Diversity and Community Structure of Mite Fauna Associated with Pulse Crops in West Bengal

India is the second largest producer of pulse crops after China, producing 133.84 lakh tons of pulses accounting  22 per cent of the world’s production from an area of 223.91 lakh ha, constituting 33 per cent of world’s areas (Bera and Nandi, 2010). Pulses are the cheapest source of dietary amino acids, vitamins and minerals. These have twice  quantity of proteins than whole grains like rice, wheat, oats and barley, that’s why pulses is considered as a poor man’s meat (Cyanam, 2020). In West Bengal, significant pulse cultivation is mainly confined in the districts of Malda, Murshidabad, Nadia, Birbhum, Midnapore and North 24 Parganas contributing approximately 384 thousand metric tons of pulses in the year 2018 (Ray et al., 2013). Various insect  pests and mites like spider mite (Tetranychus spp.), aphid (Aphis craccivora), whitefly (Bemisia tabaci), thrips (Megalurothrips distalis), spotted pod borer (Maruca vitrata), gram pod borer (Helicoverpa armigera), plant bug (Riptortus pedestris), pod bug (Clavigralla gibbosa) and blue butterfly (Catochrysops strabo) have been identified as major threats to pulse crops in West Bengal condition (Biswas and Banerjee, 2019). The annual yield losses due to insect pests and diseases have been estimated about 18-20% and 8-10%, respectively (Dhar and Ahmad, 2004). Predatory mites from the Phytoseiidae family have been recognized as a beneficial group of mites that could be utilized for controlling of harmful phytophagous mites as well as soft-bodied insect pests (Bala et al., 2019; Bala and Karmakar, 2021). Several authors have documented mite fauna associated with agro-horticultural crops (Bala and Karmakar, 2022a), fruit crops (Karmakar, 2018) vegetable  crops (Bala and Karmakar, 2022b) and flowers (Bala and Karmakar, 2023) from West Bengal. But comprehensive reports on mite fauna associated with pulse crops are lacking in West Bengal. Hence to fulfil these lacunae, the present study was undertaken to explore the diversity of mite fauna associated with pulse crops in West Bengal condition.

Study area
 
Mite samples were collected from different agro climatic zones of West Bengal, mainly covering the districts of Nadia, Malda, Murshidabad, Burdwan, North 24 Parganas, South 24 Parganas, Darjeeling, Jalpaiguri and Cooch Behar.
 
Collection and preservation of specimens
 
The mite fauna harboured in different pulse crops was examined by making an extensive survey covering different locations of West Bengal during the year 2021-2023. Different mite samples were collected and examined for identification. Phytoseiid mites are generally bigger in size and fast-moving in nature. They were collected directly from the plants with the help of fine camel hair brush (size 000) and then preserved in 70% alcohol until permanent slides were prepared. Besides, a direct beating method was adopted, simply beating the plant parts over black cardboard and collecting the dislodged mites by using a single hair brush. The mite specimens were preserved in separate small plastic vials containing 70% alcohol mentioning the name of the host plant and the location.
 
Identification of specimens
 
The specimens were brought to the All India Network Project (AINP) on Acarology Laboratory, Department of Agricultural Entomology, Bidhan Chandra Krishi Viswavidyalaya, West Bengal. The collected mite specimens were transferred in a cavity block and mounted on glass slides using modified Berlese’s medium for identification. Slide preparation was done with the help of Stereozoom microscope. The slides were dried by keeping on a hot plate at 35-40oC for 5-7 days. The mites were examined under a phase contrast microscope (BX 53, Olympus, Japan) and the species were identified following the keys provided by Chant and McMurty (2007).
 
Statistical analysis
 
To understand the diversity and community structure of different Phytoseiid and Phytophagous mites in different locations, the number of specimens for each species was enumerated reflecting the species richness (S) and the  diversity and evenness indices calculated based on the formula provided by Simpson (1949); Shannon-Weiner (1963) and Pielou’s (1975).
 
Shannon’s diversity index
 

   

 
Where,
P = Proportion (n/N) of individuals of one particular species found (n) divided by the total number of individuals found (N), In= Natural log.
Σ = Sum of the calculations.
‘S’ = Number of species.
       
The effective number of species (ENS) of each location was calculated taking the exponential of H.
 
Simpson’s index
 

 
Where,
N = Total number of individuals in a community.
‘n’ = Number of individuals of a particular species.
 
Species evenness was calculated from Pielou’s evenness index (E).
 
Pielou’s evenness index

 

 
Where,
H = Shannon’s diversity index.
‘s’ = Total number of species in the surveyed area (Pielou, 1975).

An exploratory survey programme was conducted during the year 2021 to 2023 to identify the mite fauna associated with pulse crops in West Bengal. Ten districts namely Nadia, Malda, Murshidabad, Burdwan, North 24 Parganas, South 24 Parganas, Darjeeling, Jalpaiguri and Cooch Behar of West Bengal were surveyed. Different pulse crops like lentils, green gram, black gram, pigeon pea, dolichos bean, Bengal gram, chick pea, lathyrus, garden pea, bean etc. were examined and near about 2180 mite specimens were collected. Altogether 13 species of Phytoseiid mites viz., Amblyseius largoensis, Amblyseius herbicolus, Amblyseius bengalensis, Amblyseius parbatabasii, Amblyseius dahlia, Euseius alstoniae, Euseius ovalis, Paraphytoseius orientalis, Typhlodromips syzygii, Scapulaseius asiaticus, Scapulaseius moraesi, Phytoseius kapuri, Neoseiulus pranadae were recorded (Table 1). Moreover, under the genus Amblyseius, five species like Amblyseius largoensis, Amblyseius herbicolus, Amblyseius bengalensis, Amblyseius parbatabasii and Amblyseius dhaliae and under the genus Euseius, two species viz. Euseius alstoniae and Euseius ovalis were recorded. Similarly, under the genus Scapulaseius, two species like Scapulaseius moraesi, Scapulaseius asiaticus were recorded. Single species under the genera Paraphytoseius (Paraphytoseius orientalis),Typhlodromips (Typhlodromips syzygii), Phytoseius (Phytoseius kapuri) and Neoseiulus (Neoseiulus pranadae) were recorded. The Phytoseiid mite, Neoseiulus pranadae comprised 35.36 per cent of the total Phytosiid mite population followed by Amblyseius largoensis and Typhlodromips syzygii accounting 23.04% and 10.87% of total Phytoseiid mite population, respectively (Fig 1). The species, Neoseiulus pranadae was recorded as the dominant predatory mite found in surveyed areas. Similarly, Amblyseius parbatabasii was observed as a predominant species in the Darjeeling district, Amblyseius bengalensis and Amblyseius herbicolus were regularly found in Cooch Behar and Jalpaiguri districts, Euseius alstoniae and Euseius ovalis were abundantly found in Nadia, North 24 parganas, South 24 parganas, Malda, Murshidabad and Burdwan districts of West Bengal. Other important predatory mites belong to the families Bdellidae, Ascidae, Stigmaeidae, Cunaxidae and Cheyletidae under the order Prostigmata were also noted during the period of investigation and Cunaxa spp. was the dominant one accounting 37% of the total prostigmatid predatory mite population (Fig 2). So far as the diversity is concerned, maximum diversity of Phytoseiid mite population in terms of H1 = 2.26, with effective number of species 5 and highest dominance D = 0.84 was calculated which reflected that pulse crops is highly congenial for survival of few Phytoseiid mite species but not so favourable for others. Phytophagous mites, Tetranychus urticae (Koch.), Eutetranychus orientalis (Klein), Schizotetranychus baltazari (Hirst). Schizotetranychus cajani were also recorded and fed upon lentil, black gram, green gram, cowpea, pigeon pea, chickpea, lathyrus and garden pea etc. (Table 2). Among them, Tetranychus urticae was the most common species comprising 55.67% of the total plant-feeding mite population followed by Eutetranychus orientalis accounting 22.34% Phytophagous mite population and causes damage (Fig 3). The present findings are agreed with the findings of Maheswary et al., (2015); Singh and Chauhan (2014) and Roy and Gupta (2016), they reported that Tetranychus urticae, Eutetranychus orientalis, Schizotetranychus baltazari. Schizotetranychus cajani infesting on many agro-horticultural crops and causing enormous damage. The maximum diversity of the phytophagous mite was calculated with a Shannon diversity index H1 = 2.13, corresponding effective number of species 3. Additionally, the highest dominance value (D) =0.78. These findings suggested that pulse crops provide favorable environment for the survival of phytophagous mites.










       
Predatory mites prey up on different species of arthropods was investigated and presented in Table1. In this context, Amblyseius largoensis, Amblyseius herbicolus, Amblyseius bengalensis, Amblyseius dahlia, Euseius ovalis, Euseius alstoniae, Typhlodromips syzygii, Paraphytoseius orientalis, Neoseiulus pranadae, Scapulaseius asiaticus, Phytoseius kapuri, Bdelloides spp. Lasioseius parberlesei, Agistemus industani, Cunaxa  spp. and Cheyletus spp. were preyed on Tetranychus spp., Eutetranychus orientalis, Oligonychus mangiferus, Brevipalpus phoenicis, Polyphagotarsonemus latus, eriophyoid mites, mealy bug and pupae of whitefly. The present findings are in line with the authors of Karmakar and Gupta (2011); Bala et al., (2018) and Bala and Karmakar (2021) found that Amblyseius largoensis, Amblyseius herbicolus, Typhlodromips syzygii, Paraphytoseius orientalis, Euseius ovalis, Cheyletogenes spp., Cunaxoides spp. Agistemus spp. were accompanying with agro-horticultural crops and predated upon Tetranychus spp., Polyphagotarsonemus latus, Brevipalpus spp., Eriophyid mite and mealy bug etc. The findings of this studies are also similar with the observations of Escudero and Ferragut (2005); Naher et al., (2005); Onzo et al., (2012); Sharma and Chauhan (2013); Binisha and Bhaskar (2013); Singh and Chauhan (2014). They stated that Phytoseiid mites were most common predators associated with phytophagous mites and serve as effective biological control agent against plant feeding mites.

Phytophagous mites are a serious concern for successful pulse cultivation in West Bengal. Predatory mites were found effective against phytophagous mites and other soft-bodied insects and they could be utilized for a biological control programme to minimize use of chemical pesticides.

The authors are grateful to the coordinator, All India Network Project on Agricultural Acarology for providing the funds and facilities for conducting this study.

The authors are declared that there are no conflicts of interest regarding the publication of this article. No funding or sponsorship influenced the design of the study, data collection, analysis, decision to publish, or preparation of the manuscript.