Kolekcije

Hessian Fly Mušice - naučite kako ubiti hessian muhe

Hessian Fly Mušice - naučite kako ubiti hessian muhe


Napisala: Tonya Barnett, (autor FRESHCUTKY)

Poslednjih godina popularnost je drastično porasla za uzgoj pšenice i ostalih žitarica u domaćem vrtu. Bez obzira da li se nadate da ćete postati održiviji ili uzgajati žitarice za upotrebu u domaćem pivarstvu, dodavanje žitarica u vrtu uzbudljiv je način da ojačate vašu rastuću snagu.

Kao i kod dodavanja bilo koje druge nove kulture na povrće, važno je da se uzgajivači prvo upoznaju sa svim mogućim problemima koji se mogu spriječiti i koji mogu biti uobičajeni. To je posebno tačno u slučaju zrnastih kultura, jer njihova podložnost zarazi hesijskim mušicama može dovesti do todrastičnog smanjenja prinosa. Pročitajte za više informacija o upravljanju letovima Hessian.

Šta je hesen muha?

Hesian mušice štetočine napadaju mnoge članove porodice žitarica, sa posebnim interesom za usjeve pšenice. Zbog svog malog izgleda i izgleda poput komarca, muhe hesija često ostaju neprimijećene. Iako stvarna odrasla muha nije odgovorna za štetu nanesenu usjevima pšenice, ličinke (ili crvi) ovih muha mogu prouzrokovati ozbiljne gubitke zrna. To se posebno odnosi na komercijalnu proizvodnju zrna.

Nakon izlijeganja, lisice mušice počinju se hraniti sadnicama pšenice. Iako crvi hesijske muhe zapravo nikada ne ulaze u steno biljke, njihovo hranjenje je slabi. U mnogim slučajevima to uzrokuje da se pšenica (ili druge žitarice) prevrne i slomi na mjestu hranjenja. Ove slomljene i oštećene biljke tada nisu u stanju da proizvedu žitarice koje se mogu ubrati.

Suzbijanje štetočina hesijske muhe

Uz potencijal za takvu štetu u kućnom vrtu i nekomercijalne zasade, mnogi uzgajivači se pitaju kako ubiti hessijeve muhe. Iako se malo može učiniti nakon što se zaraza već dogodi, postoje neke mogućnosti u pogledu upravljanja hessovim mušicama.

Najezde hesen muhe mogu se izbjeći sadnjom sorti žita, posebno pšenice, koje pokazuju određeni otpor mušicama. Ove sorte otežavaju odrasloj muhi polaganje jaja. To zauzvrat čini biljke manje privlačnim kao domaćin.

Uz to, uzgajivači mogu slijediti smjernice za sadnju čekajući dok u njihovoj specifičnoj regiji uzgoja ne prođe datum „hessian fly free“. Ovaj datum služi kao tačka u kojoj je aktivnost muha prestala na jesen, a ličinke muhe rjeđe utječu na usjeve.

Ovaj je članak posljednji put ažuriran


Biologija i upravljanje hesenovskom muhom na jugoistoku

ENTFACT-155: Biologija i upravljanje hesenovskom muhom na jugoistoku | Preuzmite PDF

Kathy L. Flanders, stručnjak za produženje i profesor, entomologija i patologija biljaka, Univerzitet AuburnDominic D. Reisig, stručnjak za produženje i docent, Entomologija, Državno sveučilište Sjeverne KarolineG. David Buntin, profesor, entomologija, Univerzitet u DžordžijiMatthew Winslow, diplomirani istraživač, Politehnički institut i univerzitet VirginiaD. Ames Herbert mlađi, profesor entomologije, Virginia Polytechnic Institute i UniversityDouglas W. Johnson, produženi profesor entomologije i IPM koordinator, Entomologija, Univerzitet u Kentuckyju
Slika 1. Odrasla muha hesija (Foto: Scott Bauer,

USDA Služba za poljoprivredna istraživanja, Bugwood.org)

Hesijska muha, Mayetiola destructor (Recimo), ozbiljan je štetnik ozime pšenice na jugoistoku Sjedinjenih Država. Ozbiljnost zaraze hesijskom mušicom varira iz godine u godinu i po lokaciji. Izbijanje ovog insekta periodično se događalo u Sjedinjenim Državama od njegovog predstavljanja sredinom 1800-ih. Vjeruje se da je hesijska muha unesena na Long Island u New Yorku, u slamnatu podlogu koju su hesijski vojnici koristili za vrijeme revolucionarnog rata. Hesen muha preferira hranjenje pšenicom, ali može zaraziti i tritikale, ječam i raž. Hesen muha ne napada zob ili ljulj. U narednim godinama entomolozi očekuju da će se rizik od ekonomskih gubitaka hesijeve muhe nastaviti. Razlozi za to uključuju usvajanje shema plodoreda koje vode do sadnje pšenice na istom polju uzastopne godine, upotreba pšenice kao pokrovne kulture, prelazak na raniji datum sadnje pšenice i povećane površine pod pšenicom. Pojava biotipova hesen muhe koji prevladavaju otpornost kod većine sorti pšenice dovela je do nestašice sorti pšenice otporne na hesen muhu. Ova publikacija raspravlja o biologiji hesijske muhe i daje prijedloge za upravljanje ovim insektom.

Slika 2. Jaja muhe hesija na listu (Foto: Dominic Reisig)

Opis i životni ciklus

Hesenina muha (slika 1) je mala mušica slična komarcu, dugačka oko 1/8 inča. Odrasla mužjaka hesijske muhe crvenkasto je smeđe do crne boje, dok su nešto manji mužjaci smeđe ili crne boje. Na poljima pšenice mogu se naći mnoge odrasle muhe koje nalikuju hesijskim mušicama. Odrasle muhe hesija mogu se ponekad razlikovati od ostalih malih muha slične veličine prisustvom dvanaest do šesnaest segmentiranih zrnastih antena, crno obojenih krila i nogu dugih ili dužih od dužine tijela. Odrasle ženke žive 1 do 2 dana i mogu položiti dvjesto pedeset do tristo malih, eliptičnih jajašca narandžaste boje u žljebove na gornjoj strani lišća pšenice (slika 2). Hesanske muhe često počinju taložiti jaja ubrzo nakon nicanja sadnica. Jaja se talože pojedinačno ili od kraja do kraja u „linijama jaja“ između žila na gornjoj površini mladog lišća.

Slika 3. Ličinka hesen muhe

Crvi (ličinke) se iz jaja izlegnu nakon 3 do 10 dana i narandžaste su boje 4 ili 5 dana prije nego što pobijele (slika 3). Kako larve sazrijevaju, prozirna zelena pruga pojavljuje se po sredini leđa. Crv je dugačak oko ¼ inča kada je potpuno izrastao. Posljednji stupanj ličinke provodi se unutar lanenog sjemena ili puparija. Laneno sjeme je sjajna, smeđa zaštitna futrola duga oko 1/8 inča (slika 4). Izgrađena je od kože insekata i nazvana je zbog sličnosti sa sjemenkom biljke lana. Nerijetko se mogu naći hesejski mušici ili laneno sjeme naslagani jedan iza drugog (slika 5), ​​posebno u slučaju jakih zaraza. Ako su vremenski uslovi povoljni, hesenske muhe će se olajkati (pretvoriti u odrasle osobe) unutar lanenog sjemena. Odrasli se tada pojavljuju i započinju novu generaciju. Ako je prevruće ili hladno, hesijske muhe ostaju kao crvi unutar lanenog sjemena dok se vrijeme ne ublaži.

Na jugu postoji tri do šest generacija ovog štetnika godišnje, s manje generacija na sjevernim geografskim širinama. Generacije se imaju tendenciju preklapati. Čitav životni ciklus zahtijeva oko 35 dana na 70 stepeni F, ali traje duže na hladnim temperaturama jer su insekti hladnokrvni. Crvi nastavljaju hranjenje sve dok su temperature iznad 40 stepeni F i ispod 80 stepeni F. Štetnik prekomjerno leti kao sjeme lana u pšeničnom strništu. Prva generacija razvija se tokom septembra ili oktobra, ovisno o geografskoj širini i uglavnom je pronađena na dobrovoljnim domaćinima pšenice ili divlje trave, od kojih je najvažniji mali ječam, Hordeum pusillum . U jesen i ranu zimu često postoje još dvije generacije u Alabami i Georgiji, ali samo jedna generacija tijekom jeseni i zime u Sjevernoj Karolini. Krajem zime ili u proljeće odrasli izlaze i započinju novu generaciju kada temperature dosežu između 50 i 60 stepeni F. Obično postoji jedna proljetna generacija u sjevernoj Alabami, sjevernoj Georgiji i Sjevernoj Karolini, ali mogu postojati dvije proljetne generacije u južnoj Alabami i južna Džordžija.

Slika 4. Hesian fly puparium (laneno sjeme) u podnožju biljke pšenice (Foto: Dominic Reisig) Slika 5. U teškim najezdama, mnoge muhe hesija mogu se naći iza jednokrilnog omotača. (Foto: Rudy Yates)

Novoizleženi crveni hesenski muhari migriraju iza omotača listova i kreću se prema dolje, na kraju se smještajući ispod zemlje u podnožju malih biljaka pšenice, gdje se hrane. Ličinke se mogu hraniti 14 do 30 dana, ovisno o temperaturi, a biljke mogu ozlijediti pucanjem listova ili matičnih ćelija. Oni također uzrokuju da biljka formira područje hranjivog tkiva oko baze kako bi poboljšala svoje hranjenje, što može rezultirati zaostajanjem u krmljenju i odumiranjem. Biljke zaražene hesenovskom muhom pokazuju različite simptome. Zakržljale ili mrtve freze (slika 6) i tanke sastojine pšenice tipični su znakovi rane zaraze (slike 7 i 8). Zakržljale vegetativne freze često su tamnozelene, a ponekad imaju plavu nijansu. Listovi listova na napadnutim frezama širi su i kraći od uobičajenih, a ovojnice listova kraće (slika 9). Ako kultivatori zaraženi kad su bili mali prežive i stvore glavice zrna, glavice su male, a stabljike zakržljaju.

Slika 6. Mrtve i zakržljale freze uzrokovane ranom najezdom hesenske muhe

Slika 7. Tanke sastojine i zakržljale biljke prouzrokovane ozbiljnom najezdom hesenske muhe

Slika 8. Tanke sastojine i zakržljale biljke prouzrokovane ozbiljnom najezdom hesen muhe

Slika 9. Rano obrađene pšenice imaju skraćene ovojnice lišća

Odrasle mušice hesen po mogućnosti polažu jaja na najgornje lišće. Prema tome, kako biljka raste, crvi će se nalaziti dalje uz biljku, ali uvijek iza lisne ovojnice neposredno iznad zgloba stabljike. Kraća udaljenost između zglobova simptom je zaraze hesijskom muhom. Kultivatori zaraženi u proljeće kad su stariji mogu imati oslabljene stabljike, male glavice i slabo napunjene glavice zrna sa nekvalitetnim zrnima. Pšenica često odsjeda na ozbiljno zaraženim poljima.

Tanak stalak koji se sastoji od zakržljalih biljaka pšenice s nekoliko glava znak je izuzetno teške zaraze hesenovskom muhom koja je započela kad su biljke bile male. Umjerena zaraza može rezultirati gubitkom prinosa s manje očitim simptomima. Gubitak prinosa obično je značajan ako je više od 5 do 8 posto freza napadnuto u ranoj fazi rušenja. Kasne zimske ili ranoproljetne generacije hesijske muhe također mogu nanijeti značajnu štetu. U nekim su područjima, poput Kentuckyja, proljetne invazije hesijske muhe češće od jesenjih. Ako su obradi zaražene u proljeće, mogu se očekivati ​​gubici prinosa ako je 15 do 20 posto stabljika napadnuto hesenovskom muhom. Hesen muha smanjuje prinos krme ozime pšenice, ali ne utječe mnogo na kvalitetu pšenične krme.

Strategije upravljanja

Otporne i tolerantne sorte

Ispravan odabir sorti vjerovatno je najjeftinija i najučinkovitija metoda upravljanja hesijskim mušicama. Ovaj otpor često djeluje uzrokujući staničnu smrt i utvrđivanje staničnog zida oko hranjivog tkiva gdje se hrani hesenova muha. Mnoge sorte pšenice oglašavaju se kao otporne na hesen.

U većini slučajeva otpor se temelji na jednom genu koji je prisutan u sorti i koji se mora podudarati s genom hesen-muhe. Na nesreću, hesenova muha može prevladati mehanizme rezistencije biljaka domaćina, što rezultira stvaranjem novih sojeva koji se nazivaju biotipovi. Uzgajivači biljaka pokušavaju biti ispred biotipova tako što proizvode sorte pšenice sa različitim genima otpornosti. Da bi bile učinkovite, sorte pšenice moraju biti posebno otporne na lokalni genotip hesen muhe. Uz informacije na poveznici za dodatne informacije, uzgajivači mogu dobiti informacije o sortama otpornim na hesen-muhe sa svog lokalnog univerziteta za dodjelu zemljišta. U većini slučajeva, sorte koje imaju ocjenu "dobre" otpornosti trebale bi pružiti dovoljnu zaštitu kako bi se izbjegli ekonomski gubici zbog hesijeve muhe. U područjima s ozbiljnim problemima hesen muhe, upotreba otpornih i tolerantnih sorti možda neće biti dovoljna da spriječi najezde.

Rotacija

Iako hesijska muha može postati ozbiljna u drugim situacijama, najozbiljnija zaraza događa se kad se pšenica posadi rano u strnište pšenice ili na polja pored strništa, jer hesijska muha preplavi strnište. Rotacije usjeva koje sprečavaju sadnju nove pšenice u strnište prethodnog usjeva pšenice ili u njenu blizinu, smanjit će šanse za zarazu hesen muhom. Kontinuirana pšenica koja ne obrađuje zemlju može rezultirati ozbiljnim problemima s hesenovskom muhom, kao i sa bolešću preuzimanja svih vrsta, te je treba izbjegavati. Hesenina muha slabi je letač, pa će udaljavanje mjesta između novih zasada pšenice i polja pšenice prethodne sezone pomoći u sprečavanju zaraza.

Kontrolišite dobrovoljnu pšenicu

Preporučuje se kontrola dobrovoljne pšenice dobro prije sadnje, jer hesen muhe privlače dobrovoljnu pšenicu kada se pojave u septembru. Uz to, ova praksa će smanjiti vjerovatnoću zaraze pšeničnim grinjem, vektorom mozaičnog virusa pšeničnih pruga. Sadnje pšenice u divljini, koje se često sade rano, mogu biti izvor hesijskih muha.

Cover Crops

Ozbiljne invazije hesijskim mušicama dogodile su se tamo gdje je pšenica za zrno bila zasađena blizu rano zasađene pšenice za pokriće ili gdje je rano zasađena pšenica bila prisutna za divlje životinje. U sistemima za uzgoj u kojima se koriste pokrovne kulture, kao što su proizvodnja duhana, pamuka ili kikirikija, upotreba drugih strnih žitarica smanjit će populacije hesijske muhe. Iako se hesijska muha može razviti na travama u više od sedamnaest rodova, neki su povoljniji domaćini za polaganje i razvoj jaja. Zob nije povoljna za reprodukciju hesijske muhe i ne služi kao rasadnik, što čini ovo zrno poželjnijim od pšenice za pokrivanje usjeva u područjima gdje se takođe proizvodi pšenica za žito.

Obrada tla i gorenje

Zasađena strna žitarica bez porasta obično raste sporije u jesen od one zasađene na konvencionalno obrađenim poljima. Čini se da hesijska muha istim brojem napada i ne-obrađivanu i konvencionalnu-obrađivačku hranu. Međutim, konvencionalno obrađena pšenica raste dovoljno brzo da obično može stvoriti nove obrađivače brže nego što muhavi crvi ubijaju zaražene. Suprotno tome, sporiji rast biljaka koje se ne obrađuju ne može pratiti hranjenje crvica i biljke na kraju umiru. Oranje ili diskovanje strništa pšenice nakon žetve efikasno ubija hesijsku muhu zakopavanjem prekomjernog sjemena lana. Sadnja sojinog no-till u strnište pšenice poboljšava preživljavanje hesijske muhe očuvanjem mjesta na kojem puparia provodi ljeto.

Spaljivanje pšenične slame smanjit će pretjerano puparanje, ali mnogo puparija se nalazi ispod površine tla gdje opekotine na njih ne utječu. Stoga sagorijevanje nije toliko učinkovito kao diskiranje i ne preporučuje se kao način upravljanja. Pored toga, sagorijevanje pšenice može predisponirati polja za povećanu učestalost manje zaraze kukuruznim stablom u dvostruko usjenoj soji.

Sistemski tretmani sjemena

Kada se primjenjuju u pravilnim brzinama, upotreba sistemskog tretmana sjemenjem insekticida (tretmani neonikotinoidima) može smanjiti populacije hesijskih muha u prvom dijelu vegetacije. Generalno, najviše označene stope klotianidina, tiametoksama ili imidakloprida pružaju dobru i dobru kontrolu nad hesenovskom muhom. Međutim, kada je brojnost hesijske muhe velika, upotreba ovih tretmana sjemena nije uvijek učinkovita. Tretmani sjemena neće kontrolirati kasnu zimu i proljetne generacije hesijske muhe. Najniže označene stope ovih tretmana sjemena dizajnirane su za suzbijanje lisnih uši i nisu učinkovite protiv hesanske muhe. Budući da su tretmani sjemena skupi, treba ih koristiti samo nakon pažljivog razmatranja trenutne ekonomije proizvodnje.

Folijarni insekticidi

Folijarni piretroidni insekticidi koji se primenjuju ubrzo nakon nicanja pšenice (u fazi faze od dva do tri lista) bili su efikasni u upravljanju hesenovskom muhom. Ako se primijeni u pravo vrijeme, piretroid će ubiti odrasle muhe, a može i ubiti svježe izvaljene ličinke prije nego što se ugrade iza ovojnica listova. Prije upotrebe piretroida za ranu sezonu hesenjske muhe moraju biti ispunjena najmanje tri od sljedećih uvjeta: 1) pšenica je zasađena na istom polju, u blizini ili u blizini (u krugu od 400 metara) od usjeva prethodne godine, nije zasađena otporna sorta pšenice, 3) sjeme nije tretirano neonikotinoidnim insekticidom, 4) hesijska muha je uzrokovala gubitke prinosa na ovoj farmi ili u blizini prethodnih godina ili 5) jaja hesen muhe su prisutna na lišću pšenice.

Polja koja su zimu prošla sa značajnom najezdom hesen-muha takođe će biti napadnuta sljedećom generacijom ličinki koje će se reciklirati u usevu. Polja sa malim brojem krmila trebala bi se ispitati u januaru ili februaru na hesenovu muhu prije nego što se uvedu uobičajene aplikacije dušika krajem zime. Da biste prosudili potrebu za liječenjem piretroida, pregledajte biljke zbog sjemena lana kako biste identificirali polja koja će imati velik broj muha. Iscijedite nekoliko sjemenki lana i provjerite jesu li tekućine rezultirajuće bijele i mliječne (još uvijek ličinke ili rane kukuljice) ili crvenkaste i relativno suve (odrasli koji tek treba da se pojave). Kasnije izviđanje trebalo bi se usredotočiti na jako zaražena polja za jaja na gornjoj površini novog lišća. Jaja su vrlo mala, dugačka oko 1/32 inča i možda će biti potrebno povećanje. Iskusna osoba sa dobrim vidom može otkriti jaja muhe hesen, naročito na direktnoj sunčevoj svjetlosti, jer će jaja sjajiti. Brojanje jaja od četiri ili više po listu može opravdati primjenu piretroida. Kultivatore, posebno mrtve i zakržljale freze, treba pregledati pažljivim guljenjem korica listova kako bi se potražili crvi ili kukuljice hesenskih muha. Ako je u ovom trenutku 20 posto freza zaraženo hesenskim mušicama ili kukuljicama, mogu se očekivati ​​značajni gubici prinosa, a novac potrošen na dušik možda neće dati željeni odgovor na prinos. Ako se piretroid primijeni dok muhe izlaze i polažu jajašca, može se izvršiti neka kontrola. Ovaj proljetni tretman spašavanja rijetko je učinkovit, a kad jest, uglavnom je učinkovit samo u situacijama visokog pritiska.

Odgođena sadnja

Uzgajivačima se savjetuje da sade tokom datuma sadnje koji se preporučuju za pšenicu u njihovoj državi. Sadnja prije ovih datuma povećava rizik od zaraze hesen mušicama i bolesti, kao što su ječmeni žuti patuljak i mozaik prugastih pšenica. Sadnja nakon ovih datuma obično rezultira smanjenim potencijalom prinosa. Budući da temperature smrzavanja ubijaju odrasle osobe hesen muhe, tradicionalna metoda za sprečavanje zaraze hesen muhom je odgađanje sadnje do prvog smrzavanja (često nazivanog datumom muhe). Istorijski je zabilježeno da je datum hesijskog letenja 9. oktobar na geografskoj širini sjevernog Kentuckyja, 16. oktobar na geografskoj širini sjevernog Tennesseeja i 23. do 27. oktobra u sjevernoj Gruziji, južnom Tennesseeju i sjevernoj Alabami. Ovaj koncept nije dobro uspio dalje na jugu ili u Virginiji i Sjevernoj i Južnoj Karolini jer prijevremeno zamrzavanje nije pouzdan događaj. Zapravo, smrzavanje se može dogoditi tek u decembru, dugo nakon preporučenog datuma sadnje pšenice. Čak i u područjima poput Kentuckyja, uzgajivačima se savjetuje da pogledaju vremenske izglede od 30 do 60 dana i odgodu sadnje dodatno ako se predviđaju toplije temperature od normalnih.

Post-žetvene prakse koje šire hesensku muhu

Lutke hesen muhe mogu preživjeti proces žetve slame. Stoga se hesijske muhe mogu premjestiti na nova mjesta na kojima se koristi ta slama. To može povećati brzinu širenja novih biotipova hesenske muhe.

Sažetak prakse upravljanja hesijskim mušicama

Da bi program upravljanja bio najučinkovitiji, uzgajivači moraju primijeniti kombinaciju gore spomenutih tehnika, po mogućnosti u koordinaciji sa susjednim proizvođačima. Napore proizvođača koji rotira svoju pšenicu može frustrirati komšija koji sadi pšenicu kao pokrovnu kulturu ili koji ima poljoprivredno polje sa dvostrukim usevima bez useva pored njegove farme. Jedna ili kombinacija ovih upravljačkih strategija umanjit će štetu od muhe Hesian:

  • Odaberite sortu otpornu na hesen-muhe.
  • Za ispašu ili pokrivanje usjeva posadite zob ili neku drugu kulturu koja nije domaćin hesenskoj muhi.
  • Ako je moguće, koristite metodu obrade zemlje koja će zatrpati ostatke pšenice.
  • Suzbijanje dobrovoljne pšenice.
  • Ne koristite osjetljivu pšenicu za sadnju divljih životinja.
  • Izbjegavajte sadnju u staru strniku ili blizu nje.
  • Nemojte saditi pšenicu prije preporučenog datuma sadnje za vaše područje. Ako je moguće, sadite nakon prvog mraza.
  • Razmislite o upotrebi sistemskog tretmana sjemena ako se uzgaja osjetljiva sorta pšenice.
  • Razmislite o folijarnom insekticidu u ranoj sezoni ako su tri od pet gore navedenih uslova tačna.

Izvorno izdano 1/13 od Univerziteta Alabama A&M i Auburn.

OPREZ! Preporuke za pesticide u ovoj publikaciji registrovane su za upotrebu SAMO u Kentuckyju, SAD! Upotreba nekih proizvoda možda nije legalna u vašoj državi ili državi. Prije upotrebe bilo kojeg pesticida spomenutog u ovoj publikaciji, obratite se svom lokalnom županijskom agentu ili regulatornom službeniku.

Naravno, UVIJEK PROČITAJTE I SLIJEDITE SMJERE NA OZNAKAMA ZA SIGURNU UPOTREBU BILO KOJIH PESTICIDA!


  • Pristupite svemu u JPASS kolekciji
  • Pročitajte puni tekst svakog članka
  • Preuzmite do 120 PDF-ova članaka da biste ih sačuvali i zadržali
199 dolara godišnje

Ovo istraživanje je osmišljeno kako bi se utvrdila efikasnost sistemske suzbijanja insekticida hesenske muhe (Mayetiola destructor (Say)) u pšenici (Triticum aestivum (L.). U studiji u stakleniku karbofuran u količinama od 2,2 do 9,0 kg / ha bio je vrlo efikasan u suzbijanje muhe. Suzbijanje muha suzbijeno je sa 152 lanenog sjemena (100 biljaka) u kontroli na 33, odnosno na 0 u količinama karbofurana od 1,1, odnosno 2,2 kg / ha. zabeleženo pri stopi od 1,1 kg / ha kada su karbofuran, aldikarb ili disulfoton primenjeni na sorte „Holley“, „Arthur“ ili „Arthur 71.“ U istraživanju prolećne pšenice gde su sorte „Era“, „Olaf“ i „WS 1809“ tretirani su sa 0, 1,1, 2,2, 3,3 i 4,4 kg / ha (karbofuran), plus tretiranje semena (karbofuran 75% aktivnog FT-a), svi tretmani iznad 1,1 kg / ha bili su vrlo efikasni u suzbijanju hesen-muhe. Prinos je povećan pri višim stopama tretmana karbofuranom i tretiranjem sjemena.

Časopis objavljuje originalne radove koji predstavljaju nove naučne rezultate o uzgoju, genetici, fiziologiji, patologiji i proizvodnji prvenstveno pšenice, raži, ječma, zobi i kukuruza.

Akadémiai Kiadó je najvažniji mađarski izdavač naučnih i akademskih knjiga i časopisa, kao i izdavač širokog spektra rječnika na mnogim jezicima. Tvrtka je u većinskom vlasništvu izdavačkog konglomerata Wolters Kluwer sa sjedištem u Amsterdamu, a manjina je u vlasništvu Mađarske akademije nauka. Akadémiai Kiadó već je dugi niz godina dobro poznato ime u međunarodnom naučnom izdavaštvu. Njegova aktivnost pokriva svako veće područje nauke i nauke, a veći dio rezultata objavljuje se na stranim jezicima, uglavnom na engleskom.

Ovaj predmet je dio JSTOR kolekcije.
Za odredbe i upotrebu, molimo pogledajte naše Uslove i odredbe
Komunikacije istraživanja žitarica © 1975 Akadémiai Kiadó
Zatraži dozvole


Nadzemne štetočine

Army Cutworms

Cutworms su nezrele faze sivih, smećkastih moljaca koje su najaktivnije noću. Nekoliko vrsta može oštetiti strna zrna.
Moljci rezanci odlažu jajašca na travnata, korovita polja, vojni moljci rezanci snose jaja čak i na golo tlo. Novoizleženi crvi smeđi su do crni i hrane se sadnicama sitnog zrna. Starije ličinke izgledaju sjajno ili masno (slika 7). Ličinke oduzimaju nadzemni dio biljke iz korijenskog sistema na ili ispod površine tla (slika 8). Napadnuta polja izgledaju kao da su usko napasana, a šteta se može „skupiti“ na mjestima na polju.

U Teksasu je najčešća vrsta crve koja napada strne žitarice vojska sječica (Euxoa auxiliarias). Iako je pravi crvi, hrani se slično kao vojni crv. Gusjenice su površinske hranilice i noću se prelaze u nadzemlje i u oblačnim danima da bi se hranile. Odsjekli su male biljke na ili u blizini površine tla. Danju se ličinke sakriju pod grudama tla i ostacima u blizini baze biljke. Vojni rezar ima jednu generaciju godišnje. Tokom kasnog ljeta i rane jeseni, ženka moljca odlaže 1.000 do 2.000 jajašaca dok se migrira kroz neko područje. Jaja se izlegu za nekoliko dana, a ličinke se povremeno hrane tijekom jeseni i zime u toplijim danima. Do sredine do kasne zime ličinke u malim zrnima mogu biti dugačke ⅜ do 1½ inča. Velike populacije mogu nanijeti značajnu štetu odljuštavanjem biljaka i smanjenjem sastojina, posebno u februaru i martu kada zrna počinju ozelenjavati. Naročito su ranjivi na vojsku rezanu glitu
tanke, kasno zasađene ili slabo obrađene sastojine.

U godinama izbijanja polja, polja mogu imati 10 do 20 crvi po kvadratnom metru. Za sunčanih dana bit će pod krhotinama ili malo ispod površine tla. Razmislite o primjeni insekticida kada zaraze dosegnu četiri do pet crvi po kvadratnom metru. Ličinke se u tlu kukuljice rano u proljeće i izlaze kao moljci otprilike 3 do 4 tjedna kasnije. Ove moljce privlače svjetla i mogu postati smetnja oko domova i zgrada. Moljaci migriraju iz Velike ravnice u Stjenovite planine kako bi izbjegli ljetne vrućine, vraćajući se krajem ljeta i početkom jeseni da bi opet započeli ciklus. Da biste smanjili broj reznih crva, smanjite korov i ostatke usjeva na oranicama i odgodite sadnju dok polja ne budu čisto orana.

Jesen Armyworm

Gusjenice jesenskog crva (Spodoptera frugiperda (J. E. Smith)) u jesen se hrane sadnicama, prorjeđuju sastojine i smanjuju proizvodnju krme u ranoj sezoni. Ličinke su najdosljednije nijanse smeđe, ali mogu biti i zelenkaste do gotovo crne (slike 9 i 10). Imaju bijelo obrnuto „Y“ između očiju (slika 11) i četiri različite crne mrlje na vrhu osmog trbušnog segmenta. Zrele ličinke duge su 1½ inča. Pored strnih žitarica, jesenski gliste se hrane lucernom, kukuruzom, pamukom, krastavim grahom, kikirikijem, sirkom u žitu i hibridima siraka i trave.

Rano sadenje strnih žitarica uvelike povećava rizik od napada jesenskim glistama. Moljci mogu taložiti jajne mase (slika 12) na listovima sadnica strnih žitarica. Male ličinke hrane se lisnatim tkivom, stvarajući na listovima sitna "prozorska stakla". Veće ličinke troše cijelo lišće i teže ih je kontrolirati. Na sadnicama razmotrite primjenu insekticida ako su prisutni jesenski gliste i smanjite sastojinu.

Jednom kada se biljke uspostave, predlaže se suzbijanje ako na kvadratnom metru ima 4 ili više ličinki od 1 inča ili duže i kada njihova šteta prijeti sastojini. Odlaganje sadnje može smanjiti štetu kada druge domaćinske kulture imaju veliku zarazu ili kada suhi uslovi ograničavaju privlačnost ostalih domaćina. U tim uvjetima, veliki broj armija može zaraziti tek posađenu pšenicu.

Pravi Armyworm

Ličinke pravog vojničkog crva (Pseudaletia unipuncta (Haworth)) može napadati strna zrna u velikom broju, proždirući sav materijal na njihovom putu. Izbijanju bolesti pogoduje prohladno i vlažno vrijeme od kraja marta do juna. Kad su u potpunosti odrasle, ličinke su duge 1½ inča i zelene su do smeđe sa svijetlim prugama na bokovima i na leđima (slika 13). Smeđa ili tamna traka nalazi se na vanjskoj strani svake noge (mala, mesnata noga na trbuhu). Na glavi, koja ima uzorak uskih linija koje izgledaju poput mreže, nedostaje bijelo obrnuto "Y" jesenje vojske.
Ličinke armijske gliste ne razvijaju se dobro, kada dnevni dnevni maksimum dostigne prosjek od 88 ° F. Zbog vrućine njihov se broj dramatično smanjuje. Najezde često započinju u područjima gdje su strna zrna najviša i najdeblja ili blizu ruba polja, gdje korov pruža povoljno okruženje. Danju se vojni crvi kriju u podnožju biljaka koje premještaju prema biljkama kako bi se hranili kasno popodne, noću i za vrijeme oblačnog vremena. Oni mogu nanijeti veliku štetu ispod krošnje usjeva prije nego što se otkriju. Rano otkrivanje glista je važno jer je male ličinke lakše kontrolirati. Takođe, što su larve veće, to ih više konzumiraju. Znakovi oštećenja uključuju uklanjanje lisnatosti i šišanje brade i glave. Važno je zaštititi list zastave i glavu zrna od oštećenja gliste. Predlažu se mjere suzbijanja kada se pronađu četiri do pet ličinki po kvadratnom metru u kombinaciji s dokazima o opsežnom hranjenju donjim lišćem.

Voćni crv glave pšenice

Iako su voćni crvi glava pšenice manji štetnik pšenice, oni se svake godine pojavljuju kao štetnici pšenice u poznoj sezoni na visokim ravnicama Teksasa. U rodu je poznato 13 vrsta glista glava pšenice Dargida (sinonim Faronta), a sve ličinke i moljci izgledaju slično. Moljci imaju raspon krila od oko 1¼ do 1½ inča. Moljaci su žuto-smeđi s uzdužno smeđom prugom na svakom prednjem krilu. Pojavljuju se da nose jaja u proljeće, a prva generacija ličinki izlazi krajem maja i juna. Invazije se često dešavaju uz margine polja.

Ličinke su vitke i zelenkaste do svijetložute, ovisno o zrelosti zrna (slika 14). Oni mogu biti dugi do 1½ inča. Na svakoj strani tijela uzdužno se protežu žute, bijele i smeđe pruge. Ličinke se hrane u glavama pšenice i oštećuju zrna, prvenstveno ona u fazi mekog tijesta. Najezde su veće na suhim poljima i na rubovima navodnjavanih polja. Oštećenja u hranjenju najčešće su očita nakon žetve, kada izbušena jezgra postanu vidljiva. Nije utvrđeno vrhove za liječenje. Osim toga, intervali prije berbe (PHI) za većinu dostupnih insekticida otežavaju liječenje kada ličinke nanose štetu. Većina proizvoda označenih za ostale gliste ima PHI od 14 do 35 dana za žito. Insekticidi sa aktivnim sastojcima malation i hlorantraniliprol imaju PHI od 7 dana, odnosno 1 dan.

Greenbug

Greenbugs (Schizaphis graminum (Rondani)) su blijedozelene uši koje na stražnjoj strani obično imaju tamnozelenu prugu (slika 15). Dugi su oko 1⁄16 inča. Greenbugs sišu biljne sokove i ubrizgavaju toksine u biljke pšenice, uzrokujući da listovi požute i umru. Oni su također važan vektor virusa ječmenog žutog patuljka i moguće više biljnih bolesti.

Pod povoljnim uvjetima - temperaturama između 55 i 95 ° F - zelene kuke se brzo razmnožavaju, razvijaju se u velikom broju (slika 16) i mogu prouzročiti ekonomske gubitke. Njihovi prirodni neprijatelji, međutim, polako se razmnožavaju na temperaturama ispod 65 ° F. Kao posljedica toga, zelene kuke mogu se povećati na ogroman broj po hladnom vremenu, dok se njihovi prirodni neprijatelji polako množe.

Zimi 99 posto zelenih kukaca može biti ubijeno kada temperature u prosjeku budu ispod 20 ° F najmanje 1 sedmicu. Stanovništvo takođe mora biti bez zaštite od snježnog pokrivača. Greenbugs mogu zaraziti mjesta na poljima ili na cijelim poljima. Kako se populacija povećava, područja na polju mogu požutjeti od hranjenja lisnih uši. Teške, nekontrolisane zaraze mogu ubiti biljke. Greenbugs uzrokuju veću štetu kada malim zrnima nedostaje vlage tokom blage zime i hladnog proljeća. Šteta se može zbuniti stresom vlage, nedostatkom azota ili truležom suhog korijena (trulež stopala).

Procjena zaraze zelenim kukcima: The Glance ‘n Go greenbug sampling system calculates treat- ment thresholds based on the potential crop value, cost of control, and time of year. This method is quicker and simpler than counting greenbugs.
The system was developed by wheat researchers of Oklahoma State University and USDA–ARS at Stillwater, Oklahoma. For Glance ‘n Go information and scouting forms, visit http://entoplp.okstate. edu/gbweb/index3.htm.

Producers still wanting to count greenbugs can walk diagonally across the field, making at least five random counts per 20 acres of field area. Each count should consist of 1 linear foot of row. Green- bugs can be counted while they are on small plants. For larger plants, slap the plant against the ground or a clipboard to jar the insects loose for counting. If the greenbugs are numerous, estimate the number of insects present. Sample greenbugs during the warmest part of the day, when they are most likely to be exposed on the aboveground parts of the
plants. During cool, dry weather, the insects may congregate in loose soil at the bases of plants, which makes detection and chemical control difficult.

When to treat greenbugs: Table 2 provides a general guide for determining the need for treat- ment when counting greenbugs. It is impractical to specify all the conditions under which to apply insecticides for greenbug control. Some of the factors are the number of greenbugs present, the size and vigor of the plants, air temperature, time of year, moisture conditions, plant growth stage, and effectiveness of parasites and predators. However, low temperatures slow the activity and effectiveness of most insecticides. It may take twice as long for an insecticide to kill at 45°F as it would at 70°F. For best results, apply insecticides when temperatures are above 50°F. If you must spray at lower temperatures, use the highest rate recommended.

Irrigated small grains can withstand larger greenbug populations. The presence of yellow or brown plants caused by greenbug feeding in spots in the field may indicate a need to estimate infestation levels. Occasionally, treating very young plants may be warranted when greenbug populations average 25 to 50 aphids per foot of drill row.

Heavy, rapidly increasing greenbug infestations can cause excessive damage. However, when the weather is warm, lady beetles and parasitic wasps can reduce greenbug populations. Where there are one to two lady beetles (adults and larvae) per foot of row, or 15 to 20 percent of the greenbugs are mum- mies from being parasitized, delay control measures until you can determine whether the greenbug population is continuing to increase. Other impor- tant predators include spiders, damsel bugs, lace- wing larvae, and syrphid fly larvae. When weather conditions are favorable for predators and parasites, they will significantly reduce greenbug populations within a week. More information is available in the Texas A&M AgriLife Extension publication Biological Control of Insect Pests of Wheat, which is available online at agrilifebookstore.org.

Insecticide-resistant greenbugs: In 1990, surveys conducted in sorghum fields in counties north of Amarillo found greenbugs that were resistant to some registered insecticides. And, a resistant population was again found in the western Panhandle in 2014. Resistant greenbugs may be mixed with susceptible greenbugs and be detected only after an insecticide application for greenbugs or Russian wheat aphids. To delay greenbug resistance to pesticides, apply insecticide only to fields where economic thresholds have been exceeded.

Host plant resistance: In 1996, TAM-110 was the first wheat variety to carry resistance to all current greenbug biotypes (E, I, and K). In 2005, TAM-112, which had the same greenbug resistance genes as TAM 110, was released with improved yield and milling characteristics. In some years, planting wheat varieties with resistance to disease may be equally or more important than planting varieties with resistance to insects.

Russian Wheat Aphids

The Russian wheat aphid (RWA) first appeared in the United States in March 1986 in the Texas High Plains. It has since spread throughout the Great Plains, into Canada, and to the West Coast. This aphid (Diuraphis noxia (Mordviko)) is lime green, spindle shaped, and about 1⁄16 inch long.

It has short antennae and a projection above the cauda, or tail. The projection gives the insect a “double tailed” appearance (Figs. 17 and 18).

Russian wheat aphids lack prominent cornicles. While feeding, Russian wheat aphids inject a toxin that causes white and purple streaks run- ning lengthwise on the leaves. Tillers of heavily infested plants appear flattened, and leaf edges roll inward, giving the entire leaf a tubelike appear- ance (Fig. 19). Russian wheat aphids prefer feeding on the younger, uppermost leaves of a plant. Unlike the greenbug and bird cherry-oat aphid, the Russian wheat aphid does not spread the barley yellow dwarf virus.

Because these aphids cause the most damage when small grains are moisture stressed, use cul- tural practices that reduce crop stress. Destroying volunteer wheat and planting later will delay the initial infestation.

Predators and parasites are also important in reducing Russian wheat aphid populations. Many of the natural enemies that attack greenbugs also attack Russian wheat aphids. To help conserve these natural enemies, use insecticide judiciously.

For hosts, the Russian wheat aphid prefers wheat and barley to oats, rye, and triticale. They are occasionally observed on corn and sorghum but are not known to cause any damage.

In 2003, a Russian wheat aphid biotype was detected that had developed resistance to all previ- ously resistant Russian wheat varieties with the Dn4 resistant gene. This aphid biotype, RWA2, was first found in Colorado. The formerly resistant wheat varieties are Ankor, Halt, Prairie Red, Prow- ers, and Stanton. Although adapted to the Texas High Plains, they were used primarily in Colorado and Western Kansas. A survey across the Great Plains in 2005 found that 88 percent of the Russian wheat aphids sampled from the Texas High Plains were the resistant RWA2 biotype. However, surveys in 2010 to 2013 indicated that the aphid had shifted to biotypes that were not resistant (90 percent)

to the Dn4 resistant gene. These changes in RWA biotypes indicate that to help protect against RWA damage, producers need to plant wheat varieties with the latest resistance to RWA. Also, scout the fields routinely for unexpected infestations and damage. RWA populations are largest and, consequently, the most damaging in the High Plains (Fig. 20).

Although the aphid occurs in the Rolling Plains, it is not an important pest because it cannot survive the summer (over-summer) there. In the High Plains, RWA can over-summer on warm-season grasses such as buffalo grass, green sprangletop, and several species of grama grass. Cool-season grasses that are wild hosts of the Russian wheat aphid include various brome grasses, jointed goat grass, and several species of wheat grasses. Insec- ticides applied to the seed can control early-season infestations of RWA. Once the crop has reached soft dough, an insecticide application may not be justified.

Sampling and economic thresholds for RWA: Sampling involves walking across a field and randomly selecting 100 tillers, each from a dif- ferent site. To prevent bias, reach down and grab the tillers without looking at them. Then carefully examine each tiller and record the number of tillers that are infested. Consider any tiller with one or more Russian wheat aphids as infested. Determine the percentage of tillers that are infested. Then use Table 3 to decide whether treatment is justi- fied. For example, if the market value of the crop is projected to be $50 per acre and control costs are $9 per acre, the treatment threshold is 36 percent infested tillers. The thresholds in Table 3 are for Russian wheat aphids infesting wheat in late winter and spring. The thresholds are based on the cost of control and the market value of wheat. For every
1 percent of the tillers infested, yield drops by 0.5 percent.

Table 3. Russian wheat aphid economic threshold using percent infested wheat tillers as the sampling unit

Control cost per acre $ Market value of crop ($) per acre
50 100 150 200 250 300
Percent infested tillers
4 16 8 5 4 3 3
5 20 10 7 5 4 3
6 24 12 8 6 5 4
7 28 14 9 7 6 5
8 32 16 11 8 6 5
9 36 18 12 9 7 6
10 40 20 13 10 8 7
11 44 22 15 11 9 7
12 48 24 16 12 10 8

A formula for calculating when to treat can be used instead of the table. The formula for deter- mining the economic threshold level is based on the percentage of tillers infested before flowering:

To calculate the threshold during and after flowering, substitute 500 for 200 in the formula.

Bird cherry-oat aphid

Bird cherry-oat aphids feed on various grains and grasses and are particularly abundant on small grains. These aphids (Rhopalosiphum padi (L.)) are yellowish green, dark green, or black and have a reddish-orange area around the base of the cornicles (Fig. 21). Because bird cherry- oat aphids do not inject a toxin while feeding (unlike the greenbug), they are less damaging. Control measures for the bird cherry-oat aphid are rarely needed to prevent damage from direct feeding. However, an insecticide treatment may be neces- sary when this aphid is very abundant and the crop is under moisture stress. Like the greenbug, the bird cherry-oat aphid is an important vector of the barley yellow dwarf virus and possibly other diseases. Seed treatments to control early-season infestations of greenbugs and bird cherry-oat aphids may reduce the potential spread of barley yellow dwarf virus by these aphids.

English Grain Aphid

English grain aphids (Macrosiphum (Sitobion) avenae (F.)) are about 1⁄10 inch long and larger than other cereal aphids. They are light green to brown and have long, black antennae, cornicles, and legs (Fig. 22). These aphids can be a concern in the spring, when they feed on stems during flowering and on developing kernels in the wheat heads. Their feed- ing can result in shrunken grain and lower test weight. Because many of the same predators and parasites that help control the greenbug also control English grain aphids, they seldom cause yield losses. They are a vectors of barley yel- low dwarf virus. Treatment thresholds for English grain aphid have not been developed for Texas.
Until more information is available, the thresholds used on winter wheat in Nebraska can serve as a guide for managing English grain aphid in Texas.

  1. Count the English grain aphids on each stem and each head at several sites across the
  2. Calculate the average number of aphids per stem (including those on the head).
  3. Consider applying insecticide if infestations across the field average
    1. 5 or more aphids per stem during the flowering stage
    2. 10 or more per stem during the milk stage of grain development
    3. More than 10 aphids per stem during the milk to medium dough stage

Rice Root Aphid

The rice root aphid (Rhopalosiphum rufiabdominalis (Sasaki)) feeds on plant roots in spots within wheat fields. Stunted plants may be the first indica- tion of its presence, with only a small percentage of plants infested. These aphids are olive or dark green and up to 1⁄10 inch long (Fig. 23). They usually have a reddish area at the rear between and
around the base of the cornicles. Rice root aphids vector barley yellow dwarf virus. Insecticidal control measures have not been developed for this insect. Its primary hosts are peaches and plums. Secondary host plants include rice, wheat, and other small grains.

Winter Grain Mite

The winter grain mite (Penthaleus major (Dugés)) feeds on the leaves of barley, oats, and wheat. Feeding turns the leaf tips brown, stunts the plants, and causes them to appear silvery gray. These mites range from 1⁄32 inch to 1⁄16 inch long. The adult has four pairs of reddish-orange legs, and the body is dark brown to black (Fig. 24). Winter grain mites feed primarily at night and remain around the base of the plant during the day. They are less active in hot, dry weather. The most significant damage occurs in winter and early spring. It is usually more severe in fields where small grains were planted in previous years. To reduce infestations, rotate with other kinds of crops. The appearance of feeding symptoms and the presence of mites indicate the need for control.

Brown Wheat Mite

The brown wheat mite (Petrobia latens (Müler)) is about the size of the period at the end of this sentence and is considerably smaller than the winter grain mite. Its rounded body is metal- lic dark brown with a few short hairs on the back. The front legs are about twice as long as the other three pairs of legs (Fig. 25). This mite occurs throughout the High Plains and Roll- ing Plains. Brown wheat mites are most prevalent in dry weather (Fig. 26), and populations increase when wheat suffers from deficient moisture.
Miticides are often not warranted if the crop is so drought stressed that it cannot respond.

Wheat curl mite

The wheat curl mite (Aceria tosichella Keifer) is white, sausage shaped, and about 1⁄100 inch long (Fig. 27). It has four small legs on the front. This mite vectors wheat streak mosaic, triticum mosaic, and wheat mosaic virus (formerly called High Plains virus) but causes very little damage otherwise. Mite feeding alone causes the leaves to roll and take on an onion leaf appear- ance. If the virus is present, the leaves become mottled and streaked with yellow. Wheat curl mites reproduce fastest at 75 to 80°F. They crawl very slowly and depend almost entirely on wind for dispersal. The mite is most active during warm weather and moves mostly on warm, southwesterly winds.

Consequently, most symptoms of the wheat streak mosaic virus develop from southwest to northeast across a field. The mites over-summer on grass- type hosts and volunteer wheat. Volunteer wheat is the most important host for the mite as well as for the wheat mosaic virus, wheat streak mosaic virus, and possibly the triticum mosaic virus.

Populations of wheat curl mites are likely to be highest when:

  • Mites migrate to early volunteer wheat after hail damages wheat that is nearing
  • July rains produce good stands of volunteer wheat.
  • Volunteer wheat is not destroyed, or not de- stroyed until after the planted wheat is
  • Wheat is planted
  • Summers are
  • Autumn is warm and dry, the optimum con- ditions for mite reproduction and

There are no remedial control options once a wheat plant is infected with the wheat streak mosaic virus or wheat mosaic viruses. Chemi- cals do not control the mites or prevent disease infections. Therefore, the most effective control strategies are avoiding infection and choosing

plant resistant varieties. Research has shown that TAM112 has resistance but not immunity to both the mite and the viral diseases.

Prevent the wheat curl mite from transmitting viruses by breaking the “green bridge” from one wheat crop to the next by using these management practices:

  • Eliminate grass weeds and volunteer wheat around your fields and neighboring proper-
  • Delay plantings near properties under the Conservation Reserve Program (CRP) or native stands of grasses until the grasses have
  • Destroy grass weeds and volunteer wheat by tillage or a burn-down herbicide at least 21 days before planting wheat.

Hessian Fly

The Hessian fly (Mayetiola destructor (Say)) infests wheat in the Central Rolling Plains and central and southwest Texas (Fig. 28). The mos- quito-like Hessian fly adult is 1⁄10 inch long and has dark wings, a black thorax, and a dark red abdo- men. Females deposit an average of 200 eggs in clusters of 5 to 12 glossy red eggs in the grooves on the upper leaf surface. They prefer to lay eggs on younger plants and leaves. After hatching, the lar- vae move down the leaf grooves and under the leaf sheath, coming to rest just above the plant crown or just above a node. As they develop, the larvae suck plant juices and form a shallow depression in the stem. Newly hatched larvae are red but turn lighter in a few days. Fully developed larvae are white with a semitransparent green stripe down the middle of the back (Fig. 29). At maturity, the larva forms rigid, dark brown, outer case, or puparium. This period is known as the “flaxseed” stage because the pupar- ium resembles a flax seed (Fig. 30). The Hessian fly survives the summer as a dormant, fully devel- oped larva inside the puparium. The adult fly emerges from the puparium (Fig. 31). It will live no more than 3 days.
The larvae injure wheat by feeding on stem tissue at the crown of young plants or just above the nodes on jointed wheat. They cause more damage to newly emerged and younger seedlings than to older, estab- lished plants. In the fall and early winter, feeding stunts infested tillers, and the leaves become somewhat broader and darker green. Stunted tillers, particularly in younger plants, usually wither and die. Consequently, stands are thin in the fall, less forage is produced, and more plants succumb to winterkill. If the infested tillers survive, their growth and yield will decrease. Hessian fly infestations in the spring also stunt tiller growth and cause uneven plant height. Larval feed- ing at the nodes weakens the stem at the feeding site and may cause significant lodging or stem breakage, making harvest more difficult. During kernel for- mation, feeding can also interfere with nutrient flow to the head, reducing grain quantity and quality.

Expect significant grain losses when fall infestations exceed 5 to 8 percent or when spring infestations exceed 20 percent of the stems.

Although the preferred host is wheat, infesta- tions have been seen on barley, emmer, rye, spelt, and triticale. Oats are not a host for the Hessian fly. It has occasionally been found on wild grasses such as little barley, goatgrass, quackgrass, timothy, and western wheatgrass. There are likely other grass hosts in Texas.

Management Strategies

To reduce economic losses, adopt the following cultural practices:

  • Grow adapted wheat varieties with resis- tance to Hessian Information about these varieties for your area is available from your county Extension agent and wheat seed dealer.
  • Plant later in the fall to reduce the potential for a fall generation.
  • Destroy volunteer wheat, which serves as an early-season host.
  • Bury crop residue 4 to 6 inches deep.
  • Rotate to crops other than wheat or barley to suppress the fly population.
  • Avoid moving infested straw to a non-infest- ed area.

Resistant varieties: Some wheat varieties are resistant to certain populations of the Hessian fly but susceptible to other populations of this pest. These unique populations of Hessian flies are called biotypes. They result from genetic changes that allow the flies to feed and survive on different varieties of wheat.

Some biotypes cannot survive on wheat varieties that have specific genes for resistance. This is why planting Hessian fly-resistant varieties usually works well to prevent losses.

However, Hessian flies can overcome resistance in wheat just as rust fungi develop new races. Over time, the widespread planting of one or two resis- tant varieties can favor biotypes that survive on the resistant varieties. This new, virulent biotype even- tually can become so common that the formerly resistant varieties begin to suffer damage.

The Texas Wheat Variety Trial Results lists the resistance of hard red winter varieties to Hessian fly each year. The report is posted under “Wheat Vari- ety Results – State Wide, at http://varietytesting. tamu.edu/wheat/#varietytrials. It includes a table, “Hard Red Winter Wheat Characteristics,” that lists the susceptibility or resistance of these varieties.

Delayed planting: Postponing planting mini- mizes the damage from the Hessian fly and reduces the number of fall generations.

A date in late fall after which flies do not emerge is called the fly-free date. In central Oklahoma and farther north in the wheat belt, planting after this date has effectively reduced or prevented Hessian fly infestations and damage. This practice has proved to be of limited value in Texas, where inter- mittent periods of warm weather allow the adults to emerge, mate, and lay eggs well into December.

If you must plant wheat early for grazing live- stock, minimize the risk of Hessian fly infestation by planting a variety that is resistant to the fly, or consider treating the seed with insecticide for fields with a history of Hessian fly damage.

Destroying volunteer wheat: Controlling vol- unteer wheat is a useful management tool for many wheat pests, including aphids, Hessian flies, and wheat curl mites. The lack of wheat deprives the first- generation adults of a place to deposit their eggs.

Reducing crop residue: Plowing under old wheat stubble 4 to 6 inches deep in August greatly reduces adult emergence from buried plant residue. However, soil erosion and moisture-retention prob- lems in some areas can dictate that residue burial be limited to conform to conservation practices.

Rotating crops: Although crop rotation helps reduce Hessian flies in a given field, they can remain in the old wheat residue for 2 years, and wind can carry the adults to nearby fields. Burning the straw kills the exposed pupae and larvae in the stems but not the pupae at the soil surface or below the soil line.

Containing infested straw: Avoid moving infested straw or hay to a non-infested area. When buying or selling wheat hay or straw, look for brown pupae behind the leaf sheaths at the nodes to make sure the material is not infested with live Hessian flies.

Applying pesticide: Insecticide seed treatments labeled for control of Hessian fly can suppress light infestations in seedling wheat in the fall. These treatments may not protect the seedling wheat from damage when large numbers of Hessian fly infest the crop.


Pest & Crop Newsletter, Entomology Extension, Purdue University


Hessian Fly Still a Concern in Wheat Growing States- (Brandi Schemerhorn & Sue Cambron

  • Remember to utilize fly free dates.
  • Destruction of volunteer wheat helps reduce insect reservoir to avoid spring infestations.

The Hessian fly is present in wheat growing areas throughout the US, including Indiana. The Hessian fly can survive on alternative grass hosts, and will be waiting for the next time wheat is planted in a given area. When the opportunity presents itself for a wheat infestation, there is potential for a rapid increase of fly populations as a result of weather conditions or cropping practices that favor survival of eggs and young larvae in the fall.

Following the fly-free date. A low fall infestation often goes unnoticed due to the tillering of the wheat plant. Much of the fall fly population can be avoided by planting after the fly-free date. The fly-free date is of key importance, even if you plan to use the wheat only for cattle. This fly-free date is our main protection to avoid a subsequent infestation by the spring brood. Additionally, it has been shown that following the fly-free date helps reduce other wheat disease problems and reduces winter-kill from excessive growth.

"Test plots showing resistance and susceptible wheat

Plowing fields after wheat harvest destroys the fly. The Hessian fly passes the summer in the stubble of the current wheat crop. Volunteer wheat germinates and begins growing just in time for the fall emergence of the Hessian fly. These plants are readily infested resulting in a rapid build-up of the population. Removal of volunteer wheat before the emergence of the fall brood greatly reduces the insect reservoir for a spring infestation.

Infestations in the mid-west were down this year, mainly due to adherence to the fly-free dates.

Map showing approximate dates for planting wheat to avoid first generation Hessian fly damage

Assessing WBC Damage to Field Corn - (Christian Krupke and John Obermeyer)

  • Reports of WBC damage in northern counties, both in Bt and non-Bt hybrids.
  • Slight damage may be apparent, even on Bt hybrids that control WBC.
  • Gene-check strips will soon be essential equipment for pest managers.

Many pest managers are entering fields and checking the condition of the crop just prior to harvest. You’ve all read and heard about the widespread Western Bean Cutworm flights that we experienced here in Indiana, and the damage reports have begun to come in now. One thing to keep in mind when assessing damage is that knowing the traits expressed by the hybrid you are looking at will be key in assessing damage levels – for example, Bt hybrids that advertise “control” of a given pest should be held to a higher standard than those that do not, or non-Bt varieties. The video below demonstrates the use of protein test strips - a simple, effective tool for identifying the traits in individual plants in the field. These tools will become far more useful as the industry moves toward seed mix refuges (also called refuge in a bag) – there will be no other way to tell the refuge from transgenic plants in these mixed stands. The video below gives a brief overview of a quick and relatively inexpensive way to screen plants at any time during the season.

Watch the video on assessing WBC damage to field corn.

Green Soybean Stems and Dry Grain – (Shaun Casteel)


Soybean harvest (7% as of September 12th) is about a week ahead of the five-year average (USDA-NASS, 2010). As I scout from the windshield many fields appear to be 7 to 10 days away from harvest due to the greenness of the stems. However, grain moisture is as low as 10% in many of those same fields. This scenario is a one-two punch to soybean producers. Today, we sell soybeans by weight (60-lb units at 13% moisture) and not by the volume (bushel) as in the past. Harvesting and selling soybeans at 10% moisture means that we are losing out on the opportunity to sell 3% water weight. The recommendation is to harvest soybeans at or slightly above 13% moisture to maximize yield, but green stems are tough to harvest. Two options exist for this scenario: (a) harvest at optimal grain moisture to capture water weight even with green stems that will likely slow harvest and potential increase fuel expense, or (b) harvest plants with brown stems for easier threshing at the loss of yield via water weight and potentially shattering in the coming weeks. There is no simple answer, but I will address the green-stem syndrome we are seeing in 2010.

Green-stem syndrome is where pods and seeds mature (turning harvest color and dry down) while the stems remain green (Figure 1). This is not the same as “stay-green,” which is where a plant retains the green color (chlorophyll) in the stems, leaves, and pods longer. Stay-green is often associated with varietal differences, fungicide applications, or growth regulator applications. Viral diseases, insect infestations, and environmental stresses during seed fill have been suggested as the sources of green-stem syndrome in soybean. A recent study proposes that the common link among these culprits is the effects on pod retention and seed fill (Egli and Bruening, 2006). They removed 25 and 50% of the pods at R6 (full seed) among varieties within maturity groups III, IV, and V in Kentucky. The pod removal minimally affected the rate of pod maturation, but stem maturation was delayed significantly (10 to 20 days and sometimes greater) with the greatest delay in the 50% pod removal treatments. In some cases, the stems did not mature before the first frost.

Figure 1. Two soybean plants growing side-by-side in the field. Plant on the left has mature pods and mature stem whereas, the plant on the right has mature pods and green stem (green-stem syndrome)

Similarly, stressed-soybean plants “decide” which pods to retain and seeds to fill. A loss of pods and / or seeds reduces the demand for photoassimilates (sugars and nutrients) that are transported from the leaves (the supplier). The redistribution of photoassimilates is rapid during R5 (beginning of seed fill) and continues at a slower pace through R6 (full seed). High temperatures and limited rain in August stressed many soybeans during the critical seed fill period (and pod development with the late-planted soybeans). Many pods and seeds were aborted (Figure 2) during this photoassimilates in the leaves and the stems. Late-season bean leaf beetle feeding could also be stressing some soybeans across the state. Low humidity and relatively warm temperatures in September have also provided a situation for fast grain dry down in the field. However, the stem tissue is maintained with the “extra” supply of photoassimilates and retains the green color (Figure 1). Green-stem syndrome yield losses are usually related to the stresses that caused a reduction in demand (pod or seed loss, Figure 3). Delayed harvest often results in yield loss via grain moisture and shattering. We need to be aware that this phenomenon is occurring, so we can make informed decisions about optimizing harvest and reducing losses in yield and profit.

Figure 2. Soybean seed was aborted due to drought stress

Figure 3. Arrested seed fill (upper pods) contributed to the green stem even with mature pods

Egli, D.B. and W.P. Bruening. 2006. Depodding causes green-stem syndrome in soybean. Online. Crop Management. .
USDA-NASS, 2010. Indiana crop & weather report as of September 12. Vol 60:WC091310.


DISCLAIMER: Reference to products in this publication is not intended to be an endorsement to the exclusion of others which may be similar. Persons using such products assume responsibility for their use in accordance with current directions of the manufacturer.
It is the policy of the Purdue University Cooperative Extension Service, David C. Petritz, Director, that all persons shall have equal opportunity and access to the programs and facilities without regard to race, color, sex, religion, national origin, age, marital status, parental status, sexual orientation, or disability. Purdue University is an Affirmative Action employer.


Pogledajte video: Zamka za krtice