Molecular and morphological identification of Thysanoptera species and determination of population density in barley (Hordeum vulgare L.) plants grown under different conditions

Although the Green Revolution of the 1960s increased crop yields, it also led to widespread adoption of chemical fertilizers, raising significant ecological concerns such as groundwater pollution and biodiversity loss. In contrast, sustainable alternatives like organic soil amendments have gained attention for their potential to support agroecosystem health while reducing pest pressures. In this thesis study, the effects of five soil management practices (maize stubble, maize compost, maize green manure application, inorganic fertilization, and an untreated control) on thrips (Thysanoptera) communities in barley fields were evaluated. Using integrated molecular (mtCOI barcoding) and morphological identification methods, 16 thrips species were recorded across the treatments (Aeolothrips collaris Priesner 1919, Aeolothrips fasciatus (Linnaeus 1758), Aeolothrips intermedius Bagnall 1934, Aeolothrips linarius Priesner 1948, Aeolothrips tenuicornis Bagnall 1926, Anaphothrips obscurus (Müller 1776), Frankliniella occidentalis (Pergande 1895), Frankliniella tenuicornis (Uzel 1895), Limothrips denticornis (Haliday 1836), Melanthrips tristis Priesner 1936, Thrips meridionalis (Priesner 1926), Thrips physapus Linnaeus 1758, Thrips tabaci Lindeman 1889, Haplothrips leucantemi (Schrank 1781), Haplothrips reuteri (Karny 1907), Haplothrips tritici (Kurdjumov 1912)). H. tritici was the dominant species, particularly in the maize stubble (645 individuals) and maize green manure (530 individuals) treatments. Compost-treated plots exhibited the highest species diversity (Shannon H=0.82), though they also saw an increase in the pest F. occidentalis (13 individuals). In contrast, the maize green manure treatment resulted in the lowest diversity (H=0.15) and evenness (Pielou J=0.077), suggesting favorable conditions for pest monocultures. Interestingly, inorganic fertilizer and control plots hosted the highest number of predatory thrips (7 individuals each), likely due to minimal soil disturbance. Overall, the findings highlight the differential impacts of organic amendments on thrips communities: while compost enhances biodiversity, green manure may elevate pest risks. These results underscore the importance of context-specific organic management strategies in sustainable agriculture.