農(nóng)病全部英語部分

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