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Influence of Generation and Photoperiod on Larval Development of Lobesia botrana (Lepidoptera: Tortricidae)

ARSTRACT The influence of generation (under field conditions) and photoperiod (under laboratory conditions) on Lobesia botrana larvae development was studied. Some larvae were collected during three annual generations in two grape-growing areas of northeastern Italy, and others were individually reared in the laboratory from egg to pupa on an artificial diet under two different photoperiod conditions (respectively, daylight 16 h/d [long day {LD}] and 14 h/d [short day {SD}]). The mandible lengths of collected larvae were measured and the data analyzed morphometrically to determine the number of larval instars. In the laboratory study, the number of larval moultings, the mandible length of each instar, the development time from hatching larva to pupa, and the pupal weight were considered. The measurement of mandible lengths of larvae collected in the field indicated the existence of five larval instars in all three annual generations, but the size of the two oldest larval instars was significantly higher for third-generation larvae than for the previous generations. Under laboratory conditions, the larvae usually exhibited five instars, but the mandible lengths of larvae and the pupa size were greater for individuals reared under SD. These also took a greater number of days to develop from hatching larvae to pupae. Because a larger size of the final larval instar occurs in individuals that produce diapausing pupae under SD in both the laboratory and the field, a positive association between larval size and the probability of surviving the winter can be inferred.

Occurrence of two different development patterns in Lobesia botrana (Lepidoptera: Tortricidae) larvae during the second generation

In north‐eastern Italy, the second‐generation larvae of Lobesia botrana (Den. & Schiff.) (Lepidoptera: Tortricidae) can develop with two different time patterns. In particular, in ‘warmer’ areas, the developmental time is shorter than in ‘cooler’ areas and it is associated with an earlier and more economically important third generation. Because the differences in temperature are not sufficient to explain the two patterns, research was carried out aiming to investigate whether the differences in larval development time are the result of a different number of instars and whether the photoperiod is a factor. In the field, second‐generation larvae develop through five instars in a ‘warmer’ area and through six instars in a ‘cooler’ area. Laboratory and field data showed that decreasing photoperiod, which induces diapause, is also an important cue for inducing larvae to develop six instars. In the light of climate warming and subsequent changes in L. botrana phenology over the last 30 years, the two different development patterns are interpreted as a means to ensure the best fit of the moth to environmental conditions. In ‘cooler’ areas, third‐generation larvae might not complete development before frost or harvest, and hence second‐generation larvae develop through six instars before producing overwintering pupae.

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.

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.

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.

Neodryinus typhlocybae (Ashmead) antagonista di Metcalfa pruinosa (Say). Risultati di liberazioni pluriennali effettuate in Friuli-Venezia Giulia

Neodryinus Typhlocybae (ASHMEAD) AS A BIOLOGICAL CONTROL AGENT OF metcalfa pruinoSa (SAY). RESULTS OF PLURENNIAL RELEASES CARRIED OUT IN FRIULI-VENEZIA GIULIA During the three-year period 1998-2000 the entomophagous wasp Neodryinus typhlocybae (Ashmead) (Hymenoptera Dryinidae) was released to control the planthopper Metcalfa pruinosa (Say) (Homoptera Flatidae). The releases were carried out in 88 sites of 42 localities in the Friuli- Venezia Giulia region (north-eastern Italy). Between the end of May and the beginning of June, 200 N. typhlocybae cocoons, containing pupae, were placed in each site (woods, hedgerows, parklands). The entomophagous wasp became established in 83 cases out of 88 (94%) as shown by the numerous cocoons, containing overwintering larvae, found on the leaf undersurface of various trees and bushes at the end of the year. A few years after the introduction, populations of N. typhlocybae could still be found around release sites, showing that this species can permanently colonise different environments. In the first year, cocoons of the wasp were usually found up to 20-30 m from the original point of release. In successive years they were observed even at a distance of several kilometres from the release point, indicating that the adults can cover relatively long distances. Neodryinus typhlocybae will very probably colonise all the areas in the region that are infested by M. pruinosa, resulting in a significant reduction in the quantity of insecticides needed to control this pest. Key words: Biological control, Planthopper, Dryinid wasp, release. Nel triennio 1998-2000 sono state effettuate in Friuli-Venezia Giulia immissioni dell’entomofago Neodryinus typhlocybae (Ashmead) (Hymenoptera Dryinidae) contro Metcalfa pruinosa (Say) (Homoptera Flatidae). I rilasci sono stati condotti in 88 siti di lancio di 42 localita della regione; in ogni sito (es. boschetti, siepi interpoderali, aree a parco) sono stati collocati, a fine maggio-inizi di giugno, 200 bozzoli di N. typhlocybae contenenti pupe pronte allo sfarfallamento. Le immissioni hanno avuto successo in 83 casi su 88 (94%), in quanto a fine anno e stato possibile rinvenire sulla pagina inferiore di varie piante arboree o arbustive numerosi bozzoli contenenti larve svernanti dell’entomofago. Numerosi campionamenti, anche a distanza di vari anni dal rilascio, hanno permesso di accertare che le popolazioni di N. typhlocybae permangono in loco, dimostrando cosi la capacita dell’entomofago di colonizzare permanentemente vari ambienti. I bozzoli dell’imenottero nel corso del primo anno sono stati rinvenuti di norma fino a 20-30 m dal punto di rilascio; negli anni successivi essi sono stati rilevati anche a diversi chilometri dal punto di lancio, dimostrando la capacita degli adulti dell’entomofago di percorrere distanze tutt’altro che trascurabili (anche dell’ordine di 1 km all’anno). E prevedibile che N. typhlocybae possa colonizzare nel territorio regionale tutte le zone infestate da M. pruinosa, consentendo una significativa riduzione degli interventi insetticidi contro il fitofago. Parole chiave: Lotta biologica, Flatidi, Driinidi, liberazioni.