Fruit-set in cashew is mainly influenced by the activity of pollinators (Reddi, 1993; Thimmaraju and Lakshmi Raju, 1993; Freitas and Paxton, 1996). In the East Coast of Tamil Nadu, 32 species of insects visited cashew inflorescences (Ambethgar, 2002). In the West Coast of India, Devasahayam (1986) and Sundararaju (2000, 2003) reported various species of bee such as Pseudapis oxybeloides (Smith), Ceratina smaragdula (F.), Apis spp., Lasioglossum sp., Trigona iridipennis Smith and one unidentified halictid visiting cashew. Based on the number of free pollen-grains on their bodies, honey bee (A. mellifera) and the solitary bee (Centris tarsata) were found to be efficient pollinators of cashew (Frietas, 1997; Bhattacharya, 2004). Studies were therefore undertaken to document the diversity of bee pollinators occurring on cashew in the cashew belt of coastal Karnataka and in coastal Tamil Nadu. Simultaneously, information on other flower resources (flora) occurring in cashew plantations during the lean season and flowering period of cashew was collected, in order to suggest methods for conservation and management of pollinators. Diversity of bee pollinators was assessed by collecting bees that maintained constancy on cashew flowers in the cashew belt of coastal Karnataka and in coastal Tamil Nadu, by undertaking surveys during 2004 – 2006. Bee species were identified using taxonomic keys developed by Batra (1977). Visitation of bee pollinators at fixed hours and on Diversity of bee pollinators and flora in cashew D. Sundararaju* Directorate of Cashew Research Puttur (D.K.), Karnataka-574 202, India E-mail: dsraju21@gmail.com ABSTRACT Seven species of bee that maintained constancy on cashew flowers were identified from coastal Karnataka [(Pseudapis oxybeloides (Smith), Lasioglossum sp. and Halictus sp., Halictidae; Braunsapis sp., Ceratina smaragdula (F.) and Ceratina sp., Apidae)] and four species from coastal Tamil Nadu [(Ceratina (Pithitis) binghami Cockerell, C. smaragdula, Braunsapis sp. and P. oxybeloides)]. Time spent by bees for visiting the flowers ranged from 0.8 to 25.1 seconds per flower. Diversity of flora recorded during 2003-08 as floral resources for nectar for all the above bee species during lean and flowering periods of cashew - both at coastal Karnataka and Tamil Nadu - is presented in this paper. Key words: Diversity of bees, floral resources, cashew *Present address: National Bureau of Agriculturally Important Insects, Hebbal, Bangalore-560 024 fixed spots in cashew during the flowering season of 2005- 06 was recorded. For this, one square meter of the canopy was marked in early-season (NRCC Selection-2), mid- season (Bhaskara) and late-season (Chintamani- 1) flowering varieties. In each variety, visits of bee pollinators at fixed hour (11.00 hr and 14.00 hr) were observed for a period of 10 minutes continuously for 30 days from initiation of flowering in panicles. Highest population recorded either at 11.00hr or 14.00hr was accounted as population for that day. Role of bee pollinators in fruit-set was observed by caging single trees completely with nylon net (size 40 mesh) similar to that in studies of Freitas and Paxton (1996). Total time spent per flower by some of the bees was recorded with the help of a stop-watch and video-graph. Simultaneous observations were made within cashew plantations on diversity of flora that served as floral resources during lean periods, and additional floral resources during flowering periods of cashew. Species of bees which visited cashew flowers, and bees carrying pollen grains on their legs and body hairs, were collected and identified. There were seven species from coastal Karnataka Pseudapis oxybeloides, Lasioglossum sp. and Halictus sp. (Halictidae); Braunsapis sp., Ceratina smaragdula and Ceratina sp. (Apidae), and four species from coastal Tamil Nadu: Ceratina (Pithitis) binghami Cockerell, C. smaragdula, Braunsapis sp. and P. oxybeloides. These species were observed as mainly Short communication J. Hortl. Sci. Vol. 6(1):52-55, 2011 53 collecting pollen grains, followed by feeding on nectar and were categorized either as pollen-bees native-bees, wild bees or non-Apis bees (Batra, 1994). Even though honeybees (Apis florea F., A. cerana indica and A. dorsata F., Apidae) visited cashew flowers in both the regions, these were mainly involved in feeding on nectar and, very rarely, in collecting pollen. Stingless bee (Trigona iridipennis Smith, Apidae) alone collected both nectar and pollen grains. However, pollen billets on their corbiculae were loaded in the form of a brownish, slimy mass. Though the occurrence of above species of Apis, P. oxybeloides, C. smaragdula and Lasioglossum sp. have already been reported by Devasahayam (1986), Reddi (1995), Sundararaju (2000), Ambethgar (2002) and Bhattacharya (2004), four species viz., Halictus sp., Ceratina sp., Braunsapis sp. and Ceratina (Pithitis) binghami in this study have been recorded for the first time from cashew plantations of coastal Karnataka and Tamil Nadu. As per reports of Ambethgar (2002), Apis mellifera L. was sighted in coastal Tamil Nadu, but could not be sighted in the repeat survey undertaken during 2004- 2006. Similarly, Bhattacharya (2004) reported occurrence of Bombus spp. in West Bengal, but it is surprising to note that Bombus spp. specific to the cooler high-altitude region (1350m to 8400m above MSL (Abrol, 1997) was seen on cashew. Recently, the extent of pollination in cashew with a maximum of upto 46.8%) after the visit of A. cerana indica, was documented by Sundararaju (2011). Total time spent on the flower by bees was accounted for by keeping time with a stop-watch and recording with a video camera (Tables 2 and 3) and was seen to range from 0.8 to 25.1 seconds flower. Whenever pollen alone was collected, the time spent was found to be minimum (0.8 to 5.0 sec flower-1). Combined collection of pollen and nectar, or collection of nectar alone, time spent was maximum (5.0 to 25.1 sec. / flower). This is in contrast to an earlier study by Sundararaju (2000) who observed P. oxybeloides as spending 2.0 seconds on pollen collection alone. The abundance of bees on early-(NRCC Selection-2), mid- (Bhaskara) and late-season (Chinthamani - 1) flowering varieties was 0.35, 0.16 and 0.09 bees panicle-1, respectively, in a constant period of 10 minutes, during 2005-06 (Table 1) at Puttur (coastal Karnataka). Under undisturbed video recording, in a canopy area containing 15 panicles during a period of 20 minutes, visit of 2-3 A. cerana indica and 1-5 P. oxybeloides bees was found to be low in cashew. This is in concurrence with earlier reports of Ohler (1979) and Free (1993). During 2006-07, a single tree of ‘Bhaskara’ variety was caged all over with mosquito net, in the centre of a plantation at Puttur and geitonogamous pollination (through gravitational fall of pollen grains) was completely prevented by removing the upper panicles. Every day, the tree was observed between 11.00 and 12.00h. Most of the time, at least twice or thrice, bee species P. oxybeloides dashed against the mesh of the cage from outside the of cage and ultimately, could not enter the cage because of its larger body-size, and the close mesh of mosquito net. This type of external attraction may be due to volatiles emanating post- anthesis in cashew flowers. As a result, no fruit-set was observed even upto 45 days from onset of flowering in the particle. And at the same time, normal fruit-set showing various stages of fruit development was observed on all the surrounding un-caged trees. Subsequently, in the caged tree, belated fruit-set was spotted after 45-60 days from of flowering. By this time, all the surrounding un-caged trees Table 1. Visitation by bees on different varieties of cashew trees Bee species Visit of bee within 10 minutes (no./panicle/day) during 30 observational days NRCC Bhaskara(M) Chintamani(L) Selection-2 (E) Stingless bee 0.280(30) 0.003(3) 0.036(8) (Trigona iridipennis ) Apis cerana indica 0.027(14) 0.026(10) 0.014(11) (honey bee) A. florea 0.025(17) 0.007(3) 0.000 Non-Apis spp. 0.021(9) 0.136(26) 0.036(16) Total 0.353(30) 0.162 (26) 0.086(27) Figures in parentheses are no. of days sighted out of 30 observational days; E, M, L: Early-, mid- & late-season flowering variety, respectively Table 2. Time spent by different species of bees* per cashew flower Name Mean± S.D (seconds)** Range (seconds) Apis cerana indica 2.31 ± 1.35 0.8 - 9.0 Apis florea 8.25 ± 2.61 1.2- 22.2 Ceratina 13.62 ± 1.30 5.0- 25.1 (Pithitis) binghami Braunsapis sp. 9.43 ± 1.36 2.0- 22.0 *Recorded with a stop-watch; * * Mean of minimum 10 observations Table 3. Visitation of bees on cashew flowers as recorded on video camera Bee species No. of bee visits Time on 15 panicles within a spent / flower period of 20 minutes (seconds) Day1 Day2 Day3 Mean± S.D. Range Apis cerana indica 3 2 2 3.6±1.0 2-5 Pseudapis oxybeloides 1 5 4 4.1±3.9 1-18 Diversity of bee pollinators and flora in cashew J. Hortl. Sci. Vol. 6(1):52-55, 2011 54 had panicles at an advanced stage of fruiting and were on in the verge of cessation of flowering. Since the caged tree had no panicles bearing fruits, flowering was to be observed continuous, without any cessation. Therefore, the caged tree was critically observed. Finally, through visual observation, entry of Lasioglossum sp. through the mesh of the cage was confirmed especially at the site where flower panicles touched the mesh of the cage. Also visit to new flowers of the caged tree, by bee species already present inside the cage, was seen. Since the caged tree maintained active flowering while all the surrounding trees were on the verge of cessation of flowering, bees must have been attracted to flower panicles touching the mesh of the cage. Subsequently, through the mesh of the cage, these bees may have made a forced entry. As a result, a final fruit-set in 71.2% of panicles with a mean of 1.2 nuts/panicle was recorded. Whereas, in the surrounding un-caged trees that showed activity of bees of the above-mentioned species (since onset of flowering), final fruit-set was observed in 81.3% of panicles, with a mean of 2.1 nuts/panicle. This level of fruit-set on the caged tree was possible mainly due to involvement of smaller bees that entered through the mesh of the cage. This is in contradiction with earlier studies by Freitas and Paxton (1996) who reported meager fruit-set in a completely caged tree (since larger bees were excluded and smaller bees were not involved in pollination of cashew). Diversity of flora recorded during 2003-08 as floral resources for all the above bee species in lean periods at coastal Karnataka included of Lindernia antipoda L. L. crustacean L. and L. ciliata (Colsm.) (Scrophulariaceae), Spermacoce hispida L. and S. ocymoides Burm. (Rubiaceae), Mimosa pudica L. and Acacia pennata L. Willd (Mimoceae), Rungia repens Nees (Acantheceae), Leucas aspera Willd. (Labiatae) and Muntingia calabura L. (Tiliaceae). Whereas, during the flowering period of cashew, Blumea lacera L. and B. oxydonta D.C. (Asteraceae), Rungia parviflora (Retz.) Nees and Muntingia calabura were observed as additional floral resources. In coastal Tamil Nadu, Ocimum americanum L. and O. adscendens Willd. (Labiatae), Cleome viscosa L. (Capparidaceae), Oldenlandia umbellata L. (Rubiaceae) and L. aspera were found to be floral resources during the lean period. Cleome viscosa, O. adscendens, and, L. aspera and Celosia sp. (Amaranthaceae) were observed as additional flower resources during the flowering period. Even though P. oxybeloides, Lasioglossum sp. and Braunsapis sp. visited cashew and B. lacera, B. oxydonta and R. parviflora, the respective bees maintained with specific parallel-exclusive constancy pattern on cashew alone. But, at Vridhachalam (coastal Tamil Nadu), during the flowering period of cashew, exclusive constancy by Ceratina (Pithitis) binghami, Braunsapis sp. and P. oxybeloides was also observed on Cleome viscosa and L. aspera, common weeds in cashew plantations. Similar level of exclusive parallel-constancy by these species of bees was not seen on other varieties of cashew except ‘Bhaskara’. Thus, the high-yielding variety Bhaskara, was found to be a bee-pollinator attractant variety in coastal Tamil Nadu. This can be further popularised all over coastal Tamil Nadu. Existence of the above floral resources during both lean and flowering periods of cashew in coastal Karnataka and Tamil Nadu, can help conserve/manage these bees whenever any recommended insecticides (used for management of cashew pests) caused a depression in bee population. All the same, use of existing recommended insecticides has not affected pollination in cashew in the past (Sundararaju, 2000, 2003 and 2004). This is because non-Apis bees do not have any scope for contact with insecticide-treated cashew flowers, except on the day of insecticide application. Growth of B. lacera and O. adscendens at the respective regions was noticed only in limited locations and, therefore, needs to be spread to other locations for conservation. It is also interesting to note that most of above-mentioned flora are native weeds in cashew plantations, excepting Mimosa pudica. These native weeds are fairly non-invasive and are capable of growing under partial shade of the cashew canopy. However, Muntingia calabura is an exotic fruit tree and cannot be recommended for growing within cashew plantations as it has been recorded as a refugee-host for an important, key pest of cashew, Helopeltis spp. (Miridae: Heteroptera) (Sundararaju et al, 2002). ACKNOWLEDGEMENT The author thanks the Director, Directorate of Cashew Research, Puttur for providing facilities. He also thanks Shri Laxmipathi for technical assistance and Biosystematics Unit of Department of Entomology, GKVK, University of Agricultural Sciences, Bangalore for identification of Ceratina (Pithitis) binghami. Identification of various flora of pollinators by Botanical Survey of India, Southern Regional Centre, Coimbatore, is gratefully acknowledged. Sundararaju J. Hortl. Sci. Vol. 6(1):52-55, 2011 55 REFERENCES Ambethgar, V. 2002. Insect visitors of cashew inflorescence in north-eastern zone of Tamil Nadu, India. Progr. Hort., 34:223-229 Abrol, D.P. 1997. Bees and Bee Keeping in India. Kalyani Publishers, Delhi, pp. 303-308 Batra, S.W.T. 1977. Bees of India (Apidea), their behaviour, management and a key to the genera. Orient. Insects, 11:289-324 Batra, S.W.T.1994. Diversify with pollen bees. Am. Bee J., 134:591-593. Bhattacharya, A. 2004. Flower visitors and fruit set of Anacardium occidentale. Ann. Bot. Fennici., 41:385-392 Devasahayam, S. 1986. Some observation on insects visiting cashew inflorescence. Cashew Bull., 23:1-5 Free, B.J. 1993. Insect Pollination of Crops. Academic Press, London, pp 122-124 Frietas, B.M. 1997. Changes with time in the germinability of cashew (Anacardium occidentale) pollen grains found on different body areas of its pollinator bees. Rev. Brasil Biol., 57:289-294 Frietas, B.M. and Paxton, R.J.1996. The role of wind and insects in cashew (Anacardium occidentale) pollination in NE Brazil. J. Agril. Sci.,126:319-326 Ohler, J.G. 1979. Cashew. Koniklijk Institute Voor de Tropen, Amsterdam, pp260 Reddi, E.U.B. 1993. Pollination studies of cashew in India : an overview. In: ( Eds.Veeresh , G.K., Umashaankar, R. and Ganeshaiah, K.N.). Proc. Int’l. Symp. Polln. Trop. UAS, Bangalore, pp. 321-324 Reddi, E.U.B. 1995. Insect pollination in cashew. In: ( Ed. Sihag, R.C.). Pollination Biology: Environmental Factors & Pollination. Rajendra Scientific Publishers, Hisar. pp. 68-74 Sundararaju, D. 2000. Foraging behaviour of pollinators on cashew. The Cashew, 14:17-20 Sundararaju, D. 2003. Occurrence of bee fauna and extent of pollination in insecticide sprayed ecosystem of cashew. J. Palynol., 39:121-125 Sundararaju, D. 2004. Evaluation of promising new insecticides in large plots for management of tea mosquito bug on cashew. J. Plantn. Crops, 32(Suppl.):285- 288 Sundararaju, D. 2011. Studies on extent of pollination and fruitset in cashew. J. Plantn. Crops, 39 (in press) Sundararaju, D., Raviprasad, T.N. and Bhat, P.S. 2002. New refuge host plant for Helopeltis spp. Insect Envir., 8:137-138 Thimmaraju, K.R. and Lakshmi Raju. 1993. Pollinator limited fruit-set in cashew. In: (Eds. Veeresh , G.K., Umashaankar, R. and Ganeshaiah, K.N.). Proc. Int’l. Symp. Polln. Trop. UAS, Bangalore, pp. 43 (MS Received 04 December 2010, Revised 25 April 2011) Diversity of bee pollinators and flora in cashew J. Hortl. Sci. Vol. 6(1):52-55, 2011