Distribution and Abundance of White Grubs (Coleoptera: Scarabaeidae) on Groundnut in Southern India
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ARTICLE IN PRESS Crop Protection 25 (2006) 732–740 www.elsevier.com/locate/cropro Distribution and abundance of white grubs (Coleoptera: Scarabaeidae) on groundnut in southern India V. Anithaa,1, D.J. Rogersb,Ã,2, J. Wightmanc, A. Wardd,3 aInternational Crops Research Institute for the Semi-Arid Tropics, Patancheru, Andhra Pradesh, India 502324 bFarming Systems Institute, Indooroopilly Sciences Centre, Queensland Department of Primary Industries, 80 Meiers Rd, Indooroopilly 4068, Australia cInternational Pest Management, Conondale Cottage, 931 Stanley River Rd. Maleny, Qld 4552, Australia dFarming Systems Institute, Queensland Department of Primary Industries, PO Box 23, Kingaroy, Qld 4610, Australia Received 7 October 2004; received in revised form 6 December 2004; accepted 3 October 2005 Abstract Scarab species associated with groundnuts were surveyed in Andhra Pradesh, Karnataka and Tamil Nadu, southern India, between 1995 and 2001. Scarab adults were collected from trees on which they were feeding and/or mating, and larvae (white grubs) from groundnut fields. Holotrichia species, especially H. reynaudi and H. serrata were the major species associated with groundnut. H. reynaudi predominated in the central Deccan area, while H. serrata was most abundant in the south and west. A new, undescribed, Holotrichia species near H. consanguinea was collected in south and southwest of Hyderabad in mixed populations with H. reynaudi. However, the full extent of this new species’ distribution remains uncertain. H. rufoflava was rarely associated with groundnut, but was common as an adult at some locations. Other genera encountered during surveys were Anomala, Adoretus, Schizonycha, and Autoserica. In survey data, densities of Holotrichia larvae and ‘all other white grubs’ were both very highly correlated with the percentage of damaged groundnut plants. These correlations in combination with concurrent observations of plant damage establish a causal link between white grubs and plant damage and death in southern Indian groundnut. Ranking of preferred host trees for adults were developed from field observations for four Holotrichia species and Schizonycha spp. and will assist grower-initiated surveys of pest occurrence. In combination with insecticide-efficacy data published elsewhere, the survey provides the basis for an environmentally friendly and economically viable pest- management system for white grubs on groundnut in southern India. r 2005 Elsevier Ltd. All rights reserved. Keywords: Holotrichia serrata; Holotrichia reynaudi; Peanut; Anomala; Adoretus; Schizonycha; Autoserica 1. Introduction and Sharma (1995) and Musthak Ali (2001) indicate that of the many Melolonthine genera found under the crop in Wightman and Ranga Rao (1994) reviewed the Scar- India, the genus Holotrichia includes the most important abaeids causing damage to groundnut (peanut) in the pest species in groundnut. In northern regions (Gujarat, world, listing a total of 22 species from 9 genera associated Rajasthan, Punjab, and Bihar), H. consanguinea is the with groundnut in India. More recent overviews by Yadava predominant species. At the time of the Wightman and Ranga Rao (1994) review, the predominant species known to be associated with groundnut in southern India was ÃCorresponding author. Research Connections and Consulting, PO Box 350, Toowong, Qld. 4066, Australia. Tel./fax: +61 7 3720 9065. H. serrata. Yadava and Sharma (1995) and Musthak Ali E-mail address: [email protected] (D.J. Rogers). (2001) record H. serrata as a serious pest in many parts of 1Present address: Fruit Research Station, Acharya NG Ranga western and peninsular India, including Gujarat, Mahar- Agricultural University, Sanga Reddy, Medak, Andhra Pradesh, 502001, ashtra, and parts of Karnataka, Tamil Nadu and Andhra India. Pradesh. H. reynaudi has been recognised as a significant 2Present address: Research Connections and Consulting, PO Box 350, Toowong, Qld. 4066, Australia. pest species only since the Wightman and Ranga Rao 3Present address: BeckerUnderwood Australia, RMB 1084, Pacific (1994) review, and is now known to be the major species in Highway, Somersby, NSW 2250, Australia. the central peninsular areas of India (Karnataka, Andhra 0261-2194/$ - see front matter r 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.cropro.2005.10.001 ARTICLE IN PRESS V. Anitha et al. / Crop Protection 25 (2006) 732–740 733 Pradesh and Tamil Nadu) (Anitha, 1997). Little was central peninsular India based on accurate pest identification, known of its biology or distribution prior to Anitha (1997). understanding of the pests’ damage potential on groundnut, Adults of Indian Holotrichia species become active with and minimum-dose intervention with insecticides. the arrival of the monsoon or heavy pre-monsoon showers; if the monsoon is late, the beetles’ emergence is accordingly 2. Materials and methods delayed (Yadava and Sharma, 1995). As the monsoon’s arrival initiates groundnut planting, there is a close 2.1. Adult surveys association between crop and pest phenologies. Once active, adults fly to trees at dusk for mating and feeding 2.1.1. 1995 and 1996 for a few days after the arrival of the monsoon before Adult surveys to determine species occurrence and returning to the soil each day. What constitutes a host for relative abundance were conducted in the five important adults of these species is somewhat problematic because groundnut-growing areas in Andhra Pradesh during the mating and feeding can, but do not have to, occur on the rainy seasons of 1995 and 1996. In 1995, beetles were same tree species. Mating can occur on trees not normally collected at locations near Anantapur, Tirupathi, Kurnool, fed on, with beetles subsequently moving to preferred Patancheru (ICRISAT research farm), and Mahbubnagar, species to feed (Yadava and Sharma, 1995). Females from areas known to be endemic to groundnut white grubs. subsequently lay eggs in the soil. Larvae develop rapidly, In 1996, collections were repeated at the first four reaching full size in 67 days for H. reynaudi (Anitha, 1997), locations. After suitable rainfall events, representative and 82–113 days for H. consanguinea (Yadava and Sharma samples of beetles were collected during May–August and 1995). October from trees, including neem, wild ber (Zizyphus Preferences of adult Holotrichia for mating and feeding spp.), acacia (Acacia arabica), and drumstick located on trees are known for some species in other parts of India. roadsides of the predominantly groundnut-growing region, For H. consanguinea in northern India, adult host trees or in the groundnut fields. In these areas, trees 3–5 m high include ber (Zizyphus spp.), neem, (Azadirachta indica) and are commonly found on roadsides and at the margins of drumstick (Moringa oleifera)(Yadava and Sharma, 1995) groundnut fields, as well as scattered trees through the with a 1:1 sex ratio for adults on trees (Leal et al., 1996). fields at densities of approximately 3–5 per hectare. They H. serrata occurs most commonly on neem, Butea provide shade and fodder for animals, and firewood, and monosperma and Acacia spp. (Yadava and Sharma, so are actively retained within the cropping system. 1995). Host-tree preferences of Holotrichia species in Because beetles rest in the soil during the day, and so are central peninsular India are much less known, in part not readily available for collection, they were hand-picked because the tree fauna differs, and in part because of a lack and/or shaken from the host trees during their night of knowledge of the biology of the Holotrichia species that activity period (between 1900 and 2300 h) and preserved in occur there. 70% ethyl alcohol for later identification. During the On a global scale, southern India is a major groundnut evening adult-sampling program, sites were selected along producing region, with the states of Andhra Pradesh, roads by stopping at milepost markers and searching trees Karnataka and Tamil Nadu producing more than 5 million with 20–30 m of the marker. Trees in adjacent groundnut tonnes of nuts from almost 5 million hectares in 1998/99, fields, if present, were also searched. For the purpose of i.e. almost 60% of Indian production and 16% of world this survey, any tree on which Scarabaeids adults could production (Ali, 2003; Maneepun, 2003). Groundnut is, by be collected feeding and/or mating was considered to be a far, the largest single crop grown in central Deccan area, host tree. and is almost the only cash crop that will successfully grow in the region’s demineralised soils and highly variable 2.1.2. 1998 climate. Because of this, any biotic constraints to ground- During July 1998, and at the time of the first monsoon nut productivity have significant economic impacts at both rains, adult collections were made from six villages across the village and regional levels. the Anantapur district where damage to groundnut had Early reports of white grubs damaging groundnut in the been previously reported by farmers or non-government region include Husain (1974), Rao et al. (1976) and Pal organisations (NGOs). Beetles were hand-picked and/or (1977). These authors variously identified the pest species shaken from trees, especially wild ber, kalivi (Carissa spp., in Andhra Pradesh as H. consanguinea, Phyllophaga a spiny shrub usually entwined in neem trees), between consanguinea,orH. serrata. The present study aimed (a) 1900 and 2200 h and preserved in 75% ethyl alcohol for to clarify the uncertainties of species identity and distribu- later identification. Trees in and around a village were tion from these earlier reports because susceptibility to sampled in a semi-systematic manner, ensuring that all tree insecticides differs between Holotrichia species (Anitha species at the locality were examined. et al., in press), and (b) to identify any association between white grub incidence, edaphic and cropping system factors, 2.1.3. 1999 and the incidence of plant damage. This formed part of During this season, surveys were extended with the establishing a pest-management system for groundnuts in assistance of local NGOs working in Kolar, Raichur, ARTICLE IN PRESS 734 V.