The vertical distribution of mites and aphids on hops in southcentral Washington during the summer of 1993.

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$J. NTOMOL Sc. BRIT. COLUMBIA 92, DCMBR., 1995 91 The vertical distributin f mites and aphids n hps in suthcentral Washingtn during the summer f 199. CNGIZ KAZAK\ WYATT w. CON\ and LAWRNC C.$

1 J. NTOMOL Sc. BRIT. COLUMBIA 92, DCMBR., The vertical distributin f mites and aphids n hps in suthcentral Washingtn during the summer f 199. CNGIZ KAZAK\ WYATT w. CON\ and LAWRNC C. WRIGHr JDPARTMNT OF PLANT PROTCTION, FACULTY OF AGRICULTUR UNIVRSITY OF CUKUROV A, 010 ADANA, TURKY 2IRRIGATD AGRICULTUR RSARCH AND XTNSION CNTR WASIllNGTON STAT UNIVRSITY, PROSSR, WASHINGTON 9950 ABSTRACT The distributin f a predatry mite, Galandrlllus ccidenta/is, was detennined alng with its prey, the twsptted spider mite, Tetranychus urticae, at five elevatins n W1Sprayed hps grwn n a 5-6 m trellis. The prey species was well established at all elevatins when the study began n July 20, 199. The predatr did nt reach the uppennst elevatins sampled \ll1til tw weeks later. arly in the study whle plant predatr:prey ratis were 1:90 r mre cmpared t I :20 in late August. Cunts f hp apluds, Phrdn humuli Schrank, were als made. At lugh derlsities, hp apluds and resultant hneydew n leaves interfere with mite ppulatin develpment. AplUd derlsities f 0 r mre/leaf ccurred during the last three weeks f this study and reduced mite numbers. Identificatin f predatr mites indicated ca 6% were Amblyseius (=Neseiulus)fallacis (Garmen) wlueh had nt previusly been reprted n hps in Washingtn. Key wrds: Acari, Phytseiidae, TetranyclUdae, astern Washingtn, Hwnulus, Phrdn huliiuii, Tetranychus urticae, Galandrlllus ccidentalis. INTRODUCTION Hps, HUlllulus lupulus CUrticales:Cannibinaceae), are a specialty crp used fr bittering and flavring beer. Mst f the wrld's hps are prduced in urpe (Germany, Czech Republic, and ngland) and in nrthwestern U. S. (WaslUngtn, Oregn, and Idah). Tw key arthrpd pests are the twsptted spider mite (TSSM), Tetranychus urticae Kch, (Acari:TetranyclUclae) and the hp aphid, Phrdn humuli Schrank, (Hmptera:Aphididae). Left uncntrlled, either pest can cause cmplete lss f the crp. Recent emphasis in mst crp systems has been the decreased use f petrchemical-based pesticides and the increased use f natural enemies. A number f predatry insects and mites (Anthcridae, Cccinellidae, Chryspidae, and Cecidmyidae) has been recrded frm hps (Zeleny et al. 1981; Cranham, 1982; Campbell and Cne, 1994). Phytseiid predatrs f twsptted spider mite are nt regarded as viable bilgical cntrl agents f T. urticae in urpe because f the annual nature f the management f the hp crp (Cranham, 1985). Sites and Cne (1985) fund Typhldrlllus (=Metaseiulus)(=Galendrmus) ccidentalis (Nesbitt) dispersed ver the hp plant alng \,ith its prey, Tetranychus urticae, and in an earlier study Pruszynski and Cne (1972) fund Galndrlllus ccidentalis t be a much better adapted predatr n hps than the intrduced predatr, Phytseiulus persilllilis, in Washingtn. Hps grw rapidly in May and June and are trained n a trellis 5-6 m high. Little is knwn abut the ability f G. ccidentalis t frage ver the entire hp fliage canpy in search f its

2 92 J. NTOMOL. SOC. BRIT. C OLUMBIA 92, DCMBR, 1995 prey, the twsptted spider mite. TIus study describes the distributin f the tw key pests and G. ccidentalis thrugh ne grwing seasn. MA TRIALS AND MTHODS The study was cnducted during the 199 gr\\>ing seasn in a blck f hps, Humulus lupulus, cv. Galena, at WSU-IARC, Prsser, Washingtn. The hps were unsprayed. Twenty plants were selected fr unifmlity and sampled weekly frm 20 July t 7 September, 199 at height intervals f 0-1, 1-2, 2-,-4, and 4-5 m. Three leaves were cllected frm each plant at each height interval. A pruning ple and ladder were used t pick leaves frm the three higher elevatins. Samples were returned t the labratry in plastic bags where mites and aphids were cunted Wlder a bincular dissecting micrscpe (lox). ach leaf was subsampled five times by placing a heavy paper template ver it with a x cm ex1'osed area frm which the cunts were made. The number f mites and aphids in the five bservatins per leaf was ttaled fr each leaf and the mean f these ttals was calculated frm the three leaves per height fr each plant resulting in the number f mites and aphids per 45 cm 2. The mean fr each height was then calculated fr the 20 plants, resulting in 20 bservatins per height per date. Cunts included eggs and mbile stages f bth Tetranychus urticae and Galandrmus ccidentalis, and all hp aphids. Representative specimens f predatry mites were remved frm the samples, munted n micrscpe slides in Hyer's fluid, and prepared fr identificatin. A ttal f 180 slides was prepared. RSULTS AND DISCUSSION The mean number f twsptted spider mite, hp aphid, and the predatr mite, Galandrmus ccidentalis, per 45 cm 2 leaf area frm July t September are in Fig. l. Mean numbers f each species fowld at different heights n the plants during the sampling perid are pltted in Fig Phytseiids T. unicae 8 () () 8 P. humuli 0" V) 0-7 C/) 400 V) "<:;t LO 6 \...c.q- d) L- Cl) 00 5 V) 0. '"0 C/) d) L- 4 V) Cl) D..-- >-....c: ::J p.. Z a /24 7/ /14 8/21 8/28 9/ Figure 1. Mean number f aphids (P. hul11uli), spider mites (T urticae) and predatr mites (phytseiids) per 45 cm 2 subsample per leaf (00 leaves frm 20 plants) ± SM fr each date. a p".... Z

3 J. NTOMOL. sc. BRIT. COLUMBIA 92, DCMBR, A 20 July B 2 7 J uly c August 199 r.; 00 August ;j : N U LO <::t 0.01 '- Q) Q. I '( 4 C/) '- Q) -D 00 :J 0 Z 17 August 199 L F 24 August 199 r - j., rl f il.,1!, : r IT!.. t, f:i. } --, t. t ',- :: :. " j G 1 A ugust H 7 September 199 J. m.ft 1. ' l :: i'f ir 'I.L " I ::l I Height (m) 4 Figure 2. (A-H). Mean numbers ± SM f Galandrlllus Ccidentalis, Tetrany chyus urticae, and Phrdn hulliuli per 45 cm 2 subsample per leaf at different elevatins n hp plants, July 20-Sept. 7, 199. Ph)1seiid numbers are represented by tile white bar, T urticae by lie black bar, and P. humuli by tile crss-hatched bar

94 1. NTOMOL. SOC. BRIT. COLUMBIA 92, DCMBR., 1995 There were tw peaks f aphid numbers; ne August, and the secnd peak was still increasing when the study ended n September 7 (Fig. 1).

4 94 1. NTOMOL. SOC. BRIT. COLUMBIA 92, DCMBR., 1995 There were tw peaks f aphid numbers; ne August, and the secnd peak was still increasing when the study ended n September 7 (Fig. 1). Based n field experience, there is usually an increase in aphid nwnbers in July fllwed by a sharp decline in nwnbers with the nset f ht, dry weather. A secnd increase in numbers usually begins in late August (assciated with cler weather) with peak abwldance cming in September. Aphids were least nwnerus near the grwld thrughut the study perid (Fig. 2). The twsptted spider mite ppulatin shwed a small peak in late July and a larger peak in August; these are generally assciated with ht, dry weather. In 199, the peak f TSSM abwldance was August 17 (Fig. 1). Grwth f the predatr ppulatin, G. ccidentalis, usually begins slwly but generally fllws the prey curve. In 199 ttal predatr numbers were lw ( per 45 cm 2 ) Wltil August 17 when 2.4 per 45 cm 2 were fowld. The seasn peak (.14 per 45 cm 2 ) was reached n August 1 (Fig. 1). The first range (diapause) female TSSM appeared in the ppulatin n August 25. The nset f diapause in TSSM is cntrlled by phtperid (Veerman, 1985) and triggers a dwnward migratin frm the hp plant t vemintering sites. These sites may be plant debris n the sil surface, the hp crwn, crevices in the sil r cracks r ther penings arwld the base f wden hp ples that are part f the trellis. The distributin f G. ccidentalis n the hp plant is shwn in Figs. 2A-H. TSSM was well established at the tps f the plants when this study began July 20. The nwnber f predatrs declined with increasing height abve the 2 t m heights until August 17 when the numbers amng heights were relatively unifrm. Predatr numbers at the upper elevatin (4-5 m) peaked n August 17. After that time (Figs. 2F, G,H) mre predatr mites were fund at 0-1 and 1-2 m elevatins, and by September 7 nearly all predatrs were fund clse t the grund (0-1 m). This may be a reflectin f the fraging ability f the predatr fllo\ving its prey as they mve do\\,l1 the plant. The predatrs d fllw TSSM int their verwintering sites (Cne et al., 199). The weekly predatr:prey rati was 1:90, 1:4, 1:82, 1:7, 1:61, 1:8, 1:20, and 1:2 during the study perid. The actual effectiveness f the predatr in reducing TSSM numbers was bscured by the abundance f hp aphids during the last three weeks f the study. Aphids secreted 'hneydew' which seriusly interfered,vith TSSM ppulatin develpment and pssibility interfered with Phytseiid develpment as well. Of the 180 slides f predatrs, 168 were identified as G. ccidentalis and 12 as Amblyseius fallacis (Garmen). A.fallacis was the mst abundant predatr mite reprted in a survey f hp yards in Oregn (Strng and Crft, 199), but this is tile first time it has been reprted n hps in Washingtn. CONCLUSIONS These data indicate tile variatin in numbers f pests and predatrs n hps. The interactin between tile tw pest species where ne (the aphid) by physical means reduces the ppulatin f the secnd (tile mite) means that a secnd type f management may be needed when weatiler patterns favr aphid develpment. These data als indicate tilat the initial numbers f Galandrlllus ccidentalis are t lw t maintain Tetranychus urticae numbers belw their ecnmic threshld. Partial slutins may rest,\ith the use f selective aphicides that spare natural enemies and with tile augmentative release f predatry mites earlier in the seasn fr cntrl f tw sptted spider mites The rle tilat A. Ja/lacis plays in the bilgical cntrl f TSSM n hps in Washingtn remains t be determined.

5 J. momol. sc. BRIT. COLUMBIA 92, DCMBR, ACKNOWLDGMNTS We acknwledge the assistance fm. M. Cnant and 1. Perez in cnducting this study. We are particularly grateful t TOBIT AI<, Turkish Scientific and Research Cuncil, fr financial supprt. RFRNCS Campbell CAM., and W.W. Cne Influence f predatrs n ppulatin develpment f Ph r dn humuli (Hmptera:Aphididae) n hps. nvirn. ntm!. 2: Cne, W.W., M.M. Cnant, and L.C. Wright The sil mite fauna f hp crwns. ffect f predatrs n the venvintering ppulatin ftwspned spider mites. In: Prc. Sci. Cmm. In!'!. Hp Grwers Cmmissin. R.. Gunn and C.P. Green (eds). Wye Cllege, ngland. pp Cranham, J Integrated cntrl f damsn-hp aphid, Phrdll hunru/i, n nglish hps: a re\ew f recent wrk. Agric. nvirn. 7:6-71. Cranham, J Hp. Spider mites, their bilgy, natural enemies and cntr!' V!' I B. Wrld Pruszynski, S. and W.W. Cne Relatinship between Plrylseiu/us persil1li/is and ther enemies f the twspned spider mite n hps. nvirn. ntml. 1(4):41-. Sites, R.W. and W.W. Cne levatinal dispersin f lwspned spider mites n hps thrughut the grwing seasn. 1. ntml. Sc. Brit. Clumbia 82: Strng, W.B. and BA Crft Phytseiid mites assciated with spider mites n hps in the WiUamene Valley, Oregn. J. ntml. Sc. Brit. Clumbia 90: Veennan, A Diapause in spider mites, their bilgy, natural enemies and cntrl. Vl. IA W. Helle and M.w. Sabelis (eds). lsevier. pp Zeleny Jr., I. Hardy and P.K. KaJushkv PpUlatin dynamics f aphid and mite predatrs in hps: Bhemian hp-grwing area. In!'l. Org. Brewing ChemistsIWPRS Bull. 1981,4:87-96.

Asrar Ali, Ehsan-ul-Haq, Abdul Rehman, Javed Khan, Waseem Ahmad Gillani** and Maria Rauf*

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