**2. European corn borer**

European corn borer (*Ostrinia nubilalis* Hübner) (Crambidae, Lepidoptera) (**Figure 1**) is a destructive pest on maize, but it also occurs on many other plant species such as peppers and tomatoes. In eastern Croatia, ECBs have been studied for many years [10, 11], population dynamics and intensity of attack of ECB have been monitored since 1965 (Ivezić, personal commun.). In Croatia, ECB usually develops two generations per year; however, the third generation may occur in years with favorable agro-climatic conditions [12]. Larvae feed on aboveground parts of a plant and pass through five larval stages before attaining the pupal stage. The first larval stage tends to move toward higher moisture conditions in

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**Figure 2.**

proposed [17].

**2.2 Potential of ECB natural enemies**

*Leaf damage from ECB larvae (Photo: Sarajlić, 2010).*

*The Role of Irrigation and Nitrogen Fertilization on the Feeding Behavior of European Corn Borer*

plants, and for this reason, they feed within the whorls of leaves. When all leaves are developed, typical symptoms of larval feeding can be observed as small holes on leaves, lined in one row (**Figure 2**). Third stage larvae bore into the plant stalk or fruits and disrupt physiological processes inside the plant. Larvae pupate into the stalk holes (**Figure 3**). Larvae are the most abundant in the tasseling and silking stage of maize. During these stages, maize plants are the most attractive for

High-temperature stress has a negative impact on plant growth, productivity, and metabolism, and plants are the most vulnerable in the reproductive phase [14]. Climatic stress has a significant impact on ECB oviposition and larvae mortality. The first and second larval stages are the most sensitive to stress, and mortality rates can reach up to 62% [15, 16]. Quantity of available water can be regulated by the irrigation system, but other climatic factors, such as air temperatures, cannot be manipulated in field crops. Excessive rainfalls and lower temperatures can delay ECB appearance from 10 and more days, and the intensity of attack is lower; consequently, the damage is also lowered [2]. We are already facing often deviations from average multiyear precipitation and air temperature; therefore, models to predict the occurrence of a new generation of ECB have been

During the vegetation, ECB has been exposed to different species of natural enemies, such as wasps and flies that feed on eggs or larval stages of this pest. The most investigated natural enemies of ECB are *Trichogramma* spp*.* Contradicting results on their effectiveness have been reported [18]. *Trichogramma* wasps are insect egg parasitoids. We have detected the natural parasitism of ECB eggs by these wasps in Croatia on the second generation of ECB. We reported low populations of natural enemies in the field crop, insufficient to significantly reduce the population of ECB and keep it under the economic threshold. Only artificial release of

*DOI: http://dx.doi.org/10.5772/intechopen.92598*

insects to feed on due to the low content of flavonoids [13].

**2.1 Influence of agroclimatic conditions on European corn borer**

**Figure 1.** *Female and male of European corn borer (Photo: Sarajlić, 2010).*

*The Role of Irrigation and Nitrogen Fertilization on the Feeding Behavior of European Corn Borer DOI: http://dx.doi.org/10.5772/intechopen.92598*

plants, and for this reason, they feed within the whorls of leaves. When all leaves are developed, typical symptoms of larval feeding can be observed as small holes on leaves, lined in one row (**Figure 2**). Third stage larvae bore into the plant stalk or fruits and disrupt physiological processes inside the plant. Larvae pupate into the stalk holes (**Figure 3**). Larvae are the most abundant in the tasseling and silking stage of maize. During these stages, maize plants are the most attractive for insects to feed on due to the low content of flavonoids [13].
