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- Halyomorpha halys; hazelnut; blueberry; mandarin; lemon; damage (1)
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The density of phytophagous insect pest populations is related (directly and indirectly) to several groups of factors that can be broadly divided into: abiotic, biotic and anthropogenic. Each extreme in the abiotic environment at a macro-level leads to a series of consecutive extremes in the biotic environment, which eventually results in micro-level responses in the individual organisms. The manifestation of factors acts in aggregate or in a sequence, creating a chain of processes around us. Insects very efficiently use the abundance of nutritional resources, resulting in a tremendous increase in their population density, and triggering control mechanisms through the emergence of parasitic and pathogenic infections (viruses, bacteria, fungi, microsporidia, protozoa and nematodes). The development of entomopathogenic infections in host populations is directly dependent on the characteristics of both the antagonist and the insect. It is associated with the lifestyle and life cycle of the insect, with features encoded in the mechanism of pathogen action, and limited by the pathogen’s virulence and pathogenicity.
Halyomorpha halys is an invasive, polyphagous stink bug from Asia, first reported attacking hazelnut orchards in the Republic of Georgia in 2015. A microsporidian pathogen discovered in Georgian H. halys has been identified as Nosema maddoxi by sequencing the ribosomal small subunit gene. Nosema maddoxi is native to North America and has also been found in China and South Korea; in North America it infects native stink bugs and H. halys. Investigations were carried out during different seasons in three regions of West Georgia in 2018–2019. The highest prevalence of N. maddoxi was detected among overwintered adults collected in May in the Guria region.
Feeding effects of the invasive, polyphagous brown marmorated stink bug (BMSB), Halyomorpha halys (Hemiptera:Pentatomidae), on some agricultural fruits (hazelnut, blueberry, mandarin, lemon) were investigated in Guria and Samegrelo regions of Georgia in 2019 and 2020. The damage to hazelnut kernels was evaluated when H. halys adults were allowed to feed on kernels in different stages of development. Furthermore, BMSB adults were allowed to feed on almost ripened fruits of blueberry, on small mandarin fruits which were not yet well developed, and on ripened fruits of mandarin. The evaluation of damage on lemon was recorded after allowing adult BMSB on small, not yet developed fruits and on almost developed fruits. It was shown that hazelnuts are susceptible to damage caused by feeding of BMSB throughout the entire period of kernel development (100% of kernels were damaged and did not develop at all). Furthermore, BMSB damages blueberry severely (100% damage) when the fruits are almost ripened. Damage to mandarin fruits in early development stages was over 90%, and 100% of ripened mandarin fruits dropped to the ground. We did not find any damage when BMSB was allowed to feed on Lemon throughout the development of the fruits.
Der aus Ostasien stammende entomopathogene Pilz Entomophaga maimaiga
(Entomophthoromycota: Entomophthorales) hat in Nordamerika sein Potential als wirksamer Antagonist des Schwammspinners Lymantria dispar (Lepidoptera, Erebidae) gezeigt. In den Jahren 1999 und 2000 wurde der Pilz als Maßnahme der biologischen Bekämpfung von L. dispar
in Bulgarien freigesetzt. Seither hat sich E. maimaiga rasch auf der Balkanhalbinsel und in Südosteuropa ausgebreitet. Untersuchungen an zahlreichen blattfressenden Insekten bestätigten die hohe Wirtsspezifität. In einem Kooperationsprojekt wurde der Status von E. maimaiga in Bulgarien und Österreich untersucht. Achtzehn Jahre nach der Einbürgerung ist der Pilz in Bulgarien etabliert, und hohe Mortalitäten bei L. dispar werden seither regelmäßig dokumentiert.
In Österreich wurde E. maimaiga in Screenings in den Jahren 2014 und 2018 in insgesamt 15 Eichenwäldern mit bekannten L. dispar-Vorkommen nicht nachgewiesen. Im Sommer 2019 wurden in zwei Eichenwäldern in Niederösterreich tote L. dispar Larven gefunden, die mit E. maimaiga infiziert waren.