Elena Cargnus

Assessing the influence of inflorescence traits on the susceptibility of grape to vine moths

In north‐eastern Italy during 1994–2006, studies were carried out on the susceptibility of grapevine cultivars to the first generations of the European vine moth [Lobesia botrana (Den. and Shiff.); Lep., Tortricidae] and the European grape berry moth [Eupoecilia ambiguella (Hb.); Lep., Cochylidae]. In five different years, the larval population density of both moth species and the larval age composition of L. botrana were recorded on 11 grapevine cultivars (Cabernet Sauvignon, Carmenère, Chardonnay, Pinot Gris, Merlot, Refosco dal Peduncolo Rosso, Rhine Riesling, Sauvignon Blanc, Terrano, Tocai Friulano, Verduzzo Friulano), grown in the same vineyard. The influence of inflorescence traits on these demographic parameters was also evaluated. On a 5‐year average, L. botrana significantly prevailed over E. ambiguella in nine of the 11 cultivars. Chardonnay and Pinot Gris were the most infested cultivars. Age composition of L. botrana larvae varied with cultivar type, being older on Chardonnay and Tocai Friulano than the other cultivars. Inflorescence earliness and hairiness explained the majority of the variability in cultivar susceptibility. In particular, the larval population level of the two vine moths was positively correlated with inflorescence earliness and negatively correlated with inflorescence hairiness. Lobesia botrana larval age composition was negatively correlated with inflorescence hairiness. Inflorescence earliness and hairiness could be used to predict in each grape‐growing area which cultivars are potentially more infested in the first generation. Inflorescences without pubescence, favouring an older age composition of first generation larvae, could induce an earlier second generation.

Influence of the carpophagous generations of the European grapevine moth Lobesia botrana on grape bunch rots

The second and third generations of Lobesia botrana can cause both yield losses and spreading of grape bunch rots. The aim of this study was to know to what degree these generations of L. botrana influence the rots at harvest time. The study was carried out in two grape-growing areas of northeastern Italy where the moth completes two and three generations per year, respectively. In the context of 12 insecticide trials, samplings were conducted in different plots to estimate the number of larval nests of the second and third generations and that of rotten berries at harvest time. The data sets (number of larval nests and rotten berries) from the different trials were submitted to regression analyses. Gray mold was the most important grape rot. The second generation, in the area where L. botrana has only two generations per year, and the third generation, in the area where the moth completes three generations per year, can favor gray mold on and around berries bored by larvae. In contrast, groups of rotten berries non-contiguous to larval nests did not appear to be influenced by moth activity. In the area where the moth completes three generations per year the larval nests of the second generation did not show a significant influence on bunch rots at harvest time.

Identification and phenology of Hyalesthes obsoletus (Hemiptera: Auchenorrhyncha: Cixiidae) nymphal instars.

Urtica dioica and Convolvulus arvensis are the main host plants of Hyalesthes obsoletus and play an important role in the epidemiology of Bois noir of grapevines. The earliest survey, which was carried out to compare the phenology of nymphal instars on U. dioica and C. arvensis, had highlighted some problems in the identification of the instars. Therefore, the correct identification of nymphs to species and instar level became a preliminary aim of this research. Adults and nymphs attributable to H. obsoletus were collected during 2008-2010 in three flatland vineyard habitats of northern Italy on U. dioica, C. arvensis and Artemisia verlotorum. Nymphs and morphologically identified adults of H. obsoletus were submitted to molecular identification. Morphometric and morphological studies were carried out on nymphs collected in the field or obtained in laboratory rearings. Molecular methods not only confirmed the identity of adults, but also allowed the assignment of the nymphs to this species. Morphometric and morphological characteristics (e.g. body and head-thoracic lengths, number of thoracic pits) showed the existence of five nymphal instars. Morphometric differences between newly hatched and older first-instar nymphs were observed. A key to distinguish the five instars was proposed. Evident differences between H. obsoletus nymphs studied here and elsewhere were identified. According to differences in adult-flight period, an earlier phenology of nymphs on C. arvensis than on U. dioica was observed. In particular, the typical overwintering instar was the second on U. dioica and the third on C. arvensis.

Efficacy and Mode of Action of Kaolin in the Control of Empoasca vitis and Zygina rhamni (Hemiptera: Cicadellidae) in Vineyards

During 2015, the influence of kaolin applications and bunch-zone leaf removal on the grapevine leafhoppers, Empoasca vitis (Göthe) and Zygina rhamni Ferrari, and their egg parasitoids (Anagrus spp.) was tested in four vineyards of northeastern Italy. The mode of action of kaolin on E. vitis nymphs was also investigated in the laboratory. In the treated plots, kaolin was applied at a rate of 2% w/v on two occasions separated by 5-6 d. In two vineyards, it was applied either on the whole canopy or the bunch zone at the beginning of the E. vitis second generation (preventive criterion), and in the other two vineyards, it was applied to the whole canopy at the peak of the E. vitis third generation (curative criterion). Both the preventive and curative kaolin applications caused a significant decrease in the populations of E. vitis and Z. rhamni nymphs. The effect of the preventive applications was persistent and was associated with reduced E. vitis leaf symptoms. Kaolin did not influence the activity of Anagrus spp. Bunch-zone leaf removal did not affect leafhopper populations. Laboratory experiments showed that inhibition of feeding was the main mode of action through which kaolin affected nymph populations. Based on these outcomes, kaolin could be a valuable alternative to synthetic insecticides in controlling grapevine leafhoppers.

Control of Scaphoideus titanus with Natural Products in Organic Vineyards

The leafhopper Scaphoideus titanus is the vector of ‘Candidatus Phytoplasma vitis’, the causal agent of Flavescence dorée (FD) a key disease for European viticulture. In organic vineyards, the control of S. titanus relies mostly on the use of pyrethrins that have suboptimal efficacy. During 2016, three field trials were conducted to evaluate the efficacy of kaolin, orange oil, insecticidal soap and spinosad against S. titanus nymphs, in comparison with pyrethrins. The activity of kaolin was evaluated also in the laboratory. In all field trials, kaolin had an efficacy against nymphs comparable to pyrethrins, while the other products were not effective. Laboratory results confirmed that kaolin increased nymph mortality. In organic vineyards, kaolin and pyrethrins are valuable tools in the management of FD. Nevertheless, their efficacy is lower compared to that of the synthetic insecticides used in conventional viticulture. Therefore, further research should be conducted in order to identify alternatives to synthetic insecticides for S. titanus control in the context of organic viticulture.

Mortality of Eggs and Newly Hatched Larvae of Lobesia botrana (Lepidoptera: Tortricidae) Exposed to High Temperatures in the Laboratory

Abstract The hypothesis that bunch-zone leaf removal reduces infestations of the European grapevine moth, Lobesia botrana (Denis & Schiffermüller) (Lepidoptera: Tortricidae), by increasing egg and larval mortality owing to sunlight exposure was evaluated in the laboratory by subjecting different egg stages (white, red-eyes, and blackhead) and newly hatched larvae to high temperatures. Based on temperatures recorded in a northern Italian vineyard on sun-exposed berries belonging to south-west facing bunches, eggs were subjected to constant temperatures of 40 °C and 37 °C for one or two periods of 3 or 6 h, and to 24-h temperature cycle with peak of 40 °C. Larvae were exposed to 24-h high-temperature cycles with peaks of 35, 37, and 40 °C. The results showed partial egg mortality at 40 °C, increasing with exposure hours and periods, and as eggs matured. Egg mortality was not affected by exposure to 37 °C. Larval survival already decreased significantly at 37 °C and was even lower at 40 °C. These laboratory data are in agreement with the hypothesis that temperatures reached by berries exposed to sunlight cause egg and larval mortality. Data on egg and larval susceptibility to high temperatures have also implications for species distribution and effects of climate change.

Re-examination of specimens of three species of Kampimodromus Nesbitt (Acari: Phytoseiidae) from north-eastern Italy, with first report on Kampimodromus corylosus Kolodochka in Italy

Specimens of phytoseiid previously identified as Kampimodromus aberrans (Oudemans), Kampimodromus ericinus Ragusa di Chiara and Tsolakis and Kampimodromus langei Wainstein and Arutunjan from north-eastern Italy were re-examined, with the use of morphometry. For each taxon, adult females from different collections were compared with literature information on female representatives of eight Kampimodromus species. We confirmed the identity of specimens previously identified as K. aberrans and K. langei. Specimens of K. langei differed from the holotype of Kampimodromus coryli Meshkov mainly by the absence of the gd5 dorsal idiosomal solenostomes. Specimens previously identified as K. ericinus were determined to be Kampimodromus corylosus Kolodochka, based on the length of certain dorsal setae. The largest morphometric setal variation was observed in K. aberrans; females bearing shorter setae were most similar to the topotype. Within the series of females of K. langei that were studied, those bearing longer setae were most similar to the holotype of the species. This is the first report on specimens of K. corylosus, collected from hazelnut, in Italy.

Effects of grapevine bunch exposure to sunlight on berry surface temperature and Lobesia botrana (Lepidoptera: Tortricidae) egg laying, hatching and larval settlement: Influence of bunch sunlight exposure on L. botrana

Bunch‐zone leaf removal reduced infestation by Lobesia botrana, although the mechanism responsible for this effect is unknown. Based on the mortality of eggs and newly‐hatched larvae exposed to high temperatures (≥37 °C) in the laboratory, the present study aimed to assess the influence of (i) bunch‐zone leaf removal and grapevine‐row orientation on berry surface temperature and (ii) bunch exposure to sunlight on egg and larval mortality. Berry temperatures were measured using a noncontact infrared thermometer in two vineyards and showed that, in direct sunlight, the temperatures of berry surfaces were 9 °C or more above air temperature, and the highest mean temperatures occurred on southwest‐side bunches followed by west‐ and south‐side bunches. The results of four two‐choice field assays, carried out confining fertile females in cages with two bunches, one exposed and one non‐exposed to sunlight, showed that: (i) the females did not avoid laying eggs on sun‐exposed bunches and (ii) the lowest percentages of both egg‐hatching and larval settlement occurred on sun‐exposed bunches. The hypothesis that the high temperatures reached by sun‐exposed berries cause egg and especially larval mortality is confirmed. Bunch‐zone leaf removal combined with optimized grapevine‐row orientations can improve L. botrana control.

Influence of Grapevine Cultivar on the Second Generations of Lobesia botrana and Eupoecilia ambiguella

Grapevine cultivar can affect susceptibility to Lobesia botrana and Eupoecilia ambiguella with important implications on control strategies. A four-year study was carried out in north-eastern Italy on 10 cultivars (Cabernet Sauvignon, Carménère, Chardonnay, Merlot, Refosco dal Peduncolo Rosso, Rhine Riesling, Sauvignon Blanc, Terrano, Tocai Friulano and Verduzzo Friulano) grown in the same vineyard to assess whether the cultivar affects second-generation population levels of the two vine moths and L. botrana larval age composition. The influence of bunch traits measured at the peak of egg hatching on demographic parameters was also evaluated. Over the four years, L. botrana significantly prevailed over E. ambiguella in nine cultivars. Chardonnay and Tocai Friulano were the most infested cultivars and Merlot was the least infested. At the sampling date, the age composition of L. botrana varied with cultivar, with the larvae being significantly older on Chardonnay and younger on Carménère, Merlot and Verduzzo Friulano. Older larval age was significantly associated with higher bunch compactness. Larval infestation was not significantly influenced by either bunch compactness or berry volume, which suggested a more important role for contact and volatile substances mostly originating from the berries. These results allow for the improvement of Integrated Pest Management strategy against vine moths.

Efficacy and mode of action of kaolin and its interaction with bunch-zone leaf removal against Lobesia botrana on grapevines

Lobesia botrana control strategies in vineyards aim to develop environmentally safe tools as an alternative to synthetic insecticides. The activity of kaolin on L. botrana performance was studied in laboratory and field bioassays. The efficacy of kaolin and Bacillus thuringiensis (Bt) against the moth, with or without bunch-zone leaf removal (LR), was compared in four trials carried out in vineyards in north-eastern Italy. In the laboratory bioassays, kaolin berry coverage reduced the egg-laying preference of L. botrana by 53% and decreased female survival and fecundity by 22 and 82%, respectively. Kaolin egg coverage reduced the hatching rate by 14%. The larval settlement preference for berries covered with kaolin was reduced by 72%, but larval survival and development were not affected. In the field bioassay, kaolin reduced the egg-laying preference by 84%. In the field trials, kaolin, Bt and LR reduced L. botrana infestation significantly. Although Bt was more effective than kaolin, the efficacy of the two products was similar when combined with LR. Based on the results obtained and its effectiveness also against grapevine leafhoppers, kaolin can play an important role in the context of integrated pest management in vineyards.