Nove metode u suzbijanju žičnjaka

Kukuruz je u Republici Hrvatskoj gospodarski najznačajnija kultura, s 299,161 ha zasijanih površina (FAOSTAT, 2012). Slično je i u svijetu gdje s 176,9 mil. ha zauzima drugo mjesto, odmah nakon pšenice (FAOSTAT, 2012). Klisnjaci, odnosno njihove ličinke žičnjaci, izrazito su polifagni (Čamprag, 1997). Napadaju sve poljoprivredne kulture, a najviše usjeve rijetkog sklopa kukuruz, suncokret, šećernu repu, krumpir, nasad duhana te povrće. Zabilježene su i štete na strnim žitaricama, ali samo u slučajevima jakog napada (Maceljski, 2002). Glavna šteta očituje se u prorjeđivanju sklopa i smanjenju prinosa, a preostale biljke s oštećenim korijenom zaostaju u rastu i razvoju. Kukuruz se smatra jednom od najugroženijih kultura. Biljke su osjetljive na napad žičnjaka u vrijeme klijanja i nicanja kada se žičnjaci ubušuju u sjemenku tj., prizemni dio iznikle biljke. Suzbijanje žičnjaka provodi se isključivo preventivno (Morales-Rodriguez i sur., 2011), a odluka se donosi temeljem rezultata pregleda tla ili praćenjem pojave odraslih kukaca seksualnim feromonima. Uspješno suzbijanje žičnjaka otežava i činjenica da je zbog brojnih ograničenja sve manji broj insekticida dozvoljen za suzbijanje. Neke djelatne tvari koje se koriste tretiranjem sjemena dokazano sprječavaju štete ali ne izazivaju smrtnost ličinki što dugoročno dovodi do njihove kumulacije i općeg porasta populacije (Vernon i sur., 2000). Stoga je neophodno istraživati alternativne metode suzbijanja žičnjaka koje uključuju primjenu nepesticidnih mjera i racionalnu primjenu prihvatljivijih djelatnih tvari. Jedna takva metoda bila je predmet ovog istraživanja. Nastojala se istražiti primjena pšenice (Triticum aestivum L.) i graška (Pisum sativum L.) kao lovnih biljaka, u smanjenju šteta od žičnjaka na usjevu kukuruza. Sjetvom biljaka koje su atraktivne štetnicima privlačimo iste samo na određeni dio parcele, nakon čega ih možemo suzbiti lokalizirano, tretirajući samo taj dio, što rezultira znatnim ekonomskim i ekološkim uštedama (Barsics i sur., 2013).Click beetles (lat. Coleoptera: Elateridae), respectively their larvae are known to cause major problem in arable crops. Corn, our most important field crop, is considered to be the most threatened. Damages are manifested in crop losses and reduction of yield. There are no effective ways to control the pest after the crop is planted - wireworms can be successfully suppressed only preventively. Thus, it is necessary to know the level of population before sowing or planting, which can be done by using one of the sampling methods for assessing infestation rate (number of wireworms per unit of surface). The field trial was conducted in the area of Virovitica. The aim of the research was to investigate the use of wheat (Triticum aestivum L.) and peas (Pisum sativum L.) as trap crops to control wireworms in corn fields. The impact of trap crops on the crop and yield reduction of corn was observed. Soil core sampling conducted before sowing showed infestation rate of 16 wireworms/m2, which is above the threshold. The field test consisted of three treatments with insecticidal seed treatments (tefluthrin, thiamethoxam, thiamethoxam + tefluthrin) and non-treated control. Crop density was examined 4 times in the period between 14th of May and 5th of June, and the picking of corn was conducted on 18th of October. At the end of the growing season the yield was measured. The collected data were compared statistically using the method of variance. The results indicated significant differences in yield and crop density between control field variants and insecticide treatments in the part of the experiment without the trap crops. The yield on the control field with sown trap crops was up to 69.58% higher than the yield on the control field with corn as the main crop, while the crop density is higher up to 13.1%. Simultaneously, there were no observed differences in yield and crop density between insecticide and unthreatened control fields in experiment with the trap crops