded in three villages within each block. In each village, five orchards were selected and within each orchard ten trees were selected randomly and observations on percent infestation were made on upper, middle and lower canopy level of each tree and the average were worked out. The population data of Aleurodicus dispersus was recorded at weekly intervals on ten randomly selected, untreated guava trees infested by spiralling whiteflies in the guava orchards of the Department of Horticulture, Horticultural College and Research Institute for Women, Tiruchirappalli over the seven-month study period. The data on weather parameters including maximum temperature, minimum temperature, relative humidity, sunshine, wind velocity, evaporation and rainfall were collected from the Department of Agronomy, Anbil Dharmalingam Agricultural College and Research Institute, Tiruchirrapalli. A simple correlation studies were worked out between the weekly mean level of pest incidence and weather parameters using OPSTAT online software.

Results and discussion

During the survey conducted in selected blocks of Tiruchirappalli district, a total of 35 plant species from 23 families were identified as host plants for Aleurodicus dispersus (Table 1.) with some examples shown in Figure 2. Out of hosts recorded during the present studies, 4 in Arecaceae, 3 in Euphorbiaceae, 2 each in Annonaceae, Apocynaceae, Combretaceae, Fabaceae, Meliaceae, Myrtaceae, Poaceae. Apart from these 14 other families were recorded. Among the hosts plants in this surveyed region all the life stages such as egg spirals, nymphs, adults and the damage intensity was more in the host plants such as Guava, coconut, banana, Indian almond and custard apple. Being polyphagous, A. dispersus is known to attack about 500 plants in different countries (Mware et al., 2010) [11] and 280 in India alone (Ramani et al., 2002; Mani, 2010) [16,8] . The data was collected from several villages within each block and the intensity percentage was recorded and the pooled data of each village is presented in Figure 3. The intensity of Aleurodicus dispersus was assessed across various blocks including Andhanallur, Lalgudi, Manikandam, Manapparai and Thiruverumbur blocks of Tiruchirappalli district during the period from December 2023 to June 2024. The results from the Table 2. revealed that the intensity of infestation was significantly high in manikandam block (41.3%) followed by manapparai (41.14%) and andhanallur block (40.93%). On the other hand, the intensity of infestation was significantly low in thiruverumbur block with the intensity level of (39.6%) and the intensity of incidence was slightly higher in lalgudi block (40.54%) than thiruverumbur block. The variability within each block, as indicated by the standard error, shows that the measurements were relatively consistent across villages within the same block, with the Thiruverumbur block displaying the least variability (SE = 0.08). This suggests that the infestation level of Aleurodicus dispersus is fairly uniform within individual blocks, but there are minor noticeable differences in infestation intensity between different blocks in the Tiruchirappalli district. During the study period from July 2023 (27th standard week) to June 2024 (26th standard week), the population of the spiralling whitefly fluctuations in density corresponding to changes in weather parameters. The population dynamics data from (Table 3.) revealed that in 2023, July to September the population of spiralling whiteflies disappears due to rainy season and thus increases slightly from the first week of October (40 th standard week). Then a peak population of 51.4 individuals per plant was observed during the (7th standard week) in February 2024, which significantly increased in the subsequent months of March and April due to rising temperatures in the summer season. In the first week of May, the population slightly decreased due to sudden rainfall and further declined to the lowest level of 10.5 individuals per plant by the 26th standard week in the last week of June (Figure 4). These results indicate that the spiralling whitefly population is highest in the summer when higher sunshine hours and temperatures accelerate metabolic activities in insects leading to a rapid buildup of pest populations. Conversely, the population is lower during the rainy season, as lower temperatures, high relative humidity and rainfall reduce pest numbers with heavy rains washing them away. These findings are consistent with previous research (Chaman et al., 2021; Patel et al., 2021) [3,14] . Ranjith et al.

(1996) [17] observed a sharp increase in the spiralling whitefly population during the summer followed by a decline after rainfall in Kerala. Mani and Krishnamoorthi (2000) [9] reported that the population of spiralling whitefly was higher from March to June and lower from October to January. Morde et al. (2017) [10] found that the incidence of spiralling whitefly peaked from the first week of March to the last week of May. Elango and Nelson (2020) [5] noted that the infestation of the rugose spiralling whitefly was low during the rainy season, moderate during the post-rainy season and high in the summer. Correlation studies between the mean level of spiralling whitefly population with weather parameters on standard week basis in the guava orchard shows that the population of SWF was positively correlated and highly significant with maximum temperature (r = 0.648), minimum temperature (r = 0.518) and also with sunshine hours (r = 0.637). On the other hand, a significant negative correlation shows with the parameters such as relative humidity both on morning and evening (r = -0.594 and r= -0.314) and rainfall (r =-0.382). A non-significant positive correlation was observed between Aleurodicus population with wind velocity (r= 0.230) and non-significant negative correlation (r= -0.243) with evaporation. Due to the parameters wind velocity and evaporation there was no changes that affects the population of spiralling whiteflies. The present findings are in line with earlier research. Mani (2010) and Elango and Nelson (2020) [8,5] reported a positive correlation between whitefly density and maximum temperature and a negative correlation with relative humidity. Similarly, Yadav and Singh (2013) and Patel et al. (2021) [25,14] observed a significant positive correlation with temperature and sunshine hours, and a negative correlation with relative humidity. These observations are further supported by Morde et al. (2017) [10] , who also found a significant positive correlation with temperature and a significant negative correlation with relative humidity and rainfall.

Conclusion

The exploration of the host range and population dynamics of the guava spiralling whitefly, Aleurodicus dispersus Russell in Tiruchirappalli district of Tamil Nadu has provided critical insights into its behavior and impact on local agriculture. The study identified a wide range of host plants indicating the pest adaptability and potential for widespread infestation. Population dynamics revealed significant seasonal fluctuations with peak infestations correlating with specific climatic conditions. These findings emphasize the need for integrated pest management strategies tailored to the regions unique environmental factors. Continued monitoring and research are essential to mitigate the economic impact on guava and other susceptible crops, ensuring sustainable agricultural practices in Tiruchirappalli.

References

1. Angulo-Lopez JE, Flores-Gallegos AC, Torres-León C, Ramírez-Guzmán KN, Martínez GA, Aguilar CN. Guava (Psidium guajava L.) fruit and valorization of industrialization by-products. Processes. 2021;9(6):1075.
2. Wilczek) during summer 2018. The Pharma Innovation J. 2021;10(10):1121-2.
3. David V, Regu K. Aleurodicus dispersus Russell (Homoptera: Aleyrodidae) a whitefly pest new to India. Pestology. 1995;19(3):5-7.
4. Elango K, Nelson SJ. Population dynamics of exotic rugose spiralling whitefly, Aleurodicus rugioperculatus Martin (Hemiptera: Aleyrodidae) on coconut as influenced by weather factors and natural enemies. J Plantation Crops. 2020;48(2):120-125.
5. Gupta N, Verma SC, Sharma PL, Thakur M, Sharma P, Devi D. Status of invasive insect pests of India and their natural enemies. J Entomol Zool Stud. 2018;7(1):482-489.
6. Khan MMH. Bioefficacy of insecticides on the immature and adult stages of spiralling whitefly on guava. J Entomol Zool Stud. 2017;5(5):380-384.
7. Mani M. Origin, introduction, distribution and management of the invasive spiralling whitefly, Aleurodicus dispersus Russell in India. Karnataka J Agric Sci. 2010;23(1):59-75.
8. Mani M, Krishnamoorthy AA. Population dynamics of spiralling whitefly, Aleurodicus dispersus Russell (Aleyrodidae: Homoptera) and its natural enemies on guava in India. Entomon. 2000;25(1):29-34.
9. Morde SS, Godase SK, Masal MS. Seasonal incidence of spiralling whitefly, Aleurodicus dispersus in Konkan region. Bull Environ Pharmacol Life Sci. 2017;6(2):154-156.
10. Mware B, Olubayo F, Narla R, Songa J, Amata R, Kyamanywa S, Ateka EM. First record of spiralling whitefly in coastal Kenya: Emergence, host range, distribution and association with cassava brown streak virus disease. Int J Agric Biol. 2010;12:411-5.
11. Palaniswami MS, Pillai KS, Nair RR, Mohandas C. A new cassava pest in India. Cassava Newsletter. 1995;19:6-7.
12. Patel R, Marabi RS, Nayak MK, Tomar DS, Srivastava AK. Population dynamics of major sucking insect pests of mungbean [Vigna radiata (L.) Wilczek] in relation to weather parameters. J Entomol Zool Stud. 2021;9(2):324-8.
13. Picanco MM, Silva RS, Azevedo AA, Lima LL, Ramos HJ, Souza OF, et al. Assessment of Triozoida limbata (Hemiptera: Triozidae) attacks: morphological and biochemical changes on Psidium guajava plants. Austral Entomol. 2022;61(4):472-479.
14. Ramani S, Poorani J, Bhumannavar BS. Spiralling whitefly, Aleurodicus dispersus in India. Biocontrol News Inf. 2002;23:55-62.
15. Ranjith AM, Rao DS, Thomas J. New host records of the 'mealy whitefly', Aleurodicus dispersus Russell in Kerala. Insect Environ. 1996;2(2):35-36.
16. Rashid MM, Hossain MM, Alam MZ, Ibrahim M, Bhuiyan MKA. Seasonal abundance and control of spiralling whitefly, Aleurodicus dispersus Russell on guava. Pak J Biol Sci. 2003;6(24):2050-3.
17. Reddy GRS, Chandurkar PS. First record of spiralling whitefly Aleurodicus dispersus (Russell) on guava plants at Hyderabad. Plant Protect Bull-New Delhi. 1999;51(2):24.
18. Sampiano KF, Aceres L. The spiralling whitefly, Aleurodicus dispersus Russell (Hemiptera: Aleyrodidae): A Philippine perspective. Agrikultura -Res Innov J. 2021;2(1):1-15.
19. Sathe TV. Whitefly, Aleurodicus dispersus a new pest of guava, Psidium guajava in Kolhapur, Maharashtra. Indian J Entomol. 1999;61(2):195-6.
20. Srinivasa MV. Host plants of the spiralling whitefly, Aleurodicus dispersus Russell (Hemiptera: Aleyrodidae). Pest Manag Hortic Ecosyst. 2000;6:79-100.
21. Yadav NK, Singh PS. Seasonal abundance of insect pests on mung bean and its correlation. J Entomol Res. 2013;37(4):297-299.