Current state of wheat insects entomofauna in Dnepropetrovsk, Zaporizhia and Poltava regions

Abstract

Cereals are the basis of world crop production. In Ukraine, winter wheat crop plays a rolea strategic agricultural product. The basis of food security and the formation of the national export potential depend on this crop species. Wheat has a steadydemand on the internal and foreign markets. In the structure of crops, it occupies about 6 million hectares, which is more than 22% of all cultivated areas and almost 42% of grain crops. Like most other crops, cereals serve as food supply for a wide range of insect phytophages. Conventionally, the entire fauna of endangeredspecies can be divided into multiphages, oligophages and monophages. Cereal plants are damaged by insects during the entire growing season, from germination to harvesting. There are more than 230 species of wheat insects. Territory of the steppe zone of Ukraineamounted 17 most common and criticallyendangeredspecies on. The degree of harmfulness of each species in different vegetation periods is not the same. The goal of the paper was to reveal a current state of the most common endangeredspecies (wheat phytophages) within Dnepropetrovsk, Poltava and Zaporizhia Oblasts, and to assess a degree of their harmfulness (according to literature data). Harmful insects were accounted using conventional manual sampling method. The accounting was carried out on plots of 50 × 50 cm (0.25 m2), staggered evenly over an entire field, using a frame placed onto the plants randomly. All wheat stems inside the frame were shaken to a ground surface, and the number of harmful insects was counted. At the same time, the upper layer of soil (0–25 cm) was visually inspectedfor the presence of insect larvae and imagos. 16 samples were collectedon each field. The average number of each insect species per 1 m2 of wheat crops was calculated. As a result of 50 fields survey in Dnepropetrovsk, Zaporizhia and Poltava Oblast, a list of the most common endangeredspecies (wheat phytophages) in the steppe and forest-steppe zones was created. It includes 17 species belonging to 7 families from three orders. The most recorded representatives of Coleoptera order were 12 species, four species from Hemiptera order and one from Thysanoptera. On average, three species of wheat phytophages belong to each of the families; the largest number of endangeredspecies is represented by Scarabaeidae family. Among the identified phytophages, the most common were Harpalus rufipes (De Geer, 1774) 88% of infected fields, Zabrus tenebrioides (Goeze, 1777) 78% and Anisoplia austriaca (Herbst, 1783) 72%. Specimenof endangeredspecies as Eurygaster integriceps (Puton, 1881) were found on 34 fields, Haplothrips tritici (Kurdjumov, 1912) on 22 fields, Oulema lichenis (Heyden, 1879) on 21 fields, and Aelia acuminata (Linnaeus, 1758) on 18 fields. A brief description of each of 17 endangeredspecies was presented, taking into account their harmfulness in different periods of wheat vegetation. The degree of harmfulness of each species in different vegetation periods is not a same. A distinction is made between the early period, spring and the second half of the growing season. Early vegetation period is from the seedling emergence to the period of grass tillering. During this period, an impact of harmful insects is particularly dangerous, and a damage they cause can lead to a death of plants over large areas. The species most dangerous for wheat at this time are Harpalus rufipes and Zabrus tenebrioides. It is difficult to establish a clear distinction between the impact of endangeredspecies on plants during different periods of vegetation. With a beginning of spring vegetation, Oulema lichenis, Phyllotreta vittula and Chaetocnema aridula and Tropinota hirta are added to the above-mentioned species. Harmfulness during this period consists will be represented by leaf blade damage. The middle of vegetation coincides with an ear formation and grain filling phases. The most active endangeredwheat species during this period are considered to be Haplothrips tritici, Opatrum sabulosum, Pedinus femoralis and Blaps lethifera. The quality indicators of a cereal crop yield are reduced by Eurygaster integriceps and E. maura, Aelia acuminata and A. rostrata. Before the harvest the grain is damaged by various Scarabaeidae, in particular Anisoplia austriaca, A. agricola , A. segetum. As a result of controlling the number and species composition of endangeredwheat species, it is necessary to adapt the application of integrated methods of wheat protection to the soil and climatic conditions of the steppe and forest-steppe zones of Ukraine.