engleski

Are spatial variations in wireworm population assemblages related to climate change?

Wireworms are important pests of agricultural crops, damaging the seeds and plant roots. Previously, treatments against wireworms were applied regardless of the species forming the pest complex. Latest studies have shown that the level of damage varies among different wireworm species. For successful, species adjusted wireworm control it is therefore important to define the dominant species in geographically diverse population assemblages. Recent studies in Croatia have shown differences in distribution and dominance of the adult Agriotes species in some areas of continental Croatia, compared to data from the middle of the last century. It is assumed that the reason for the change in population assemblages are changed climatic conditions which occurred in the last 50-60 years. The goal of this study was to analyze the distribution and abundance of five most important Agriotes species in Croatia (A. brevis, A. lineatus, A. obscurus, A. sputator and A. ustulatus) and determine the relationship between climatic factors and species’ dominance and spatial patterns. Agriotes adults were captured in 2010 and 2012 using sex pheromone traps set in 21 fields within four continental regions. Capturing period was between middle of April (middle of May for A. ustulatus) and middle of August. Four species specific YATLORf pheromone traps were installed on each field ; for A. ustulatus VARb3 traps were used. Adults were collected weekly, preserved in 70% ethanol, species were verified and counted. The climatic data, i.e. mean annual air temperature and total annual amount of rainfall, were gathered from the nearest meteorological stations for each locality and year. The data about mean annual air temperature and total annual rainfall during three periods of time (1948-1960, 1961-2000 and 2003-2012) were analyzed for each region. Analysis of variance, Duncan's multiple range test and correlations were calculated. Species A. sputator and A. ustulatus were confirmed as dominant in eastern region, but also had high dominance in Podravina, located between west and east regions. Species A. lineatus was established as dominant in western part, and also dominant in west Slavonia region (between west and east regions). A. obscurus was detected as dominant in all regions, except for the most eastern part. Species A. brevis was rarely mentioned by previous literature in Croatia and was not considered as an important pest. Recently, it has been proven as one the most harmful Agriotes species. This study found it significantly present in all areas, representing, if it continues to spread, a major threat to our crops. The results of climatic data analysis showed a significant increase in temperature, determined in the ten-year period (2003-2012), compared to the reference period (1961-2000) and the oldest data analyzed (1948-1960). Temperature and rainfall have a significant impact on some species dominance (A. lineatus, A. ustulatus). This study confirmed wireworm population assemblages have changed in some parts of Croatia over the 50-60 year period, for which climate change could be largely responsible. Consistent monitoring of Agriotes species in all regions should be implemented in order to track any spatial or dominance changes, which would help to predict where future pest outbreaks might occur.

Agriotes, climatic factors, distribution, dominance

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