Nicola Mori

Translocation of Neonicotinoid Insecticides From Coated Seeds to Seedling Guttation Drops: A Novel Way of Intoxication for Bees

ABSTRACT The death of honey bees, Apis mellifera L., and the consequent colony collapse disorder causes major losses in agriculture and plant pollination worldwide. The phenomenon showed increasing rates in the past years, although its causes are still awaiting a clear answer. Although neonicotinoid systemic insecticides used for seed coating of agricultural crops were suspected as possible reason, studies so far have not shown the existence of unquestionable sources capable of delivering directly intoxicating doses in the fields. Guttation is a natural plant phenomenon causing the excretion of xylem fluid at leaf margins. Here, we show that leaf guttation drops of all the corn plants germinated from neonicotinoid-coated seeds contained amounts of insecticide constantly higher than 10 mg/1, with maxima up to 100 mg/1 for thiamethoxam and clothianidin, and up to 200 mg/1 for imidacloprid. The concentration of neonicotinoids in guttation drops can be near those of active ingredients commonly applied in field sprays for pest control, or even higher. When bees consume guttation drops, collected from plants grown from neonicotinoid-coated seeds, they encounter death within few minutes.

Non-crop plants used as hosts by Drosophila suzukii in Europe

The invasive spotted wing drosophila Drosophila suzukii, a fruit fly of Asian origin, is a major pest of a wide variety of berry and stone fruits in Europe. One of the characteristics of this fly is its wide host range. A better knowledge of its host range outside cultivated areas is essential to develop sustainable integrated pest management strategies. Field surveys were carried out during two years in Italy, the Netherlands and Switzerland. Fruits of 165 potential host plant species were collected, including mostly wild and ornamental plants. Over 24,000 D. suzukii adults emerged from 84 plant species belonging to 19 families, 38 of which being non-native. Forty-two plants were reported for the first time as hosts of D. suzukii. The highest infestations were found in fruits of the genera Cornus, Prunus, Rubus, Sambucus and Vaccinium as well as in Ficus carica, Frangula alnus, Phytolacca americana and Taxus baccata. Based on these data, management methods are suggested. Ornamental and hedge plants in the vicinity of fruit crops and orchards can be selected according to their susceptibility to D. suzukii. However, the widespread availability and abundance of non-crop hosts and the lack of efficient native parasitoids suggest the need for an area-wide control approach.

Correlation of bois noir disease with nettle and vector abundance in northern Italy vineyards

The phytoplasmas associated with bois noir (BN) tuf-type a are transmitted to grapevines by means of Hyalesthes obsoletus Signoret using Urtica dioica L. as the inoculum source. In the period 2003–2008, a research was carried out in six vineyards of northern Italy where a large amount of nettles in the ditches surrounding vineyards was detected. The aim was to establish the nettle control effects on the presence of H. obsoletus and new symptomatic grapevines. PCR and RFLP analyses showed the presence of the BN tuf-type a phytoplasmas in symptomatic grapevines of all vineyards and in the vector. Weed control strategies along ditches were always associated with decreases in nettle coverage and H. obsoletus numbers. A reduction in the percentage of new symptomatic grapevines occurred in all vineyards except for one vineyard where the least reduction in nettle and H. obsoletus was observed. The decrease in H. obsoletus population was significantly correlated with a decrease in nettles along ditches, and the reduction in H. obsoletus population was correlated with a decrease in incidence of new symptomatic grapevines compared with the incidence before the application of weed control measures. Nettle weeding can reduce the incidence of BN tuf-type a, but weed control costs and impacts need to be considered.

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.

Comparison of attractants for monitoring Drosophila suzukii in sweet cherry orchards in Italy

The invasiveness of Drosophila suzukii Matsumura is causing sizable damage to soft fruits and cherry. In order to define a targeted strategy for D. suzukii management, it is important to have access to highly sensitive trapping tools for detection, monitoring and control that are also selective, practical in use, economic, and with low environmental impact. The aim of this study was to compare different combinations of traps and lures to define a best practice approach for D. suzukii monitoring in Italy, extended over a wide elevational gradient and landscape complexity. The high attractiveness was not always combined with high selectivity, as in some cases up to 95% of the Drosophila spp. captured were belonging to species different from D. suzukii. The commercial Droso‐Trap was very efficient providing high capture ability. Overall, the most attractive lure was Droskidrink while Suzukii Trap was the most selective one. Lure attractiveness and selectivity, however, changed during the season in relation to environmental temperatures and phenological developmental stages, suggesting the need for implementing different lures in different periods and for the different purposes (monitoring or mass trapping). In terms of trap management, Droskidrink showed the problem of bacterial‐gel formation, while Suzukii Trap and Pherocon SWD were easier to handle as they did not need to be checked at weekly interval. Finally, these results were gathered to convey the most efficient combination of trap and bait able to efficiently perform mass trapping and attract and kill technique.

Spillover of Drosophila suzukii between noncrop and crop areas: implications for pest management: D. suzukii between crop and noncrop habitats

Semi‐natural areas may promote Drosophila suzukii population dynamics by providing alternative host resources, overwintering habitats and refuge areas during cold, warm or dry periods, or when crops are sprayed with insecticides. In the present study, we investigated the spillover of D. suzukii between noncrop and crop areas using sweet cherry as a model crop. We sampled the pest at different heights and at different distances from the forest, from the the winter dormancy stage to the post‐harvest period. Drosophila suzukii activity‐density in the orchards declined strongly with increasing distance from the forest margin and with increasing height above the ground. The observed patterns varied over the crop phenological development stages, indicating that the pest used multiple habitats throughout the year. When the host plant was not suitable for reproduction, D. suzukii preferred to fly closer to the forest margin and at lower heights. When the host plant was suitable (i.e. ripe cherries), D. suzukii further colonized the orchards both horizontally and vertically, exploring the canopy volume more in depth. The results of the present study will contribute to the development of more effective and practical approaches for protecting fruit crops from D. suzukii and improving chemical, physical or mechanical control measures.

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.

Metagenomic analysis reveals changes of the Drosophila suzukii microbiota in the newly colonized regions

The spotted wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) is a highly polyphagous pest of a wide variety of wild or cultivated berry and stone fruit. Originating from Southeast Asia, it has recently invaded a wide range of regions in Europe and North America. It is well known that insect microbiotas may significantly influence several aspects of the host biology and play an important role in invasive species introduction into new areas. However, in spite of the great economic importance of D. suzukii, a limited attention has been given so far to its microbiota. In this study, we present the first in‐depth characterization of gut bacterial diversity from field (native and invasive range) and lab‐reared populations of this insect. The gut bacterial communities of field insects were dominated, regardless of their origin, by 2 families of the phylum Proteobacteria: Acetobacteraceae and Enterobacteriaceae, while Firmicutes, mainly represented by the family Staphylococcaceae, prevailed in lab‐reared population. Locality was the most significant factor in shaping the microbiota of wild flies. Moreover, a negative correlation between diversity and abundance of Enterobacteriaceae and the time elapsed since the establishment of D. suzukii in a new region was observed. Altogether our results indicate that habitat, food resources as well as the colonization phase of a new region contribute to shape the bacterial communities of the invasive species which, in turn, by evolving more quickly, could influence host adaptation in a new environment.

Vineyard Colonization by Hyalesthes obsoletus (Hemiptera: Cixiidae) Induced by Stinging Nettle Cut Along Surrounding Ditches.

Abstract Stinging nettle (Urtica dioica L.) is the most important host plant for both phytoplasma associated with Bois noir disease of the grapevine and its vector Hyalesthes obsoletus Signoret (Hemiptera: Cixiidae). Vector abundance in vineyards is favored by stinging nettle growing in surrounding areas. Nettle control by herbicides or cutting can reduce vector population in vineyards. However, chemical weeding can cause environmental problems. Many authors suggest that stinging nettle control applied during H. obsoletus flight could force adults to migrate into vineyards. We evaluate if cutting of nettle growing along ditches during adult flight favors vineyard colonization by H. obsoletus. Three different weed management regimes (“no cuts,” “one cut” just before the beginning of adult flight, and “frequent cuts” over the whole vegetative season) were applied to the herbaceous vegetation in ditches bordering two vineyards. The flight dynamics of H. obsoletus were recorded by placing yellow sticky traps on the vegetation along the ditches and at different positions in the vineyards. Frequent stinging nettle cuts (compared with a single cut) in surrounding areas favored the dispersion of vectors inside the vineyards. Stinging nettle control should be based on an integration of a single herbicide application before H. obsoletus emergence followed by frequent cuts to minimize negative side effects of chemical weeding. In organic viticulture, a frequent-cuts strategy should avoid cuts during H. obsoletus flight period, at least in the first year of adoption.

Temperature Alters the Response to Insecticides in Drosophila suzukii (Diptera: Drosophilidae)

Abstract Drosophila suzukii Matsumura (Diptera: Drosophilidae) is an invasive pest in Europe and is a major threat to the soft fruit industry. Because of an ample temperature range, the pest spans from low to high elevation crops in mountain areas of the Southern Alps. Starting from field observations on the variable efficacy of insecticides under different temperatures, experiments were designed to test the efficacy of chemical families of insecticides available against this pest. Pyrethroids and spynosins proved to be the most effective under all temperature conditions (14, 22, and 30°C) in all assays. Organophosphates and neonicotinoids showed significantly lower efficacy at low temperatures, indicating that they are not suitable to protect crops under those conditions. The management of the pest in cold habitats, which are suitable for the cultivation of high-quality berries as for example in mountain farming systems, is constrained by a limited number of molecules available for fruit protection. Temperature has to be considered among factors affecting the decision-making process for the choice of registered formulations to be used in pest control.