Pest Management in Horticultural Ecosystems, Vol. 21, No. 2 pp 214-218 (2015)
RESEARCH NOTE Nectar robbing by Purple Sunbird, Nectarinia asiatica (L.) in Pomegranate reduces reproductive success P. D. KAMALA JAYANTHI1, B. N. S. MURTHY2, T. NAGARAJA1 , T. RAGHAVA1, M. A. RAVINDRA1, VIVEK KEMPRAJ1 , HEMANT BYATROY2, PALLAVI2, ABRAHAM VERGHESE3 and A. KRISHNAMOORTHY1 1
Division of Entomology and Nematology, ICAR-Indian Institute of Horticultural Research, Hessaraghatta Lake PO, Bengaluru - 560089, Karnataka, India 2 Division of Fruit Crops, ICAR-Indian Institute of Horticultural Research, Hessaraghatta Lake PO, Bengaluru - 560089, Karnataka, India 3 ICAR-National Bureau of Agricultural Insect Resources, Hebbal Farm Post, Bengaluru - 560024, Karnataka, India E-mail:
[email protected] ABSTRACT: A primary report of nectar robbing and deleterious damage by Purple sunbird on pomegranate flowers in India. Nectar robbing through external pecking at the base of flower was observed at significant heights (11.45%). This unusual foraging behavior sternly damaged the setting ovary with deep uneven peck holes (0.59 + 0.02 cm dia; 0.31+0.02 cm deep) resulting in drop off from plants and deformed fruits. Presence of sufficient nectar secretion in bisexual (16.33+1.94 µl) and staminate (14.43+1.93 l) flowers encouraged the nectar robbery. The higher foraging rates had profound negative effect on plant reproductive fitness affecting the fruit set and quality. Keywords: Flower damage, nectar robber, Nectarinia asiatica, Punica granatum
Plant-pollinator interactions are legitimate and mutualistic with varied degree of dependency and type of rewards being exchanged. Nevertheless, there are certain nectar robbers (usually birds or insects) that horn on this deal by picking nectar without rendering the pollination service. This illegitimate behavior often results in positive, negative as well as null effects on particular plant representing a complex relationship (Zhang et al., 2007). In the positive effect, the body of nectar robbers frequently touches the sex organs of plants during their visit to the flowers causing pollination. The neutral effect nectar robbers’ behavior may destruct the corollas of the flowers, but they neither touch the sex organs nor destroy the ovules. On the other hand, the negative effect nectar robbers’ behaviour often damages the reproductive organs (flower) thereby reducing the reproductive success. The net consequence of nectar robbing on reproductive success of plants is usually negative and the positive effect is rarely produced (Singh et al., 2014).
quality fruits both for fresh use as well as processing thus there is an increasing worldwide demand for this fruit for its superior pharmacological and therapeutic prope rtie s (J alikop, 2010). T he pomegra na te is andromonoecious as hermaphrodite (bisexual) and staminate (male) flowers develop on the same plant. Flowers are large (1.5 to 3.0 cm in length), companulate or cylindrical and have an attractive red calyx and corolla. The flower size, vigor and quantum of female flowers have influence on the pomegranate fruit production (Wetzstein et al., 2013). Both male and bixesual flowers produce sufficient high quality pollen as pomegranate is both self-pollinated and often cross-pollinated by insects viz., Camponotus spp, Apis spp. and Papilio demoleus L. and there is very little wind dispersal of pollen (Nath and Randhawa, 1959). However, honey bees are reported as principal pollinators. In recent study the honey bees pollination have exhibited increase in the fruit setting and their weight in China provinces (Tao et al., 2010).
Pomegranate (Punica granatum L.) is commercially important fruit for its attractive, juicy, sweet acidic and refreshing arils and there is a growing demand for good
Birds are rarely reported as the pollinators and floral pests in pomegranates, an unfamiliar host. This paper evaluates the unusual damage by Nectariniidae birds in 214
Purple sunbird and reproductive success of pomegranate high-value crop Pomegranate and the new nectar host of sunbird. We investigated the extent of bird damage, and discussed few control measures. Further evaluation of nectar composition and their calorific value helps to determine the adaptability to new host by the Nectariniidae birds. The study was conducted in pomegranate garden (P. granatum cv. Bhagwa) at Madapura near Bidadi (12.86°N, 77.40°E), Ramnagaram district, Karnataka, India (Fig.1). Observations were made between 7:30 to 18:00 in a 1 hectare area containing 1600 number of 18 months old plants with 12 x 10 m spaced. Detailed observations on foraging period, fora ging/vis iting behavior, visiting frequencies of these nectar robbers along with damage pattern were visually recorded during January to February, 2015. Observations were also made to understand the flowering propensity on the bird visitation. The plants were visually graded for flowering propensity on 1-3 scale based on per cent flowering, where 1= 30 to 60% (categorized as high). Surveys were also conducted in other parts of Karnataka viz., Hosadurga (13.80° N, 76.29° E) and subsequent farmer reports about bird damage from other regions [Mettur (11.80° N, 77.80° E) of Salem district in Tamil Nadu, India] were also recorded.
Fig. 1. Purple sunbird, N. asiatica damage on pomegranate flowers in the plant and flower drop on the ground
ovary resulting in deep uneven peck holes (0.59+0.02 cm dia; 0.31+0.02 cm deep) and the damaged flowers normally drop off (Fig. 1, 3) and rarely develop in to malformed fruits affecting the market quality. Further, their swift flight movements and fluttering of wings within the plant canopy also caused direct damage to flowers/ buds making them fall. Significant positive correlation was found between number of flowers dropped and number of flowers damaged by N. asiatica (r = 0.53, N=30 plants). The variability in the flower drop to the tune of 29% (F=11.17; P=0.002; edf=28, y = 8.52+0.03x; R2=0.285) could be attributed to bird damage alone. Further, the bird damage also positively correlated (r=0.52) with flowering propensity (%) and significant difference (P=0.01) for mean flower damage (numbers/ plant) i.e., 8.50+1.28, 13.10+1.31, 14.0+0.94 was noticed in low, medium and high flowering plants respectively. Estimation of variance-to-mean ratio (V/M) (>1) and parameter k of the negative binomial distribution (1) and parameter k of the negative binomial distribution (
