View of First report of Diuraphis (Holcaphis) frequens as a pest of wheat in Finland

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Vol.6(1997): 337-339.

Research Note

First report of Diuraphis (Holcaphis) frequens

as a pest of wheat in Finland

Jonathan Robinson

AgriculturalResearch Centreof^Finland,^Institute of^Cropand Soil Science, PlantBreeding Section, FIN-31600Jokioinen, Finland,e-mail:jonathan.robinson@mtt.fi

ColoniesofDiuraphis (Holcaphis) frequens^(Walker) werefoundonwheat, Triticum aestivumL. in thevicinityof Jokioinenin south-westFinland insummer 1997.Theaphidwaspresent inall wheat fieldsinspected,andwasparticularlyabundantonspringwheat plantsof field andplot margins.The aphid wasalso common ^onitsrecognised, hostElymus repens (L.) ^Gould (couch grass). Damage symptoms,longitudinal chloroticstreaking oftightlyrolled leaves,resembled those causedbyDiu- raphis noxia (Mordvilko), the Russian wheataphid. Diuraphis frequensappearsunlikely to becomea

seriouspest ofwheat,and itsrelative abundance during 1997may haveresulted fromparticularly hot,dry weather.

Keywords^:aphid, Aphididae, Elymus^repens, Homoptera, Insecta,pest, Triticum aestivum

ntroduction

Diuraphis ⁽Holcaphis⁾frequens (Walker) is widespread in the Nordiccountries,Europe and Asia where its host plant is couch grass, Elymus repens (L.)Gould(Heie 1992),a common weed of agricultural land. It wasrecorded on wheat, Triticum aestivum L. from Idaho(Halbert etal.

1992)and Colorado(Anderson ^et al. 1995) in the UnitedStates, although itwas notrecorded as a seriouspest, nor was it anticipated tobe- come one.To date this aphid has ^not been esti- mated^tobe a pest of wheat inFinland, although

it was observed on wheat in Finland in 1994 (HannuAhokas pers. comm.).

Material and methods

Observations were made on spring wheat plants, and plants of E. repens, in and around the Jokioinen area in south-west Finland (60°

49’N, 23° 30’E) during July and August 1997.

Leaves withsymptoms of D. frequens infesta- tion wereremoved^to the laboratory where they

©Agricultural and Food ScienceinFinland Manuscriptreceived August 1997

337 AGRICULTURAL AND FOOD SCIENCE IN FINLAND

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Robinson, J.Diuraphis frequenson wheat

were unrolled and aphids, including viviparous

apteratesandalates,and nymphs, wereobserved and photographed underabinocular microscope.

Results and discussion

Diuraphis frequens is widespread in Finland (Heie 1992),but hasnotpreviously been recog- nised _{as a pest} of wheat. The aphid was found on spring wheat plants from all wheat plotssam- pled in the vicinity ofJokioinen,during July and August 1997. It _was also noted in other wheat fields of south-west Finland (Marja Jalli pers.

comm.)andcanbe presumed ^tohave been more widely distributed than wasimmediately appar- ent. It was foundon all leaves, up to the flag leaf. It wasparticularly abundantonwheat plants around field and plot margins. Itwasalso found in abundance oncouch grass, its preferred host.

Plants of barley, Hordeum vulgäreL., oats,Are- na saliva L. and rye, Secale cereale L. were observed but the aphid was ^not recorded on hosts other than wheat and couch grass.

Theapterous viviparous female aphid is light green and wax-powdered, with black antennae, cauda and legs. The^apterate is upto 2.5

mm

^long.

The alate viviparous female hasa light green abdomen andadark head and thorax. Diuraphis frequens is described in detail by Heie(1992).

Damage symptoms on ^{wheat and} ^E. repens resembled those caused by D. noxia ^(Robinson 1994). The aphid formed colonieson new leaves, which remained tightly rolled, effectively _con- cealing the aphid (Figure 1).Longitudinal chlorotic streaks wereevident in infected leaves in- dicating that the aphid injects a toxin into the plant while feeding similarly^toD. noxia^.While chlorotic streakingwas evident on leaves of couch grass, itwas moreevidentonwheat leaves.

Diuraphis frequens wasfrequently found in association with the bird-cherry ^oat aphid, Rho- palosiphum padi (L.).There is no evidence that

D. frequens transmits virus, but interestingly Bremer (1964)failedtotransmit Agropyron mo-

saic with severalcommoncerealaphids, but did not testthe ability of D. frequensto transmit it.

Diuraphis frequenswasadversely affectedon wheat by heavy rain during late July/early Au- gust, but appeared less affectedon couch grass.

Following heavyrain,colonies became infected by several species of entomopathogenic fungi.

Syrphid larvaeappeared^tobe the principal pred- ators of the aphid.

Diuraphisfrequens was thought unlikely ^to reach seriouspest^statuson wheat in Idaho^(Hal- bertet al. 1992)and has not been recorded as causing economic loss on wheat in Colorado (Anderson et al. 1995).It appears that it is un- likelytoreach seriouspest statusin Finland. Due

toits cryptic feedinghabits,and association with R. padi, it may have been present onwheat for

Fig. I.Colonyof Diuraphis (Holcaphis) frequensfeeding withinatightlyrolled wheat leaf. (Photo: Jonathan Robin- son).

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Vol.6(1997): 337-339.

sometime in Finland but has goneunnoticed, or unrecorded. Attempts tomaintain the aphid in the greenhouse on wheat enclosed in transpar- entplastic tubeswas unsuccessful,probably due

toits inability^totolerate high humidity. The par- ticularly hot and drysummerof 1997 may have been conducive to its seemingly uncharacteris- tic prominence.

References

Anderson, A.E., Holtzer,^TO.^&Michels,G.J. 1995.Com- parative growth rates of the Russian wheat aphid, Diuraphis^noxia(Homoptera, Aphididae),and other Diuraphis speciesinColorado. Bulletinof the Eco- logical Societyof America^{76: 4-5.}

Bremer, K. 1964.^Agropyronmosaic virusinFinland. An- nates Agriculturae Fenniae3: 324-333.

Halbert,S.E., Connely, B.J.^&Feng, M.-G. 1992.Occur- rence of Diuraphis ⁽Holcaphis) frequens(Walker) (Homoptera: Aphididae)onwheat,newtoIdaho,and akey to North American Diuraphis. Pan-PacificEn-

tomologist68: 52-61.

Heie,O.E. 1992.The Aphidoidea (Hemiptera) of Fenno- scandia and Denmark. IV. Fauna Entomologica Scandinavica25. E. J.Brill, Leiden,The Netherlands p.98-105.

Robinson,J. 1994.Identification and characterization of resistance to Russian wheat aphid in small-grain cereals:investigations at CIMMYT,1990-1992. ClM- MYTResearchReport^No.3Mexico,D.F.:CIMMYT.

44 p.

SELOSTUS

Diuraphis frequens -kirva vehnässä

Jonathan Robinson Maatalouden tutkimuskeskus

Diuraphis (Holcaphis) frequens^(Walker)yhdyskun- tialöytyi vehnästä, Triticum aestivum L., Lounais- Suomesta Jokioisten lähiympäristöstä kesällä 1997.

Kirvoja esiintyikaikissa tutkituissa vehnäpelloissa, erityisesti kevätvehnäpeltojen ja -ruutujen reuna- alueilla.Kirvojaoli runsaasti myös senvarsinaisella

isäntäkasvillajuolavehnällä, Elymus repens (L.) Gould. Vioitusoireet,pitkittäiset kloroottiset juovat

vahvasti kiertyneissä lehdissä, muistuttavat toisen vehnää vioittavankirvan, Diuraphisnoxia (Mordvil- ko), ‘Russian wheat aphid’, aiheuttamia oireita.

Diuraphis frequens-kirvasta ei todennäköisesti tule vakavaa vehnäntuholaista,sillä erityisenlämmin ja kuiva sää kesällä 1997mahdollisti kirvan runsaan esiintymisen.