Studies on Lobesia botrana and Scaphoideus titanus for their successful management in organic and conventional viticulture

Lobesia botrana Den & Shiff (Lepidoptera: Tortricidae) and Scaphoideus titanus Ball (Hemiptera: Cicadellidae) are considered major pests in European viticulture. Lobesia botrana is native from the Mediterranean basin and now is present in America while Scaphoideus titanus native from North America is an exotic pest for Europe. They are both present in north-eastern Italy. Their importance comes from the big damage they cause to the quality and the quantity of grape production. This damage is caused directly through larval feeding of Lobesia botrana, and indirectly by Scaphoideus titanus as a vector of a dangerous quarantine Phytoplasma disease Flavescence doree). Consequently, they are the target of different pest anagement strategies. They are mainly controlled with the use of pesticides and mating disruption for L. botrana only. The raising awareness on the impact of pesticides on the human health and the environment, concerns about pesticide resistance, the spread of these species into new regions and the recent challenges such as climate change all underline the necessity of more efficient control for those pests based on an improved knowledge of their biology and ecology. A more comprehensive understanding of the insect phenology and behaviour could be the first step in building a coherent and successful control strategy. This is the main motivation to conduct this research. In this thesis the phenology (I) and the genetic structure of populations (II) of L. botrana and regarding S. titanus the phenology (III), behavior (IV) and Grapevine Phytoplasmas interaction (V) were studied (I) the phenology of grape berry moths Lobesia botrana and Eupoecilia ambiguella was investigated in several sites in Veneto region during the period of 2010 and 2011. Few sites were also studied in 2012. The results show a clear preference for E. ambiguella to hilly areas and for L. botrana to plain areas. Number of generations per year varied among the sites, and the beginning of the flights were generally earlier in 2011. For E. ambiguella the observed generation numbers was 2 to 3. Regarding L. botrana 2 to 4 flights were recorded. In some areas L. botrana showed a long flight period which made it difficult to determine whether it was one or two overlapping flights. However, this phenomenon could be associated with larval aestivation. Moreover, four flights were noticed for Lobesia botrana in some areas, but no evidence for fourth generation was provided. Temperature was found to have an influence on the second flight of E. ambiguella and the beginning of this flight for L. botrana. (II) The genetic structure of populations of L. botrana was studied, because, in spite of the importance of grape berry moth, little is known about its genetic structure. In this study, six microsatellite loci were used to analyse 16 population of Lobesia botrana from the Middle East and Europe, to investigate their variation and structure. The results showed moderate levels of genetic differentiation among the different populations. An excess heterozygosity was noticed in most of the populations due to the mating among the populations. The populations coming from Middle East and Spain belong to different genetic clusters, while the German and Italian ones were mixed. No clear geographical effect was detected on the different studied populations. These data are relevant for the development of pest control strategies because, the study of the gene flow of populations could help in knowing the distance over which the population could disperse, consequently, knowing the spatial scale within which the forecasting techniques could be effective. (III) The phenology of S. titanus was studied in several sites in Veneto region in 2010-2012 in order to know the best time to apply the different pest management practices. The collected data showed that the S. titanus nymphs appear in May, while the adults appeared, between the third part of June and the mid of July, and disappeared between September and early October. In general, S. titanus nymphs and adults appeared earlier in 2011 and 2012 than in 2010 with some variations among the sites depending on altitude and sun exposure. The temperature affects the nymphs phenology and the nymphs appearance and development are synchronized with the host phenology, while for the adults there are other factors that could affect the phenology beside the temperature such as altitude and photoperiod. (IV) The study on the preference of Scaphoideus titanus to different grape cultivars, and the role of stimuli in host recognition was conducted because these aspects are not well known and explained for this leafhopper. In this study four grapevine Cultivars were used (Chardonnay, Cabernet franc, Merlot and Glera) to study their attractiveness to different life stages of S. titanus. Furthermore, healthy and infected shoots by Grape Yellow Phytoplasma Diseases (Flavescence doree and Bois noir) were used to investigate the ability of the leafhopper to distinguish among their different stimuli. The results of this study showed that there are different levels of preference rates for S. titanus towards the investigated cultivars. This preference varied according to the age and throughout the experiment period. Chardonnay was more attractive to the young nymphs and nymphs. Young nymphs and adults seemed to prefer Cabernet Franc. Moreover, S. titanus was found to be able to distinguish among healthy and GYs infected stimuli, while no strong attraction was detected of this insect to the stimuli of FD, BN phytoplasma. These results could provide help in understanding the insect behaviour and distribution within the vineyard. Hence, they could contribute to the development of stronger tools for the monitoring and control strategy. (V) The effect of the Grapevine Yellow Phytoplasmas on the development and the survival of Scaphoideus titanus was studied using grapevine leaves as phytoplasma infection source. In addition to Flavescence doree (FD) the Bois noir (BN) causal agent was also investigated because its importance and occurrence are increasing in many Italian regions, and because it was detected inside Scaphoideus titanus. Although this leafhopper is not involved in BN transmission and spread, the BN phytoplasmas could have an effect on the insect life. Newly hatched nymphs were collected on asymptomatic shoots and reared artificially on healthy, FD or BN infected leaves, under controlled conditions. The results showed that nymphs reared on phytoplasma infected leaves had a greatly longer longevity and lower survival rate, while no differences between FD and BN were found. The phytoplasmas detection analyses confirmed the ability of S. titanus in acquiring the causal agent of BN.