Rainfall and Temperature Influence Expression of Foliar Symptoms of Grapevine Leaf Stripe Disease (Esca Complex) in Vineyards

Phytopathologia Mediterranea (2018), 57, 3, 488−505 DOI: 10.14601/Phytopathol_Mediterr-23787

RESEARCH PAPERS - 10TH SPECIAL ISSUE ON GRAPEVINE TRUNK DISEASES Rainfall and temperature influence expression of foliar symptoms of grapevine leaf stripe disease (esca complex) in vineyards

1 2 3 2 Francesco CALZARANO , Fabio OSTI , Miroslav BARÁNEK and Stefano DI MARCO

1 Università degli Studi di Teramo, Facoltà di BioScienze e Tecnologie Agro-Alimentari ed Ambientali, Via Renato Balzarini 1, 64100 Teramo, Italy 2 CNR, IBIMET, Via Gobetti 101, 40129 Bologna, Italy 3 Mendeleum–Department of Genetics, Faculty of Horticulture, Mendel University in Brno, Valtická 334, Lednice, Czech Republic

Summary. Two vineyards in the Abruzzo Region, central Italy, affected by grapevine leaf stripe disease (GLSD), were monitored for incidence and severity of foliar symptoms of the disease for 21 consecutive years (1994 to 2014). Each year, rainfall and temperature were recorded. Correlations between symptom incidence or severity and rainfall or temperature of different periods of the year or single months were assessed. July rainfall and temperature were highly correlated with incidence and severity of leaf symptoms. The vineyards were characterized by high longevity, vigour and yields, and a particular dynamic of GLSD. In the period following 2005, the year of peak vine mortality, there was a decrease of the expression of foliar symptoms, which was not correlated with both of the climate parameters. Greater mortality occurred for vines showing severe symptoms at the first appearance of GLSD than for vines with low severity.

Key words: rainfall, temperature, mortality, GLSD foliar symptoms.

Introduction wood of GLSD diseased vines can affected by white rot, caused by the basidiomycete Fomitiporia medi- Grapevine trunk diseases are destructive in vine- terranea. However, the role of F. mediterranea in the yards. Among these diseases, grapevine leaf stripe formation of foliar symptoms has not been demon- disease (GLSD), a syndrome of the esca complex, is strated, but the basidiomycete is probably involved in the most widespread, occurring in almost all grape vine apoplexy. Therefore, foliar symptoms are prob- growing areas (Fontaine et al., 2016). The expression ably associated with tracheomycotic fungi (Calzarano of GLSD in vineyards is characterized by appearance and Di Marco, 2007; Surico et al., 2008, 2009; Bertsch of foliar symptoms and progressive weakening of af- et al., 2013). fected plants. GLSD has been recently described as a The characteristic leaf symptoms of GLSD are tracheomycosis, mainly caused by Phaeomoniella chla- chlorosis developing between the leaf veins. Chloro- mydospora and Phaeoacremonium spp. (P. minimum in sis can expand and the leaf tissues partially necrotize. particular). These fungi colonize the woody tissues of Leaves finally assume the tiger-stripe pattern charac- grapevines, causing black streaking and brown necro- teristic of the disease. Foliar symptoms are generally sis (Mugnai et al., 1999; Marchi et al., 2001; Calzarano associated with wilting of shoots and, in some cases, and Di Marco, 2007; Surico, 2009). In most cases, the with black measles of berry skins and withering of the bunches (Mugnai et al., 1999; Surico et al., 2009). Plants affected by GLSD may not exhibit symp- Corresponding author: F. Calzarano toms for several years after the first appearance, and E-mail: [email protected] produce yields that are similar to that of healthy

488 ISSN (print): 0031-9465 www.fupress.com/pm ISSN (online): 1593-2095 © Firenze University Press

© 2018 Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (CC-BY-4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Rainfall, temperature and GLSD foliar symptoms plants (Calzarano et al., 2004). Furthermore, the inci- expression. A statistically significant correlation be- dence of foliar symptoms was not correlated with the tween rainfall in July and May-July, and expression extent of wood alterations (Calzarano and Di Marco, of leaf symptoms was observed in two of three vine- 2007). In any case, the incidence and severity of GLSD yards, for a period of 4 and 8 years of assessment foliar symptoms is associated with quantitative and (Marchi et al. 2006). qualitative yield losses (Calzarano et al., 2001, 2004; These results are consistent with observations in Bertsch et al., 2013). Reduction of symptom expres- Tuscany vineyards, where greatest foliar symptom sion has been obtained with the use of Trichoderma (Di expression was noticed in vineyard areas subject to Marco et al., 2004), fungicides (Di Marco et al., 2011a, water accumulation and/or waterlogging (Surico et 2011b), and foliar fertilizers (Calzarano et al., 2014, al, 2000). It was then hypothesized that increased soil 2017a; Calzarano and Di Marco, 2018). water availability may increase vine transpiration, Surico et al. (2000) investigated the erratic nature with increased translocation of phytotoxic substances of appearance of GLSD symptoms: only a limited to the leaves (Marchi et al., 2006). Although the mech- number of plants that were symptomatic in a given anisms leading to formation of GLSD leaf symptoms year exhibited symptoms the following year, and are still debated, the most agreed hypothesis is based even fewer exhibited symptoms in each of the years on production of phytotoxic substances by tracheo- of their study. Therefore, the proportion of sympto- mycotic fungi, or on substances produced during matic plants assessed in a given year was not a relia- wood degradation induced by the pathogens (Spara- ble indicator of the incidence of the disease in affected pano et al., 1998; Mugnai et al., 1999; Evidente et al., vineyards. 2000; Tabacchi et al., 2000). These substances can be Further studies confirmed that several consecutive translocated to grapevine canopy, causing alterations years of symptom assessment are necessary to define of leaf photosynthesis and plant defense responses the cumulative incidence (diseased plants showing (Petit et al., 2006; Andolfi et al., 2011; Bertsch et al., symptoms at least in a given year of investigation) 2013; Calzarano et al., 2016, 2017a, 2017b). as a more accurate determination of GLSD incidence The increased expression of leaf symptoms in in each vineyard (Di Marco et al., 2011a; Zanzotto et rainy seasons was confirmed in a further 4-year study, al., 2013). Plants may not express symptoms for 8-10 where a large amount of water, regularly supplied to consecutive years after the first symptom appearance. 20-year old esca-affected vines transplanted in pots, Vineyards surveyed in Tuscany (central Italy) favoured the expression of foliar symptoms. These showed that most of the vines (>70%) were already appeared in most plants every year for the first three symptomatic for GLSD at the end of July each year. years of the trial (Surico et al., 2010). In the fourth year, The same was observed in Sicilian and Sardinian symptoms in plants regularly irrigated appeared be- vineyards (Surico et al., 2000). In contrast, in other re- fore, and to a greater extent, than observed in plants gions of central Italy, such as Abruzzo, symptoms on irrigated only at the beginning of water stress. The ap- most plants appeared later, in August and September pearance of symptoms in potted plants also anticipat- (Calzarano et al., 2016). However, the dynamics of fo- ed what occurred in the vineyard, probably because liar symptom expression during the grapevine grow- of the constant irrigation carried out in April and May ing season indicated that the mechanisms involved in (Surico et al., 2010). In the same experiment, in addi- the symptom development are effective until the end tion to the role of water, relatively high temperatures of July each year (Surico et al., 2000). assessed in June (when the mechanisms leading to the The erratic nature of GLSD symptoms has been foliar symptom expression can occur) seemed to fa- related to environmental and/or cultural factors vour the expression of symptoms (Surico et al., 2010). (Mugnai et al., 1999; Surico et al., 2000; Marchi et However, in the absence of consistent data, the role al., 2006; Calzarano et al., 2009; Surico et al., 2010; of temperature in the expression of foliar symptoms Gramaje et al., 2018; Lecomte et al., 2018). Surico et remains to be verified. al. (2000) demonstrated that cool and rainy sum- The aim of the present study was to confirm and mers were favourable to foliar symptom expression. extend knowledge of the influence of rainfall on These results were confirmed by Marchiet al. (2006). GLSD symptom expression, and to assess the role of In that study, rainfall throughout the first part of temperature in the expression of leaf symptoms on the growing season seemed to increase symptom grapevines affected by this disease.

Vol. 57, No. 3, December, 2018 489 F. Calzarano et al.

Materials and methods Region. Data were recorded hourly by the weather Evaluation of leaf symptoms station equipment. All data were grouped on a daily base. The weather stations were located approx. 2 km The leaf symptoms of GLSD were recorded for 21 from the vineyards as the crow flies. consecutive years in two vineyards of cv. Trebbiano d’Abruzzo on rootstock 420A. Both vineyards are now Correlations between leaf symptoms and rainfall or 40 years old, and are located in Controguerra and Gi- temperature ulianova, two parts of the province of Teramo (central Italy). The Controguerra vineyard was trained to the In both vineyards, for each year, sums of daily Geneva Double Courtain (GDC) system, with a plant- rainfall and active temperature (Amerine and Win- ing pattern of 2m within rows and 4 m between rows, kler, 1944; Winkler, 1962) were calculated. Data of both and had average grape yield of 13 to 17 kg per vine. climatic parameters were grouped for different peri- The Giulianova vineyard was trained to the Tendone ods or considered for a single month, corresponding system, with a vine spacing of 3 × 3 m, and an average to grapevine growth stages, as follows: i) April-May, annual yield of 20 kg per vine. Each year, approx. 500 “Bud burst” (BBCH 09) to “Inflorescence clearly visi- vines in the Controguerra and 2,000 in the Giulianova ble” (BBCH 53); ii) April-June, “Bud burst” (BBCH 09) vineyard were individually inspected for symptom. to “Fruit set” (BBCH 71); iii) April-July, “Bud burst” The symptom assessments were carried out on all the (BBCH 09) to “Berries beginning to touch” (BBCH vines, though vines tested in trials aimed at GLSD 77); ìv) April-August, “Bud burst” (BBCH 09) to “Ber- control were excluded from analyses to avoid inter- ries developing colour” (BBCH 83); v) May-June, “In- ference of these vines on the foliar symptom expres- florescence clearly visible” (BBCH 53) to “Fruit set” sion. (BBCH 71); vi) May-July, “Inflorescence clearly visi- Each year, leaf symptoms were detected in the ble” (BBCH 53) to Berries beginning to touch” (BBCH second half of September, at the time of maximum 77); vii) May-August, “Inflorescence clearly visible” seasonal symptom incidence and severity in the in- (BBCH 53) to “Berries developing colour” (BBCH 83); vestigated area. In a given year, the number of plants viii) June-July, “Fruit set” (BBCH 71) to “Berries be- showing foliar symptoms were identified and com- ginning to touch” (BBCH 77); ix) June-August, “Fruit pared to the total number of plants in the vineyard. set” (BBCH 71) to “Berries developing colour” (BBCH This value was the percentage of symptomatic vines 83); x) July-August, “Berries beginning to touch” in a given year, and represented the annual incidence (BBCH 77) to “Berries developing colour” (BBCH 83); of GLSD. For each year of observation, the severity and the months of April, May, June, July and August. of the disease was assessed on each plant using an The periods and single months were during the arbitrary scale of 0 to 5, where 0 = no leaf symptoms; grapevine growing season, except for in September 1 = 1‒10%; 2 = 11‒30%; 3 = 31‒50%; 4 = 51‒70%; or because symptoms did not develop further in the in- 5 = 71‒100% of leaves with symptoms. Severity for vestigated vineyards. The periods and single months each year was calculated according to the following were chosen according to symptom expression previ- formula: SN × 100 / (Y × Z), where SN = sum of all ously assessed at various growth stages in the same the values of the arbitrary severity scale attributed to vineyards (Calzarano et al., 2016). In particular, the each symptomatic vine of the vineyard in that year; first foliar symptoms appeared sporadically in July. Y = number of plants observed; and Z = maximum From the end of July (pre-bunch closure), the number value of the symptom scale (McKinney, 1923). of symptomatic vines increased rapidly, particularly between veraison and harvest, reaching the maxi- Rainfall and temperature measurements mum in the second half of September, just before the harvest. It was therefore likely that the environmental Daily rainfall and temperature data for the 21 factors associate with symptom expression applied in years of leaf symptom assessments were recorded the April to August period, as also shown by Marchi from weather stations by: i) “Servizio Idrografico e et al. (2006). Mareografico” - Abruzzo Region; ii) “Centro Agro- The sum of active temperatures (SAT) was calcu- meteorologico” (CAR) - Abruzzo Region; and iii) lated using the Winkler Index (Amerine and Winkler, “Direzione L. L. P. P. e Protezione Civile” - Abruzzo 1944; Winkler, 1962). This was calculated for the pe-

490 Phytopathologia Mediterranea Rainfall, temperature and GLSD foliar symptoms riod April 1 to August 31, using the formula: IW = Σ In the 2007–2014 period, symptom severity was from 01.04/31.08 (Tmed-10). For each day, the Index indicates 4.0 to 8.6%, except for 2010 (10.5%) and 2011 (11.8%), the thermal time useful for grapevine growth, as the and were generally less than recorded in the period difference between the average daily temperature 1994–2006. and 10°C, the minimum grapevine growth tempera- In the Giulianova vineyard, differences in symp- ture. For each period, the daily thermal units are then tom expression assessed in 1994–2006 compared to in summed. Only temperatures above zero were consid- 2007–2014 were more obvious than in Controguerra ered. For each vineyard, temperature data were cor- vineyard (Table 3). In the period 1994–2006, annual related with the incidence and severity of the GLSD incidence was from 5.8% in 2004 to 25.9% in 1999, and symptoms. symptom severity was from 4.2% in 2004 to 16.8% in For each year, the annual data of symptom inci- 1999 (Table 3). In the period 2007–2014, annual in- dence and severity were compared with sums of rain- cidence was from 2.8% in 2010 to 6.4% in 2009, and fall or sums of active temperature for each period. The symptom severity was from 1.7% in 2012 to 3.8% in climatic data for each of these periods were correlated 2008 (Table 3). The greatest annual incidence and with the incidence and severity of leaf symptoms, ac- symptom severity both occurred in 1999, whereas the cording to the Pearson correlation coefficient (from least annual incidence was recorded in 2012, and least -1 to 1) and its probability was also calculated and severity was recorded in 2008 (Table 3). reported. Pearson correlation coefficient was considered significant at P = 0.05. Statistical analyses were Rainfall and temperature measurements carried out using SAS version 9.3 (SAS Institute Inc.). In both vineyards, rainfall showed high variation from year to year over the 21 years of observations Symptom severity and vine mortality (Table 1 and 3). The greatest average rainfall for the In both vineyards, for each year of assessment, the growth season periods (April–August) was recorded percentage of vines in each symptom class was cal- in both vineyards during the 1994–2006 interval, in culated to evaluate the dynamics of severity of each 1999, 2002 and 2004, from 309.2 to 431.2 mm for the class of foliar symptom throughout the 21-year pe- Controguerra vineyard, and 238.4 mm to 392.6 mm riod of this study. Annual and cumulative vine mor- in the Giulianova vineyard (Tables 1 and 3). In the tality was also assessed in both vineyards (Di Marco 2007–2014 interval, the years with greatest average and Osti, 2009). Mortality of the symptomatic vines rainfall were, in decreasing order, 2013, 2009 and 2012 was also assessed in relation to the level of symptom in Controguerra (from 377.6 to 509.6 mm), and 2013, severity shown during the first appearance of symp- 2014 and 2010, in Giulianova (from 282.0 to 436.0 toms. mm) (Tables 1 and 3). In both vineyards, the greatest rainfall for the 21 years of observations (1994–2014) was in 2013, when 509.6 mm was recorded in Con- Results troguerra and 436.0 mm in Giulianova (Tables 1 Evaluation of leaf symptoms and 3). In both vineyards, low rainfall was recorded more frequently in the 1994–2006 interval, with least In the Controguerra vineyard, the greatest annual amounts in 1994 in the Controguerra vineyard (121.8 incidences of GLSD were recorded in the period from mm) and in 2003 in the Giulianova vineyard (92.8 1994 to 2006, with an annual incidence in most cases mm) (Tables 1 and 3). greater than 20% and greatest at 35.6% in 1999 (Table In both vineyards, the average monthly rainfall for 1). Also in the 1994–2006 period, the severity of foliar the April-August periods, for the 1994–2006 interval, symptoms followed a similar trend of annual inci- were greatest in April (Controguerra 58.1 mm and Gi- dence, and was generally never less than 12%, with ulianova 58.6 mm). The least average monthly rainfall greatest severity of 22.9% in 1999 (Table 1). During were in July in Controguerra (40.7 mm) and in June in the following period of 2007–2014, annual incidence Giulianova (34.2 mm). In the 2007–2014 interval the and particularly severity generally decreased (Table average monthly rainfall was normally greater than 1). The lowest annual incidence and severity were re- recorded in the 1994–2006 interval, with the excep- corded in 2007, at 7.3 and 4.0%, respectively (Table 1). tion of August, the month with the lowest rainfall,

Vol. 57, No. 3, December, 2018 491 F. Calzarano et al. 6.4 6.3 7.0 4.0 4.0 7.5 7.2 6.6 8.6 (%) 11.8 10.5 11.5 13.2 14.4 17.5 14.6 22.9 13.5 12.9 13.3 13.4 Severity Severity 9.6 7.3 (%) 16.4 18.1 22.4 26.1 17.3 15.0 27.2 25.4 15.9 29.3 24.5 11.5 24.4 35.6 28.2 23.4 26.0 24.5 20.9 Foliar symptoms Foliar Incidence Incidence 2.8 0.0 0.0 5.8 9.0 19.8 63.4 66.2 42.2 30.8 84.0 38.2 19.8 52.8 62.4 44.0 39.4 60.4 10.0 155.6 107.0 August 0.0 10.6 11.2 64.2 17.6 62.8 23.0 11.4 19.2 39.4 14.4 59,0 38.0 31,0 64.8 July 42.4 24.6 46.0 111.6 112.0 174.2 9.8 85.8 16.4 48.2 54.4 32.0 64.4 33.0 84.0 62.4 35.0 33.2 80.4 17.6 47.8 35.2 43.6 54.2 54.4 June 178.2 101.4 6.0 11.0 31.6 37.2 13.4 41.4 65.2 36.2 65.8 41.4 14.8 38.2 36.4 24.8 75.2 37.0 16.0 May 223.4 104.6 103.6 116.4 34.2 16.6 36.0 59.6 36.6 32.2 64.8 99.4 38.4 58.8 80.6 53.8 76.0 33.4 84.4 26.6 64.4 42.6 97.6 112.6 April 124.8 9.0 67.0 81.0 23.0 11.4 42.0 77.6 34.2 43.8 75.0 85.0 56.0 Aug July- 111.8 166.2 131.8 129.0 153.8 103.2 236.6 104.2 149.4 96.6 44.6 53.6 92.6 63.2 Aug Jun- 115.2 252.0 148.2 135.4 307.2 124.4 185.8 106.4 136.2 161.6 146.8 110.4 317.0 152.0 184.6 128.6 96.4 72.0 75.6 52.2 76.8 94.0 44.6 47.8 48.6 July 77.6 68.2 54.2 Jun- 112.4 128.4 241.0 124.4 143.6 123.4 112.6 254.6 100.4 Rainfall (mm) 86.0 68.4 79.2 Aug 226.8 475.4 117.4 252.8 146.8 172.6 320.6 165.8 251.0 May- 172.4 227.4 102.6 250.4 355.2 129.0 176.8 259.8 165.6 86.6 88.4 82.8 86.0 62.6 85.0 July 70.2 216.8 319.8 233.0 144.0 109.2 254.4 165.8 208.8 May- 189.2 197.6 292.8 137.4 152.8 105.2 Jun 79.8 91.6 97.2 75.4 69.2 68.4 74.6 24.6 54.0 72.6 80.6 70.2 170.8 309.2 121.0 191.6 142.8 May- 118.6 149.8 110.4 138.6 Aug Apr- 324.4 509.6 377.6 163.4 208.6 433.2 225.4 287.6 149.6 237.2 326.8 141.0 309.2 166.6 122.2 431.2 162.4 261.2 286.4 230.0 121.8 July Apr- 314.4 354.0 118.8 357.8 160.6 145.2 367.0 225.4 245.4 116.4 153.2 118.4 288.6 121.2 256.4 166.6 112.8 368.8 221.8 179.4 169.6 96.4 78.4 87.4 Apr- June 268.4 343.4 245.8 127.6 304.2 202.4 133.8 107.6 134.0 249.2 106.8 197.4 155.2 112.8 194.6 157.0 137.0 145.0 48.2 73.2 43.2 44.4 68.6 69.8 58.6 May Apr- 214.0 257.6 229.4 126.0 101.0 101.8 114.2 101.0 165.2 162.4 122.0 109.2 101.8 101.4 Year 2014 2013 2012 2011 2010 2009 2008 2007 2006 2005 2004 2003 2002 2001 2000 1999 1998 1997 1996 1995 1994 Controguerra vineyard: Total rainfall for different periods in 21 years, and annual incidence severity of GLSD foliar symptoms. rainfall for different Total vineyard: 1. Controguerra Table

492 Phytopathologia Mediterranea Rainfall, temperature and GLSD foliar symptoms 0.41 0.14 0.03 0.51 0.22 -0.10 0.801 0.176 0.549 0.933 0.074 0.336 August 0.82 0.33 July 0.72 0.24 -0.25 -0.31 0.514 0.007 0.148 0.397 0.016 0.299 0.09 -0.14 -0.21 -0.10 June -0.12 -0.24 0.713 0.747 0.363 0.799 0.689 0.296 0.58 0.57 May -0.11 -0.19 -0.06 -0.04 0.607 0.024 0.633 0.885 0.037 0.873 0.51 0.08 0.01 0.40 0.12 -0.25 April 0.508 0.070 0.727 0.983 0.177 0.601 0.79 0.33 0.77 0.33 Aug -0.29 July- -0.21 0.444 0.002 0.138 0.577 0.032 0.148 0.72 0.16 0.64 0.14 Aug Jun- -0.30 -0.22 0.415 0.001 0.493 0.562 0.015 0.552 0.11 0.69 July 0.52 0.02 Jun- -0.33 -0.34 0.370 0.001 0.639 0.352 0.064 0.927 0.80 0.06 0.72 0.08 Aug -0.33 -0.18 May- 0.375 0.002 0.798 0.630 0.015 0.722 0.82 0.01 July 0.68 -0.45 -0.32 -0.01 May- 0.186 0.011 0.008 0.989 0.390 0.980 Jun 0.53 0.38 -0.27 -0.22 -0.12 -0.17 May- 0.469 0.059 0.348 0.760 0.208 0.447 0.84 0.11 0.08 0.75 Aug Apr- -0.38 -0.16 0.291 0.016 0.742 0.671 0.021 0.643 0.85 0.03 July 0.69 0.03 Apr- -0.41 -0.23 0.249 0.018 0.915 0.560 0.012 0.922 0.62 0.46 Apr- -0.34 -0.15 -0.09 June -0.10 0.354 0.113 0.006 0.526 0.807 0.673 0.71 0.63 0.03 May Apr- -0.30 -0.05 -0.04 0.421 0.003 0.828 0.910 0.015 0.899 Parameter Probability Pearson coefficient Probability Pearson coefficient Probability Pearson coefficient Probability Pearson coefficient Probability Pearson coefficient Probability Pearson coefficient

Year Year interval 2007–2014 1994–2006 1994–2014 2007–2014 1994–2006 1994–2014 Foliar Foliar = 0.05 are in bold. Significant values of probability are in bold- italics. are in bold. Significant values of probability Pearson coefficients significant at P = 0.05 are symptoms

Severity

Incidence Table 2. Rainfall Table vs GLSD annual symptom incidence or severity correlations at the Controguerra vineyard: Pearson coefficients and values of Pearson periods for 1994–2014, 1994–2006 and 2007–2014. probability for different coefficient

Vol. 57, No. 3, December, 2018 493 F. Calzarano et al. 2.5 1.7 3.4 1.9 3.6 3.8 1.7 5.5 8.6 4.2 4.3 9.8 4.4 6.7 5.5 7.9 5.6 5.1 2.7 (%) 16.8 10.1 Severity Severity 3.9 3.1 4.4 2.8 6.4 5.5 3.5 9.7 5.8 7.4 8.3 7.5 7.7 4.3 (%) 13.9 14.6 12.2 25.9 12.3 18.6 16.5 Foliar symptoms Foliar Incidence Incidence 4.8 0.4 0.0 9.8 2.2 9.0 9.0 8.8 93.6 59.8 35.2 45.6 83.8 40.8 10.4 25.0 57.6 63.8 63.2 66.0 121.8 August 3.6 1.0 4.0 7.4 43.0 75.8 91.8 14.0 18.6 13.2 19.2 28.6 72.4 25.0 16.2 21.8 July 25.6 41.4 58.2 144.4 168.4 6.4 7.6 86.8 38.2 12.6 36.2 19.6 21.0 69.0 43.4 59.2 26.0 16.8 17.0 28.0 70.8 18.4 10.0 10.2 45.2 52.4 June 8.2 1.2 96.0 42.0 32.4 87.6 17.4 44.0 22.0 29.8 43.6 86.6 34.4 16.0 22.6 93.6 34.2 39.8 40.6 22.8 May 170.8 15.2 92.4 40.6 30.2 66.0 24.6 41.8 64.4 75.6 26.6 85.4 95.0 25.2 40.2 86.2 29.6 45.6 41.0 79.8 April 106.0 105.8 6.2 47.8 76.2 49.2 18.6 13.4 46.6 97.0 60.0 39.0 34.0 73.8 85.6 88.8 16.4 67.0 Aug July- 238.0 151.6 194.2 193.4 107.4 54.2 85.4 38.2 34.4 65.0 23.2 62.0 81.4 98.8 61.6 Aug Jun- 114.4 324.8 115.6 119.2 164.2 211.0 140.4 117.6 119.4 264.2 104.0 49.4 50.2 38.2 24.6 70.0 56.6 78.4 54.6 89.2 21.0 53.0 23.8 July 40.2 35.6 51.6 52.6 Jun- 114.0 231.2 104.4 110.6 239.2 Rainfall (mm) 96.2 82.2 56.4 66.2 57.6 78.0 84.4 Aug 290.2 420.8 146.8 251.8 102.8 123.8 May- 170.2 162.8 297.6 286.8 175.0 138.2 138.6 158.2 91.4 67.6 82.2 46.6 78.2 86.4 55.8 55.4 69.0 July 74.4 75.4 92.2 75.4 281.4 327.2 146.4 192.0 May- 122.0 117.4 175.8 261.8 Jun 48.4 70.6 53.6 63.6 43.0 77.2 73.2 27.2 51.4 44.0 93.4 52.6 49.8 50.8 68.0 223.2 182.8 100.2 May- 102.8 103.4 101.2 81.0 92.8 Aug Apr- 370.0 436.0 188.6 187.4 282.0 208.8 148.2 165.6 234.6 238.4 383.0 152.6 103.2 392.6 215.2 224.4 168.2 203.8 125.4 71.2 82.4 94.2 July Apr- 361.2 342.4 183.8 187.0 222.2 173.6 148.2 120.0 150.8 197.6 261.2 150.4 116.4 367.6 157.6 160.6 105.0 137.8 67.6 53.8 69.2 79.4 96.4 Apr- 111.2 June 303.0 198.0 119.0 140.8 130.4 159.6 129.6 137.6 178.4 188.8 146.4 199.2 141.4 138.8 109.0 73.0 46.6 50.0 94.2 27.8 41.2 69.4 86.2 63.8 May Apr- 111.2 117.8 110.0 250.6 134.4 119.2 123.4 172.0 129.4 128.4 133.8 120.4 Year 2014 2013 2012 2011 2010 2009 2008 2007 2006 2005 2004 2003 2002 2001 2000 1999 1998 1997 1996 1995 1994 Giulianova vineyard: Total rainfall for different periods in 21 years, and annual incidence severity of GLSD foliar symptoms. rainfall for different Total 3. Giulianova vineyard: Table

494 Phytopathologia Mediterranea Rainfall, temperature and GLSD foliar symptoms 0.27 0.32 0.25 0.31 -0.20 -0.18 0.602 0.372 0.161 0.630 0.409 0.165 August 0.86 0.32 July 0.73 0.21 -0.14 -0.40 0.705 0.151 0.266 0.005 0.360 0.0002 0.24 0.27 0.15 0.19 0.13 0.06 June 0.532 0.370 0.508 0.610 0.682 0.798 0.05 0.09 May -0.15 -0.22 -0.27 -0.22 0.695 0.870 0.342 0.476 0.766 0.333 0.32 0.56 0.36 0.52 0.45 0.30 April 0.394 0.045 0.106 0.094 0.125 0.183 0.80 0.40 0.69 0.32 Aug -0.18 July- -0.33 0.858 0.092 0.225 0.008 0.078 0.0009 0.83 0.39 0.68 0.29 Aug Jun- -0.08 -0.21 0.970 0.011 0.099 0.519 0.125 0.0005 0.80 0.31 July 0.63 0.18 Jun- -0.01 -0.21 0.758 0.001 0.104 0.546 0.020 0.282 0.73 0.22 0.62 0.14 Aug -0.12 -0.27 May- 0.893 0.005 0.259 0.441 0.025 0.436 0.79 0.12 July 0.65 0.03 -0.08 -0.27 May- 0.996 0.001 0.467 0.488 0.016 0.746 Jun 0.29 0.73 0.21 -0.11 -0.02 -0.13 -0.16 May- 0.954 0.331 0.642 0.490 0.495 0.76 0.31 0.63 0.22 Aug Apr- -0.04 -0.14 0.922 0.003 0.120 0.925 0.020 0.259 0.02 0.79 0.24 July 0.65 0.13 Apr- -0.10 0.767 0.001 0.224 0.959 0.017 0.456 0.13 0.51 0.10 0.13 0.39 0.03 Apr- June 0.731 0.074 0.663 0.739 0.183 0.907 0.05 0.40 0.04 0.06 0.35 May Apr- 0.894 0.178 0.857 0.865 0.241 0.990 0.003 Parameter Probability Pearson coefficient Probability Pearson coefficient Probability Pearson coefficient Probability Pearson coefficient Probability Pearson coefficient Probability Pearson coefficient

Severity

Incidence Rainfall vs GLSD annual symptom incidence or severity correlations at the Giulianova vineyard: Pearson coefficients and values of Pearson coef - Pearson of values and coefficients Pearson vineyard: Giulianova the at correlations severity or incidence symptom annual GLSD vs Rainfall 4. Table periods for 1994–2014, 1994–2006 and 2007–2014. for different ficient probability

Vol. 57, No. 3, December, 2018 495 F. Calzarano et al. especially in the Giulianova vineyard, with 26.6 mm single months only July rainfall was significantly cor- (Tables 1 and 3). related with both symptom incidence and severity, The greatest temperatures as sums of active tem- with Pearson coefficients of 0.73 for incidence and perature for the April-August periods, over the 21 0.86 for severity (Tables 3 and 4). April rainfall was years of observations, were recorded in 2003, with significantly correlated with symptom severity (Pear- 1918.9°C in Controguerra and 1913.5°C in Giulianova son coefficient = 0.56 : Tables 3 and 4). (Tables 5 and 7). In both vineyards, the years with the In both vineyards the strongest rainfall-symptom greatest average sums of active temperatures were correlations were in July each year, and in the periods recorded in 1994–2006 and 2007–2014 intervals. The including this month. years with the lowest temperatures, i.e. 1995, 1996, Also in both vineyards, in the 2007–2014 period, 1997, 1999, 2001, 2004 and 2005, were all in the 1994– no statistically significant correlations were recorded 2006 interval, except for 2014 in Controguerra vine- between rainfall and symptoms (Tables 1, 2, 3 and 4). yard, with 1475.3°C (Tables 5 and 7). In the Controguerra vineyard, in the 1994–2006 For each month of the April-August period, the period, in the periods April–July, April–August, average monthly sums of active temperatures were May–August, June–July, June–August, and July–Au- similar in both vineyards in the two intervals, 1994– gust, significant inverse correlations were recorded 2006 and 2007–2014. The exception was the month of between the sums of active temperatures and symp- April, when greater temperatures were recorded in tom incidence or severity; the Pearson coefficient the 2007–2014 interval (126.0°C in Controguerra and values ranged from -0.54 to -0.61 (Tables 5 and 6). In 131.7°C in Giulianova), compared to 92.3°C in Con- particular, in April–July and June–July the correla- troguerra and 92.1°C in Giulianova for the 1994–2006 tions between temperature and symptom incidence interval (Tables 5 and 7). were not significant. Similarly, the correlations for May–August temperature-symptoms severity were Correlations between leaf symptoms and rainfall or also not significant. Among single months, only the temperature July sum of temperatures was significantly correlated with both symptom incidence and severity, with The correlations were weak or absent between Pearson coefficient values of -0.61 (Tables 5 and 6). rainfall and leaf symptoms for each of the different In the Giulianova vineyard, in the 1994–2006 pe- periods of each year from 1994 to 2014 (Tables 1, 2, 3 riod, the correlation between sum of active tempera- and 4). A decrease in the annual incidence and sever- tures and symptoms was verified only for July, with ity of GLSD symptoms occurred since 2007, when the correlation coefficients of -0.61 for symptom incidence vines were 29 years old. Therefore, analyses were car- and of -0.49 for symptom severity (Tables 7 and 8). ried out considering two main intervals, 1994–2006 In the Controguerra vineyard, also in 1994–2014, and 2007–2014. an inverse and statistically significant correlation In the Controguerra vineyard, in 1994–2006, for was detected between sum of active temperatures each of the annual periods and single months, ex- and both incidence and severity of symptoms, with cept for May–June, April, June and August, rainfall Pearson coefficients ranging from -0.47 to -0.51, de- was significantly correlated with both symptom inci- tected for the periods April–July, April–August and dence and severity. In the period 1994–2006, Pearson July–August (Tables 5 and 6). In May–August and coefficients ranged from 0.57 to 0.85 in the periods June–August only the correlations between tempera- or months significantly correlated with rainfall. In ture and symptom incidence were statistically signifi- April–June and in June–July the rainfall and symp- cant, with values of -0.43 for May–August and -0.44 tom correlation was significant only for the symptom for June–August (Tables 5 and 6). In the 1994–2014 severity (Tables 1 and 2). period, only the sum of temperatures for July was sig- In the Giulianova vineyard, in the 1994–2006 in- nificantly correlated with either symptom incidence terval, the rainfall-incidence and the rainfall-severity or severity, with Pearson coefficients of -0.51 for inci- correlations were statistically significant for the same dence and -0.53 for severity (Tables 5 and 6). periods as for the Controguerra vineyard, except for In the Giulianova vineyard, in the 1994–2014 peri- April–May and April–June. The significant Pearson od, only temperature-symptom correlations for July– coefficients values ranged from 0.62 to 0.86. Among August and July were statistically significant, with

496 Phytopathologia Mediterranea Rainfall, temperature and GLSD foliar symptoms 6.4 6.3 7.0 4.0 4.0 7.5 7.2 6.6 8.6 (%) 11.8 10.5 11.5 13.2 14.4 17.5 14.6 22.9 13.5 12.9 13.3 13.4 Severity Severity 9.6 7.3 (%) 16.4 18.1 22.4 26.1 17.3 15.0 27.2 25.4 15.9 29.3 24.5 11.5 24.4 35.6 28.2 23.4 26.0 24.5 20.9 Foliar symptoms Foliar Incidence Incidence 465.1 501.4 501.5 435.3 472.4 472.0 445.2 397.2 379.0 451.0 559.8 408.9 532.1 496.4 444.2 477.6 406.4 408.5 400.7 585.4 413.5 August July 458.2 509.7 436.1 488.3 457.0 452.5 514.2 411.9 470.4 459.3 454.8 488.5 422.9 452.3 409.0 476.4 399.1 423.5 483.5 495.2 394.7 June 320.9 420.1 372.9 351.1 337.9 349.4 381.1 340.9 365.5 340.7 471.0 399.2 337.8 382.4 354.8 367.6 353.8 372.2 313.9 362.5 349.6 May 207.8 221.7 262.5 235.1 319.2 239.0 286.9 252.1 275.0 173.4 312.3 245.9 263.1 301.8 257.6 216.0 232.9 246.7 220.3 253.6 203.4 82.8 78.1 87.4 96.2 65.7 89.7 33.9 85.6 119.9 129.6 April 106.0 161.9 106.2 108.8 161.3 130.0 134.1 114.2 101.6 109.2 105.8 Aug July- 923.3 937.6 923.6 929.4 924.5 959.3 867.6 838.3 905.8 831.7 984.4 908.3 853.2 954.0 805.5 832.0 884.2 808.2 1011.1 1048.2 1080.5 Aug Jun- 1244.1 1431.1 1310.5 1274.7 1267.3 1273.9 1340.4 1208.5 1203.7 1246.4 1159.3 1519.2 1230.9 1198.0 1322.2 1290.7 1157.7 1208.0 1321.6 1204.2 1443.0 July Jun- 811.3 779.1 929.8 809.0 839.4 794.9 801.9 895.3 824.8 795.5 959.4 822.1 790.1 794.3 763.8 844.0 752.9 795.7 797.3 857.7 744.3 Aug May- 1361.1 1451.9 1652.8 1572.9 1509.8 1586.5 1512.8 1627.3 1460.6 1478.7 1419.8 1831.5 1476.8 1585.3 1592.4 1465.5 1537.6 1392.2 1450.8 1418.3 1696.6 July 947.7 986.9 May- 968.9 985.8 1114.1 1151.4 1111.3 1182.1 1071.4 1074.5 1040.9 1063.4 1099.7 1271.7 1067.9 1053.2 1096.0 1021.4 1060.0 1042.3 1017.6 Jun 553.0 528.7 641.7 635.3 586.2 657.1 588.4 668.0 May- 593.0 640.4 514.1 783.3 645.1 600.9 684.2 612.4 583.6 586.7 618.8 534.2 616.1 Aug Apr- Sums of active temperatures (°C) (WinklerSums of active symptoms temperatures and GLSD foliar Index) 1475.3 1581.5 1758.7 1734.8 1615.9 1695.3 1632.7 1788.6 1590.5 1561.5 1497.9 1918.9 1573.0 1651.0 1726.5 1555.3 1639.2 1426.1 1560.0 1503.9 1802.4 July Apr- 1116.5 1111.1 1180.6 1160.7 1118.9 1061.9 1193.3 1257.4 1182.5 1233.3 1222.9 1164.1 1343.4 1161.6 1047.0 1359.1 1151.5 1103.2 1230.1 1019.7 1217.0 Apr- June 667.2 658.3 747.7 797.2 692.4 765.9 708.2 829.3 723.0 723.2 592.2 870.7 741.3 666.6 818.2 702.1 685.2 620.6 728.0 619.8 721.8 May Apr- 317.6 337.4 327.6 424.4 341.3 428.0 358.8 448.2 382.1 357.8 251.5 399.7 342.1 328.8 435.8 347.3 317.6 266.8 355.8 305.9 359.3 Year 2014 2013 2012 2011 2010 2009 2008 2007 2006 2005 2004 2003 2002 2001 2000 1999 1998 1997 1996 1995 1994 Controguerra vineyard: Sums of active temperatures for different periods, and annual incidence severity of GLSD foliar symptoms. for different Sums of active temperatures vineyard: 5. Controguerra Table

Vol. 57, No. 3, December, 2018 497 F. Calzarano et al. 0.01 -0.40 -0.30 -0.06 -0.48 -0.36 0.984 0.191 0.189 0.112 0.884 0.096 August July -0.39 -0.61 -0.53 -0.31 -0.61 -0.51 0.011 0.285 0.032 0.404 0.021 0.024 -0.06 -0.26 -0.12 -0.07 June -0.20 -0.10 0.869 0.388 0.591 0.891 0.521 0.667 May -0.12 -0.28 -0.15 -0.28 -0.23 -0.20 0.756 0.369 0.505 0.451 0.442 0.378 0.01 -0.28 -0.38 -0.35 -0.21 -0.40 April 0.973 0.359 0.087 0.347 0.497 0.065 Aug -0.27 -0.54 -0.47 July- -0.25 -0.61 -0.50 0.480 0.049 0.034 0.500 0.021 0.024 Aug Jun- -0.21 -0.54 -0.42 -0.21 -0.57 -0.44 0.570 0.050 0.055 0.543 0.037 0.042 July Jun- -0.28 -0.58 -0.42 -0.24 -0.53 -0.40 0.456 0.024 0.054 0.531 0.058 0.071 Aug -0.22 -0.53 -0.40 -0.29 -0.54 -0.43 0.551 May- 0.056 0.069 0.435 0.049 0.045 July -0.28 -0.54 -0.38 -0.33 -0.48 -0.39 0.460 May- 0.053 0.084 0.382 0.096 0.077 Jun -0.13 -0.30 -0.17 -0.27 -0.24 -0.18 0.730 May- 0.329 0.473 0.473 0.435 0.432 Aug Apr- -0.20 -0.56 -0.48 -0.35 -0.55 -0.51 0.589 0.041 0.031 0.346 0.046 0.024 July Apr- -0.25 -0.56 -0.49 -0.39 -0.49 -0.49 0.512 0.038 0.030 0.290 0.086 0.025 Apr- -0.10 -0.35 -0.34 -0.35 June -0.28 -0.34 0.788 0.246 0.137 0.349 0.365 0.131 May Apr- -0.08 -0.34 -0.38 -0.38 -0.28 -0.40 0.823 0.261 0.089 0.381 0.365 0.067 Parameter Probability Pearson coefficient Probability Pearson coefficient Probability Pearson coefficient Probability Pearson coefficient Probability Pearson coefficient Probability Pearson coefficient

Severity

Incidence Table 6. Table Sums of active temperatures vs symptom incidence or severity correlations at the Controguerra vineyard: periods for 1994–2014, 1994–2006 and 2007–2014. probability for different Pearson coefficient Pearson coefficients and values of

498 Phytopathologia Mediterranea Rainfall, temperature and GLSD foliar symptoms 2.5 1.7 3.4 1.9 3.6 3.8 1.7 5.5 8.6 4.2 4.3 9.8 4.4 6.7 5.5 7.9 5.6 5.1 2.7 (%) 16.8 10.1 Severity Severity 3.9 3.1 4.4 2.8 6.4 5.5 3.5 9.7 5.8 7.4 8.3 7.5 7.7 4.3 (%) 13.9 14.6 12.2 25.9 12.3 18.6 16.5 Foliar symptoms Foliar Incidence Incidence 468.2 497.1 475.9 433.4 475.1 464.3 449.3 409.6 386.6 433.8 549.7 402.4 467.4 451.0 483.5 512.4 416.0 407.0 402.0 515.1 427.9 August 485 July 459.5 503.6 487.6 478.7 463.2 465.4 491.8 462.2 448.4 438.8 421.7 471.5 386.0 425.3 450.0 402.1 395.6 474.5 466.6 413.4 June 334.3 312.4 370.5 346.7 343.4 337.1 382.9 339.6 361.9 332.8 464.8 393.7 298.2 353.0 357.0 378.0 362.9 367.6 298.8 335.7 359.3 May 311.0 311.5 233.1 254.3 235.0 234.9 294.5 245.9 262.0 172.3 316.3 247.6 230.5 286.7 277.7 235.5 245.9 237.9 215.0 245.0 217.1 88.0 73.2 97.8 95.8 55.5 38.9 94.4 73.2 88.9 119.4 114.8 April 119.1 130.7 156.4 122.8 130.0 147.9 117.7 130.4 124.4 131.3 Aug July- 927.6 963.5 912.0 938.3 929.7 941.0 871.8 835.0 872.6 824.1 938.9 837.0 908.8 962.4 818.1 802.5 876.4 981.7 841.3 1000.7 1034.7 Aug Jun- 1211.4 1196.8 1261.9 1313.0 1334.0 1258.7 1281.7 1266.7 1190.0 1323.9 1205.3 1181.0 1170.1 1499.5 1175.2 1217.8 1237.1 1265.7 1340.4 1317.4 1200.6 July Jun- 793.8 815.9 858.1 825.4 806.6 802.5 874.6 801.8 810.3 771.5 949.8 815.4 769.7 739.0 782.3 828.0 765.0 763.1 773.2 802.3 772.7 Aug May- 1417.7 1572.9 1546.1 1588.2 1493.7 1593.2 1501.6 1618.3 1457.3 1458.8 1377.6 1815.8 1465.4 1467.6 1476.7 1543.4 1575.9 1426.9 1407.9 1390.1 1562.4 July 989.8 May- 943.8 988.2 1112.4 1118.1 1104.8 1169.1 1049.0 1060.3 1037.3 1047.7 1072.2 1266.1 1063.0 1000.2 1025.7 1059.9 1063.5 1010.9 1001.0 1047.3 Jun 576.4 645.3 545.5 624.8 581.7 654.9 571.9 May- 677.3 585.5 623.8 505.1 781.1 641.3 528.7 639.7 634.6 613.5 608.8 605.4 513.7 580.7 Aug Apr- Sums of active temperatures (°C) (WinklerSums of active symptoms temperatures and GLSD foliar Index) 1549.0 1703.6 1665.5 1744.6 1608.5 1715.9 1631.5 1766.2 1576.3 1546.7 1450.8 1913.5 1561.2 1523.1 1607.0 1661.0 1700.3 1465.8 1502.3 1463.3 1651.2 July Apr- 1121.1 1168.4 1175.1 1167.3 1166.7 1160.2 1235.5 1268.8 1158.8 1240.8 1156.0 1316.9 1177.6 1187.9 1017.0 1363.8 1136.2 1055.7 1049.8 1095.4 1061.3 Apr- June 707.7 711.8 776.0 664.8 781.2 696.5 777.7 701.9 825.2 704.6 578.2 878.8 737.1 584.2 770.0 752.3 737.9 647.7 699.8 586.9 669.6 May Apr- 348.4 441.7 352.5 410.7 349.8 434.3 364.8 442.3 365.0 349.9 245.5 414.0 343.4 286.0 417.0 395.3 359.9 284.8 332.3 288.1 333.9 Year 2014 2013 2012 2011 2010 2009 2008 2007 2006 2005 2004 2003 2002 2001 2000 1999 1998 1997 1996 1995 1994 Giulianova vineyard: Sums of active temperatures for different periods, and annual incidence severity of GLSD foliar symptoms. for different Sums of active temperatures 7. Giulianova vineyard: Table

Vol. 57, No. 3, December, 2018 499 F. Calzarano et al. 0.16 0.22 -0.18 -0.21 -0.16 -0.20 0.664 0.547 0.357 0.565 0.601 0.393 August July -0.35 -0.49 -0.59 -0.35 -0.61 -0.65 0.346 0.048 0.010 0.346 0.021 0.002 0.93 0.03 0.10 0.15 0.16 0.19 June 0.719 0.506 0.994 0.005 0.599 0.407 0.07 0.30 0.05 0.31 0.33 0.07 May 0.861 0.335 0.823 0.404 0.281 0.745 0.57 0.21 0.14 0.08 0.16 -0.34 -0.35 April 0.643 0.113 0.135 0.825 0.591 Aug -0.13 -0.35 July- -0.44 -0.10 -0.39 -0.47 0.738 0.246 0.043 0.793 0.190 0.031 Aug Jun- -0.12 -0.23 -0.30 -0.10 -0.23 -0.30 0.760 0.459 0.191 0.788 0.454 0.188 July Jun- -0.26 -0.22 -0.30 -0.28 -0.25 -0.32 0.484 0.473 0.182 0.451 0.420 0.154 0.11 Aug -0.04 -0.09 -0.21 -0.08 -0.21 May- 0.923 0.747 0.355 0.767 0.782 0.367 0.04 July -0.11 -0.01 -0.17 -0.02 -0.18 May- 0.911 0.768 0.948 0.451 0.965 0.446 Jun 0.07 0.21 0.12 0.25 0.26 0.15 May- 0.854 0.492 0.602 0.499 0.398 0.502 0.01 0.12 Aug Apr- -0.05 -0.27 -0.04 -0.27 0.988 0.841 0.235 0.756 0.898 0.236 0.03 0.06 July 0.03 Apr- -0.05 -0.26 -0.26 0.894 0.904 0.265 0.884 0.920 0.251 0.11 0.22 0.24 0.27 Apr- -0.04 June -0.02 0.764 0.476 0.883 0.531 0.383 0.952 0.13 0.27 0.30 0.30 May Apr- -0.15 -0.15 0.734 0.384 0.516 0.418 0.322 0.525 Parameter Probability Pearson coefficient Probability Pearson coefficient Probability Pearson coefficient Probability Pearson coefficient Probability Pearson coefficient Probability Pearson coefficient

Year Year interval 1994-2014 2007–2014 1994–2006 1994–2014 2007–2014 1994–2006 Foliar Foliar = 0.05 are in bold. Significant values of probability are in bold- italics. are in bold. Significant values of probability Pearson coefficients significant at P = 0.05 are symptoms

Severity

Incidence Sums of active temperatures vs symptom incidence or severity correlations at the Giulianova vineyard: Pearson coefficients and values of Pearson of values and coefficients Pearson vineyard: Giulianova the at correlations severity or incidence symptom vs temperatures active of Sums 8. Table periods for 1994–2014, 1994–2006 and 2007–2014. probability for different coefficient

500 Phytopathologia Mediterranea Rainfall, temperature and GLSD foliar symptoms

Pearson coefficients -0.47 for July–August and -0.65 particularly in July, on symptoms incidence and se- for July for symptom incidence, and -0.44 and -0.59 verity, as has already been ascertained by Marchi et for the same periods for symptom severity (Tables 7 al. (2006). In the Controguerra and Giulianova vine- and 8). yards the rainfall-symptoms correlations were great- In the 2007–2014 period, in both vineyards, no est in July and in the periods including this month, consistent statistically significant correlations were confirming the importance of July rainfall conditions recorded between the sums of active temperatures for expression of foliar symptoms. and incidence or severity of symptoms (Tables 5, 6, In contrast to the hypothesis of Surico et al. (2010), 7, and 8). in both vineyards in the period of 1994 to 2006, inverse correlations between sums of active tempera- Level of symptom severity and vine mortality tures and symptom expression were recorded for July each year. In the Controguerra vineyard, these corre- Decreases of symptom expression were observed lations also involved periods including July, while in in the Giulianova and Controguerra vineyards during the Giulianova vineyard significant correlations were the years of this study. The number of vines of each detected only for July. The inverse July correlations severity rating class decreased from 1994 to 2014 (Fig- between sums of active temperatures and symptoms ure 1). This decrease was most evident for the vines in were verified, and in some periods including July, also greater classes of symptom severity (Figure 1). for the 21 years of observations, from 1994 to 2014. In both vineyards, the percentage of annual vine This strengthens the hypothesis that temperatures in mortality decreased after 2006, with the maximum (Northern Hemisphere) July play an important role in mortality occurring in 2005, in Controguerra, and the expression of GLSD symptoms. in 2003 and in 2005 in Giulianova. Cumulative vine July rainfall was a key factor in the symptom ex- mortality stabilized after 2007 (Figure 2). pression. It is important to note that in the vineyards In both vineyards, in the 1994-2014 period, the per- observed in this study the first symptoms of GLSD centages of dead vines which showed GLSD symp- appeared regularly at the end of July. toms in a previous year, increased with increasing the Growing seasons with high rainfall in July charac- levels of severity of symptoms observed at first ap- terized by low temperatures, favoured higher expres- pearance (Figure 3). sion of foliar symptoms. Fresh and rainy summers are favorable to GLSD, probably increasing plant physi- Discussion ological processes, maybe including the movement of fungal toxins to the leaves (Di Marco and Osti, 2009; This study was carried out in Trebbiano d’Abruzzo Surico et al., 2000, 2009, 2010). vineyards trained to the expanded trellis system e.g. The symptoms-rainfall and symptoms-temper- “Tendone”, with each vine trunk being 2 m high and ature correlations assessed in 1994–2006, were no with four permanent branches from which abun- longer found in the following period, 2007–2014. dant foliage developed. The vineyards are character- Although rainfall and temperature appeared to be ized by extended longevity, vigour and yields. These favourable, this period has been characterized by a characteristics may have to particular GLSD dynam- decrease of symptom expression. ics, with plants remaining asymptomatic for several The lack of a correlation between the leaf symp- years after the first appearance of symptoms. These toms and wood deterioration was demonstrated by characteristics, as well as cultural practices, can play Calzarano and Di Marco (2007). On the other hand, fo- important roles in the expression of GLSD (Lecomte liar symptom expression of esca was associated with et al., 2011; Pancher et al., 2012; Travadon et al., 2016; the amount of internal necrosis in French vineyards Kraus et al., 2017). (Maher et al. 2012). This should not be surprising be- Rainfall plays a significant role in the modulation cause of the difference in the vineyard characteristics of leaf symptom expression (Surico et al., 2000; Marchi and the peculiarities of disease, with several factors et al., 2006; Surico et al., 2010; Latinovic and Latinovic, involved. It is common belief that a plant with severe 2017; Serra et al., 2018). In the present study, results symptoms will be easier to die respect to a plant with obtained in the period 1994–2006 confirmed the in- low or no foliar symptoms. The present study dem- fluence of rainfall in the first half of each summer, onstrated this belief: plants with high severity symp-

Vol. 57, No. 3, December, 2018 501 F. Calzarano et al.

"1" foliar symptom class "1" foliar symptom class

12,0 25,0 10,0 20,0 8,0 15,0 % 6,0 % 10,0 4,0

2,0 5,0

0,0 0,0 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014

"2" foliar symptom class "2" foliar symptom class 8,0 15,0

6,0 10,0

% 4,0 %

5,0 2,0

"3" foliar symptom class "3" foliar symptom class 10,0 20,0

8,0 15,0 6,0 % % 10,0 4,0 5,0 2,0

"4" foliar symptom class "4" foliar symptom class 12,0 20,0

10,0 15,0 8,0

% 6,0 % 10,0

4,0 5,0 2,0

"5" foliar symptom class "5" foliar symptom class 18,0 18,0 16,0 16,0 14,0 14,0 12,0 12,0 10,0 10,0 % % 8,0 8,0 6,0 6,0 4,0 4,0 2,0 2,0 0,0 0,0 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014

Figure 1. Percentages of grapevines in different GLSD foliar symptom classes from 1994 to 2014 at the Controguerra vineyard (left) and Giulianova vineyard (right).

502 Phytopathologia Mediterranea Rainfall, temperature and GLSD foliar symptoms

25,0 12,0

20,0 10,0

8,0 15,0 % % 6,0 10,0 4,0

5,0 2,0

25,0 10,0

20,0 8,0

15,0 6,0 % % 10,0 4,0

5,0 2,0

Figure 2. Annual and cumulated vine mortality at Controguerra vineyard (above) and Giulianova vineyard (below).

40,0 70,0

35,0 60,0

30,0 50,0 25,0 40,0 % 20,0 % 30,0 15,0 20,0 10,0

5,0 10,0

0,0 0,0 1 2 3 4 5 1 2 3 4 5 foliar symptoms rating scale values foliar symptoms rating scale values

Figure 3. Mortality of GLSD symptomatic vines, in relation to the level of symptom severity shown during the first appearance of leaf symptoms, at the Controguerra vineyard (left) and Giulianova vineyard (right).

toms at the first appearance of the disease, died more reduced the yield loss but also might contribute to re- frequently than plants showing low severity symp- duce the possibility that the plant die (Calzarano et al., toms. Therefore, foliar symptom is particularly im- 2004, 2014, 2017a; Di Marco and Osti, 2009; Di Marco portant in the outcome of GLSD and attempts aimed et al., 2011a, 2011b; Calzarano and Di Marco, 2018). at decreasing in foliar symptom expression not only Furthermore, in this study the highest mortality of

Vol. 57, No. 3, December, 2018 503 F. Calzarano et al. the vines was recorded in the years just before 2006. plex)/grapevine pathosystem. Phytopathologia Mediterranea In the following years the vineyards were character- 55 (3), 410–426. ized by low mortality, low severity of expression, and Calzarano F., F. Osti, V. D’Agostino, A. Pepe and S. Di Marco, 2017a. Mixture of calcium, magnesium and seaweed affects vine symptoms no longer appeared related to rainfall leaf phytoalexin contents and grape ripening on vines with or temperature. It might not to be excluded that ma- grapevine leaf stripe disease. Phytopathologia Mediterranea ture vines, although still in full production, reduced 56 (3), 445–457. their attitude to respond to the disease by external Calzarano F., F. Osti, V. D’Agostino, A. Pepe, F. Della Pelle, M. symptoms. De Rosso, R. Flamini and S. Di Marco, 2017b. Levels of phytoalexins in vine leaves with different degrees of grapevine This study showed once again the complex in- leaf stripe disease symptoms (Esca complex of diseases). teraction among the expression of the disease, and Phytopathologia Mediterranea 56 (3), 494–501. agronomical and environmental factors (Mugnai et Di Marco S. and F. Osti, 2009. Effect of biostimulant sprays on al., 1999; Bertsch et al., 2013). Finally our results con- Phaeomoniella chlamydospora and esca proper infected vines firmed the correlation between rainfall and symptom under greenhouse and field conditions. Phytopathologia expression and demonstrated the role of temperature Mediterranea 48, 47–58. Di Marco S., F. Osti and A. Cesari, 2004. Experiments on the on annual incidence and severity of foliar symptoms, Control of Esca by Trichoderma. Phytopathologia Mediterranea highlighting age-related differences in the level of this 43, 108‒115. correlation, over a many-year observation period. Di Marco S., F. 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Accepted for publication: December 10, 2018

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