Nutrient-Poor Breeding Substrates of Ambrosia Beetles Are Enriched With Biologically Important Elements

Fungus-farming within galleries in the xylem of trees has evolved independently in at least twelve lineages of weevils (Curculionidae: Scolytinae, Platypodinae) and one lineage of ship-timber beetles (Lymexylidae). Jointly these are termed ambrosia beetles because they actively cultivate nutritional “ambrosia fungi” as their main source of food. The beetles are obligately dependent on their ambrosia fungi as they provide them a broad range of essential nutrients ensuring their survival in an extremely nutrient-poor environment. While xylem is rich in carbon (C) and hydrogen (H), various elements essential for fungal and beetle growth, such as nitrogen (N), phosphorus (P), sulfur (S), potassium (K), calcium (Ca), magnesium (Mg), and manganese (Mn) are extremely low in concentration. Currently it remains untested how both ambrosia beetles and their fungi meet their nutritional requirements in this habitat. Here, we aimed to determine for the first time if galleries of ambrosia beetles are generally enriched with elements that are rare in uncolonized xylem tissue and whether these nutrients are translocated to the galleries from the xylem by the fungal associates. To do so, we examined natural galleries of three ambrosia beetle species from three independently evolved farming lineages, Xyleborinus saxesenii (Scolytinae: Xyleborini), Trypodendron lineatum (Scolytinae: Xyloterini) and Elateroides dermestoides (Lymexylidae), that cultivate unrelated ambrosia fungi in the ascomycete orders Ophiostomatales, Microascales, and Saccharomycetales, respectively. Several elements, in particular Ca, N, P, K, Mg, Mn, and S, were present in high concentrations within the beetles’ galleries but available in only very low concentrations in the surrounding xylem. The concentration of elements was generally highest with X. saxesenii, followed by T. lineatum and E. dermestoides, which positively correlates with the degree of sociality and productivity of brood per gallery. We propose that the ambrosia fungal mutualists are translocating essential elements through their hyphae from the xylem to fruiting structures they form on gallery walls. Moreover, the extremely strong enrichment observed suggests recycling of these elements from the feces of the insects, where bacteria and yeasts might play a role.

Semiochemical-based integrated pest management of ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) in British Columbia’s forest industry: implemented in 1982 and still running

Three species of ambrosia beetles (Trypodendron lineatum (Olivier), Gnathotrichus sulcatus (LeConte), and G. retusus (LeConte) (Coleoptera: Curculionidae: Scolytinae)) have been estimated to cause annual losses of $95–$189 million in degrade of logs and lumber on the British Columbia coast, in Canada. A consultant-run semiochemical-based integrated pest management programme was implemented in 1982 against these beetles, following fulfilment of four prerequisites: (1) presence of receptive potential clients, (2) availability of semiochemical lures, (3) invention of an operational trap, and (4) proof of concept of mass trapping technology. The programme is based on two broad strategies: maintain the problem at a tolerable level and, if necessary, reduce the problem to a tolerable level. One measure of effectiveness over 12 years of mass trapping at a dryland sort near Sooke, on Vancouver Island, British Columbia, was 16.4 million beetles trapped and an estimated five to one benefit-to-cost ratio. Despite success, several factors have conspired to reduce the programme from 50 sites serviced in early years to 7 in 2018. Timber companies in British Columbia are currently showing renewed interest and are taking steps to incorporate the integrated pest management programme as a formal component of their overall operations.

Testing the Effect of Snag and Cavity Supply on Deadwood-Associated Species in a Managed Boreal Forest

Standing deadwood is an important attribute of old-growth boreal forests and it provides essential microhabitats for deadwood-associated species. In managed boreal forests, short rotations tend to limit the amount and diversity of standing deadwood. This study evaluates if the anthropogenic supply of deadwood attributes through tree girdling or by providing nest boxes may favor deadwood-associated species. We studied the short-term response of saproxylic beetles, foraging woodpeckers, and secondary cavity users to snag and cavity supply in 50 to 70-year-old black spruce stands. In spring 2015, we girdled 8000 black spruce according to two spatial distributions (uniform and clustered), and we also installed 450 nest boxes of six different sizes at three distances from the forest edge. Using trunk window traps, we captured significantly more beetles in sites with girdled trees than in control sites in both 2015 and 2016. We also recorded a trend of a greater abundance of beetles in clusters of girdled trees than within uniformly distributed girdled trees. Trypodendron lineatum (Oliver) dominated beetle assemblages, representing 88.5% of all species in 2015 and 74.6% in 2016. The number of beetles captured was 7× higher in 2015 than in 2016. In contrast, we observed greater amounts of woodpecker foraging marks in fall 2016 than in either fall 2015 or spring 2016. Woodpeckers foraged significantly more in clusters of girdled trees than within uniformly distributed girdled trees. Woodpeckers’ foraging mark presence was positively associated with the proportion of recent cuts at 1 km around the study sites. Five Boreal Chickadee (Poecile hudsonicus Forster) pairs used nest boxes and occupied smaller box sizes that were located away from the forest edge. Our study showed that structural enrichment can be effective in rapidly attracting deadwood-associated species within managed forest stands.

Occurrence of Gnathotrichus Materiarius (Fitch, 1858) (Coleoptera, Curculionidae, Scolytinae) in South-Western Poland

Gnathotrichus materiarius is listed as an alien ambrosia beetle in European fauna. This is an invasive species from North America, which was found in Europe (France) in the 1930s. In Poland, it was recorded in 2015. Already in 2017 numerous infestations of G. materiarius on lying Pinus sylvestris wood were obsereved. G. materairius is a xylomycophagous species and wood damage to its feeding is similar to that caused by striped ambrosia beetle Trypodendron lineatum. The paper presents sites of G. materairius occurrence found in 2016 and 2017. These include 15 sites located in managed forests (5 forest districts) as well as in 2 national parks situated along south-western border of Poland. G. materairius beetles were found in pheromone-baited traps used to monitor Ips duplicatus and I. amitinus or collected from infested Scots pine wood. The paper presents the description and characteristics of wood damage due to G. materiarius as well as its distinguishing features.

Extremely low infection levels of pathogens and nematodes in Trypodendron spp. (Coleoptera: Curculionidae)

The striped ambrosia beetles Trypodendron lineatum and T. domesticum are timber forest pests in the Palearctic region and North America. Because only a few pathogens are known for Trypodendron species, the aim of this work was to determine the spectrum of pathogen species of T. lineatum, T. laeve, and T. domesticum. Trypodendron species were collected in pheromone traps at nine localities in the Czech Republic, five localities in Poland, and one locality in Austria. In total, 2,439 T. lineatum, 171 T. domesticum, and 17 T. laeve beetles were dissected and examined. Infection was found in only two of the 17 specimens of T. laeve and in only two of the 171 specimens of T. domesticum; in all four cases, the parasites were nematodes. Parasitisation of T. lineatum by nematodes was found in T. lineatum at eight localities with a mean (± SE) parasitisation level of 8.1 ± 4.7%. A Chytridiopsis sp. was detected in cells of the midgut epithelium of one T. lineatum specimen, and Gregarina sp. was detected in the midgut lumen of two T. lineatum specimens; no other pathogens were found in T. lineatum. The low infection rates and the tendency for infection by nematodes can be explained by the monogamy of Trypodendron spp. and their feeding on fungi in short galleries that are not connected to the galleries of conspecifics.

Comparison of Trypodendron lineatum, T. domesticum and T. laeve (Coleoptera: Curculionidae) flight activity in Central Europe

The main goal of work was to compare the flight activity of Trypodendron lineatum, T. domesticum and T. laeve in Central Europe. Field trapping experiments were conducted in 70- to 100-year-old Norway spruce stands located at three study sites in the Czech Republic. At each study site five pheromone traps were used. Pheromone-baited, black, window-slot traps (Theysohn, Germany) were used. Traps were placed at log landing areas 10–15 m apart from the nearest forest edge. Each trap was baited with a standard synthetic pheromone lure, XL Ecolure (Fytofarm, Slovakia). Three species of Trypodendron were recorded. T. lineatum was the most abundant, followed by T. domesticum and T. laeve. Flight activity began at the end of March or in mid-April. Only one another peak of the flight activity of T. lineatum and T. domesticum was observed at one study site in May 2011. Statistically significant relationships were found between catches of all species with the exception of T. lineatum vs. T. laeve and T. domesticum vs. T. laeve at one site. Males were more abundant than females mainly in T. lineatum samples. On the other hand, T. domesticum and T. laeve abundances of males and females were more equal, but in all cases of all Trypodendron species these abundances were not significantly different at all sites.