No abstract

Megaplatypus mutatus (Chapuis) (Coleoptera: Platypodidae) is an ambrosia beetle native to South America that causes economic loss and was recently introduced to Italy, where it attacks and damages live poplar trees. Sulcatol and sulcatone are male‐produced pheromone components involved in the mating process of M. mutatus. Their relative proportions are highly variable among insects, although the temporal pattern shows that initially only sulcatol is present, and sulcatone increases with time, until they are finally both depleted. Sulcatol and sulcatone may be produced de novo by the beetles, they may be produced by fungi, or both pathways may contribute to their production. Sulcatol is stored in the males’ hindgut but sulcatone is only present in emissions, so there is an oxidation process to transform the alcohol to the ketone before or during pheromone release. It is our hypothesis that fungi associated with M. mutatus are responsible for this process. In this work, we studied a possible contribution of associated microorganisms in the conversion of sulcatol into sulcatone and its consequent role in the temporal release pattern of these sex pheromone components observed in male insects. Moreover, we inhibited the postulated enzymes involved in this pheromone conversion process – 3‐hydroxy‐3‐methyl‐glutatyl‐CoA reductase (HMGR) and P450 enzymes of a fungal strain – and added an antibiotic and a fungicide to the homogenate during sulcatol‐sulcatone conversion. Among the fungal species, particular interest was given to Graphium basitruncatum (Matsush.) Seifert & Okada (Microascales), as it is present in male but not in female exoskeletons and in insect gallery samples, suggesting a possible different role in pherome production, as the male is the pheromone‐producing sex. Several isolated strains were able to convert sulcatol to sulcatone, whereas the fungus G. basitruncatum showed the highest production of this ketone. Additionally, inhibition of P450 enzymes and HMGR from G. basitruncatum on this alcohol‐ketone conversion demonstrated that HMGR is involved in sulcatone generation using sulcatol as precursor, and that P450 enzymes are not. Finally, sulcatone production diminished significantly in homogenized tissues of male and female M. mutatus following addition of an antibiotic and a fungicide. The results suggest that fungi associated with M. mutatus are involved in pheromone production.

This work shows the way to develop a monolithic device for the release of an active agent. Different waxes to prepare monolithic dispensers were used. Studies to characterize the release rate of the pheromone dispensers, and to determine many physicochemical properties of the active components and waxes utilized as matrices, were conducted. The advantages of using monolithic devices as an insect pheromone dispenser in order to control an insect that attacks commercial poplar plantations were demonstrated. Also, the practical application employing monolithic dispensers manufactured in this paper with the sex pheromone of the ambrosia beetle Megaplatypus mutatus (Coleoptera: Platypodidae) was verified. This forest pest is known to attack tree plantations in South America. The release rates were mainly dependent of matrix hardness and viscosity, as well as the particle size of fillers. A good performance of the formulated monolithic dispensers was observed during the field trials, with a reduction of damage levels of 40%.

Studies involving biological control of wood decay fungi and pests in forest areas are scarce. The basidiomycete Granulobasidium vellereum (Ellis & Cragin) Jülich has been isolated as wood endophyte from London Plane trees (Platanus acerifolia (Ait.) Willd). This basidiomycete produces a variety of sesquiterpenes with antifungal activity. In this study we evaluated the potential activity of G. vellereum against wood decay fungi and fungi associated with the ambrosia beetle Megaplatypus mutatus Chapuis, an important forest pest in Populus sp. A combination of in vitro assays was made, in cultures and on wood blocks. Granulobasidium vellereum's Volatile Organic Compounds (FVOCs) were characterized and their potential role in biocontrol was assessed. Granulobasidium vellereum did not cause a significant loss of weight on P. acerifolia and Populus wood and inhibited the growth of the target fungi, mainly when inoculated first. Up to nineteen volatile compounds were determined in G. vellereum strains. The growth of all target fungi was inhibited by FVOCs and in some cases the morphology of the fungi was altered. These results indicate that G. vellereum can be used as a Biological Control Agent (BCA) of xylophagous fungi and fungi related to forest pests. Further investigations should focus on developing application strategies for M. mutatus management.