Plant Protection Science, 56, 2020 (1): 35–45 Original Paper https://doi.org/10.17221/53/2019-PPS Predicting aphid abundance on winter wheat using suction trap catches Alois Honěk1*, Zdenka Martinková1, Marek Brabec2, Pavel Saska1 1Crop Research Institute, Prague-Ruzyně, Czech Republic 2Department of Statistical Modelling, Institute of Computer Science AS CR, Prague, Czech Republic *Corresponding author: [email protected] Citation: Honěk A., Martinková Z., Brabec M., Saska P. (2020): Predicting aphid abundance on winter wheat using suction trap catches. Plant Protect. Sci., 56: 35–45. Abstract: The relationship between the number of cereal aphids in flight (recorded by a national grid of suc- tion traps in the Czech Republic) and their occurrence on winter wheat (in Prague) was established between 1999–2015. The flight of all the species was bimodal. Except for Rhopalosiphum padi, whose flight activity peaked in autumn, > 80% of individuals were trapped during April to mid-August. The species frequency was different between the winter wheat and aerial populations. R. padi, the dominant species in the trap catches, formed a small proportion of the aphids on the winter wheat, while Sitobion avenae and Metopolophium dirhodum, which were underrepresented in the suction traps, alternately dominated the populations on the wheat. The aphid abundance in the wheat stands was correlated with the suction trap catches in the “spring” peak (April to mid-August), and the maximum flight activity occurred 4–10 days after the peak in the number of aphids on the wheat. In contrast, the prediction of the aphid abundance in the wheat stands using the total suction trap catches until the 15th of June (the final date for the application of crop protection actions) was reliable only for M. dirhodum. Its maximum abundance on the wheat exceeded 40 aphids per tiller if the total suction trap catch until the 15th of June was ≥ 60 individuals per trap. The prediction of R. padi and S. avenae abundance using the suction trap catches was not reliable. Keywords: Triticum aestivum; Metopolophium dirhodum; Rhopalosiphum padi; Sitobion avenae; flight In central Europe, cereal crop stands are colonised are holocyclic and dioecious when overwintering by three abundant aphid (Hemiptera: Aphididae) on Rosaceae (R. padi, M. dirhodum) (Dixon 1971; species, Rhopalosiphum padi (L. Linnaeus, 1758), Hand & Williams 1981) or monoecious overwin- Metopolophium dirhodum (Walker, 1849) and Sito- tering on Poaceae (S. avenae) (Müller 1977). The bion avenae (Fabricius, 1775). As important pests, fundatrices hatch in March–April, and the next few they deserve extensive research attention (Vicker- generations then live on the primary hosts. In May, man & Wratten 1979; Dixon 1987; Dedryver et alate migrants move to stands of small-grain cereals al. 2010). These species are native in the Holarctic and maize (Bode 1980; Leather & Walters 1984), and have been introduced to South America, South where several generations of their offspring grow Africa and Australia, which are regions where cere- in number until late June – early July, when their als and maize are intensively cultivated (Blackman populations collapse because of alate emigration & Eastop 1984). In central Europe, these species (Howard & Dixon 1992) and mortality (Honěk Supported by the Ministry of Agriculture of the Czech Republic, project No. QK1910281. 35 Original Paper Plant Protection Science, 56, 2020 (1): 35–45 https://doi.org/10.17221/53/2019-PPS 1991; Honěk et al. 1998; Honěk & Martinková population changes and anticipate the pest potential 2004) caused by the worsening host plant quality, the of aphids at a regional level (Taylor 1977). onset of diseases and the actions of natural enemies. The relationship between the aphid abundance in The migrants then populate alternative hostplants the cereal stands and the catches in the suction traps (e.g., grasses, bulrushes, and cereal volunteers), has been extensively investigated. The suction trap where they survive until the autumn migration to catches reflect the emigration of the alate aphids the primary hosts, which takes place in September following the build-up of the aphid populations in to October (Blackman & Eastop 1984). particular areas (Cochrane 1980; Clark et al. 1992; Dispersal and migration by flight, thus, constitutes Elberson & Johnson 1995; Davis et al. 2014). a regular and important part of the cereal aphid life The annual and seasonal variation in the catches cycle. The factors involved in the flight activity have was recorded and analysed in western (Hullé et been extensively studied in different aphid species al. 1994), southern (Coceano et al. 2009), central (Johnson 1969; Kring 1972). The alate individuals (Ruszkowska & Zlotkowski 1977; Węgorek & may begin flying after the teneral period. A portion Stacherska 1977) and northern Europe (Kirchner of the individuals then take flight, aiming to move to et al. 2013). The geographic differences in the timing new hostplant stands. Other than these long-distance of the aphid migration reveals the variation in the fliers, most alate individuals make short flights among aphid performance among the regions with different neighbour hostplants within stands (Moericke 1955). climatic conditions (Dewar et al. 1980; Zhou et al. The amount of take-off activity depends on the light 1995; Basky & Harrington 2000). intensity, temperature and wind speed. Active flying In this paper, we used the 15-year data on the can last for a few hours, but aphids may be captured flight activity of cereal aphid species collected by in moving aerial masses and be passively transported the national grid of suction traps run in the Czech over long distances (Johnson 1969). Republic and maintained by the Central Institute for In cereal aphids, the migration from and to pri- Supervising and Testing in Agriculture and the data of mary hosts is carried out by individuals called alate aphid abundance in the plots of winter wheat grown "migrants", and movements within and among stands at the Crop Research Institute at Prague-Ruzyně of secondary hosts are carried out by alate "exules" (CRI). We addressed four issues: (i) the seasonal pat- A proportion of the individuals that are capable of terns of the flight activity in the particular species as sustained flight may become a component of the revealed by the suction trap catches, (ii) comparing “aerial plankton”, which is the assemblage of airborne the species composition of the aphid populations organisms that are unable to maintain their flight in the suction trap catches and in the winter wheat independently of the movement of air masses. The stands, (iii) establishing the relationship between fliers captured in aerial plankton assemblages can be the aphid abundance on the winter wheat stands transported for a long distance and colonise hostplant on the ensuing size of the suction trap catches and stands not yet occupied by aphids. The number of (iv) predicting the abundance in the winter wheat aphids in the aerial plankton is, thus, a proxy for the stands from the suction trap catches. ability of aphids to colonise new habitats and, thus, is useful for predicting the development of the aphid abundance. The process of sampling aerial plankton MATERIAL AND METHODS aphid populations was standardised by using Johnson- Taylor suction traps (Johnson 1969; Taylor 1972). Aphids in the suction traps. The flight of the aphids The trap is a chimney-shaped suction device with was monitored by a national grid of suction traps an opening at a height of 12.2 m. The trap attracts operated by the Central Institute for Supervising aphid migrants flying above the approximately 9 m and Testing of the Czech Republic. The grid con- high boundary layer of air where aphids are behav- sists of five standard Johnson-Taylor suction traps iourally conditioned to move (Taylor 1960; Carter (12.2 m high), which were placed at Čáslav (49.902N, 1961) and samples the aerial plankton at the height 15.409E, 260 m a.s.l.), Chrlice (49.121N, 16.634E, where its composition is not determined by the local 190 m a.s.l.), Lípa (49.552N, 15.535E, 505 m a.s.l.), conditions, but reveals the mean aphid abundance Věrovany (49.470N, 17.671E, 207 m a.s.l.) and Žatec and temporal fluctuation over a large area (Davis et (50.302N, 13.519E, 285 m a.s.l.). The map of the trap al. 2014). This trapping makes it possible to monitor positions and more geographic details are available 36 Plant Protection Science, 56, 2020 (1): 35–45 Original Paper https://doi.org/10.17221/53/2019-PPS at http://eagri.cz/public/web/ukzuz/portal/skodlive- density of 270–290/m2). Since the aphid numbers organismy/aphid-bulletin/. The suction traps are in the cleared stands were greater than those in the placed in different agricultural production areas in dense stands (Honěk & Martinková 1999; 2002), the country. They are operated in March–November, this design increased the spatial diversity of the aphid and weekly catches of the particular aphid species abundance and contributed to estimating the range are published in the "Aphid Bulletin" (Anonymous that was likely to occur in the production stands. 2018). This periodical publishes weekly catches of Each year, the weekly aphid counts were conducted 16 aphid species of economic importance and of a on 30–300 tillers per plot during the 6–10 weeks mixed sample of aphids not identified to the species that the aphids were present in the wheat, and the level. The aphid catches are summed over the civil maximum abundance (the cumulative number of the calendar weeks starting from Monday to Sunday. In individuals on the leaves and ears) of the particular this paper, the weeks are marked by the median Julian aphid species in the particular plots was ascertained. day of the weekly sampling interval. To compare data Data analysis.