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1、APPLESCABApplescabexistswldwidebutismesevereinareaswithcoolmoistspringssummers.Similarscabdiseasesaffectpears(Venturiapyrina)hawthns(V.inaequalissp.f.pyracanthae).Scabisthemostimptantdiseaseofapples.Itsprimaryeffectisred
2、uctionofthequalityofinfectedfruit.Scabalsoreducesfruitsizeresultsinprematurefruitdefoliationpofruitbuddevelopmentfthenextyearitreducesthelengthoftimeinfectedfruitcanbekeptinstage.Lossesfromapplescabmaybe70%meofthetotalfr
3、uitvalue.Inmostappleproducingareasnomarketablefruitcanbeharvestedifscabcontrolmeasuresarenottaken.Symptoms?Atfirstlightolivecoledirregularspotsappearonthelowersurfaceofsepals(萼片)(萼片)youngleavesoftheflowerbuds.Soonafterth
4、elesionsbecomeolivegreengraywithavelvetysurface.?Laterthelesionappearmetallic(金屬的)(金屬的)blackincolmaybeslightlyraised.?Lesiononolderleavesgenerallyfmontheuppersurfaceoftheleaves.Lesionsmayremaindistincttheymaycoalesce(聯(lián)合)
5、(聯(lián)合).?Leavesinfectedyoungremainsmallcurledmaylaterfalloff.Occasionallysmallscabspotsareproducedontwigsblossoms.?Infectedfruitdevelopcircularscablesionsvelvetyolivegreenatfirstbutlaterbecomingdarkerscabbysometimescracked.
6、?Thecuticleofthefruitisruptured(破裂、裂開)(破裂、裂開)atthemarginofthelesions.?FruitInfectedearlybecomemisshapen(畸形)(畸形)crackedfrequentlyprematurely.?Fruitinfectedwhenapproachingmaturityfmonlysmalllesionswhichhowevermaydevelopint
7、odarkscabspotsduringstage.ThePathogen:Venturiainaequalis?Themyceliuminlivingtissuesislocatedonlybetweenthecuticletheepidermalcells.?Thereitproducesshterectbrownishconidiophesthatgiverisetoseveralonetwocelledspilocaeatype
8、(環(huán)痕式環(huán)痕式)conidiaofratheracteristicshape.?Indeadleavesthemyceliumgrowsthroughtheleaftissuesproducesogoniaantheridiafollowingfertilizationpseudotheciafm.Thelatteraredarkbrowntoblackwithaslightbeakanopening.?Eachpseudotheciu
9、m(假囊殼)(假囊殼)contains50to100ieachwitheightospesconsistingoftwocellsofunequalsize.DevelopmentofDisease?Thepathogenoverwintersindeadleavesonthegroundasimmaturepseudothecia.Pseudotheciacompletetheirgrowthinlatewinterspringosp
10、esmatureastheweatherbecomesfavablefgrowthdevelopmentofthehost.?Mostpseudotheciaimatureintheperiodduringwhichthefruitbudsopen.?Whenpseudotheciabecomethoughlywetinthespringtheifciblydisgetheospesintotheairwhichcarrythemtos
11、usceptiblegreenappletissues.?ospedisgemaycontinuef3to5weeksafterpetalfall.?ospesgerminatecauseinfectionwhenkeptwetattemperaturesrangingfrom6to26C.Finfectiontooccurthespesmustbecontinuouslywetf28hoursat6Cf14hoursat10Cf9ho
12、ursat1824Cf12hoursat26C.DevelopmentofDiseaseThetobaccomosaicvirusisverystablecanpersistindrycontaminatedsoilininfectedtomatodebrisonintheseedcoat.Thevirusistransmittedreadilyfromplanttoplantbymechanicalmeans.Thismaysimpl
13、yinvolvepickinguptheviruswhilewkingwithinfectedplantmaterialtheninoculatinghealthyplantsbyrubbingbrushingagainstthemwithcontaminatedtoolsclothinghs.Aphidsarenotvectsofthetomatomosaicvirusalthoughcertainchewinginsectsmayt
14、ransmitthepathogen.Thecucumbermosaicvirusoverwintersinperennialweedsmaybetransmittedtohealthyplantsbyaphidvects(althoughtomatoesarenotthepreferredhostofaphids)bymechanicalmeans.Thecucumbermosaicviruscannotwithstdryingper
15、sistinthesoil.Italsoismedifficultthantobaccomosaictotransmitmechanically.Thuscucumbermosaictendstoprogressmeslowlythantobaccomosaicinafieldgarden.Thespottedwiltvirusistransmittedfromplanttoplantbyseveralspeciesofsmallins
16、ectscalledthrips.Thripsarelessthanonequarterinchinlengthlightgreentobrownareextremelydifficulttofindontheplants.Severalweedyhostsnamentalplantsmayserveasalternatehostsfthevirus.ControlVirusdiseasescannotbecontrolledoncet
17、heplantisinfected.Therefeeveryefftshouldbemadetopreventintroductionofvirusdiseasesintothegarden.Manyvarietiesoftomatoareavailablewithresistancetotobaccomosaicvirus.Sanitationistheprimarymeansofcontrollingtheothertwovirus
18、diseases.Infectedplantsshouldberemovedimmediatelytopreventspreadofthepathogens.Perennialweedswhichmayserveasalternatehostsshouldbecontrolledinadjacenttothegarden.Avoidplantingtomatoesnexttocucurbitsspinachothervegetables
19、flowerssusceptibletothesediseases.Controlofinsectsespeciallyaphidsthripswillhelpreducethelikelihoodofcucumbermosaicspottedwilt.TomatoLeafMould?Leafmouldisadiseaseoftomatoesonly.?Leafmoldisprimarilyaproblemongreenhousetom
20、atoes.?Thediseaseismostdestructiveinthegreenhouseduringthefallearlywinterspringwhentherelativehuityismostlikelytobehighairtemperaturesaresuchthatheatingisnotcontinuous.Whenhuityishighthefungusdevelopsrapidlyonthefoliageu
21、suallystartingonthelowerleavesprogressingupward.Ifthediseaseisnotcontrolledlargeptionsofthefoliagecanbekilledresultinginsignificantyieldreductions.Earlyinfectionsaremostthreatening.SymptomsMajsymptomsoccuronthefoliagebut
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