Arthropod-Plnt Interctions DOI 1.17/s11829-17-951- ORIGINAL PAPER Susceptibility of germinting cruciferous seeds to Bgrd hilris (Hemipter: Penttomide) feeding injury Shimt V. Joseph 1 In M. Grettenberger 2 Lrry D. Godfrey 2 Noel Zvl 1 Received: 22 Mrch 216 / Accepted: 31 Jnury 217 Springer Science+Business Medi Dordrecht 217 Abstrct Bgrd hilris (Burmeister) (Hemipter: Penttomide) is serious pest tht ttcks both germinting nd seedling stges of vriety of cruciferous crops grown in the Centrl Cost of Cliforni. B. hilris feeding on germinting seeds cn cuse severe stunting nd plnt mortlity, nd little is known bout the feeding preference of B. hilris for germinting seeds of mjor cruciferous hosts nd vrieties of hosts. No-choice nd choice experiments were conducted in which germinting seeds in soilless nd soil settings were exposed to B. hilris dults for 7 dys. Susceptibility scores were developed using B. hilris feeding injury sites, distorted leves, nd deformed nd ded plnts to determine the overll B. hilris preference for germinting host seeds. Bsed on the scores, the order of preference ws rugul (Eruc stiv L.) > turnip (B. rp L. vr. rp) > mizun (B. rp L. nipposinic) > kle (B. olerce L. cephl) > choi (Brssic rp L. vr. chinensis) > broccoli (B. olerce vr. itlic Plenck) > culiflower (B. olerce L. vr. botrytis) > lettuce (Lctuc stiv L.) > sweet lyssum (Lobulri mritim [L.] Desv.). The lowest feeding injury ws recorded on germinting lettuce nd sweet lyssum seeds. Furthermore, no-choice nd choice experiments were conducted with four vrieties ech of rugul nd mizun, twelve vrieties ech of kle nd choi, nd nine vrieties/types of lefy Asin greens. The Hndling Editor: Heikki Hokknen. * Shimt V. Joseph shimtbug@gmil.com 1 2 Agriculture nd Nturl Resources, University of Cliforni Coopertive Extension, 1432 Abbott Street, Slins, CA 9391, USA Deprtment of Entomology nd Nemtology, University of Cliforni, Dvis, CA 95616, USA rugul vrieties Wild Rocket nd Spirit were more dmged by B. hilris thn other vrieties tested. Among mizun vrieties, Beir F1 ws more ttrctive to B. hilris thn Scrlet or Strbor F1. The choi vrieties Tokyo Bekn, Feng Qing Choi F1, Joi Choi F1, nd Win- Win Choi F1 were more ttrctive thn Rosie F1. The lefy Asin greens vriety Crlton F1 ws more ttrctive to B. hilris thn Yukin Svon, Ttsoi OG, Komtsun Summerfest F1, Red Rin F1, nd Shungiku. Therefore, the results suggest tht not ll vrieties were eqully susceptible to B. hilris feeding nd possibly be utilized for further field evlution s trp crop or developing more resistnt vrieties to B. hilris. Keywords Cliforni s Centrl Cost Brssiccee Asin lefy vegetbles Stink bug Introduction Bgrd hilris (Burmeister) (Hemipter: Penttomide) is n invsive stink bug species ntive to southern Afric, Middle Est, nd Asi (Reed et l. 213). It ws first detected in North Americ in Los Angeles Co., Cliforni in 28 (Plumbo nd Ntwick 21). Since then, it hs been found in most of the counties in Cliforni nd hs become well estblished in the northern Centrl Cost of Cliforni since 212 (Joseph 214). In ddition, B. hilris hs been detected or hs estblished in Arizon, New Mexico, Nevd, Texs, Oklhom, nd Hwii (Bundy et l. 212; Vitnz 212; Reed et l. 213; Mtsung 214) s well s in Mexico (Snchez-Pen 214). Bgrd hilris preferentilly feeds on cruciferous crops (Fmily: Brssiccee), including broccoli (Brssic olerce vr. itlic Plenck), culiflower (B. olerce L. vr. Vol.:(123456789)
S. V. Joseph et l. botrytis), kle (B. olerce L. cephl), choi (B. rp L. vr. chinensis), rugul (Eruc stiv Mill.), mizun (B. rp L. nipposinic), nd turnip (B. rp L. vr. rp) (Reed et l. 213; Hung et l. 214). In Cliforni lone, cruciferous crops were vlued t n estimted 1 billion USD in 213 (U.S. Deprtment Agriculture, NASS 214). Cruciferous crops were grown on >439 h in 213 nd vlued t 679 million USD, with lefy Asin sld crops in Monterey Co. vlued t 64 million USD (Monterey County Crop Report 214). Mny stink bug species cuse economic dmge by feeding on fruits or seeds on mture plnts, with dmge of germinting seeds nd seedlings occurring infrequently (McPherson nd McPherson 2; Chocorosqui nd Pnizzi 24). In contrst, B. hilris is most problemtic when feeding in freshly seeded or trnsplnted fields (Reed et l. 213). B. hilris kill seedlings, reduce plnt stnds, nd severely stunt surviving plnts when they feed in fields immeditely following plnting nd during the erly stges of plnt growth (Reed et l. 213; Hung et l. 214b). The hrlequin bug [Murgnti histrionic (Hhn)] is specilist of plnts in the fmily Brssiccee nd cn lso be pest of cruciferous crops, but it tends to ttck crops lter in the growing cycle thn B. hilris (White nd Brnnon 1933). Bgrd hilris feeds vi lcerte-nd-flush method in which it repetedly inserts its stylets between lyers of epiderml cells (Reed et l. 213). This feeding pttern physiclly injures the epiderml cellulr tissue nd the injury mnifests s strbursts on lef surfces. With time, strburst dmge chnges into necrotic tissue. This feeding injury on leves, even when primrily cosmetic, cn render lefy cruciferous crops such s choi, rugul, mizun, nd kle unmrketble. In broccoli nd culiflower, economic injury lso occurs when feeding by B. hilris kills the picl meristem of young seedlings, cusing plnts to not produce hed ( blind hed ; Plumbo nd Ntwick 21). On some plnts, B. hilris feeding lso stimultes the growth of multiple secondry shoots, which produces unmrketble nd undersized broccoli nd culiflower heds. Germinting seeds provide potentil window of vulnerbility for direct-seeded crops nd re therefore criticl stge for evluting dmge by B. hilris. The yield loss ttributble to mortlity or dmge to germinting seeds hs not been quntified for cruciferous crops. However, lrge numbers of dults nd nymphs hve been found in the soil crcks nd crevices on production beds during germintion or emergence of the seeds, nd these high popultions cn inflict substntil dmge (SVJ unpublished dt). For instnce, extensive feeding injury by B. hilris ws evident on newly germinted broccoli, rugul, nd mizun (SVJ unpublished dt). These crops, s well s other lefy greens, re entirely direct seeded in the Slins Vlley in conventionl production, while culiflower is entirely trnsplnted. For instnce, broccoli is typiclly plnted to stnd with ~15.2 cm spcing between seeds. Seedling mortlity reduces the number of plnts in the stnd, nd dmge cused from feeding cn cuse plnts to produce smll nd unmrketble heds. Plnt mortlity or stunting cn cuse nerby plnts to produce lrger, unmrketble heds, cusing further yield loss. Typiclly, lefy greens like rugul nd mizun re densely plnted nd their tender folige re hrvested severl times within six weeks fter plnting. Bgrd hilris feeding injury symptoms on these tender folige of these lefy crops reduce the lef qulity nd cn result in complete rejection of the hrvested produce. Dmge to germinting seeds nd cotyledons just emerging from the soil is significnt thret for direct-seeded crops, nd both heding nd lefy cruciferous crops cn suffer significnt economic losses from B. hilris feeding. To prevent dmge by B. hilris, growers typiclly rely on pyrethroid, neonicotinoid, or crbmte insecticides tht re pplied during the vulnerble seedling nd young plnt stges (Plumbo 211, b, c; Plumbo et l. 215). Effective lterntive methods to mnge B. hilris re still limited. Some growers hve even trnsitioned from directseeding to trnsplnting for broccoli, which is more expensive, to reduce yield loss (Reed et l. 213) or hve voided plnting some crops during periods of gretest B. hilris pressure (SVJ unpublished dt). For mny cruciferous crops, including bby lefy greens, direct-seeding remins stndrd prctice, nd B. hilris cn therefore dmge germinting seeds. Becuse B. hilris quickly find nd colonize newly plnted cruciferous crop fields nd dmge seeds s they germinte, there is n urgent need to reduce B. hilris feeding on germinting seeds. A better understnding of plnt dmge by B. hilris nd the preference for different crops will fcilitte more effective mngement of this pest nd better predictions of when economic dmge will occur. Previous work hs determined how ttrctive nd susceptible seedlings of different cruciferous crops re to B. hilris using cotyledon-stge plnts (Hung et l. 214). Adult B. hilris were most ttrcted to rdish (Rphnus stivus L.) seedlings, followed by those of red cbbge (Brssic olerce L. vr. cpitt) nd were less ttrcted to seedlings of rugul, Np cbbge (Brssic rp vr. pekinensis [Lour.], nd green mustrd (Brssic junce vr. rugos [Roxb.]) (Hung et l. 214). For red nd green cbbge, the combined chrcteristics of high ttrctiveness, but lower susceptibility to dmge compred to rdish, suggested these crops my be good cndidtes s trp crop (Hung et l. 214). In contrst, susceptibility of germinting seeds to B. hilris feeding is not well understood, nor is the preference of B. hilris for these seeds. In ddition, vrieties of individul my vry in their susceptibility nd ttrctiveness.
Susceptibility of germinting cruciferous seeds to Bgrd hilris (Hemipter: Penttomide) This informtion is necessry to predict dmge to recently seeded crops. Additionlly, differences in preference mong germinting seeds could be used for developing sustinble mngement tctics. Trp cropping is tctic used to ttrct or divert invding pests using preferred plnt host or cultivr (Hokknen 1991; Shelton nd Bdenes-Perez 26; Wllingford et l. 213). This tctic could be used to divert or concentrte colonizing B. hilris protecting the germinting min crop by plnting seeds of more ttrctive host plnts. Lbortory screening experiments cn serve s first step to selecting trp crop cndidtes by determining the ttrctiveness of vrious potentil hosts to the trgeted pest, nd cn be complemented by subsequent field tests (Shelton et l. 1991; Shelton nd Nult 24; Cook et l. 26). It will be necessry to evlute vrious stges of potentil trp crop (germinting, cotyledon, seedling). Developing non-chemicl tctics to reduce B. hilris feeding (e.g., trp cropping) is necessry for orgniclly mnged frms nd could increse the sustinbility of conventionl frms. Thus, the mjor objectives of this study were to (1) ssess the reltive feeding preference of B. hilris for different germinting cruciferous crop types nd susceptibility of the crop types to feeding injury nd to (2) evlute the preference of B. hilris for different germinting lefy cruciferous crop vrieties nd susceptibility of the vrieties to B. hilris injury. Mterils nd methods Generl methods nd insects We conducted no-choice nd choice ssys for both types of crops nd crop vrieties for certin crops (Tble 1). In the crop type experiments, we tested eight crops in nochoice nd choice tests: broccoli ( Heritge ), culiflower ( Hermn ), turnip ( Tokyo ), choi ( Mei Qing Choi ), kle ( Red winter ), rugul ( Astro ), mizun ( unknown ), nd lettuce (Lctuc stiv L., Rouge d hiver ), s well s the insectry plnt sweet lyssum (Lobulri mritim [L.] Desv., Snow Seeds Co., Slins, Cliforni). Lettuce, which typiclly does not incur dmge by B. hilris, ws included s non-host. No-choice nd choice ssys were conducted both with nd without soil substrte for the seeds. Lettuce nd kle were not included in the choice test with soil, while sweet lyssum ws only included in this test. Becuse B. hilris encounter soil when they interct with plnted seeds, experiments were conducted with nd without soil substrte. The soil type used ws Cler lke cly nd ws collected from field in Slins, Cliforni. For both ssy types, only dult bugs, rther thn nymphs, were used becuse dults re more mobile nd re the life stge tht typiclly colonizes newly plnted beds. Crop vriety experiments were conducted with multiple vrieties of five crop types: rugul, mizun, kle, choi, nd lefy Asin greens. We used four vrieties ech of rugul nd mizun, twelve vrieties ech of kle nd choi, nd nine vrieties/types of lefy Asin greens. The vrieties used were rugul: Sprint, Astro, Wild Rocket, nd Roquette Cultive ; mizun: Mustrd, Mizun OG, Kyoto, nd Drk Purple ; kle: Scrlet, Beir F1, Strbor F1, Olympic Red OG, Premier OG, Toscno, Red Russin OG, Siberin, Blck Mgic, Lcinto, Redbor F1, nd Rogue ; choi: Tokyo Bekn, Rosie F1, Gunsho F1, Red Choi F1, Blck Summer F1, Feng Qing Choi F1, Joi Choi F1, Win-Win Choi F1, Red PAC F1, White Flsh F1, Shiro F1, nd Mei Qing Choi ; ssorted lefy Asin greens: Yukin Svon (B. rp), Hon Tsi Ti (B. rp), Koji F1 (B. rp), Ttsoi OG (B. rp vr. nrinos), Vitmin Green (B. rp vr. nrinos), Komtsun Summerfest F1 (B. rp vr. perviridis), Crlton F1 (B. rp vr. perviridis), Red Rin F1 (B. junce), nd Shungiku (Glebionis coronri (L.) Css. ex Spch) (Johnny s Seeds, Winslow, Mine [USA], Snow Seeds Co., Slins, Cliforni, USA). All ssys were conducted in plstic tool orgnizer boxes, ech of which contined number of individul open-top plstic comprtments (Tble 1). For ech ssy, n individul comprtment served s replicte, nd B. hilris dults were given ccess to seeds within the comprtment. Bgrd hilris dults were restricted to the individul comprtments by securing the tops with no-see-um mesh (Bioquip, Rncho Dominguez, Cliforni, USA) held in plce with rubber bnd or Velcro, or plstic lid with twelve 2-mm-dimeter holes to ensure irflow. Tretments were rndomly ssigned to comprtments of different crop types nd vrieties were rndomly rrnged within comprtments. Comprtments vried in size for different ssys, s did the number of comprtments per orgnizer box (Tble 1). Comprtments were lrger for the choice tests compred to the no-choice tests to ccommodte multiple types of seeds nd more B. hilris individuls (one in no-choice vs. five in choice). For the crop type ssys, both no-choice nd choice tests were performed with nd without soil, wheres the crop vriety ssys were only conducted using potting mix substrte (Sun Gro, Sunshine Aggregte Plus Mix 4, Agwm, Msschusetts, USA) for the seeds to rest on. Groups of replictes were completed in successive trils nd number of trils nd replictes re listed in Tble 1. All ssys were evluted fter seven dys of exposure time to B. hilris to llow sufficient time for seeds to germinte nd for feeding dmge to become visible. After three dys of exposure time, ny ded B. hilris were replced with helthy dults. This mortlity ws likely due primrily to old ge becuse dults used in the experiment were of vrying ges. All experiments were conducted in controlled
S. V. Joseph et l. Tble 1 Tretments nd experimentl design for choice nd no-choice tests with B. hilris in no-choice nd choice tests Crop type or vriety test Choice or nochoice Comprtment size (cm) Trils Tretments Substrte Box mfr. No. comprtments Replictes per tretment d No. B. hilris per comprtment Crop type No -choice Choice Arugul, broccoli, choi, culiflower, kle, lettuce, mizun, nd turnip Arugul, broccoli, choi, culiflower, kle, lettuce, mizun, nd turnip Arugul, broccoli, choi, culiflower, mizun, turnip, lyssum Arugul, broccoli, choi, culiflower, kle, lettuce, mizun, nd turnip Vriety No-choice Vrieties of rugul nd mizun Vrieties of kle nd choi nd types of lefy Asin greens Choice Vrieties of rugul nd mizun Vrieties of kle nd choi nd types lefy Asin greens Mnufcturer unknown, but purchsed from Wlmrt, Slins, CA b Stnley Tools, New Britin, CT c Meridin Interntionl Co., Shnghi, Chin d All the replictes were combined by tril type for nlysis purpose Pper towel NA 16 5.5 4 4.2 4 16 1 Soil Stnley b 48 5. 3.5 3.8 3 12 1 Pper towel Tctix c 18 7. 1. 6. 2 36 5 Soil Tctix c 9 12.2 8.3 9.7 4 36 5 Potting mix NA 16 5.5 4 4.2 2 8 1 Potting mix Stnley b 48 5. 3.5 3.8 2 12 1 Potting mix Tctix c 18 7. 1. 6. 2 28 5 Potting mix Tctix c 9 12.2 8.3 9.7 2 18 5 environmentl chmber (21 ± 1 C, 45% reltive humidity, nd L:D 16:8 photoperiod). Seeds used in the experiments were not treted with ny pesticides. The experiments were conducted in University of Cliforni Coopertive Extension-Monterey County Lbortory, Slins, Cliforni. Bgrd hilris dults were collected from broccoli fields in Slins nd Chulr, Cliforni nd mintined in n environment chmber t 21 ± 1 C; 45% reltive humidity; nd L:D 16: 8 photoperiod in cges. Two- to fiveweek-old potted-broccoli plnts were provided s food source for the B. hilris nd the plnts were chnged every week. Crop type studies No choice ssys In the no-choice ssy, single B. hilris were given ccess to only one type of seed. For the ssy without soil, three seeds of host plnt were plced inside the comprtment in seed holder. The seed holder ws constructed from plstic vil lid (1.5 cm dim.) tht hd been inverted nd glued to the center of 5.3 3.8 cm piece of crdbord nd lined with 2 2 cm of moistened pper towel nd followed
Susceptibility of germinting cruciferous seeds to Bgrd hilris (Hemipter: Penttomide) by introduction of one B. hilris dult into ech comprtment to strt the ssy. The pper towel within the inverted vil tops ws moistened three times during the 7 dys period with.5 ml of distilled wter strting from the set-up. For the no-choice ssys with soil, the seed holder consisted of modified single well of plstic seed sprouting try (1.5 1.5 1.5 cm; Hummert Greenhouse Supplies, Topek, Knss, USA), which ws glued directly in the center of the comprtment. The well ws modified by removing the top of the well to produce totl height of 1.5 cm. Ech well ws filled with oven-dried soil to 3 mm from the top, nd three seeds of ech crop type were plced on the soil surfce. One B. hilris dult ws introduced into ech comprtment to strt the ssy nd wter ws dded. Choice ssys Bgrd hilris were given choice mong different crop types in the choice ssys. In the choice ssy without soil, the seed holder in the comprtment comprised eight inverted plstic vil lids (1.5 cm dimeter) glued to piece of crdbord in two rows with 1.5 cm between rows nd 1 cm between lids within rows. Ech vil lid ws lined with folded 2 2 cm of pper towel moistened with distilled wter. Three seeds of ech crop type were plced in ech inverted vil top. Five B. hilris dults were introduced into the comprtment t the strt of the ssy. The pper towel within the inverted vil tops ws moistened three times during the 7 dys period with.5 ml of distilled wter. The experiment with soil used group of 24 wells of plstic seed sprouting try (12 8.5 3.7 cm, 2 2 cm per well) s the seed holders. The group of wells completely filled the bottom of the comprtment. Six of the 24 wells were used for the ssy nd the rest of the wells were closed using pper tpe. Open wells were spced 2 cm prt. Ech well ws filled with oven-dried soil up to 3 mm from the top, nd three seeds of ech crop type were plced on the soil surfce. Five B. hilris dults were introduced to ech comprtment t the strt of the ssy. Crop vriety test No choice ssys In the no-choice ssys, B. hilris were given ccess to only one crop vriety t time. For the ssy with rugul nd mizun, the seed holder consisted of single well of seed try (1.5 1.5 1.5 cm) glued directly to the center of piece of crdbord (5.3 3.8 cm). The well ws filled with potting mix to 3 mm from the top, nd three seeds of ech vriety were dded to the surfce of the potting mix. One B. hilris dult ws introduced into ech comprtment t the strt of the tril. The no-choice ssys for kle, choi, nd lefy Asin greens lso used well of seed try (1.5 1.5 1.5 cm) s the seed holder, lthough it ws glued directly in the center of the comprtment. Ech well ws filled with.37 g of potting mix. Three seeds of ech species/vriety were plced on the surfce of the potting mix. One B. hilris dult ws introduced into the comprtment to strt the tril. Choice ssys Choice ssys for rugul nd mizun used seed try wells (1.5 1.5 1.5 cm) glued to piece of crdbord (7 1 cm). There were four wells per repliction rrnged 2 2 nd ech well ws filled with potting mix. Three seeds of ech host species were plced in ech well on the potting mix. At the strt of the ssy, five B. hilris dults were introduced into the comprtment. For choice ssys with kle, choi, nd lefy Asin greens, the seed holder consisted of multiple wells from seed sprouting try cut nd glued to the piece of crdbord (12.2 8.3 cm). The number of wells per comprtment depended on the number of crop vrieties for given crop type, which vried (Tble 1). The wells were rrnged in two rows in ech comprtment. Three seeds of ech vriety were plced on the surfce of the potting mix in the different wells. Five B. hilris dults were introduced into cell to strt the ssy. Evlution Seeds or newly germinted seedlings (mximum of two leves) or were evluted fter 7 dys of exposure to B. hilris. We determined the number of germinted seeds, seedlings with B. hilris feeding injury on leves, discrete feeding injury sites on leves, distorted leves with discrete feeding sites colesced, nd completely deformed or ded plnts. Seeds nd seedlings were evluted with dissecting microscope t 1 mgnifiction. Seeds were determined to be germinted if the rdicle hd emerged from the seed cot. Intct seeds nd seeds with crcked seed cot but no visible rdicle were grouped s un-germinted seeds. Becuse there were severl vritions of strburst injury on leves, ll discrete discolored spots cused by B. hilris feeding on intct leves were quntified s injury sites (Fig. 1, b). Distorted or misshpen leves with completely discolored ded tissue were quntified s distorted leves (Fig. 1c, d). Severe B. hilris feeding cn deform the seedling to the point where no leves re present. Those completely destroyed seedlings were clssified s deformed or ded (Fig. 1e, f). Individul feeding injury sites were indistinguishble for both distorted leves nd deformed seedlings.
S. V. Joseph et l. Bgrd hilris feeding on vrious crops nd vrieties ws evluted using three mesures of feeding dmge: number of feeding sites on leves, distorted leves, nd ded or deformed seedlings. There could be subtle differences in expression of B. hilris feeding on these hosts s mesured by these different types of feeding dmge. To ccommodte these differences nd provide mesure of overll susceptibility levels to B. hilris feeding, susceptibility scores were generted where the number of feeding injury sites per germinted seeds ws converted to scle ( 9) denoted s (); 1 (.1 1.); 2 (1.1 2.); 3 (2.1 3.); 4 (3.1 4.); 5 (4.1 5.); 6 (5.1 6.); 7 (6.1 7.); 8 (7.1 8.); nd 9 ( 8.1). The number of distorted leves nd ded or deformed seedlings per germinted seeds were converted to scle ( 9) denoted s, (); 1 (.1.25); 2 (.26.5); 3 (.51.75); 4 (.76 1.); 5 (1.1 1.25); 6 (1.26 1.5); 7 (1.51 1.75); 8 (1.76 2.); nd 9 ( 2.1). FS(Scle) + DL(Scle) + DS(Scle) SC = 1. (1) Sumofmximumsclevlue The bbrevitions re s follows: SC, susceptibility score; FS, number of feeding sites; DL, number of distorted leves; DS, number of deformed plus ded seedlings. To generte susceptibility scores, the sum of individul scores for the two or three prmeters ws divided by the sum of the mximum vlues for ech scle (27 for no-choice ssys nd 18 for choice ssys) nd percentge ws clculted for ech repliction (1). Susceptibility scores were clculted for ssys with or without soil in both the no-choice nd choice tests. Sttisticl nlyses SAS ws used for ll sttisticl nlyses (SAS Institute 212). Anlyses were conducted for ech ssy type (choice/ no-choice) for ech tril type (crop type/crop vrieties), s well s for ech substrte type (soil/soilless) for crop type experiments nd crop type (e.g., rugul) for crop vriety experiments (see Tble 1). Number of seeds germinted per well mong crop types nd crop vrieties were nlyzed with nlysis of vrince (ANOVA) using generl liner model (PROC GLM), nd mens were seprted using Tukey s HSD test. All sttisticl comprisons were considered significnt t α =.5. The number of B. hilris feeding injury sites, distorted leves, nd ded/deformed seedlings were stndrdized for the number of seeds tht germinted by dividing them by the number of germinted seeds per well. For some dmge mesures, dt were not vilble for certin replictes becuse high levels of some dmge mesures (e.g., no seeds germinted) precluded dt collection for other dmge mesures (e.g., distorted leves), nd these dt were excluded from the nlyses. Ech dmge mesure ws nlyzed with ANOVA using the PROC GLM procedure. Susceptibility scores were nlyzed with ANOVA fter rcsine squre root trnsformtion using the PROC GLM procedure. Mens were seprted using Tukey s HSD method. Averges of scores by crop type or vriety were rnked to determine the overll susceptibility of ech host to B. hilris feeding. Becuse kle nd sweet lyssum were not included in the choice soil ssy, the ssy ws excluded from these verges. Results Crop type studies No choice ssys Fig. 1 Bgrd hilris feeding injury types:, b strburst or discolored spots s pointed out using blck rrows, c, d distorted leves, nd e, f completely destroyed leves or ded seedlings In soilless ssys, culiflower seeds germinted t the lowest rte (<5%) fter exposure to B. hilris compred to
Susceptibility of germinting cruciferous seeds to Bgrd hilris (Hemipter: Penttomide) ll other crop types, with the exception of choi, which ws intermedite to culiflower nd the other crops (Tble 2). The number of B. hilris feeding sites ws significntly greter for rugul thn for kle, culiflower, nd lettuce, lthough number of feeding sites ws similr between rugul, broccoli, mizun, nd choi (F = 6.8; df = 7, 13; P <.1; Fig. 2). The number of leves deformed by B. hilris feeding in rugul ws significntly greter thn in broccoli, culiflower, kle, lettuce nd turnip; however, the number of distorted leves ws not significntly different between rugul, mizun nd choi (Fig. 2b) (F = 2.5; df = 7, 13; P =.17). The number of ded or deformed seedlings ws highest for rugul nd turnip compred to ll other hosts except mizun, for which the difference ws not significnt (Fig. 2c) (F = 3.2; df = 7, 13; P =.3). There ws no significnt difference in number of deformed or ded seedlings between culiflower nd lettuce. In the ssys with soil, the number of seeds tht germinted for culiflower nd mizun were significntly lower thn for lettuce (Tble 2). The number of B. hilris feeding sites for seeds tht did germinte ws significntly greter in kle thn in broccoli nd lettuce (Fig. 2d) (F = 3.3; df = 7, 73; P =.4). There were no differences in number of feeding sites between rugul, culiflower, kle, mizun, choi, nd turnip. A similr number of leves were deformed by B. hilris feeding cross hosts, lthough no leves of lettuce were fed upon (Fig. 2e) (F = 1.8; df = 7, 73; P =.89). The number of ded or deformed seedlings ws significntly greter in mizun thn in broccoli, culiflower, lettuce, nd choi (Fig. 2f) (F = 2.4; df = 7, 73; P =.29), nd similr numbers of seedlings did not successfully germinte for rugul, kle, mizun, nd turnip. Choice ssys In soilless ssys, the number of seeds tht hd germinted fter 7 dys ws greter in rugul thn choi nd culiflower (Tble 2). Among germinted seeds of rugul, broccoli, kle, mizun, turnip, nd lettuce, there were no significnt differences. After 7 dys, number of feeding injury sites ws significntly greter in turnip nd rugul thn in broccoli, culiflower, kle, mizun, nd lettuce (F = 26.7; df = 7, 236; P <.1), but ws not significntly different from choi (Fig. 3). Number of leves distorted by B. hilris feeding ws significntly greter in mizun thn in kle nd lettuce (F = 5.2; df = 7, 236; P <.1) nd it ws not significntly differently mong rugul, broccoli, choi, culiflower, nd turnip (Fig. 3b). In the ssys with soil, the number of germinted choi seeds fter 7 dys ws significntly lower thn germinted broccoli nd sweet lyssum seeds (Tble 2). Significntly more feeding sites were found in turnip thn in choi, culiflower, nd sweet lyssum but number of feeding sites in turnip ws not different from rugul, broccoli, nd mizun (F = 11.2; df = 6, 14; P <.1) (Fig. 3c). The number of distorted leves ws significntly less in sweet lyssum thn in ll other hosts (F = 3.2; df = 6, 14; P =.5) (Fig. 3d). Susceptibility scores In the no-choice ssy without soil, the susceptibility scores were significntly lower in kle, lettuce, nd culiflower thn in other hosts (Tble 3). However, in the no-choice ssys with soil, the susceptibility score ws only lower in lettuce thn other hosts. In choice ssys without soil, susceptibility scores were significntly greter in turnip thn in kle, culiflower, nd lettuce, wheres there ws no difference in susceptibility scores in choice ssys with soil. Tble 2 Men (±SE) number of seeds germinted out of three fter 7 dys in the test ren Host plnt No-choice Choice Soilless Soil Soilless Soil Arugul 2.35 ±.18 2.16 ±.27 2.88 ±.5 2.32 ±.12b Broccoli 2.7 ±.13 2.83 ±.11b 2.83 ±.6b 2.74 ±.11 Choi 2.2 ±.22b 2.5 ±.19b 2.47 ±.11 2. ±.19b Culiflower 1.45 ±.22b 1.25 ±.25c 2.33 ±.13c 2.44 ±.15b Kle 2.45 ±.17 2.5 ±.15b 2.74 ±.9b Mizun 2.35 ±.18 1.91 ±.28 2.56 ±.12 2.57 ±.14b Turnip 2.7 ±.13 2.25 ±.3b 2.6 ±.12 2.6 ±.12b Lettuce 2.65 ±.18 2.91 ±.8 2.77 ±.7 b S. lyssum 2.86 ±.26 F (df1, df2) 5.7 (7, 137) 6.3 (7, 77) 4.2 (7, 236) 3.2 (6, 14) P <.1 <.1 <.1.4 Mens followed by the sme letters within column re not significntly different (Tukey s HSD Test, α =.5)
S. V. Joseph et l. No. feeding sites per germinted seed No. distorted leves per germinted seed No. deformed nd ded plnts per germinted seed 5 4 3 2 1 1.5 1.2.9.6.3.6.5.4.3.2.1 (A) (B) (C) b cd c c b d c c b b b b 5 4 3 2 1 1.5 1.2.9.6.3.6.5.4.3.2.1 (D) b (E) (F) b b b b b c b b b b b b Fig. 2 Bgrd hilris feeding injury (men ± SE) on germinting seeds in the no-choice ssys using of different crop types without soil ( c), nd with soil (d f). Assys were evluted fter 7 dys of B. hilris exposure. Brs with the sme letter within figure re not significntly different (P >.5) No. feeding sites per germinted seed No. distorted leves per germinted seed 5 4 3 2 1 1.5 1.2.9.6.3 (A) (B) cd b b b de e c b 5 4 3 2 1 1.5 1.2.9.6.3 (C) b b cd d Arugul Broccoli Bok choi Culiflower Mizun Sweet lyssum (D) b b Turnip b Fig. 3 Bgrd hilris feeding injury (men ± SE) on vrious germinting host seeds in the choice ssy in the bsence (, b) nd presence of soil (c, d) when evluted fter 7 dys of exposure. No plnts were severely deformed or ded nd therefore these dt re not included in the figure. Within figure, brs mrked with the sme letter re not significntly different (P >.5)
Susceptibility of germinting cruciferous seeds to Bgrd hilris (Hemipter: Penttomide) The verge of men susceptibility scores by host indicted tht the order of preference/susceptibility to B. hilris feeding from highest to lowest ws s follows: rugul > turnip > mizun > kle > choi > broccoli > culiflower > lettuce (Tble 3). Assys with crop vrieties On rugul, the number of feeding sites, distorted leves, nd ded or deformed seedlings ws significntly lower in Wild Rocket thn other vrieties in the no-choice ssy (Tble 4). In the choice ssy, significntly lower number of seeds germinted in Roquette Cultive vriety thn Wild Rocket nd Sprint. The number of feeding sites ws significntly greter on Spirit thn on Wild Rocket nd Roquette Cultive, lthough there ws no difference between Spirit nd Astro nd or Sprint. The number of distorted leves ws significntly greter on Wild Rocket thn on Spirit nd Roquette Cultive. The ded nd deformed seedlings were significntly greter on Wild Rocket thn on Astro nd Roquette Cultive. On mizun, there were no significnt differences mong vrieties in both no-choice nd choice ssys (Tble 4). On kle in the no-choice ssy, the vrieties did not differ for number of germinted seeds, feeding injury sites, distorted leves, nd ded or deformed seedlings. In the choice ssy, number of seeds germinted mong vrieties ws not significntly different. The number of feeding injury ws significntly greter on Beir F1 thn Scrlet nd Strbor F1. Similrly, number of distorted leves ws significntly greter on Beir F1 thn on Strbor F1. There ws no difference mong vrieties for ded nd deformed seedlings. In no-choice ssys with choi, numbers of germinted seeds, feeding injury sites, nd distorted leves were similr mong vrieties, lthough ded nd deformed seedlings were significntly greter on Rosie F1 thn Mei Qing Choi (Tble 4). In the choice ssy, number of seeds germinted ws not different mong vrieties. The number of feeding injury sites ws significnt greter on Tokyo Bekn, Feng Qing Choi F1, Joi Choi F1, Win-Win Choi F1 thn on Rosie F1, while the number of distorted leves ws significntly more on Win-Win Choi F1 thn on Rosie F1. The choi vriety Joi Choi F1 hd significntly greter number of ded nd deformed seedlings compred to Rosie F1. For the no-choice ssy with lefy Asin greens, number of germinted seeds, feeding injury sites, distorted leves, nd ded or deformed seedlings did not differ significntly mong vrieties (Tble 4). In choice ssy, number of germinted seeds nd ded or deformed seedlings ws not significntly differently mong vrieties but number of feeding injury sites nd distorted leves vried with vrieties. The feeding injury sites were significntly greter on Crlton F1 thn on Yukin Svon, Ttsoi OG, Komtsun Summerfest F1, Red Rin F1, nd Shungiku. The leves distorted fter B. hilris feeding were significntly greter on Hon Tsi Ti nd Crlton F1 thn on Shungiku. Discussion We ssessed the reltive susceptibility of germinting seeds of cruciferous species nd vrieties to B. hilris feeding injury under controlled environmentl conditions. First, the bility of B. hilris to feed on germinting cruciferous host Tble 3 Reltive susceptibility of germinting host plnt seeds to B. hilris feeding injury bsed on susceptibility scores (%) Plnt host No-choice Choice Ave. susceptibility Rnk b Soilless Soil Soilless Soil score Arugul 23.8 ± 3.8 21.9 ± 5.5 25.4 ± 3.1b 43.9 ± 4.8 23.7 1 Turnip 11.2 ± 1.8b 23.9 ± 6.9 28.1 ± 2.5 43.9 ± 4.8 21.6 2 Mizun 15.9 ± 2.9b 23.6 ± 6.1 23.6 ± 2.6 36.2 ± 3.9 21.3 3 Kle 9.9 ± 1.6 2.9 ± 3.9 14.6 ± 1.7 cd 15.13 4 Choi 16.7 ± 2.8b 17.9 ± 3.7 1.6 ± 2.6b 27.4 ± 5.9 15.6 5 Broccoli 13.8 ± 2.9b 8.3 ± 3.1b 16.5 ± 2.2 36.9 ± 4.6 12.87 6 Culiflower 2.8 ± 1. cd 12.1 ± 6.2b 1.6 ± 2.6d 32.9 ± 3.9 8.5 7 Lettuce 1. ± 1.d.3 ±.3b.3 ±.2e.53 8 Sweet lyssum 5.2 ± 2.9b F (df1, df2) 8.2 (7, 13) 4.9 (7, 73) 21.9 (7, 236) 7.5 (6, 14) P <.1 <.1 <.1 <.1 Generted by verging the percentge susceptibility scores in ech tests excluding soil test in choice ssy b Generted bsed on the verge susceptibility score. Highest susceptibility score corresponds to higher levels of dmge. Vlues followed by the sme letter within the column re not significntly different (Tukey s HSD Test, α =.5)
S. V. Joseph et l. Tble 4 B. hilris feeding injury on germinting seeds of lefy cruciferous crop vrieties Host vrieties No-choice Choice Germinted seeds Feeding sites Distorted leves Ded seedlings Seeds germinted Feeding sites Distorted leves Ded seedlings Arugul Sprint 3. ±. 5.7 ± 1.4 1.2 ±.3.6 ±.2 2.8 ±.1 7.4 ±.7.8 ±.1b 1.6 ±.9b Astro 2.6 ±.2 5.7 ± 1.4 1.3 ±.3.6 ±.2 2.6 ±.2b 5.8 ±.6b.6 ±.1.3 ±.1b Wild 2.5 ±.3.1 ±.1b.1 ±.1b. ±.b 2.9 ±.1 4.4 ±.5b 1.6 ±.2 4.7 ± 1.5 Rocket Roquette Cultive 2.6 ±.2 5.4 ± 1.1 1.7 ±.1.9 ±.1 2.1 ±.2b.3 ±.1c.1 ±.1c.2 ±.2b F df1,df2 ; P F 3, 21 = 1.5; P =.252 Mizun b F 3, 18 = 7.9; P =.1 F 3, 21 = 1.8; P <.183 F 3, 21 = 1.8; P <.1 F 3, 71 = 4.6; P =.6 F 3, 67 = 21.6; P <.1 F 3, 67 = 13.4; P <.1 F 3, 69 = 4.8; P =.5 Mustrd 1.9 ±.3 3.8 ± 1.4.3 ±.2.5 ±.2 2.3 ±.1 6.5 ± 1..8 ±.1.6 ±.1 Mizun 1.3 ±.3 6. ± 1.3 1. ±.4.7 ±.2 2. ±.2 7.2 ±.8.8 ±.1.6 ±.1 OG Kyoto 2. ±.3 4.1 ± 1.1.5 ±.2.6 ±.1 2.3 ±.2 6.4 ±.8.9 ±.2.6 ±.1 Drk Purple 2.3 ±.2 3.6 ±.6.5 ±.1.3 ±.1 2.4 ±.1 7.6 ±.9.9 ±.1.5 ±.1 F df1,df2 ; P F 3, 33 = 2.1; P =.113 Kle c F 3, 13 = 1.2; P =.325 F 3, 12 = 1.9; P =.183 F 3, 26 = 1.1; P =.387 F 3, 8 = 1.6; P =.23 F 3, 42 =.8; P =.515 F 3, 47 =.1; P =.938 F 3, 77 =.3; P =.89 Scrlet 2.1 ±.3 6.3 ± 1.1.8 ±.3.5 ±.2 2.1 ±.3 1.2 ±.4c.2 ±.1.2 ±.1 Beir F1 2.3 ±.4 6.2 ±.7.8 ±.3.5 ±.1 2.8 ±.1 6.8 ± 1.1.8 ±.1.4 ±.1 Strbor F1 2.8 ±.2 3.2 ± 1.2.2 ±.1.2 ±.1 2.5 ±.2 1.6 ±.4c.1 ±.1c.1 ±. Olympic 2.6 ±.4 2.5 ±.9.2 ±.1.2 ±.1 2.3 ±.2 3.4 ±.6.5 ±.2.2 ±.1 Red OG Premier 1.8 ±.3 3.8 ± 1.2.2 ±.1.3 ±.2 2.4 ±.2 3.1 ±.5.4 ±.1.2 ±.1 OG Toscno 1.8 ±.5 3.8 ± 1.5.8 ±.3.6 ±.2 2.6 ±.2 3.2 ±.5.4 ±.1.2 ±. Red Russin 1.9 ±.5 2.8 ±.9.8 ±.4.4 ±.2 2.3 ±.2 3.3 ±.4.6 ±.1.3 ±.1 OG Siberin 2.1 ±.3 6.1 ±.7.8 ±.2.5 ±.2 2.6 ±.1 4.8 ±.9b.5 ±.1.3 ±.1 Blck 2.4 ±.4 4.8 ± 1.4.6 ±.3.3 ±.1 2.4 ±.2 2.9 ±.6.3 ±.1.3 ±.1 Mgic Lcinto 2.3 ±.4 2.6 ± 1.5.5 ±.2.5 ±.2 2.6 ±..5 ±.5.7 ±.1.3 ±.1 Redbor F1 1.8 ±.4 3.8 ± 1.9.6 ±.2.4 ±.2 2.4 ±.2 3.3 ±.7.3 ±.1.2 ±.1 Rogue 2.4 ±.3 6.1 ± 1.5.6 ±.2.3 ±.1 2.5 ±..6 ±.6.4 ±.1.2 ±.1 F df1,df2 ; P F 11, 77 =.9; P =.474 Choi d Tokyo Bekn F 11, 53 = 1.6; P =.132 F 11, 57 = 1.1; P =.356 F 11, 68 =.7; P =.71 F 11, 187 =.9; P =.555 F 11, 172 = 5.1; P <.1 F 11, 176 = 2.9; P =.2 F 11, 182 = 1.7; P =.76 2.8 ±.2 2.3 ± 1.1.5 ±.3.3 ±.1b 2.3 ±.2 7.3 ±.8 1. ±.3b.2 ±.1b Rosie F1 2. ±.4 2. ± 1. 1.6 ±.3.8 ±.1 2.7 ±.1 2.5 ±.7b.3 ±.1b.1 ±.1b Gunsho F1 1.8 ±.4 3. ± 1.3.5 ±.3.2 ±.2b 2.4 ±.2 5.3 ±.8b.8 ±.2b.3 ±.1b Red Choi 2.2 ±.4 4.8 ± 1.6.9 ±.2.5 ±.1b 2.4 ±.2 5.1 ± 1.1b.5 ±.1b.2 ±.1b F1 Blck Summer 2.8 ±.2 3.6 ± 1.2.9 ±.3.5 ±.2b 2.3 ±.2 5.3 ± 1.2b.4 ±.1b.2 ±.1b F1 Feng Qing 2.6 ±.3 3.7 ±.9.6 ±.3.4 ±.2b 2.7 ±.1 6.9 ± 1.2.6 ±.1b.3 ±.1b Choi F1 Joi Choi F1 2.6 ±.3 5.6 ± 1.7.9 ±.3.9 ±.3b 2.8 ±.1 7.3 ± 1.2.8 ±.2b.5 ±.1
Susceptibility of germinting cruciferous seeds to Bgrd hilris (Hemipter: Penttomide) Tble 4 (continued) Host vrieties No-choice Choice Germinted seeds Feeding sites Distorted leves Ded seedlings Seeds germinted Feeding sites Distorted leves Ded seedlings Win Win 2.8 ±.2 3.5 ± 1.4.4 ±.2.4 ±.2b 2.5 ±.2 8.5 ± 1. 1.2 ±.3.4 ±.1b Choi F1 Red PAC 2.3 ±.3 3.1 ±.9.5 ±.3.5 ±.3b 2.3 ±.2 4.3 ±.8b.4 ±.2b.2 ±.1b F1 White Flsh 2.4 ±.2 3.2 ±.9.4 ±.2.3 ±.1b 2.4 ±.2 4.9 ± 1.b.6 ±.2b.3 ±.1b F1 Shiro F1 2.8 ±.2 5.8 ± 1.6 1.2 ±.3.6 ±.1b 2.4 ±.2 6.3 ± 1.3b.5 ±.2b.3 ±.1b Mei Qing Choi 2.6 ±.2 2.8 ± 1.3.1 ±.1. ±.b 2.7 ±.2 6.9 ± 1.2b.7 ±.1b.3 ±.1b F df1,df2 ; P F 11, 77 = 1.7; P =.94 Lefy Asin greens e F 11, 56 =.7; P =.771 F 11, 64 = 1.6; P =.19 F 11, 74 = 2.1; P =.34 F 11, 187 =.9; P =.539 F 11, 168 = 3.1; P =.1 F 11, 168 = 2.1; P =.22 F 11, 18 = 2.7; P =.3 Yukin 2.3 ±.4 2.4 ±.7.1 ±.1.1 ±.1 2.2 ±.2 2.1 ±.7.5 ±.1b.2 ±.1 Svon f Hon Tsi 2.3 ±.3 1.9 ±.9.3 ±.3.1 ±.1 2.6 ±.2 3.5 ± 1.1b.9 ±.2.4 ±.1 Ti f Koji F1 f 1.9 ±.4 5.2 ± 2.6.6 ±.4.2 ±.2 2.6 ±.2 3.6 ±.6b.6 ±.2b.2 ±.1 Ttsoi OG g 1.2 ±.4 1.5 ± 1.5.4 ±.4.2 ±.2 1.8 ±.2 1.8 ±.6.6 ±.2b.3 ±.1 Vitmin 2. ±.4 3.8 ± 1.8.9 ±.4.4 ±.2 2.6 ±.2 1.7 ±.5.3 ±.1b.1 ±.1 Green g Komtsun 1.5 ±.4 1.8 ± 1.1.6 ±.3.4 ±.2 2.6 ±.2 1.7 ±.6.6 ±.2b.2 ±.1 Summerfest F1 h Crlton 1.1 ±.3 4.2 ± 1.8 1. ±.4.7 ±.2 2.4 ±.2 5.7 ± 1.2.9 ±.2.5 ±.1 F1 h Red Rin 1.9 ±.2 5.3 ± 1.3 1. ±.4.4 ±.2 2.3 ±.2 1.6 ±.6.4 ±.2b.4 ±.2 F1 i Shungiku j 1.4 ±.5. ±.. ±.. ±. 2.2 ±.2. ±.c. ±.b. ±. F df1,df2 ; P F 8, 56 = 1.4; P =.28 F 8, 37 = 1.3; P =.259 F 8, 42 = 1.; P =.439 F 8, 43 = 1.6; P =.154 F 8, 133 = 1.7; P =.117 F 8, 13 = 6.5; P <.1 Vlues followed by the sme letter within host type re not significntly different (Tukey s HSD Test, α =.5) Eruc stiv b B. junce vr. nipposinic c B. olerce d B. rp vr. chinensis e Vrious species of Brssic spp. f B. rp g B. rp vr. nrinos h B. rp vr. perviridis i B. junce j Glebionis coronri F 8, 124 = 2.7; P =.8 F 8, 124 = 1.6; P =.138 seeds, s well s non-host (lettuce), ws evluted in no-choice setting. Next, feeding preference ws ssessed in choice setting. For the crop type experiments, ptterns of dmge vried widely mong the tested hosts, including mong only cruciferous crops. In the crop vriety experiments, difference in dmge ws evident mong vrieties, lthough in some cses, there were no vrietl differences. In the no-choice ssys, B. hilris fed on ll cruciferous hosts, lthough germinting seeds of rugul, turnip, nd mizun were most ffected by feeding dmge such s lef distortion nd seedling deformity or mortlity. This suggests tht B. hilris is cpble of feeding on germinting stges of ll cruciferous hosts tht we tested if they cn physiclly ccess the seeds. Interestingly, the choice ssy
S. V. Joseph et l. results lso show tht rugul, turnip, nd mizun hd more feeding injury thn other hosts, suggesting tht germinting seeds of these hosts were most preferred by B. hilris, lthough ptterns could lso be driven by susceptibility to injury. Previous reserch on host preference used seedlings (Mkwli et l. 22; Hung et l. 214) tht were lredy pst the germintion stge. With seedlings, B. hilris dults preferred seedlings (cotyledon-stge) of rdish nd red nd green cbbge over sweet lyssum, rugul, nd broccoli plnts (Hung et l. 214). Rdish ws not used in our study becuse this crop is not grown extensively in the Centrl Cost of Cliforni. By describing the susceptibilities of germinting seeds of vrious crop types nd vrieties, our results expnd the informtion vilble on crop susceptibility to include the time period when seeds first begin germinting. It is uncler why certin crop types or vrieties suffered more dmge thn others (e.g., rugul, turnip, nd mizun in the crop type experiment). First, these species/vrieties my germinte more quickly thn others. The seeds in this study were evluted fter 7 dys to provide sufficient time for ll seeds to germinte. It is possible tht erly geminting seeds re more vulnerble to B. hilris feeding thn slowly germinting seeds. Second, it is lso possible tht B. hilris is more ttrcted to germinting seeds of certin hosts. This could be relted to preference of vrying levels nd blends of voltiles relesed. Germinting culiflower seeds relese voltile chemicls such s cynides nd isothiocyntes fter hydrolysis of glucosinoltes (Vlette et l. 26). The strength of the voltiles relesed vries cross cruciferous species nd vrieties (Vlette et l. 26; Hong nd Kim 213). Vrition in defensive chemicl content cn be importnt for feeding by herbivores on cruciferous host. For two specilist herbivores, the fle beetle, Phyllotret crucifere (Goeze) nd dimondk moth, Plutell xylostell (L.), feeding ws gretest when glucosinolte levels in B. rp (syn. cmpestris) (L.) were intermedite (Siemens nd Mitchell-olds 1996). It is likely tht B. hilris re similrly responding to chemicl compounds relesed by germinting seeds of ll of the tested cruciferous hosts nd tht this ffects preference. Moisture content in the seeds my further ffect the type nd mount of voltiles relesed from the seeds, which could influence B. hilris behvior nd feeding dmge (Jorgensen 21; Hudib et l. 21). Our results show tht germinting seeds of lettuce were not ttrctive to B. hilris. Lettuce ws included in this study becuse it is the mjor, high-vlue crop (US$1.4 billion) in the Slins Vlley of Cliforni (Monterey County Crop Report 214). Our results dismiss the necdotl reports tht B. hilris cn dmge germinting seeds of lettuce. Sweet lyssum ws included becuse it is commonly used insectry plnt in the Centrl Cost of Cliforni which is direct seeded in beds interspersed with the min crop to enhnce predtion of phids by syrphid flies (Bugg et l. 28). Mture sweet lyssum is ttrctive to B. hilris (Joseph 214), but our results show tht germinting stges of sweet lyssum ws not very ttrctive. This suggests tht t lest when seeds re still germinting, sweet lyssum would likely not be useful s trp crop. Trp crops could provide n dditionl tool for reducing dmge by B. hilris to germinting crops, nd our results cn inform their development. Although lefy Asin crops, rugul, turnip, nd mizun pper to hve reltively similr levels of ttrctiveness compred to ech other, these crops could still be used s trp crop when the lefy Asin crops re grown s min crops. Crops with the sme level of ttrctiveness cn be developed s trp crop by mnipulting the sptil nd temporl plnting of trp nd min crops, thereby diverting or concentrting the incidence nd coloniztion of the pest (Shelton nd Bdenes-Perez 26). Erly plnting of rugul, turnip, nd mizun, possibly before the min crop, my trp invding B. hilris, llow them to be mnged, nd reduce the impct on the min crop s it germintes. When heding crops such s broccoli or culiflower re the min crop, lefy Asin crops could be developed s trp crop becuse the germinting stges of broccoli nd culiflower were less ttrctive to B. hilris reltive to lefy Asin crops. These tctics would function better if the B. hilris dults ttrcted to the trp crop re killed or removed vi chemicl controls (conventionl or orgnic) or with mechnicl controls, such s incorportion of the trp crop into the soil or vcuuming. Lettuce, or nother non-preferred crop, could serve s brrier crop in between the trp crop nd the min crop, limiting movement of B. hilris into the min crop. It is possible tht plnting trp crop before the min crop could ttrct B. hilris dults erlier to the field nd increse dmge to the min crop. Thus, this tctic needs to be crefully evluted in the field to determine its utility for effective B. hilris mngement. Although ll vrieties of lefy Asin crops developed B. hilris feeding injury symptoms fter week of B. hilris exposure, certin vrieties of rugul, kle, choi, nd Asin greens were fed upon more nd developed more symptoms of dmge. Perhps, these differences in feeding preferences could be utilized for mngement of B. hilris feeding t the germintion stges. Those highly preferred vrieties could be potentilly considered s trp crop, wheres the less preferred vrieties which suffer less feeding injury could be plnted s the min crop. These differences in susceptibility or ttrctiveness to B. hilris could be lso be used to develop more resistnt vrieties for B. hilris mngement. The rugul vrieties Wild Rocket nd Spirit were more ttrctive to B. hilris thn other vrieties tested. On mizun, the vriety
Susceptibility of germinting cruciferous seeds to Bgrd hilris (Hemipter: Penttomide) Beir F1 ws more ttrctive to B. hilris thn Scrlet nd Strbor F1. The choi vrieties Tokyo Bekn, Feng Qing Choi F1, Joi Choi F1, nd Win-Win Choi F1 were most ttrctive. The lefy Asin greens vrieties Crlton F1 ws more ttrctive to B. hilris thn Yukin Svon, Ttsoi OG, Komtsun Summerfest F1, Red Rin F1, nd Shungiku. In conclusion, our results suggest tht germinting stges of rugul, mizun, choi, nd turnip seeds re more ttrctive to B. hilris thn culiflower or broccoli nd my be utilized s trp crop when seeds re first plnted. Although the results did not provide cler indiction of B. hilris feeding preference mong rugul, mizun, choi, nd turnip in the choice tests, when plnted erly long the field edges, one or more of these hosts my diffuse B. hilris pressure nd my produce lower feeding injury on the min crop thn if the min crop ws plnted lone. Sweet lyssum plnts hve been found to be ttrctive to B. hilris in the field (Joseph 214), but B. hilris dults did not show ny preference for germinting seeds of sweet lyssum in this study, suggesting tht it would likely not be useful s trp crop but lso tht new plntings should not be highly ttrctive. Similrly, lettuce ws not preferred by B. hilris dults when provided in no-choice nd choice studies. Vrieties of severl cruciferous sld crops demonstrted spectrum of preference. Our results demonstrte tht when seeds first germinte, the susceptibility nd ttrctiveness of different crop types nd crop vrieties cn be useful for determining the thret of B. hilris injury to newly plnted fields nd for developing effective mngement tctics. Acknowledgements The uthors pprecite the technicl ssistnce provided by C. Rmirez nd J. Mrtinez with experiments, nd grochemicl compnies, Cliforni Deprtment of Food nd Agriculture (CDFA) Specilty Crop Block Grnt (greement#scb1459) nd University of Cliforni Integrted Pest Mngement (UC IPM) sttewide progrm for providing funding for this project. References Bugg, RL, Colfer RG, Chney WE, Smith HA, Cnnon J (28) Flower flies (Syrphide) nd other biologicl control gents for phids in vegetble crops. University of Cliforni Division of Agriculture nd Nturl Resources ANR Public: 1 25 Bundy CS, Grsswitz TR, Sutherlnd C (212) First report of the invsive stink bug Bgrd hilris (Burmeister) (Heteropter: Penttomide) from New Mexico, with notes on its biology. Southwest Entomol 37: 411 414 Chocorosqui VR, Pnizzi AR (24) Impct of cultivtion systems on Dichelops melcnthus (Dlls) (Heteropter: Penttomide) popultion nd dmge nd its chemicl control on whet. Neotrop Entomol 33:487 492 Cook SM, Smrt LE, Mrtin JL, Murry DA, Wtts NP, Willims IH (26) Exploittion of host plnt preferences in pest mngement strtegies for oilseed rpe (Brssic npus). Entomol Exp Appl 119: 221 229 Hokknen HMT (1991) Trp cropping in pest mngement. Ann Rev Entomol 36:119 138 Hong E, Kim G-H (213) GC MS nlysis of the extrcts from Koren cbbge (Brssic cmpestris L. ssp. pekinensis) nd its seed. Prev Nutr Food Sci 18: 218 221 Hung T, Reed DA, Perring TM, Plumbo JC (214) Host selection behvior of Bgrd hilris (Hemipter: Penttomide) on commercil cruciferous host plnts. Crop Prot 59:7 13 Hung T, Reed DA, Perring TM, Plumbo JC (214b) Feeding dmge by Bgrd hilris (Hemipter: Penttomide) nd impct on growth nd chlorophyll content of Brssicceous plnt species. Arthropod Plnt Interct 8:89 1 Hudib T, Hyes W, Brown S, Edy PE (21) Effect of seed moisture content nd D-limonene on oviposition decisions of the seed beetle Cllosobruchus mcultus. Entomol Exp Appl 137:12 125 Jorgensen EE (21) Emission of voltile compounds by seeds under different environmentl conditions. Am Midl Nt 145:419 422 Joseph SV (214) Effect of trp color on cptures of Bgrd bug, Bgrd hilris (Hemipter: Penttomide). J Entomol Sci 49:318 321 Mkwli JA, Wnjl FME, Khemb BM (22) Rphnus rphnistrum L s diversionry host of Brevicoryne brssice L nd Bgrd cruciferrum Kirk. In: Proceedings of the Horticulture Seminr on Sustinble Horticulturl Production in the Tropics October 3rd to 6th 21. Jomo Kenytt University of Agriculture nd Technology, JKUAT, Juj, Keny Mtsung JN (214) Bgrd bug, Bgrd hilris (Burmeister) (Hemipter: Penttomide). stte of Hwii deprtment of griculture, new pest dvisory. 14 2, December 214 McPherson JE, McPherson R (2) Stink bugs of economic importnce in Americ north of Mexico. CRC Press, Boc Rton Monterey County Crop Report 214. Office of Agriculturl commissioner- Monterey County, Cliforni. http://www.co.monterey. c.us/home/showdocument?id=1581 Plumbo JC (211) Control of Bgrd hilris with folir insecticides on broccoli, 21. Arthropod Mng Tests 36:E8. doi:1.4182/mt.211.e8 Plumbo JC (211b) Evlution of soil systemic insecticides for control of Bgrd hilris on broccoli, 21. Arthropod Mnge Tests 36: E1. doi:1.4182/mt.211.e1 Plumbo JC (211c) Evlution of experimentl insecticides ginst Bgrd hilris on broccoli, 21. Arthropod Mng Tests 36:E9. doi:1.4182/mt.211.e9 Plumbo JC, Ntwick ET (21) The Bgrd bug (Hemipter: Penttomide): new invsive pest of cole crops in Arizon nd Cliforni. Online. Plnt Hel Prog http://www.plntmngementnetwork.org/pub/php/brief/21/bgrd /doi:1.194/ PHP-21-621-1-BR Plumbo JC, Prbhker N, Reed DA, Perring TM, Cstle SJ, Hung T (215) Susceptibility of Bgrd hilris (Hemipter: Penttomide) to insecticides in lbortory nd greenhouse biossys. J Econ Entomol 18:672 682 Reed DA, Plumbo JC, Perring TM, My C (213) Bgrd hilris (Hemipter: Penttomide), n invsive stink bug ttcking cole crops in the southwestern United Sttes. J Integ Pest Mngmt 4(3). doi:1.163/ipm137 Snchez-Pen SR (214) First record in Mexico of the invsive stink bug Bgrd hilris on cultivted crucifers in Sltillo. Southwest Entomol 39: 375 377 SAS Institute (212) SAS Version 9.4. SAS Institute Inc., Cry, NC Shelton AM, Bdenes-Perez FR (26) Concepts nd pplictions of trp cropping in pest mngement. Annu Rev Entomol 51:285 38