Bio-diversity and Seasonal Activity of Arthropod Fauna in Brassicaceous Crop Ecosystems of Meghalaya, North East India 
,
Damitre Lytan2 
,
G. T. Behere1 2. College of Post Graduate Studies (CAU), 793103, Barapani, Meghalaya, India
Author Correspondence author
Molecular Entomology, 2012, Vol. 3, No. 4 doi: 10.5376/me.2012.03.0004
Received: 14 Dec., 2012 Accepted: 24 Dec., 2012 Published: 07 Jan., 2013
Firake et al., 2012, Bio-diversity and Seasonal Activity of Arthropod Fauna in Brassicaceous Crop Ecosystems of Meghalaya, North East India, Molecular Entomology, Vol.3, No.4 18-22 (doi: 10.5376/me.2012.03.0004)
Biodiversity of arthropod fauna was assessed in brassicaceous ecosystems of Meghalaya during 2010-12. Three species of aphids viz., Liphaphis erysimi, Brevicoryne brassicae and Myzus persicae and large white cabbage butterfly (Pieris brassicae) were found to be a major pests of brassicaceous plants in this region; while pentatomid bugs (Nazara viridula), flea beetle (Phylletreta cruciferae), leaf beetle (Monolepta signata), saw fly (Athalia lugens proxima) and small white cabbage butterfly (Pieris repae) were appeared to be a minor pests. Natural enemies, especially, predators of aphid viz., coccinellid beetles, syrphids flies and spiders were recorded in this ecosystem. Parasitoids include nymphal-adult parasitoid of aphids, Diaeretiella repae, larval parasitoids of cabbage butterfly, Hyposoter ebeninus and Cotesia glomerata. Besides, activities of several pollinators were also observed during flowering stage. Major predators of aphids were Coccinella septumpuncata complex and C. transvarsalis complex. This study also recorded a seasonal activity of above mentioned pests and natural enemies and it would certainly be useful in understanding the biodiversity and role of different tropic levels in this ecosystem.
Several control tactics have been recommended and followed to reduce the damage intensity by these pests; although chemical control unfortunately till date a dominant weapon to fight against them. Protective measures using different chemicals can cause undesirable side effects to human health, as the cole crops are being used as fresh vegetables in human diet. These chemicals are not only expensive but also cause critical health related issues in animals including humans (Dasgupta, 2007). Moreover, uncontrolled use of synthetic chemicals causes severe damage to on-farm biodiversity as well. Therefore, biological control is now, emerging as an important component of pest management (Balevski et al., 2007). Biological control of brassica pests has traditionally relied on microbial pesticides, predators and parasitoids (Van Driesche et al., 2003). Additionally, natural biological control also plays a crucial role in almost every crop ecosystems. The Meghalaya is the part of north eastern Himalayas (India) and considered to be a one of the components of mega-biodiversity hot spot. Unstable weather conditions of the region are highly conducive for the occurrence and multiplication of several insect pests. Large portion of the region are still undisturbed, where natural biological control plays a significant role in management of major pests and overall conservation of ecosystem. Thus, before initiating further biological control attempts in brassica crops, it is very essential to know the arthropod fauna in this ecosystem of the region and it also crucial to understand various tropic levels in these crops. Therefore, studies were carried out to know the exact biodiversity and seasonal activities of arthropod fauna residing into it.
2 Results
A total of 15 insect pests were observed in brassicaceous crop ecosystems of the region. The large white cabbage butterfly (P. brassicae) and Lipaphis erysimi was a most serious pest of vegetable brassica (cole crops) and oilseed brassica, respectively. Besides, diamondback moth (Plutella xyllostella) was found to be major pest of late planted cole crops. Insect pests of brassica crops, their status and seasonal activity recorded during the study are presented in Table 1. About 24 natural enemies and pollinators observed in brassicaceous crops of the region (Table 2 and Figure 1). Among predators, Coccinella septumpunctata complex was found to be the most abundant predator of aphids throughout the season followed by syrphid flies; while Hyposoter ebeninus and Diaeretiella repae were the dominant parasitoid of Pieris species and aphids, respectively. In C. septumpunctata complex, about three different types of polymorphic and polychromic elytral patterns were observed (Plate No. 1 to 3); while two chromic pattern (orange and red) were found in case of C. transversalis complex. Among non-insect predators, four types of spider’s viz., Jumping spiders (Marpissa calcuttaensis and Phidippus spp), Lynx Spiders (Argiope pulchella and Oxyopes rubisternum), Wolf spiders (Lycosa pseudoannulata) and Orb Spinners (Leuchge decorate, Larinia tabia and Cyrtophora carrisae) were commonly seen throughout the season. Different species of syrphid flies, bumble bee, carpenter bee and honey bees were observed as chief pollinators of oilseed brassica (Table 2).
.png) Table 1 Biodiversity and seasonal activity of insect pests in brassicaceous crops of Meghalaya, India |
 Table 2 Biodiversity and seasonal activity of natural enemies and pollinators in brassicaceous crops of Meghalaya, India |
.png) Figure 1 Natural enemies and pollinators observed in brassicaceous crops of the region |
3 Discussions
The North-Eastern Himalayan region of India is exceptionally rich in terms of flora and fauna. Bio-diversity of arthropod fauna in particular crops is varied from region to region. Therefore, the complete knowledge on this aspect is crucial for formulating proper management techniques and especially in case of implementation of biological control programmes where each tropic level have significant impact on other organism. Bhat and Bhagat (2009) studied the biodiversity of natural enemies in cole crops and reported three potential hymenopteran parasitoids viz., H. ebeninus, C. glomerata and B. femorata of cabbage butterflies from Kashmir valley of India. Razmi et al. (2011) reported ten species of primary parasitoids of P. brassicae from different cole crops in Iran. Few other natural enemies viz., Trichogramma evenescens, Compsilura concinnata and Phryxe vulgaris were also reported by Patriche et al. (2005) in brassica ecosystem.
The data generated from present study would be helpful in further understanding of the biodiversity of arthropod fauna associated with brassicaceous crops in other regions of the country and it is also useful in understanding the role of different tropic levels in this ecosystem; which has immense significance in biological control programmes.
4 Materials and Methods
All the studies were conducted at experimental farm of the Division of Crop Improvement (Entomology), ICAR Research Complex for the NEH Region, Umiam, Meghalaya (India) during 2010~12. Different fields (pesticide free) of brassicaceous crops (cabbage, cauliflower, knol-khol, brocolii, radish, rapeseed, mustard, toria and sarso) were randomly selected and utilized for this study. These experimental fields were geographically situated at N 25°41′01.91″ E 91°54′46.24″. Observations on seasonal activity of insect pests and their natural enemies were taken at weekly interval in all these crops till their harvest.
Different life stages of the pests were collected randomly from infested plants and reared in the laboratory (20 ± 2ºC temperature, 75 ± 5% relative humidity, 14:10 Light: Dark period) till their full growth or emergence of parasitoids. Newly emerged parasitoids were collected and preserved in the 75% ethyl alcohol. Further, the parasitoids were identified either with the help of reference collection of the ICAR research complex for NEH Region, Umiam. Some specimens were also identified with the help of expert taxonomist of Division of Biosystematics, Indian Agricultural Research Institute, New Delhi (India). Observations on pollinators were also taken regularly during flowering stage and common pollinators were preserved in the laboratory. Pollinators and predators, viz., coccinellid beetles, syrphid flies, honey bees, wasps, bumble bees, carpenter bees and reduvid bugs were collected directly by hand or through sweep net from the field, preserved and identified with the help of reference collection in the division. Spiders were manually collected from the field and preserved in 75% ethyl alcohol.
Total fifteen observations were recorded at weekly basis throughout the season in each crop and those arthropods recorded continuously for more than four times was considered as a frequently occurred agent; while remaining were considered as a rarely occurred arthropod in brassica ecosystem.
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