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European corn borer (ECB) is one of the most significant maize pests in the world and also in Croatia. ECB causes yield reduction from 2 to 25%, even more in years favorable for its development. According to estimations, these losses are around 7%. About 90% of the hybrids had some resistance to whorl-leaf feeding (first-generation ECB) and 75% had some resistance to sheath and sheath-collar feeding (secondgeneration ECB). Along with resistance, modern maize hybrids possess certain level of tolerance. The main aim of this paper was to determine moth eclosion of the overwintering generation and presence of the parasites of ECB larvae during the overwintering as well as to estimate population density of ECB on maize growing area in Croatia. Also, the aim was to establish the differences among maize FAO maturity groups in damage caused by ECB larvae. Estimated overwintering population was over 8,000 moths/ha i.e. more than 4 million larvae of first generation. During the overwintering four different parasites attacked the larvae. Two species belong to the order Hymenoptera (Cotesia marginiventris Cresson and Eriborus terebrans Gravenhorst) and two species belong to the order Diptera (Ramonda spathulata Fallén and Lydella thompsoni Herting). One caterpillar predator species Paragymnomerus spiricornis Spinola (Hymenopetra) overwinters in maize stalks as well. The highest attack of the first ECB generation was recorded on FAO maturity group 500. The damage from second ECB generation was the highest on FAO groups 400 and 500. The maize of the higher FAO groups has high and robust stems with large number of big leaves. That intensive vegetative growth is a biological characteristic that attracts first generation of ECB to intensifying egg lying. High population level of the first generation may lead to high level of second ECB Original scientific paper

Bažok R., Šatvar M., Radoš I., Drmić Z., Lemić D., Čačija M., Virić Gašparić H. (2016): Comparative efficacy of classical and biorational insecticides on sugar beet weevil, Bothynoderes punctiventris Germar (Coleoptera: Curculionidae). Plant Protect. Sci., 52: 134-141.The contact and ingestion activity and the potential of the insecticide spinosad for the control of sugar beet weevil were evaluated and compared with commercially used insecticides lambda-cyhalothrin and chlorpyriphos + cypermethrin. Results of three laboratory trials proved very good efficacy of spinosad applied at the dose of 72 g a.i./ha. Its efficacy was similar to chlorpyriphos + cypermethrin and significantly higher than that of lambda-cyhalothrin. Due to its favourable eco-toxicological properties and good ingestion activity, spinosad is a good candidate to be introduced in the integrated pest management strategy against beet weevil.

European sugar beet was mostly grown from seeds treated by neonicotinoids which provided efficient control of some important sugar beet pests (aphids and flea beetles). The EU commission regulation from 2018 to ultimately restrict the outdoor application of imidacloprid, thiamethoxam, and clothianidin could significantly affect European sugar beet production. Although alternative insecticides (spinosad, chlorantraniliprole, neem) are shown to have certain effects on particular pests when applied as seed treatment, it is not likely that in near future any insecticide will be identified as a good candidate for neonicotinoids’ substitution. The aim of this research is to evaluate residue levels (LC-MS/MS method) of imidacloprid and thiamethoxam applied as seed dressing in sugar beet plants during two growing seasons in fields located in different agro-climatic regions and in greenhouse trials. In 2015, 25 to 27 days post planting (PP) maximum of 0.028% of imidacloprid and 0.077% of thiamethoxam were recovered from the emerged plants, respectively. In 2016, the recovery rate from the emerged plants 40 days PP was 0.003% for imidacloprid and 50 days PP was up to 0.022% for thiamethoxam. There were no neonicotinoid residues above the maximum residue level in roots at the time of harvesting, except in case of samples from thiamethoxam variant collected from greenhouse trials in 2016 (0.053 mg/kg). The results of this research lead to the conclusion that the seed treatment of sugar beet leaves minimal trace in plants because of the complete degradation while different behavior has been observed in the two fields and a glasshouse trial regarding the residues in soil. Dry conditions, leaching incapacity, or irregular flushing can result in higher concentrations in soil which can present potential risk for the succeeding crops. The results of our study could provide additional arguments about possible risk assessment for seed treatment in sugar beet.

Maize and sugar beet productions are often threatened by various pests, causing high yield losses. Economically, most important maize pest is European corn borer, while sugar beet moth and noctuid moths cause serious damage on the sugar beet. This chapter highlights an introduction to several case studies representing long-term field research results on these pests. Depending on the pest, each study investigated the population level, dynamics of emergence or flight, damage levels and possibilities of forecasting on different localities in Croatia. The results could be of great importance in management of these pests. The European corn borer management depends mainly on timely conducted control, but the damage level also depends on maize hybrid and climatic conditions of investigated area. Damages caused by sugar beet moth depend on the population level and on locality's specific climate in a particular year. Sugar beet moth population and flight dynamics can be monitored by using pheromones, while pheromone application in forecasting and control showed to be disputable. Noctuid moths feed on the sugar beet foliage, causing high damages, especially on young plants. The damage level depends on the climatic conditions of the research area, and visual inspections of caterpillars are necessary for forecasting and control decision.

The abundance of ground beetles (Coleoptera, Carabidae) in oilseed rape field can be an important indicator of different agricultural measures in arable land fauna. Surveys about ground beetle fauna in Croatia are generally very scarce and only few research on oilseed rape were conducted. The aim of this study was to determine the endogaeic ground beetle fauna in oilseed rape field and to determine species abundance and frequency. The study was carried out in Podravina region of Croatia, from the end of May till the mid-September in 2015. Ground beetles were collected using endogaeic traps incorporated in the soil. Altogether, 487 individuals classified into 8 species were collected. Species with the highest abundance and frequency was Brachinus (Brachinus) psophia Audinet-Serville, 1821, which was classified as eudominant and constant species. The highest ground beetle abundance was observed in summer period. All of the species found were spring breeders, except for species Trechus (Trechus) quadristriatus (Schrank, 1781) which breeds in autumn.

The sugar beet weevil (SBW), Bothynoderes punctiventris Germar, 1824, is a significant pest in most of Eastern Europe. Here, the SBW is described and its seasonal activity characterized, in terms of its different developmental stages in relation to Julian days (JDs), degree-day accumulations (DDAs), and precipitation, as a key to improving monitoring and forecasting of the pest. The phenology and population characteristics of SBW were investigated in sugar beet fields in eastern Croatia over a 4-year period (2012–2015). By using the degree-day model (lower development threshold of 5°C, no upper development threshold, biofix 1 January), the first emergence of overwintering adults was determined as becoming established when the DDA reached 20. The adult emergence was completed when the DDA reached 428. SBW males emerged first, following which the females dominated the adult population. Overwintering adults were present in the field until early July. In August, adults of the offspring generation began to appear. The eggs laid by the overwintering generation required, on average, 10–15 days to develop into larvae; however, eggs were found in soil samples over a period of 102 days (between JDs 112 and 214). Larvae were present in the soil samples over a period of a maximum of 143 days (the first larvae were established on JD 122 and the last one on JD 265), and pupae were established in the soil over a period of 102 days (between JDs 143 and 245). This study provides important data for understanding SBW population dynamics and developing potential population dynamic models for pest forecasting on a regional scale.