DAMAGE FROM WESTERN CORN ROOTWORM (Diabrotica virgifera virgifera LeConte) IN DIFFERENT GROWING CONDITIONS

Pojavu kukuruzne zlatice (Diabrotica virgifera virgifera LeConte) možemo očekivati ukoliko se ne poštuje plodored kao jedna od najvažnijih mjera borbe. U istraživanju u Gorjanima na OPG-u Stjepan Lović u 2020. godini korišteni su različiti uzgojni uvjeti pri uzgoju kukuruza kako bi se utvrdila pojava, štete te potencijalno smanjenje prinosa uzrokovano pojavom kukuruzne zlatice. U istraživanju je zasijan hibrid OS 378. Kukuruz je zasijan na dvije parcele, drugu (parcela P1), odnosno treću godinu u monokulturi (parcela P2). Na obje površine polovica sjemena bila je tretirana insekticidom (Force, a. t. teflutrin) dok druga polovica nije bila tretirana (eko sjeme). Kukuruzna zlatica pojavila se na obje parcele. Na P1 let imaga je započeo 5. srpnja, ukupno je trajao 91 dan s maksimumom 2. kolovoza. Na P2 let je započeo 30. lipnja, ukupno je trajao 98 dana s maksimumom 19. srpnja. Let je na obje površine završio 27. rujna. Ukupna brojnost imaga nije se razlikovala (388 na obje površine). Po danu i mamcu iznosila je 1,07 (P1), odnosno 0,99 (P2), što nije kritično za daljnji uzgoj kukuruza na istoj površini. Oštećenje korijena (Iowa Node Injury Scale 0-3) ocijenjeno je ocjenom 0,59 (P1), odnosno 1,22 (P2). Veličina korijena (skala 1-6) ocijenjena je ocjenom 2,73 (P1), odnosno 3,70 (P2), a porast sekundarnog korijenja (skala 1-6) ocjenom 2,88 (P1), odnosno 3,45 (P2). Ocjene korijena pokazuju značajnu oštećenost te slab porast korijena i sekundarnog korijenja, što može imati utjecaj na smanjenje prinosa. Kukuruz zasijan na P1 imao je manja oštećenja, razvijeniji korijen i bolji porast sekundarnog korijenja u odnosu na P2, što pokazuje kako se svakom sljedećom godinom monokulture mogu očekivati veća oštećenja. Hibrid ima slabu mogućnost regeneracije korijena. Polegnutost biljaka nije utvrđena. Tri godine uzgoja kukuruza u monokulturi imale su utjecaja na smanjenje prinosa za 1,09 t/ha u odnosu na dvije godine uzgoja kukuruza u monokulturi. Prinos kukuruza na P1 iznosio je 8,52 t/ha, dok je na P2 iznosio 7,43 t/ha. Petogodišnji prosjek za Hrvatsku iznosi 7,88 t/ha (www.fao.org). Daljnji uzgoj kukuruza na ovim površinama nije preporučljiv zbog moguće veće pojave štetnika, dodatnih oštećenja te ekonomskih šteta koje uzrokuju. Preporuča se višegodišnji plodoredThe appearance of the western corn rootworm (WCR) (Diabrotica virgifera virgifera LeConte) can be expected if crop rotation is not respected as one of the most important control measures. In the research in Gorjani on the family farm Stjepan Lović in 2020, different growing conditions were used in the cultivation of corn to determine the appearance, damage and potential reduction of yield caused by the appearance of the WCR. An OS 378 hybrid was sown in the study. Corn was sown on two plots, the second (plot P1), and the third year in monoculture (plot P2). On both plots, half of the seeds were treated with insecticide (Force, tefluthrin) while the other half was not treated (eco seeds). WCR appeared on both plots. On the P1 flight of adults began on July 5, lasting a total of 91 days with a maximum on August 2. On the P2, flight began on June 30, lasting a total of 98 days with a maximum on July 19. On both plots, the flight ended on September 27th. The total number of adultsdid not differ (388 on both plots). Per day and trap it is 1.07 (P1) and 0.99 (P2), which is not critical for further corn cultivation on the same area. Root damage (Iowa Node Injury Scale 0-3) was rated 0.59 (P1) and 1.22 (P2). Root size (scale 1-6) was rated 2.73 (P1) and 3.70 (P2) and secondary root regrowth (scale 1-6) was rated 2.88 (P1) and 3.45 (P2). Root ratings show significant root damage, reduced root size and secondary rooth regrowth, witch may have an impact on yield reduction. Maize sown at P1 had less damage, better rooth size and secondary root regrowth compared to P2, indicating that grater damage can be expected with each subsequent year of monoculture. The hybrid has poor rooth regeneration ability. The plant lodging has not been determined. Three years of corn cultivation in monoculture had the effect of reducing the yield by 1.09 t/ha compared to two years of corn cultivation in monoculture. Corn yield on P1 was 8,52 t/ha, while on P2 it was 7.43 t/ha. The five-year average for Croatia is 7.88 t/ha (www.fao.org). Further cultivation of corn on these areas is not recommended due to the possible higher appearance of pests, additional damage and economic damage they cause. Wide crop rotation is recomende