**Conflict of interest**

*Pests, Weeds and Diseases in Agricultural Crop and Animal Husbandry Production*

however, the widest C/N ratio was measured for hybrid C2 (18:1).

observed in other hybrids.

stalks (**Table 3**).

**6. Conclusion**

may have an impact on larval feeding such as phenols, carbohydrates, and other components [46]. The highest nitrogen concentrations on average were determined in 2012, while the lowest was found in 2014 (**Figure 9**). In both years, a statistically significant difference occurred between C2 and C4 hybrid. On average, hybrid C4 had the highest nitrogen concentration, and it was higher from 2.75 to 9.45% than

The C/N ratio was found to be significantly different among several hybrids only in 2012. The hybrid C1 had significantly wider value than the hybrid C4 (**Figure 10**). On average, no significant difference occurred between the hybrids;

The relationship between nitrogen concentration and C/N ratio was strong negative in all years and all treatments. The relationship between tunnel length in stalks caused by the ECB larvae and nitrogen concentrations was weak or moderately strong but inconsistent over the years of investigation. Plants require carbon and nutrients for growth. If nutrients are limited, plants tend to accumulate more carbohydrates that can be immediately used. When the ratio of carbon is increased to nutrients, some carbohydrates can be incorporated into secondary metabolism of plant. Secondary metabolites have a defensive role in plants [47]. Carbon, water, and mineral nutrient allocation in a plant depend on genotype and plant environment [48]. The concentration of secondary metabolites increases with drought stress [49]. Nitrogen fertilization leads to a high concentration of nitrogen in plant tissue and a lower concentration of secondary metabolites, but drought stress limits nitrogen adsorption, and such plants are not attractive to herbivores. Our investigation did not give strong evidence that nitrogen concentration and the C/N ratio impact the feeding behavior of ECB larvae in maize

Nitrogen uptake was increased in irrigation treatments in drought year characterized by high temperatures and a small amount of rainfall. Decreased plant nitrogen concentrations were observed in optimal or extremely wet years with a large amount of rainfall. By increasing the level of nitrogen fertilization, the C/N ratio was significantly reduced. The highest nitrogen concentration in this research and the lowest damage from ECB larvae were observed in maize hybrid C4. The relationship between nitrogen concentration and C/N ratio was strongly negative. We found a weak or moderately strong relationship between damage caused by the ECB larva and nitrogen concentration. Our results indicate that maize damage caused by ECB is negatively affected by plant nitrogen concentrations only when plants are under drought stress. However, the relationship between ECB larval damage and plant nitrogen concentration depends on the nitrogen fertilization rates. We did not find strong evidence for this hypothesis and did not prove that plant nitrogen concentration or more quality plants would be more damaged by European corn borer. Further studies, in controlled environments, are needed since our results were inconsistent over the years and indicate the great impact of agrocli-

matic conditions (drought) on the potential of ECB to create damage.

the Republic of Croatia (Project: 079-0790570-2208).

The research was financed by the Ministry of Science, Education, and Sports of

**88**

**Acknowledgements**

All authors saw and approved this book chapter. We warrant that the chapter is the authors' original work and is not under consideration for publication elsewhere. All coauthors agree that the corresponding author will be responsible for the submission. We warrant that all authors have contributed significantly to the work.
