Paola Gonzalez-Audino

Effect of release rate and enantiomeric composition on response to pheromones of Megaplatypus mutatus (Chapuis) in poplar plantations of Argentina and Italy.

Megaplatypus mutatus (=Platypus sulcatus Chapuis) is an Ambrosia beetle native to South America, which was recently introduced in Italy and its presence there is causing severe damage to the local poplar plantations. The male M. mutatus pheromone is composed of (S)-(+)-6-methyl-5-hepten-2-ol [(+)-sulcatol], 6-methyl-5-hepten-2-one (sulcatone) and 3-pentanol. A series of field trials testing dose, blend and enantiomer composition performed in Argentina and Italy evaluated attraction and found that the optimal release rate of pheromone components as baits in cross vane baited traps (CIPEIN-CV) was 6, 6 and 30 mg day−1 of sulcatone, (+)-sulcatol and 3-pentanol, respectively. It was also determined that racemic sulcatol is as effective as the pure (+)-isomer for the purpose of beetle catch, due to the inert nature of the (−)-isomer allowing the usage of low cost racemic sulcatol instead of highly expensive (+)-sulcatol. The results of our work contribute to the development of pheromone-based local technologies with low environmental impact and low cost for control or monitoring of an important pest.

Pheromone detection of the introduced forest pest Megaplatypus mutatus (=Platypus mutatus) (Chapuis) (Platypodinae, Curculionidae) in Italy

Megaplatypus mutatus (Chapuis) (=Platypus mutatus), an ambrosia beetle native to South America, attacks standing live trees of a wide range of forest and fruit tree species, and it is particularly damaging to commercial poplar plantations. In 2000, M. mutatus was observed for the first time in Italy, in the province of Caserta, near Naples. The development of a pheromone-based monitoring system, for detecting the spread and for managing M. mutatus infestations, is an important goal for both European and South American control and surveillance programs. Using a three component pheromone blend developed in Argentina into commercial funnel traps we were able to asses the level of dispersion of this pest in the Italian Campania region. Insects were captured in all the plantations suspected of being infested based on the presence of active parental and larval galleries. We also provide the first report of the attack followed by completion of the life cycle of M. mutatus in European hazelnut, Corylus avellana L. (Betulaceae), an important nut species native to Europe and Western Asia.

Anatomical site of pheromone accumulation and temporal pattern of pheromone emission in the ambrosia beetle Megaplatypus mutatus

Megaplatypus mutatus (Chapuis) is a native South American ambrosia beetle that attacks live hardwood trees (e.g. Populus spp.), causing important economic losses to commercial plantations. Male beetles release the main components of the sex pheromone, namely (+)‐6‐methyl‐5‐hepten‐2‐ol [(+)‐sulcatol, or retusol] and 6‐methyl‐5‐hepten‐2‐one (sulcatone), when colonizing suitable hosts. The hindgut is shown to be the anatomical site of pheromone accumulation within males, the enantiomeric composition of sulcatol in this tissue is 99%‐(+) and sulcatol is first detectable in this tissue on days 1–2 after gallery initiation. Peak accumulation of sulcatol occurs on days 5–12 after gallery initiation. Trace quantities of sulcatone are also observed during the same period. Both pheromone components are present in male emissions from three host species (Populus×canadensis, Populus alba and Casuarina stricta) between days 2 and 12 after gallery initiation, although sulcatone is always present in low concentrations. The temporal patterns of sulcatol and sulcatone accumulation or storage in male M. mutatus correspond to the temporal patterns of emission.

Modulation of the behavioral and electrical responses to the repellent DEET elicited by the pre-exposure to the same compound in Blattella germanica.

Insects under different stimuli from the environment modify behavioural responses due to changes in the sensitivity of neurons at the peripheral and/or at the central level of the nervous system. This phenomenon is called neuronal plasticity, and sensory adaptation is an example of it. An insect repellent is a chemical that produces oriented movements of the insects away from its source. In this work we studied the modulation of the behavioural and electrical response to the repellent N, N-diethyl-3-methylbenzamide (DEET) in males of the German cockroach B. germanica produced by previous exposure to the same repellent. Methods. We determined repellency using a circular arena, one half of which was treated with DEET. The time spent by insects in each half of the arena was measured, and a repellency coefficient (RC) was calculated. The RCs of pre-exposed and non-pre-exposed insects were compared. To determine a possible role of nitric oxide in the modulation of the response to DEET after pre-exposure, the nitric oxide donor S-nitroso-acetyl-cysteine (SNAC) was applied on cockroaches’ antennae. The electrical activity of the cockroaches’ antennae in response to DEET was recorded using electroantennogram (EAG) technique. The response to DEET was recorded also after a long stimulation with the same repellent, and after topical application of SNAC and dbcGMP (a cGMP analogue) on the antennae. Results. We found that previous exposure of B. germanica males to the repellent DEET produced an increase of the repellency at the behavioural level, measured as RC. A possible role of nitric oxide (NO) in the transduction pathway of this phenomenon is suggested, since treatment of the cockroaches with the NO donor SNAC also produced an increase of the repellency elicited by DEET. On the other hand, the response of the cockroaches’ antennae exposed to DEET was determined electrophysiologically. The electrical activity in response to DEET decreased when the insects’ antennae were stimulated with a long pulse of the repellent. The activity of the antennae was restored after 10 min. Treatment of the antennae either with SNAC or dbGMPc also produced a decrease in the response of the antennae to the repellent. Discussion.The previous exposure to a chemical stimulus can modify the behaviour associated to the same stimulus, increasing or decreasing the behavioural response. In the case of DEET we found that pre-exposure increased DEET repellency in male cockroaches. We also found NO involvement in a similar phenomenon. On the other hand, the test showed that DEET is perceived by insects’ antennae as an odour. A long exposure of the antennae to DEET caused a transient decrease in the response of the antennae to the same compound. The same effect was achieved by treating the antennae with SNAC or dbcGMP, suggesting the involvement of the NO/cGMP system in the transduction pathway of the sensory adaptation phenomenon elicited by an odour in this species.

A floral‐derived attractant for Aedes aegypti mosquitoes

The reproductive success of Aedes aegypti (L.) (Diptera: Culicidae) is strongly dependent on the availability of carbohydrates in the environment and the ability of the mosquitoes to locate them. The most significant source of carbohydrates for mosquitoes is nectar from flowering plants, which mosquitoes locate by their volatile compounds. The aim of our work was to identify plant volatile compounds that elicit a behavioral response in Ae. aegypti, which may be included in a mosquito trap for surveillance and/or control purposes. Landing‐preference bioassays were performed with plants of three species—Plectranthus neochilus Schltr. (Lamiaceae), Tagetes patula L. (Asteraceae), and Lobularia maritima (L.) Desv. (Brassicaceae)—as lures and toxic sugar baits as landing markers. Mosquitoes landed only on L. maritima. Freshly cut inflorescences of L. maritima elicited a positive flight response in both sexes of mosquitoes. The analysis of the compounds in the static head space of L. maritima was performed by solid phase microextraction (SPME). Of the single volatile compounds tested, acetophenone was attractive and 1‐octanol caused a flight aversive response. These findings are relevant as there are no reported plant‐derived compounds attractive to A. aegypti. As both the male and female mosquitoes sugar feed, traps baited with plant odors are able to lure the whole adult population, making it an interesting option for including in future mosquito surveillance traps.

Monolithic dispensers for pheromones and their use in mating disruption of the ambrosia beetle Megaplatypus mutatus in poplar plantations

Megaplatypus mutatus (formerly Platypus mutatus) (Chapuis) is an ambrosia beetle native to South America that attacks standing live trees, mining deeply into the xylem through large tunnels. This activity weakens the structural integrity of the tree, causing severe stem‐breakage and mortality. Attacks are initiated by pioneer males that select a host tree and build short nuptial galleries to which they attract females using a sex pheromone. Volatiles emitted are composed of (+)‐6‐methyl‐5‐hepten‐2‐ol [(+)‐sulcatol], 6‐methyl‐5‐hepten‐2‐one (sulcatone) and 3‐pentanol. Previously, we showed the potential of the strategy of pheromone‐mediated mating disruption of M. mutatus in commercial poplar and hazelnut plantations in South America and Europe using polyethylene reservoir dispensers for pheromones and found that damage reduction was greater than 56% in all cases. In the present study, the polymeric reservoir dispensers were replaced by matrix dispensers made by dispersion of the pheromone in natural waxes or polyethylene glycols that act as a matrix with the addition of a filler. After treatment, the number of mating galleries was significantly higher (70%) in control than in treated areas. Using natural materials for dispensers, we confirmed that mating disruption is a viable tool for the management of M. mutatus in poplar plantations.

Response of Pediculus humanus capitis (Phthiraptera: Pediculidae) to Volatiles of Whole and Individual Components of the Human Scalp

Abstract The head louse Pediculus humanus capitis (De Geer) (Phthiraptera: Pediculidae) is a cosmopolitan human ectoparasite causing pediculosis, one of the most common arthropod parasitic conditions of humans. The mechanisms and/or chemicals involved in host environment recognition by head lice are still unknown. In this study, we evaluated the response of head lice to volatiles that emanate from the human scalp. In addition, we identified the volatile components of the odor and evaluated the attractive or repellent activity of their pure main components. The volatiles were collected by means of Solid Phase microextraction and the extract obtained was chemically analyzed by gas chromatograph-mass spectrometer. Twenty-four volatile were identified in the human scalp odor, with the main compounds being the following: nonanal, sulcatone, geranylacetone, and palmitic acid. Head lice were highly attracted by the blend human scalp volatiles, as well as by the individual major components. A significant finding of our study was to demonstrate that nonanal activity depends on the mass of the compound as it is repellent at high concentrations and an attractant at low concentrations.The results of this study indicate that head lice may use chemical signals in addition to other mechanisms to remain on the host.

Physicochemical Properties and Field Evaluation of Monolithic Wax Formulations for the Controlled Release of a Forest Pest Pheromone

Fil: Slodowicz, Mariel Pamela. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Instituto de Investigaciones Cientificas y Tecnicas para la Defensa. Centro de Investigacion de Plagas e Insecticidas; Argentina

Volatile Organic Compounds from the Clone Populus x canadensis “Conti” Associated with Megaplatypus mutatus Attack

Megaplatypus mutatus (Chapuis) (Coleoptera, Platypodidae) is an ambrosia beetle native to South America. It builds internal galleries that weaken the tree trunks, causing them severe stem breakage and mortality in commercial poplar plantations. The host selection by male M. mutatus has previously been correlated with the increasing diameter. This work explores the possibility that differential susceptibility of individual plants to M. mutatus could be associated with volatiles emitted. The comparison of the VOCs profiles of attacked and nonattacked P. x canadensis “Conti” 12 during M. mutatus flying season showed both qualitative and quantitative differences. The attacked plants, but not the nonattacked ones, showed the following compounds: a long chain aldehyde, α-ylangene, δ-cadinene, α-gurjunene, and β-cubebene; on the other side, β-sesquiphellandrene and β-chamigrene were detected only in nonattacked plants. α-Copaene is a common component of all the samples analyzed, but its proportion is increased in attacked individuals. Behavioral bioassays showed that males but not females M. mutatus are attracted to α-copaene. The relative increase of α-copaene in attacked individuals and the positive behavioral answer of males to it suggest that this compound could play a role in the orientation of the pioneer male towards the most suitable host.