Legume Research

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Legume Research, volume 45 issue 6 (june 2022) : 775-779

Diversity of Insect Fauna Associated with Summer and Monsoon Cowpea [Vigna unguiculata (L.) Walp.]

Gaurang Chhangani1,*, M.K. Mahla1, R. Swaminathan1, H.K. Jain2, K.C. Ahir1, Kuldeep Sharma1
1Department of Entomology, Rajasthan College of Agriculture, Maharana Pratap University of Agriculture and Technology, Udaipur-313 001, Rajasthan, India.
2Department of Agricultural Statistics and Computer Application, Rajasthan College of Agriculture, Maharana Pratap University of Agriculture and Technology, Udaipur-313 001, Rajasthan, India.
  • Submitted13-10-2020|

  • Accepted05-02-2021|

  • First Online 08-03-2021|

  • doi 10.18805/LR-4529

Cite article:- Chhangani Gaurang, Mahla M.K., Swaminathan R., Jain H.K., Ahir K.C., Sharma Kuldeep (2022). Diversity of Insect Fauna Associated with Summer and Monsoon Cowpea [Vigna unguiculata (L.) Walp.] . Legume Research. 45(6): 775-779. doi: 10.18805/LR-4529.
Background: Cowpea [Vigna unguiculata (L.) Walp.], is one of an important pulse grown throughout the world. The cowpea crop helps in fixation of atmospheric nitrogen; besides, it supports the natural enemies’ population. The study on diversity of pestiferous insect associated with cowpea crop help to understand the population dynamics of these pests depending on location and seasons. These diversity studies are useful to formulate management practices which are area specific.

Methods: An extensive survey was conducted at different locations (Udaipur, Bhilwara, Banswara, Chittorgarh and Pratapgarh) of southern Rajasthan during summer (Zaid) and monsoon (Kharif) seasons of 2019 and 2020. The randomly selected plants were observed for pestiferous insect population to calculate different diversity indices.

Result: The insect pest complex of cowpea categorized into 5 orders viz., Hemiptera, Thysanoptera, Coleoptera, Diptera and Lepidoptera comprising 14 families. The pestiferous fauna includes population of flea beetle, jassids, whiteflies, sap sucking bugs, leaf miner, thrips, aphids, spotted pod borer and lycaenid caterpillar. During the study, it was found that overall species richness was more during the monsoon season as compared to that during the summer. The relative diversity of aphids was the maximum on account of the clumped distribution and exponential growth. In 2019, the maximum diversity was recorded in Banswara (Simpson index= 6.49 and Shannon index= 2.04) during monsoon; whereas, in 2020, the maximum diversity was recorded in Bhilwara (Simpson index= 4.03 and Shannon index= 1.81) during summer.
Cowpea [Vigna unguiculata (L.) Walp], an important annual legume improves the protein source in vegetarian diet. The herbaceous plant known as mini-factory of fertilizer as they fix the atmospheric nitrogen with the help of rhizobium bacteria. Cowpea is known to harbor many natural enemies of pestiferous insects, which exert a significant role in their suppression.
       
The damage by insect pests is one of the major constraints accounting for low level of yield. Cowpea crop is extensively infested by 21 insect pests from different groups cultivated during summer and monsoon season (Sardana and Verma, 1986). Some of the insects also act as vectors of various virus diseases or as defoliators, damage to flowers and pods. Cowpea crop is infested by the legume aphid (Aphis craccivora Koch), foliage beetles (Ootheca sp., Medythia spp.), the flower bud thrips (Megalurothrips sjostedti Trybom), the legume pod borer (Maruca vitrata Fabricius) and the sucking bug complex including: Clavigralla spp., Anoplocnemis spp., Riptortus spp., Mirperus spp., Nezara viridula Fab. and Aspavia armigera Linnaeus (Meena et al., 2017).
       
The different diversity indices accounts for species richness and abundance. A large number of species can increase diversity. Similarly, increasing the uniformity of individuals’ distribution among species will also increase diversity. The biodiversity studies will facilitate researchers to understand the abundance and species richness of insect fauna associated with cowpea. It gives an account to quantify the interaction between the insect pest and their associated natural enemies. This knowledge helps to understand the insect ecology, hence provides a guide for developing management tools which are area specific and result in efficient reduction in pest damage.
With a view to estimate the comparative diversity of insect pests of summer (Zaid) and monsoon (Kharif) seasons cowpea at Department of Entomology, Rajasthan College of Agriculture, MPUAT during 2019 and 2020. Population data for insect pests were recorded from the 5 different locations in districts viz., Udaipur, Bhilwara, Banswara, Chittorgarh and Pratapgarh. Observations for both the sucking complex and foliage feeder were taken from 10 randomly selected plants of cowpea by the visual-count-technique at 15 days interval using pest-specific standard sampling methodology.
 
i.    The populations of jassids, whiteflies, flea beetles, minor and sap sucking bugs were estimated either during 6 to 8 am or 4 to 6 pm depending upon the time of arrival at the location surveyed.
ii.    Nymphs and adults of aphids were counted from the plants directly by visual method taking at least a 10 cm twig sampling.
iii.   The associated natural enemies like coccinellids, wasps and predatory bugs were recorded by the visual count technique from the same plants randomly, during their peak activity.
 
The following mathematical analyses have been done
 
a) Mean density


Where
Xi = No. of insects or natural enemies in ith sample.
N = Total No. of plants sampled.
 
b) Relative density
 
               
       
c)     Diversity indices
 
Suitable alpha-diversity indices were computed as per the recorded data:
     
                               
 
Where
pi = The decimal fraction of individuals belonging to ith species.
The biodiversity of insect fauna associated with cowpea was observed from different locations of southern Rajasthan. The insect collected from cowpea were belongs to order Lepidoptera, Coleoptera, Hemiptera, Thysanoptera and Diptera; whereas, the families comprised Agromyzidae, Aleyrodidae, Alydidae, Aphididae, Chrysomelidae, Cicadellidae, Coccinellidae, Coreidae, Geocoridae., Lycaenidae, Noctuidae, Pentatomidae, Reduviidae, Sryphidae and Thripidae. The flea beetle (Phyllotreta spp.) was first to appear at all the surveyed location and lycaenid borer (Lampides spp. and Euchrysops spp.) was last to invade the crop. Both of these insects were also recorded by Patel et al., 2010, Patient et al., 2019 and Sharma et al., 2019 from different locations.
       
During the study, it was noticed that overall species richness was more during the monsoon season as compared to summer season. It is evident from Table 1 to 3, that the total spices abundance was the maximum at Banswara during monsoon, 2019; whereas, it was the maximum for Bhilwara during monsoon, 2020. The relative diversity of aphids was the maximum on account of the clumped distribution and exponential growth (Table 1 and 2). Thrips population was not observed at Chittorgarh and Pratapgarh during summer, 2019; while it was noticed at Pratapgarh during monsoon, 2019.

Table 1: Diversity of pestiferous insect fauna associated with cowpea at different locations during 2019.



Table 2: Diversity of pestiferous insect fauna associated with cowpea at different locations during 2020.



Table 3: Summarized indexation of pestiferous insect faunal diversity over the two-year study in cowpea.


       
During summer, Udaipur had the highest value of Simpson index (3.35) followed by Bhilwara (2.79), Banswara (2.45) and Chittorgarh (2.34), while, Pratapgarh (2.16) had the lowest value. The Simpson index was calculated to be highest for Banswara (6.49) followed by Bhilwara (3.40), Chittorgarh (3.35), Udaipur (3.14) and lowest diversity index was recorded for Pratapgarh (2.84) during monsoon.
       
Similarly, the highest Shannon index was recorded at Udaipur (1.67) during summer followed by Bhilwara (1.54), Banswara (1.43) and Chittorgarh (1.35). The Shannon index was lowest for Pratapgarh (1.26) during summer. The Shannon index was highest for Banswara (2.04) followed by Bhilwara (1.69), Udaipur (1.63) and Chittorgarh (1.58) during monsoon, while, the lowest value was recorded for Pratapgarh (1.46) (Table 3).
       
During summer season, Simpson index was highest for Bhilwara (4.03) followed by Banswara (3.75), Pratapgarh (3.45) and Chittorgarh (3.43), while, the highest Simpson index was observed for Bhilwara (3.96) followed by Chittorgarh (3.76), Pratapgarh (3.67), Banswara (3.61) during monsoon. The lowest Simpson index was observed for Udaipur (2.67 and 3.49) during summer and monsoon, respectively (Table 3).
       
The value of Shannon index was calculated to be highest for Bhilwara (1.81) followed by Banswara (1.76), Pratapgarh (1.56) and Chittorgarh (1.53) during the summer. Similarly, it was highest for Bhilwara (1.80) and was followed by Chittorgarh (1.76), Pratapgarh (1.75) and Banswara (1.73) during monsoon. The lowest Shannon index (1.51 and 1.71) for summer and monsoon season was recorded in cowpea grown at Udaipur (1.51 and 1.71) (Table 3).
       
The present study observed that the insect fauna in monsoon cowpea were more diverse in higher and lower levels of taxa. The present findings are more or less  in accordance with the earlier work of Pinjara (2017) who reported that Shannon diversity indices ranged from1.72 to 1.54 as per crop and location in Udaipur. As much work has not been done on comparative studies on insect pest diversity of cowpea, there is a need to initiate further research work.
From the present study it can be concluded that, the species richness and abundance of insect species was more during monsoon season as compared to that in summer. The diversity was found to be different for different locations. However, the aphid population was the most dominant species in both seasons at all the locations of southern Rajasthan.

  1. Meena, B.M., Swaminathan, R., Meena, A.K. and Kumar, A. (2017). Impact of farmscaping on the comparative population of pestiferous insects of cowpea and their associated natural enemies. Journal of Entomology and Zoology Studies. 5: 253-257.

  2. Patel, S.K., Patel, B.H., Korat, D.M. and Dabhi, M.R. (2010). Seasonal Incidence of major insect pests of cowpea, [Vigna unguiculata (Linn.) Walpers] in relation to weather parameters. Karnataka Journal of Agricultural Sciences. 23: 497-499.

  3. Patient, D.F., Nchiwan, N.E. and Koehler, H. (2019). Abundance and diversity of insect pests on maize, cowpea and akra in a comparative experiment testing effects of intercropping and insecticide in the cameroonian Guinean Savannah and Sudano Sahelian agro-ecological zones. Journal of Experimental Agriculture International. 29: 1-20.

  4. Pinjara, I.M., Purushan, G.S., Meena, A.K. and Swaminathan, R. (2017). Diversity of coleopteran fauna in Kharif pulses from three different locations of southern Rajasthan. Journal of Entomology and Zoology Studies. 5: 616-618.

  5. Sardana, H.R. and Verma, S. (1986). Preliminary studies on the prevalence of insect pests and their natural enemies on cowpea crop in relation to weather factors at Delhi. Indian Journal of Entomology. 48: 448-458.

  6. Sharma, P., Rana, B.S., Mordia, A. and Kumawat, K. (2019). Seasonal incidence of sucking insect pests of cowpea, [Vigna unguiculata (Linn) Walpers] in relation to abiotic factors. Journal of Entomology and Zoology Studies. 7: 1242-1244.

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