Importance of meteorological variables for aeroplankton dispersal in an urban environment

Passive wind dispersal is one of the major mechanisms through which organisms disperse and colonize new areas. The detailed comprehension of which factors affect this process may help to preserve its efficiency for years to come. This is especially important in the current context of climate change, which may seriously alter weather regimes that drive dispersal, and is crucial in urban contexts, where biodiversity is dramatically threatened by pollution and fragmentation of natural patches. Despite its interest, the analysis of factors affecting aeroplankton dispersal in urban environments is rare in literature. We sampled aeroplankton community uninterruptedly every 4 hours from 17th May to 19th September 2011 in the urban garden of Parco d'Orléans, within the campus of the University of Palermo (Sicily). Sampling was performed using a Johnson-Taylor suction trap with automatized sample storing. Weather variables were recorded at a local meteorological station. Overall, 11,739 insects were caught during the present study, about 60% of these belonged to the order Hymenoptera, with particular presence of families Agaonidae and Formicidae. The suction trap also captured specimens of very small size, and in some cases, species caught were new records for Italy. Composition and abundance of aeroplankton community was influenced by alternation day/night, as well as by daily fluctuations of climatic variables, for example fluctuating temperature . The diversity of samples was also studied and resulted higher when wind blew from the nearby green area. Our findings confirm that passive transport of arthropods strictly depends on weather conditions, and that the presence of natural areas within the urban environment significantly contribute to raise aeroplankton diversity, eventually fuelling overall biodiversity at a local scale. We discuss how climate change may affect future dispersal of these organisms

Cumulative vector intensity and seed potato virus infection in Hungary

Aphids were collected by Moericke yellow pan traps placed in the potato fields. The cumulative vector intensity is an index that describes the vector abundance and their propensity to transmit PVY (3). The vector intensity was obtained as the number of known PVY vector species caught and multiplied by their relative vector efficiency value. Cumulative vector intensity for the season was calculated by accumulating species-specific vector intensity values at each trapping date. In those places where the number of PVY vectors caught by yellow pan traps were the highest (1194, 1495 and 663, 570, respectively), the cumulative vector intensity was also the highest (322 and 570, respectively). This high vector intensity resulted in high progeny tuber infection 21 and 31 %, respectively. In those years when the cumulative vector intensity did not reach the value of 10 until the end of June and the beginning of July the proportion of PVY infected progeny tubers met the requirements of the standard, it was less than 5 %. The cumulative vector intensity seems to be a reliable way to forecast virus threat to seed potato. Both seasonal variation and vector abundance is reflected in cumulative vector intensity, above all propensity of different vector species is included in the calculation. As the virus translocation from leaves to tubers takes 12-14 days. Therefore it is imperative that immediately after weekly trap catches cumulative vector intensity values are calculated, as when values reach around ten growers in seed potato growing region will have 12 days to execute killing leaves and stems of seed potatoes

Cumulative vector intensity and seed potato virus infection in Hungary

Aphids were collected by Moericke yellow pan traps placed in the potato fields. The cumulative vector intensity is an index that describes the vector abundance and their propensity to transmit PVY (3). The vector intensity was obtained as the number of known PVY vector species caught and multiplied by their relative vector efficiency value. Cumulative vector intensity for the season was calculated by accumulating species-specific vector intensity values at each trapping date. In those places where the number of PVY vectors caught by yellow pan traps were the highest (1194, 1495 and 663, 570, respectively), the cumulative vector intensity was also the highest (322 and 570, respectively). This high vector intensity resulted in high progeny tuber infection 21 and 31 %, respectively. In those years when the cumulative vector intensity did not reach the value of 10 until the end of June and the beginning of July the proportion of PVY infected progeny tubers met the requirements of the standard, it was less than 5 %. The cumulative vector intensity seems to be a reliable way to forecast virus threat to seed potato. Both seasonal variation and vector abundance is reflected in cumulative vector intensity, above all propensity of different vector species is included in the calculation. As the virus translocation from leaves to tubers takes 12-14 days. Therefore it is imperative that immediately after weekly trap catches cumulative vector intensity values are calculated, as when values reach around ten growers in seed potato growing region will have 12 days to execute killing leaves and stems of seed potatoes

Effect of indigenous aphids on the development of invasive common ragweed, Ambrosia artemisiifolia (L.) in Hungary

The common ragweed, Ambrosia artemisiifolia (L.), is a widespread invasive weed species in Europe. In order to estimate the hampering effect of native arthropods on the invasive ragweed, the effect of three indigenous aphid species on plant development and pollen production was studied. Common ragweed plants grown in a greenhouse were artificially infested with five apterous individuals of either Aphis fabae Scopoli, Brachycaudus helichrysi (Kaltenbach) or Myzus persicae (Sulzer) at the 4-leaf stage. Feeding by all three aphid species over a five-week period significantly reduced plant height, the number of male inflorescences, the length of racemes, pollen emission and plant dry weight. Brachycaudus helichrysi produced the largest colonies, followed by A. fabae and M. persicae. In a field experiment, the growth rate of A. fabae on caged ragweed plants was similar to that in the greenhouse, but the final numbers of B. helichrysi and M. persicae after 30 days was ten and seven times lower, respectively than under greenhouse conditions. On exposed field plants, B. helichrysi was significantly more abundant than the other two species. However, no aphid species affected the height or dry weight of either caged or exposed plants during a 30 days period. However, during longer exposure (83 and 112 days) the exposed plants suffered more from aphid feeding and this resulted in significant plant height and dry weight decrease regardless of the aphid species. However, statistical significance is not necessarily equivalent to biological significance. Naturally occurring aphids can enhance the ability of native vegetation to counter the weed but their effect is not strong enough on its own to drive down the number of this invasive species

Cereal aphid flight activity in Hungary and England compared by suction traps

Cereal aphid flight was monitored by 12.2 m suction traps at SzoInok in the middle of the Great Hungarian Plain and at Rothamsted, UK. Flight activities of Rhopalosiphum padi, Metopolophium dirhodum and S. avenae were compared by the cross correlation function (CCF) between Hungary and UK There was significant synchrony between flight activity in Hungary and UK of R. padi, M. dirhodum and S. avenae based on the eight years weekly sample data. The peak flight occurred 1, 3 and 2 weeks later at Rothamsted than at Szolnok for the three species (the CCF values were at -1, week lag, r = 0.854, -3 week lag r = 0.809, -2 week lag r = 0.883, P<0.05 respectively). When the flights in individual years were compared within species and between places the synshrony was lowest for R padi: in 4 years out of 8 and there was no synchrony, in the other years when synchrony occurred the time lag varied between - 1. week and -4 weeks. For M. dirhodum the time lag varied between 1 and -5 weeks, the synchrony was the best for S. avenae the week lag varied between 0 and -3 weeks. Our results show that flight activity of cereal aphids at SzoInok occurs 1-3 weeks earlier than at Rothamsted. The crop season is earlier in Hungary than in England

The Effectiveness of Catching Aphids (Hemiptera: Sternorrhyncha: Aphidinea) in Moericke and Light Traps

The studies were conducted in an urban greenery area of Poznań, Poland to compare the effectiveness of Moericke colour traps and light traps used to catch aphids. The combined methods yielded 61 aphid species from the area. The light trap caught 51 species, while 44 species were caught using the Moericke trap. Over 4,000 specimens were collected with each method separately