IL •i

Biology and Management Potential for Three Orchard Bee Species (Hymenopte ra: ): Osmia ribifloris Cockerell, 0. lignaria (Say) and 0. chalj'hea Smith with Emphasis on the Former

B.J. Sampson', J.H. Cane 2 . G.T. Kirker', S.J. Stringer', J.M. Spiers' USDA-ARS Thad Cochran Southern Horticultural Laboratory P.O. Box 287, Poplarville. Mississippi 39470 USA 2 USDA-ARS Bee Biology Lab and Department of Biology Utah State University. Logan, Utah 84322-5310 USA

Kewords: rabbiteyc blueberry. southern highbush blueberry, development, fruit pollination, sex ratio. pollinator inbreeding

Abstract What follows is comprehensive information on the biology and techniques for propagating select species of orchard bees for blueberry pollination, especially Osinia ribj/loris Cockerell. Before we introduce 0. ribifloris or any other bee species to a blueberry t'arin commerciall y, we must rear enough adults for field-scale release, design cheaper, lightweight nesting materials and increase grower awareness of the bee's value. We hope that by delivering reproductively viable bees onto farms, berry producers will gain a secondar y source of revenue from selling surplus Osmia cocoons and nesting supplies. The results we present here represent 14 years of rearing orchard bees in the Deep South (Alabama andMississippi), and should apply to blueberry growing regions west of the Mississippi River where one of the bee species, Osinia i'ihifloris, is endemic (e.g., Texas, California and Oregon). We also discuss some ecological, physiological and genetic costs of keeping a small pollinator population in captivit y for almost a decade.

INTRODUCTION Weaker honey bee hives, hibernating nati\ e bees, blustery weather, and blossom bli ghts can make southern blueberry farms stand eerily silent when they Should hum with pollinator activity in late winter (January through March). Without bees to remove nectar under cooler conditions, Boir i/s and Colletoti'échum diseases further depress fruit set and yield (Smith. 1998: Ngugi and Scherin. 2006: Sampson. personal observation). About one native bee and four to five honey bees, or some combination of the two, per 1000 open blueberry flowers generates the loudest hum in a field. Filly to sixty days later. 70-80% of these blooms set marketable berries (Cane, 1997: Cane and Pa yne. 1993: Sampson and Spiers, 2002: Sampson et al.. 2004h). Below this 5-6 bee threshold, fruit set losses become more frequent, especially in large 10-100 ha fields where set drops 50-70 percentage points as bee density falls below 0.5 bees per 1,000 blooms (Danka and Sampson, unpublished data). With little or no pollination from wild pollinators, each hectare of blueberry would need -600-1200 manageable bees (Sampson et al.. 2004b). To supplement blueberry pollination by wild native bees and hone y bees, we explore ways to conserve or mass-rear species of Osmia, exotic and native.

CANDIDATE Osmia SPECIES: NOT ALL POLLINATORS ARE EQUAL! Compared with honey bees or bumble bees, non-beekeepers will find raising solitary bees easier and safer. In most cases, farmers grow a specific crop, which certain species of solitary bees recognize as their principal floral host. Whether exotic. e.g. Osinia cornifrons Radoszkowski. or native. e.g. 0. Iignaiwi /71'opmqua Say, orchard bees have profitabl y pollinated such major fruit crops as apples. almonds and cherries in the United States for -IS years. Wild 0. alrit'cnhris Cresson in the Northeast show promise as

Proc. IXth IS on Vaccitfinin 549 Fits.: K.E. Hummer ci at. Ada I-tort. Stt). 1S1-IS 2009 pollinators of blueberry and cranberry. Another species. 0. rib//loris Cockerell (Fins. lA- G) is native to the western United States where it nests in natural cavities of stumps or dilapidated buildings. Cage studies show 0. rib//loris and the South's premier blueberry pollinator Habropoda lahoriosa (F.) set ample fruit loads between 50-75% after their first visit to flowers of rahhiteye blueberry Vaccinium ashei Reade (syn. V virgo/am Ait.) and southern highbush blueberry ( V. corvmbosu,n L. x V. (Iarrowii Camp: Sampson and Cane. 2000: Sampson et al., 2004h). Two subspecies of 0. ribi/loris occur west of the Mississippi River. Easternmost populations of the first subspecies o. r. rib//loris occur in central Texas where they feed from flowering trees of Dmospvm'os, Rosa, Cercis, Sophora, and Berberis (Cripps and Rust, 1985: Rust, 1986). The western subspecies of 0. r. hieder,nannii occurs from California to Oregon and Arizona to Utah, where it prefers as floral hosts shrubs of Arctoslaphrlos, Berheris and iviahonia. Wherever we find Manzanita or Berberis bushes at dry upland sites, we trap-nest Osmnia in hollow reeds or paper straws, then ship dormant cocoons eastward for evaluation as pollinators of Gulf Coast blueberries (Sampson et al.. 995: Sampson and Cane 2000). Most manageable species ol0smia often adopt as nests narrow cylindrical cavities drilled into lumber or other fiber-based media (trap-nests). By setting up additional trap- nesting stations at II coastal farms between Texas and Alabama we discovered two native orchard bees that have management potential: 0. lignaria hnaria Say and 0. cha/vhea Smith (Mitchell, 1962: Torehio, 1990: Javorek et al.. 2002; Sampson. personal observation 2006). A mud-loving orchard bee 0. lignaria produces viable progeny when confined on blueberry (Dogteroni, 1999: Sampson. unpublished data 2007). However, 0. lig;maria's preferred diet is pollen of almond, cherry and apple. When using blueberry pollen, each captive female 0. 1/guano lays about nine eggs, scattering her clutch by laying two or fewer eggs per straw - usually males. Leaf plugs as well as tubes stuffed with brood typify those 0. rho/thea nest blocks that we placed in blueberry fields. Brood provisions, however, could not have been blueberry, as captive female 0. cha/vhca avoid gathering pollen from blueberry flowers, producing in two weeks zero nest cells. This makes sense, as 0. cha/vbea and its western relatives prefer as floral hosts, thistles (Asteraceae) and California lilacs (Rhamnaceae). thus making this species a more promising pollinator of such crops as sunflowers and jujubes. The most promising species of orchard bee for pollinating blueberry is 0. rib//loris. Females are cold hardy and capable of fora ging 13 h each day at temperatures as cool as 9°C. Even when experiencing a climate very different from their own in Mississippi, female 0. rib//loris from distant populations or different subspecies mated freely with males from either subspecies and after nesting. 80% of their nest straws contained —5 male and 3 female nest cells. Where fimale 0. nih//lom'i.s come from. not where their mates come from, affected brood productivity. Nests of Texas 0. n. ci hi/loris or those they co-founded with California and Utah bees contained more nest cells and greater biomass as well as more female cocoons. On an exclusive diet of blueberry pollen. female 0. rib//loris were 9% more likely to survive winter than their brothers were and 8% more likely to survive than 0. lignania were (Sampson. unpublished data). 75% of flowers a female 0. rib//loris visits once will set seedy blueberry fruits. They never rob flowers for nectar like carpenter bees or honeybees. Instead, the y remove pollen from flowers by shaking anthers with their feet. and for every minute that female bees forage. five or six flowers set marketable berries (Cane, 1997; Sampson et al.. 2004a, 2004b).

WINTERING DORMANT Osmia ribifloric It takes —10 days after removal from winter chill before female 0. rib//loris are ready to pollinate blueberries. We can hasten 0. rib//loris emergence and give females more foraging days by warming or cooling cocoons until a perfect overlap isachieved between pollinator nesting and crop flowering. If all goes well, in three months, 0. rib//loris broods will develop from eg gs to adults and then overwinter in tough silken cocoons (Fig. IF). Because larval Osmnia deplete fat bodies faster at higher summer

550 OF

temperatures in the South (25-30'C), we must slow their metabolic activity to prevent winter starvation by promptly chilling cocooned adults at --6°C (43°F) for 90-120 days after October 31 (Fig. IG). Thereafter, dormant cocoons can he packaged in vials surrounded by leak-proof ice packs and shipped by mail. Populations of 0. rihi/loris raised in the South emerge from late January to early March, while northern populations emerge from April to May (Kromhien. 1967; Stubbs et al.. 1994). In some years, one in live adult bees forego emergence altogether when premature chilling stops them from pupating the first year, forcing them into premature larval dormancy. Next spring, larvae will resume pupal development (Bosch and Kemp, 2003, 2004; Sampson et al., 2004b).

Osinia riliffloris NESTING BEHAVIOR Once an 0. rib/floris female has chosen a nest cavity, she starts collecting waxy leaf tissue. When this pulpy leaf tissue dries into hard leaf disks, females press together two or more disks to make nest cells or entrance plugs that quarantine brood from each other as well as from diseases and parasites. After completing a cell partition and before laying an egg, a female will make about 15 to 20 pollen trips and visit —1000 blueberry blooms to amass a food ball of -1.5 million pollen tetrads (Sanipson et al.. 1995: Sampson et al.. 2004b). As soon as an egg hatches 24 hours later, the young larva will slowly consume its moist food ball until ready to pupate 10 to 12 weeks later. Although captive 0. rib//loris nest gregariously in wooden shelters in Poplarville, Mississippi, and Auburn, Alabama (Figs. 113-E), free-flying populations newly introduced to southern highhush blueberries near Medford, Oregon, seem to have a strong instinct to leave release sites (Cane, unpublished data). Curbing this pre-nesting dispersal away from natal release points requires one or more management actions. We can allow adult bees to emerge from the shelter intended for nesting. Alternatively, we can cage them with flowering hushes until nesting is well underway. To corral adults inside a large cage or screenhouse, we furnish a plywood shelter with untreated wood blocks 4 x 9 x 15 cm or 9 x 9 x 15 cm (Fig. 113). Holes drilled into wood blocks are lined with hollow tubes of paper or cardboard that are sealed at one end with durable metal tape or a thin ply of wood (Fig. IC). Cavities having interior diameters 6-9 mm (6-7 mm preferred) and a len gth of 15 cm (6 inches) provide ample space for female 0. ribijloris to array 8-] 1 nest cells (Fig. IF): female eggs laid atop innermost pollen masses, male eggs laid atop outermost pollen masses (Fig. I G). We drill holes slightly larger than 7 mm (dia. 8.2 mm) to fit thin paper liners, which we peel apart in autumn or winter to recover dormant adults inside in their cocoons. Cheaper domiciles made from lightweight PVC tubes crammed with paper or cardboard tubes are less attractive to bees than wood blocks. Providing a surplus of high quality nesting habitat along a field's border, which accommodates female bees and nest competitors (e.('.. mLid dauhers, potter wasps) should improve pollinator recovery on a farm. If females must compete for too few straws, some will resort to usurping nests of' other bees, though such behavior can kill a third of the brood (Eickwort, 1975: McCorquodale and Owen, 1994', Tepedino and Torchio, 1994; Sampson ci al., unpublished data). Female bees find straws more attractive when nest blocks are propped 1.0 to 1.5 m above the ground on a post or attached to a wood structure (Figs. IC-F). Moving active nests should he avoided whenever possible, and never beyond 100 m from their original position. If moving nesting bees is necessary. then do it at ni ght. Zigzag-like morning flights will reacquaint females with their nest's new location. We can help females better discern their nest entrance from those of other bees by painting contrasting blotches on a nest block's face (Fig. IB). A white under- painting of latex or acrylic has an added benefit of stimulating earlier pre-flight warm-ups in basking bees. Finally, a female might look beyond a farm's border to find suitable leaf material for fashioning entrance plugs (Fig. 1E) and nest cell partitions (Fig. 1(i). Therefore, growing a preferred (glabrous, waxy) leaf source such as rose near a shelter should promote greater site fidelity. I 551 COURTSHIP, POLLINATOR SEX RATIOS AND OTHER MANAGEMENT CONSIDERATIONS In late winter through early spring, male 0. rihifloris emerge three to four days ahead of females to patrol areas where they are likely to encounter mates, i.e. at hushes and at nest sites. Courtship is long for this bee. Copulation attempts by males follow stereotypical displays of buzzing, antenna] flicking and wing flexing lasting 30 to 90 minutes (Torchio, 1990). Such long courtship displays resemble "serenades" of fruit flies, and for this reason, such displays might convey a suitor's fitness to receptive females (Webb et al., 1984; Whittier et al., 1994). Female 0. rib//loris remain receptive for at least six days, time enough to mate, to mature eggs and to find a nest. Like all bees, a female orchard bee can control her progeny's sex so that sons outnumber daughters about two or three to one. Male bees are crucial to a females overall reproductive success in two important ways. First, inseminated females are 50% more successful at founding nests (Sampson, unpublished data). If females go unmated for too long, they nest late or attempt to usurp nests of other bees though unsuccessfully. Second, the only female replacements for next years' pollination season come from fertilized eggs. Even a fertilized egg intended to become a female can develop into a sterile, diploid male. This occurs when inbreeding depression introduces higher genetic loads at the complementary sex determiner (csd) locus, thus irreparably inflating male/female sex ratios to the point of a population's extinction (Fig. 2, Zayed and Packer 2005). By identifying diploid males within our small Osmia i'ihifloris population, we will eventually confirm male-biased sex ratios resulted from homozygosity at the csd-locus. Even without such confirmation, Fig. 2 clearly shows that ongoing propagation of'a small isolated population of a solitary bee is not a stable long-term solution for pollinator conservation or management. Larger scale approaches are needed if managing a solitary bee pollinator is to be successful long-term.

NATURAL ENEMIES OF Osn,ia BEES Predators and nest associates of orchard bees could become more problematic in the southeastern US (Tscharntke et al.. 1998) and may contribute to heavy bee losses or even a population's extinction. We eliminated some natural enemies that accompanied a shipment of 0. i'ibifloris by trapping parasitic wasps Sapi'ga pain//a Cresson inside 000- sized gelatin capsules after they emerged from host cocoons. No other parasites or diseases of 0. i'ihifloris were detected. However, warm humid conditions spur outbreaks of mold and endemic C'haetodactt'/us mites. These mites are inquilines of all three 0cm/a species that we tested. Chaetodactrlus mites are beneficial when feeding on nest molds or yeasts, but under humid conditions become dangerous when an enormous number of juveniles or hypopi crawl onto emerging adult 0cm/a, befoul wing joints, fatally crippling bees. No truly effective way exists for cleansing all mites from bees. Removing hypopi from a cocoon's exterior with a stiff paintbrush or dunking cocoons in 5% bleach are both effective. A wet, fine-haired paintbrush is safe for removing mites from torpid adults. Bee brood will need protection from woodpeckers, lizards, ants, other predators and parasites. To protect brood from larger predators and scavengers, a chicken wire sheath projecting over nest holes guard against birds; a very fine mesh wire placed over sealed entrances or tanglefoot barriers on supports protect bees from small lizards and fire ants. Thicker cardboard liners or dry hollow reeds are better barriers against such minute pests as Monodontomeru,c wasps (parasitoids of 0c177/(l).

Literature Cited Bosch, J. and Kemp. W.P. 2003. Effect of winterin g duration and temperature on survival and emergence time in males of the orchard pollinator 0cm/a //gnai'ia (I lymenoptera: Megachilidae). Environ. Entomol. 32:711-716. Bosch. J. and Kemp W.P. 2004. Effect of pie-wintering and wintering temperatures on weight loss, survival, and emergence time in the Osmnia cornula (1 lyinenoptcra: Megachi lidae): Apidologie. 35:469-479.

552 Cane, J. II. 1997. Lifetime monetary value of individual pollinators of the bee 1-Jabropocla lahoriosa at rabbiteye blueberry (Vacciniwn ashci Reade): Acta Ilort. 446:67-70. 1997. Cane, J. H. and Payne, J. A. 1993. Regional, annual, and seasonal variation in pollinator guilds intrinsic traits of bees ( I lynienoptera: Apoidea) underlie their patterns of abundance at facciniion as/wi ( Ericaceac): Ann. Entomol. Soc. Am. 86:577-588. 1993. (ripps. C. and Rust. R. W. 1985. Biology and suhgeneric placement of Osmia pikei (Ftymenoptera. Megachilidae). Entomological News. 96:109-113. Dogterom. M. H. 1999. Pollination by four species of bees on highhush blueberry. 1-116. Simon Fraser Univ., Burnaby, B.C., Canada. Ref Type: Thesis/Dissertation. Eickwort, G. C. 1975. Gregarious nesting of the mason bee hop/it/s anthocopoii/cs and the evolution of parasitism and sociality among megachilid bees. Evol. 29:142-150.. ,lavorek S. K., Mackenzie, K. E. and Vander Kloet S. P. 2002. Comparative Pollination Effectiveness Among Bees (: Apoidea) on Lowbush Blueberry : Vaccinium (Ingucti/ilium). Ann. Entoniol. Soc. Amer. 95:345-351. Kromhein, K. L. 1967. Trap-nesting wasps and bees, life histories, nests and associates. Smithsonian Press. Washington. DC. McCorquodale 1). B. and Owen R. E. 1994. Laying sequence, diploid males, and nest usurpation in the lea0utter bee, ivlegachile r000idata (Hymenoptera: Megachilidae) J. Insect Behav. 7:731-738. Mitchell, T. B. 1961 Bees of the eastern United States. Volume 2. Technical Bulletin. North Carolina Agricultural Experiment Station. 152. 557 p. Ngugi, H. K. and Scherm, H. 2006. Biology of 11over-infecting fungi. Ann. Rev. Phytopathology. 44:261-282. Rust, R. W. 1986. Biology of Osinia (Osmia) rib//Jails Cockerel] (Hymenoptera: Megachilidae). J. Kan. Ent. Soc. 59:89-94. Sampson. 13. J. and Cane, J. H. 2000. Pollination efficiencies of three bee (Hymenoptera: Apoidea) species visiting rabhiteye blueberry. J. Econ. Entomol. 93:1726-1731. Sampson, B. J.. Cane, J. H. and Neff J. 1995. Blue bees for blueberries. Ala. Agric. Exp. Stn. Auburn Univ. I iighlights Agric. Res. 42:12, 13, 15. Sampson, B. J. and Spiers J. M. 2002. Evaluating Bumblebees as pollinators of >Misty= southern highhush blueberry growing inside plastic tunnels. Acta Hort. 574:53-61. Sampson. B. J., Danka, R. G. and Stringer, S. J. 2004a. Nectar Robbery by Bees .Vilocopa ti/gin/ca and Apis nwhhif'ra Contributes to the Pollination of Rabhiteye Blueberry. J. Econ. Entomol. 97:735-740. Sampson. B.J., Stringer. S. J.. Cane. J. 11. and Spiers J. M. 2004b. Screenhouse Evaluations of a Mason bee Osmia rib/flails (Hymenoptera: Megachilidae) as a Pollinator for Blueberries in the Southeastern United States.. Small Fruits Review. 3:381-392. Smith B.J., 1998. Botrytis blossom blight of southern blueberries: cultivar susceptibility and effect ol chemical treatments. Plant Disease. 82:924-927. Stubbs, C. S., Drummond, F. A. and Osgood, E. A. 1994. Osmia rib//loris biederinannii and jt1e'achi/e roiundata ( H ynienoptera: Mcgachi lidae) introduced into lowbush blueberry agroecosvstems in Maine. J. Kans. Ent. Soc. 67:173 185. Tepedino, V. J. and Torchio, P. F. 1994. Founding and usurping: Equally eflcient paths to nesting success in Os,nia hignaiia prop/n qua ( Flymenoptera: Megachilidae). Ann. F.ntomol. Soc. Amer. 87:946-953. Torchio P. F. 1990. O.smia ,ib/floris. a native bee species developed as a commercially managed pollinator ofhighbush blueberry. J. Kansas Ent. Soc. 63:427-436. Tscharntke I.. Gathmann, A. and Steffan-Dewenter. 1. 1998. Bioindication using trap- nestin g bees and wasps and their natural enemies: community structure and interactions. J. AppI. Ecol. 35:708-719. I 553 Webb, C., Sivinski, J. and Litzkow, C. 1984. Acoustical behavior and sexual success in the Caribbean fruit fly. Ana.sirepha suspensa (Leow) (Diptera: Tephritidae). Environ. Entomol. 13:650-656. Whittier T. S., Nam, F. Y., Shelly, T. E. and Kaneshiro. K. Y. 1994. Male courtship success and female discrimination in the Mediterranean fruit fly (Diptera: Tephritidae). J. Insect Behav. 7:159-170. Zayed, A. and Packer, L. 2005. Complementary sex determination substantially increases extinction proneness ofhaplodiploid populations. PNAS 102:10742-10746.

Figures

1llI AP

I.o 'e

y. 'uI

I :.

Fig. I. (A) Osmia rib/lions courtship; (B) sheltered nest blocks; (C) nest block: (D) more sheltered nest blocks; (E) styrofoam nest substrate; (F) 0. rib/floris cocoons: (G) nest cell array inside a hollow reed.

554 I i2 y(x) = 2.58 + 0 . 04*exp(0 . 59x) , Ch = 4.52, p = 0.03

4.0 in = 178)

3.8

3.6 Adult male/female 34 Emergence Sex Ratio 3.2

3.0

2.8 (n=

2.6

2.4 2000 2001 2002 2003 2004 2005 year of captivity

Fig. 2. A small breeding population of 0. ri/J!f1oIL (50 nesting females per year) are difficult to keep in captivity because of increasingly male-bias sex ratios. If this trend were to continue, this population would go extinct. (n) is the total number of male and female adults to emerge that year. Also shown is the regression equation and chi-test results showing an upward trend in adult emergence sex ratio (#maIes/females).

555