Davide Rassati

Improving the early detection of alien wood-boring beetles in ports and surrounding forests

Summary 1. International ports are generally considered the most likely points of entry for alien woodboring beetles. A better understanding of the factors affecting their arrival and establishment at ports and their surrounding areas is of utmost importance to improve the efficacy and the cost-effectiveness of early detection programmes. Our work aimed at understanding how port size and the characteristics of the landscape surrounding the port, in terms of forest cover and forest composition, influence the occurrence of alien wood-boring beetles. 2. From May to September 2012, 15 Italian international ports and the surrounding forests were monitored with multi-funnel traps baited with a multi-lure blend (a-pinene, ethanol, ipsdienol, ipsenol, methyl-butenol), three in each port and three in forests located 3–5 km away from the port. We identified both alien and native Scolytinae, Cerambycidae and Buprestidae beetles. 3. Fourteen alien species, among which four are new to Italy, were trapped. Alien species richness was positively related to the amount of imported commodities at the port scale. Broadleaf forests surrounding ports received larger number of alien species than conifer forests. By contrast, total forest cover in the landscape surrounding ports was positively related to the occurrence of native but not alien species. The alien and native species richness was higher in the surrounding forests than in the ports. 4. Synthesis and applications. The simultaneous use of traps in ports with large volume of imported commodities and in their surrounding broadleaf forests can strongly increase the probability of alien wood-boring beetle interceptions. The identification of sites where the arrival and establishment of alien species is more probable, combined with an efficient trapping protocol, can substantially improve the efficacy of early detection. Similar approaches may be used in other countries as early warning systems to implement timely measures to eradicate or contain alien invasions at the European scale.

Monitoring of the pine sawyer beetle Monochamus galloprovincialis by pheromone traps in Italy

The pine sawyer beetle Monochamus galloprovincialis (Olivier) (Coleoptera Cerambycidae) gained importance as a pest in Europe after the introduction in Portugal of the pine wood nematode Bursaphelenchus xylophilus, the agent of pine wilt disease. As the nematode is transmitted by the adult beetles during both maturation feeding and oviposition, effective methods of monitoring of the longhorn beetle populations are needed for the surveillance of the disease spread in Europe. Although in the last years many studies focused on the efficacy of different trapping methods, the general results are still controversial. In this study, we compared the efficiency of two trap types, cross-vane and multi-funnel, and two attractive blends, a kairomonal lure (α-pinene, ipsenol and methyl-butenol) and a commercial kit specific for M. galloprovincialis (pheromone plus kairomonal lure), in order to identify the trap/blend combination more appropriate for the surveillance of the M. galloprovincialis populations. Moreover, the trap efficiency was tested also in a pine stand colonized by M. galloprovincialis after a hailstorm and in a control stand. The results showed that the multi-funnel traps baited with the specific commercial kit was the most effective combination. Interestingly, trap catch was similar in the two pine stands, despite a different density of the target species. As the trapping method was effective also at low population density of M. galloprovincialis, it may be adopted as a general tool for beetle surveillance in the forest and at ports of entry.

Exploring the role of wood waste landfills in early detection of non-native wood-boring beetles

Non-native wood-boring beetles (Coleoptera) represent one of the most commonly intercepted groups of insects at ports worldwide. The development of early detection methods is a crucial step when implementing rapid response programs so that non-native wood-boring beetles can be quickly detected and a timely action plan can be produced. However, due to the limited resources often available for early detection, it is important to identify the best locations where to concentrate surveillance efforts. The aim of this study was to investigate the role of wood waste landfills in the early detection of non-native wood-boring beetles. From June to September 2013, insects were collected in multi-funnel traps baited with a multi-lure blend (α-pinene, ethanol, ipsdienol, ipsenol, and methyl-butenol) at the main port and a nearby wood waste landfill in 12 Italian towns. Overall, 74 species of wood-boring beetles (Buprestidae, Cerambycidae, and Scolytinae) were trapped, among which eight were non-native to Italy. We found that species richness and species abundance of both non-native and native beetles were significantly higher in the wood waste landfill than in the ports. However, the non-native and native communities were similar in the two environments. The main conclusion emerging from this study is that wood waste landfills, given their similarity with ports of entry, should be considered when surveying for non-native wood-boring beetles. Therefore, within the framework of creating long-term monitoring programs that include both coastal and continental areas, both ports and wood waste landfills should be monitored to improve the probability for early detection of non-native species.

Alien Wood-Boring Beetles in Mediterranean Regions

The suitable climate and the high diversity of woody plants and ecological conditions characterizing the Mediterranean regions have favored the establishment of several alien species in the Mediterranean Basin during the last decades. Among them, the vast majority is represented by wood-boring beetles, which can be easily transported between continents within all kinds of woody materials. Up to now, 34 alien wood-boring beetles are recorded as established in Mediterranean countries, and the bulk of them is represented by Scolytinae and Cerambycidae. Italy, France and Spain report the highest number of established alien species. Besides giving an overview of their origin, introduction pathways, biology and distribution in the Mediterranean Basin, we discuss the potential impact of these insects in the invaded environment, the survey and early-detection protocols, the main ecological processes driving their establishment and spread, and how climate change could affect their invasion process in the near future.

Common pathways by which non-native forest insects move internationally and domestically

International trade and movement of people are largely responsible for increasing numbers of non-native insect introductions to new environments. For forest insects, trade in live plants and transport of wood packaging material (WPM) are considered the most important pathways facilitating long-distance invasions. These two pathways as well as trade in firewood, logs, and processed wood are commonly associated with insect infestations, while “hitchhiking” insects can be moved on cargo, in the conveyances used for transport (e.g., containers, ships), or associated with international movement of passengers and mail. Once established in a new country, insects can spread domestically through all of the above pathways. Considerable national and international efforts have been made in recent years to reduce the risk of international movement of plant pests. International Standards for Phytosanitary Measures (ISPMs) No. 15 (WPM), 36 (plants for planting), and 39 (wood) are examples of phytosanitary standards that have been adopted by the International Plant Protection Convention to reduce risks of invasions of forest pests. The implementation of ISPMs by exporting countries is expected to reduce the arrival rate and establishments of new forest pests. However, many challenges remain to reduce pest transportation through international trade, given the ever-increasing volume of traded goods, variations in quarantine procedures between countries, and rapid changes in distribution networks. It is therefore likely that many more human-assisted invasions of forest insects will take place. New geographic expansions by natural modes are also made possible due to changes in host distribution and/or climate.

National Trade can Drive Range Expansion of Bark- and Wood-Boring Beetles

Abstract Several native species of bark- and wood-boring beetles (Coleoptera) have expanded their range within their native biogeographic regions in the last years, but the role of human activity in driving this phenomenon has been underinvestigated. Here we analyze 3 yr of trapping records of native bark- and wood-boring beetles (Cerambycidae and Scolytinae) collected at 12 Italian ports and their surrounding forests to help elucidate the human role in the movement of native species within their native biogeographic region. We trapped several species that occurred either inside or outside their native distributional range within Italy. Species richness and abundance of those species found in the ports located within their native range were most strongly associated with the amount of forest cover in the surrounding landscape, suggesting that they could have arrived in the ports from the nearby forests. The abundance of the species found outside their native range was instead most strongly linked to the amount of national imports arriving at the port where trapping occurred, suggesting that they were likely introduced to the ports from other parts of Italy. This study demonstrates that national sea transportation can favor species range expansion within a country, and confirms that the forests that surround ports can serve as a source of species that can be potentially moved with exports.

Habitat and climatic preferences drive invasions of non-native ambrosia beetles in deciduous temperate forests

The introduction of non-native ambrosia beetles can cause severe damage in forest ecosystems. Understanding the environmental drivers affecting their invasion at the local scale is of utmost importance to enhancing management strategies. Our objectives were: (1) to determine the influence of forest composition, forest structure, and climate on invasion success of non-native ambrosia beetles in deciduous temperate forests, and (2) to test the effect of host tree species on colonization success by non-native ambrosia beetles. In 2013, we sampled 25 forest stands located in North-East Italy belonging to three forest types dominated respectively by hop hornbeam, chestnut, and beech. Both ethanol-baited traps and trap-logs of five tree species (hop hornbeam, chestnut, beech, manna ash, and black locust) were used to sample non-native and native ambrosia beetle communities. We found a clear effect of forest composition on non-native species richness and activity-density, as measured in ethanol-baited traps, both of which were higher in chestnut-dominated forests. Furthermore, we found a positive effect of temperature on both the number of trapped non-native species and their activity-density, with cold temperatures limiting beetle spread in high-elevation forests. Only Xylosandrus germanus successfully colonized the trap-logs. The number of colonized logs was higher for chestnut and in chestnut-dominated forests. Both trapping and log-baiting indicated that chestnut-dominated forests were at greater risk of invasion than hop hornbeam- and beech-dominated forests. Given the economic and ecological importance of chestnut, ambrosia beetle communities present in chestnut-dominated forests should be monitored to determine where protective measures must be taken.

Developing trapping protocols for wood-boring beetles associated with broadleaf trees

Longhorn and jewel beetles are often moved intercontinentally within woody materials. The common use of hardwoods in solid wood-packaging requires efficient trapping protocols for broadleaf-associated species. We tested the effect of lure (ethanol vs multi-lure), trap color (green vs purple), and trap height (understory vs canopy) on the longhorn and jewel beetle species trapped in multi-funnel traps set up in both seminatural forests and reforested forests in Italy. Traps were deployed in a 2 × 2 × 2 factorial scheme, and the eight different treatments were replicated 17 times in a randomized complete block design, in which each block was a different site. Thirty-five longhorn beetle species (2 non-native) and 15 jewel beetle species (all native) were trapped. The multi-lure was more effective than ethanol at detecting most longhorn beetles at both the species and subfamily level (except Lepturinae), but had no effect on the detection of jewel beetles. Trap color affected both jewel (green better than purple) and longhorn beetles with mixed responses among subfamilies. Species richness and/or abundance of both families was greater in the canopy than the understory, but trends were more heterogeneous at lower taxonomic levels (i.e., significant effect on Cerambycinae and Lepturinae but not on Lamiinae). In general, we showed that green multi-funnel traps baited with multi-lure, and setup in the canopy may be an efficient trapping protocol for European longhorn and jewel beetles associated with broadleaf trees. This information can increase efficacy of early-detection programs carried out both inside and outside of Europe.

Bark and Ambrosia Beetles Show Different Invasion Patterns in the USA.

Non-native bark and ambrosia beetles represent a threat to forests worldwide. Their invasion patterns are, however, still unclear. Here we investigated first, if the spread of non-native bark and ambrosia beetles is a gradual or a discontinuous process; second, which are the main correlates of their community structure; third, whether those correlates correspond to those of native species. We used data on species distribution of non-native and native scolytines in the continental 48 USA states. These data were analyzed through a beta-diversity index, partitioned into species richness differences and species replacement, using Mantel correlograms and non-metric multidimensional scaling (NMDS) ordination for identifying spatial patterns, and regression on distance matrices to test the association of climate (temperature, rainfall), forest (cover area, composition), geographical (distance), and human-related (import) variables with β-diversity components. For both non-native bark and ambrosia beetles, β-diversity was mainly composed of species richness difference than species replacement. For non-native bark beetles, a discontinuous invasion process composed of long distance jumps or multiple introduction events was apparent. Species richness differences were primarily correlated with differences in import values while temperature was the main correlate of species replacement. For non-native ambrosia beetles, a more continuous invasion process was apparent, with the pool of non-native species arriving in the coastal areas that tended to be filtered as they spread to interior portions of the continental USA. Species richness differences were mainly correlated with differences in rainfall among states, while rainfall and temperature were the main correlates of species replacement. Our study suggests that the different ecology of bark and ambrosia beetles influences their invasion process in new environments. The lower dependency that bark beetles have on climate allowed them to potentially colonize more areas within the USA, while non-native ambrosia beetles, being dependent on rainfall, are typically filtered by the environment.

Two newly introduced tropical bark and ambrosia beetles (Coleoptera: Curculionidae, Scolytinae) damaging figs ( Ficus carica ) in southern Italy

In summer 2014, the bark beetle Hypocryphalus scabricollis (Eichhoff) and the ambrosia beetle Xyleborus bispinatus Eichhoff, species new to Italy and Europe, respectively, were found for the first time in south-eastern Sicily (Italy). Large infestations of the two species were recorded in many plantations of common fig (Ficus carica L.) both in 2014 and 2015. Data concerning insect characteristics, taxonomy, and distribution are briefly reported.