Cent. Eur. J. Biol. • 8(8) • 2013 • 756-764 DOI: 10.2478/s11535-013-0195-0 Central European Journal of Biology The growing abundance of Helicoverpa armigera in Hungary and its areal shift estimation Research Article Sándor Keszthelyi1,*, László Nowinszky2, János Puskás2 1Department of Botany and Plant Production, Kaposvár University, H-7400 Kaposvár, Hungary 2Institiute of Geography and Environmental Sciences, University of West-Hungary, H-9700 Szombathely, Hungary Received 11 January 2013; Accepted 18 April 2013 Abstract: The invasive Cotton Bollworm (Helicoverpa armigera Hübner, Lepidoptera: Noctuidae) has become a serious pest of several agricultural plants since its first mass occurrence in Hungary (1993). During the decades of the species’ presence in the Carpathian Basin, a remarkable fluctuation was detected in its abundance and flight phenology. We analysed long term light trap records and meteorological data to identify the possible factors behind these fluctuations. This study presents an overview of the areal dispersion and the rate of accumulation and flight phenology of this invasive pest, from its first Hungarian mass occurrence until the present, focusing on the influence of climatic factors on the Hungarian distribution of H. armigera. According to our estimation, this pest occupied 94% of the area of Hungary within eight years. There were significant differences in pest pressure by regions, corroborated by the average number of trapped specimens and the regression coefficients. Fluctuations of specimen numbers in the different years are clearly visible in the flight phenology diagrams, which depend on the rate of the growing abundance. The results indicate that abiotic elements may also play a significant role in the areal dispersion of this important invasive insect. Keywords: Cotton Bollworm • Direction of distribution • Area reservation • Flight phenology • Climatic factors © Versita Sp. z o.o. 1. Introduction the possibility of Hungarian overwintering too [12,13]. Naturally, the strong correlation was proven between The Cotton Bollworm, Helicoverpa armigera Hübner the mass accumulation and the agricultural damage (Lepidoptera: Noctuidae) is one of the most detrimental caused by the larval stage of this pest in certain years insect pests in the world. In Europe it causes substantial (e.g. 1997, 2003) [8,14,15]. losses to maize, legume, fibre, cereal oilseed and H. armigera is considered to be a facultative vegetable crops [1]. Its original distribution area covers migrant, emigrating in response to a deterioration of tropical and subtropical regions [2-5]. The species used its local environmental conditions to improve chances to be recorded in Central Europe and also in Hungary, of adult survival and larval development elsewhere. cycling in even larger numbers every 16th or 17th year, due The effects of temperature, vapour-pressure deficit to a possible major outbreak in its primary distribution and the availability of sugar solution over the pre- area. In the past, this pest was unable to overwinter reproductive period have been investigated by Colvin in Hungary due to cold winter temperatures and frost and Gatehouse [16]. Migrant individuals usually appear [6,7]. An unexpected presence in larger numbers has in the Carpathian Basin at the beginning of the summer been observed all over the country since 1993 [8]. Its [17], with populations arriving in Hungary from south Hungarian accumulation can be considered continuous European areas, primarily from Serbia and Croatia. from this time. This phenomenon was reported by Its occurrence in the former Yugoslavia was reported more cautionary publications [9-11], which suggested in the monograph of Čamprag [18]. According to this * E-mail: [email protected] 756 S. Keszthelyi et al. monograph, the moth had two or three generations on insect pests that follow their host plants. The objective in Serbia, Bosnia-Herzegovina and Macedonia. The of this study was to gain a deeper knowledge on the extreme accumulation and areal dispersion of the pest trends and pace of dispersion and flight phenology in this region and country was studied in detail and of H. armigera adults in Hungary and to evaluate the reported [18-21]. Meanwhile, a constant increase of influence of weather fronts on the Hungarian distribution the Hungarian population of the Cotton Bollworm was of this serious agricultural pest. experienced by the years of millennium (2000-2013), a fact that might only be explained by the successful overwintering and subsequent local breeding of the 2. Experimental Procedures species in the Carpathian Basin. Climate change may affect both crop production We examined changes in the temporal patterns of CBW areas and the distribution of their insect pests [22]. by processing imaginal catch data of the Hungarian Tiedemann [23] predicted a northward shift in the Light Trap Network (Plant Protection Information areal border of some cultivated plants. This might System of the National Food Chain Safety Office) and result in a parallel northward shift of the distribution of the Hungarian Forestry Light Trap Network (Hungarian insect pests of xerotherm plant species. By comparing Forest Research Institute). Using data from both light agroecosystem models, Gourdiaan and Zadoks [24] trap networks allowed us to cover the whole area of concluded that climatic changes have a great influence Hungary (Figure 1). Figure 1. Locations of working light traps during 1993-2011 in Hungary as a function of the Péczely’s climate disctricts. Explanation: the working period of the light trap indicated in brackets. Light traps of the Hungarian plant protection information system: 1.Andorháza-Pacsa (1959- 2002), 2. Balassagyarmat (1968-2011), 3. Balatongyörök (1997-2006), 4. Balástya (1991-2007), 5. Beled (1991-98), 6. Bodrogkisfalud (1993-2007), 7. Budapest-Haraszti str. (1989-2007), 8. Budakalász (1999-2001), 9. Celldömölk (1968-2004), 10. Csákvár (2001-04), 11. Csávoly (1991-2006), 12. Cserkeszőlő (1991-2008), 13. Csongrád (2003-2007), 14. Csopak (1959-2004), 15. Debrecen (1995-2004), 16. Dunaföldvár (2001), 17. Dusnok (1991-2006), 18. Eger (1978-2007), 19. Fertőd (2002-08), 20. Gödöllő (2002-2004), 21. Győr-Bácsa (1991-2008), 22. Hódmezővásárhely (1959-2010), 23. Jászberény (1991-2008), 24. Kálócfa (1991-2006), 25. Kelebia (1993-2006), 26. Kenderes (1960-2008), 27. Kiskőrös (1993-2006), 28. Kóny (1994-2008), 29. Kőszárhegy (2003-10), 30. Kunszentmiklós (1998-2004), 31. Mezőhegyes (1999-2005), 32. Mezőkövesd (1992-2007), 33. Mikepércs (1958-94), 34. Nadap (1987-94), 35. Nagybajom (2000-06), 36. Nagytőke (1991-2008), 37. Nemesgulács (1990-2006), 38. Nemessándorháza (1991-2006), 39. Nyárliget (1997-98), 40. Nyársapát (1980-2007), 41. Oszkó (1999-2011), 42. Örkény (1999-2007), 43. Pálhalma (2004-05), 44. Pápa (1968-2006), 45. Pécs (1977-2006), 46. Rácalmás (1984-2000), 47. Sukoró (1995-2010), 48. Szabadbattyán (1997-2000), 49. Szekszárd (1991-2010), 50. Székkutas (1991- 2008), 51. Szob (1999-2003), 52. Tanakajd (1959-2011), 53. Tarhos (1959-2005), 54. Tass (1959-97), 55. Tata (1976-2004), 56. Tiszaigar (1991-2008), 57. Vasvár (1968-1998), 58. Zimány (1992-1998), 59. Zsombó (1991-2008). Hungarian forestry light traps: [1.] Bakonybél (1991-2006), [2.] Kishuta (1998-2011), [3.] Mátraalmás (1993-2011), [4.] Répáshuta (1962-2011). 757 Hungarian distribution of the Cotton Bollworm We examined the catch data of traps for the period 6 moderately warm–wet, 7 moderately cool–dry, between 1993 and 2011. The Hungarian dispersion of 8 moderately cool–moderately dry, 9 moderately cool– this pest and its growing distribution area was mapped moderately wet, 10 moderately cool–wet, 11 cool– year by year on the basis of specimen numbers caught wet, 12 very cool–wet. We assorted every light trap by light traps. The estimated growth of the Hungarian station into one of the Péczely-type climate zones and distribution area of CBW was determined in absolute calculated mean values of trapped specimen numbers (km2) and percentage (%) values, from its first mass for each night and by climate zones. We established appearance (1993) up to its current Hungarian significance levels for each zone compared to the mean distribution (2011). These calculations (the pixel of all other zones, using Student’s t-test. numbers of pest dispersion area for different years) were carried out by C++ implementation methods [25]. The effect of climatic factors on the total number 3. Results of trapped CBW over the years was examined by correlation-regression data analysis using SPSS 11.5, 3.1 Hungarian distribution and areal dispersion relating the total number of trapped specimens in of H. armigera Hungary to the climatic index (CI): CI=[(yi-Yi)^2/Di^2], One representation of possible progression of invasion i=1,2,3... (where: CI = the value of the difference of by year and potential shift of the area of H. armigera in the mean; i = the macrosynaptic situations; y = the Hungary is shown in Figure 2. As shown, the Central frequency in the given year; Y= the average frequency European invasion of this noctuid pest started in 1993 relating to reference period; D^2 = variance of the from the southern part of the Great Hungarian Plain. It reference period) [26]. According to Major et al. [26] occupied the central parts of Hungary, approximately the difference of the mean of the years to average 20% of the country, within the same year. After this, value was dependent on its climatic variability. The the areal dispersion is considered as continuous. significance of the calculated correlation coefficient The species first conquered the low-lying areas and (R) was determined by the following equation: then the mountainous regions (e.g. Bakony, Northern T=R/√(1-R2)×√(n-2), at P≤0.05. Hungarian Mountains). The largest Hungarian areal Mean values of the number of trapped CBW growth was recorded in 2000, and the smallest in 1998. specimens (±SE) were calculated for the areas of the The new light trap location cannot be noticed in 1997 different Hungarian counties and were mapped on as compared to the previous years.