Ambrosia beetles have emerged as significant pests of avocado ((Persea americana Mill. [Laurales: Lauraceae])) due to their association with pathogenic fungal symbionts, most notably Raffaelea lauricola T.C. Harr., Fraedrich & Aghayeva (Ophiostomatales: Ophiostomataceae), the causal agent of the laurel wilt (LW) disease. We evaluated the interaction of ambrosia beetles with host avocado trees by documenting their flight height and daily flight periodicity in Florida orchards with LW. Flight height was assessed passively in three avocado orchards by using ladder-like arrays of unbaited sticky traps arranged at three levels (low: 0–2 m; middle: 2–4 m; high: 4–6 m). In total, 1,306 individuals of 12 Scolytinae species were intercepted, but six accounted for ~95% of the captures: Xyleborus volvulus (Fabricius) (Coleoptera: Curculionidae), Xyleborinus saxesenii Ratzeburg (Coleoptera: Curculionidae), Euplatypus parallelus (Fabricius) (Coleoptera: Curculionidae), Xyleborus bispinatus Eichhoff (Coleoptera: Curculionidae), Xyleborus affinis Eichhoff (Coleoptera: Curculionidae), and Hypothenemus sp. (Coleoptera: Curculionidae). The primary vector of R. lauricola, Xyleborus glabratus Eichhoff (Coleoptera: Curculionidae), was not detected. Females of X. volvulus showed a preference for flight at low levels and X. bispinatus for the low and middle levels; however, captures of all other species were comparable at all heights. At a fourth orchard, a baiting method was used to document flight periodicity. Females of X. saxesenii and Hypothenemus sp. were observed in flight 2–2.5 h prior to sunset; X. bispinatus, X. volvulus, and X. affinis initiated flight at ~1 h before sunset and Xylosandrus crassiusculus (Motschulsky) (Coleoptera: Curculionidae) at 30 min prior to sunset. Results suggest that ambrosia beetles in South Florida fly near sunset (when light intensity and wind speed decrease) at much greater heights than previously assumed and have species-specific patterns in host-seeking flight.

Like other ambrosia beetles, Xyleborus volvulus Fabricius (Coleoptera: Curculionidae) lives in a mutualistic symbiotic relationship with fungi that serve as food source. Until recently, X. volvulus was not considered a pest, and none of its symbionts were considered plant pathogens. However, recent reports of an association between X. volvulus and Raffaelea lauricola T.C. Harr., Fraedrich & Aghayeva (Ophiostomatales: Ophiostomataceae), the cause of the laurel wilt disease of avocado (Persea americana Mill. [Laurales: Lauraceae]), and its potential role as vector of the pathogen merit further investigation. The objective of this study was to evaluate three artificial media containing sawdust obtained from avocado or silkbay (Persea humilis Nash) for laboratory rearing of X. volvulus. The effect of R. lauricola in the media on the beetle’s reproduction was also evaluated. Of the three media, the one with the lowest content of sawdust and intermediate water content provided the best conditions for rearing X. volvulus. Reproduction on this medium was not affected by the sawdust species or the presence of R. lauricola. On the other two media, there was a significant interaction between sawdust species and R. lauricola. The presence of R. lauricola generally had a negative effect on brood production. There was limited colonization of the mycangia of X. volvulus by R. lauricola on media inoculated with the pathogen. From galleries formed within the best medium, there was 50% recovery of R. lauricola, but recovery was much less from the other two media. Here, we report the best artificial substrate currently known for X. volvulus.

Introduction: Ambrosia beetles maintain strict associations with specific lineages of fungi. However, anthropogenic introductions of ambrosia beetles into new ecosystems can result in the lateral transfer of their symbionts to other ambrosia beetles. The ability of a Florida endemic ambrosia beetle,Xyleborus bispinatus, to feed and establish persistent associations with two of its known symbionts (Raffaelea subfuscaandRaffaelea arxii) and two other fungi (Harringtonia lauricolaandFusariumsp. nov.), which are primary symbionts of invasive ambrosia beetles, was investigated.Methods: The stability of these mutualisms and their effect on the beetle’s fitness were monitored over five consecutive generations. Surface-disinfested pupae with non-developed mycangia were reared separately on one of the four fungal symbionts. Non-treated beetles (i.e., lab colony) with previously colonized mycangia were used as a control group.Results: Xyleborus bispinatuscould exchange its fungal symbionts, survive, and reproduce on different fungal diets, including known fungal associates and phylogenetically distant fungi, which are plant pathogens and primary symbionts of other invasive ambrosia beetles. These changes in fungal diets resulted in persistent mutualisms, and some symbionts even increased the beetle’s reproduction. Females that developed onFusariumsp. nov. had a significantly greater number of female offspring than non-treated beetles. Females that fed solely onHarringtoniaorRaffaeleasymbionts produced fewer female offspring.Discussion: Even though some ambrosia beetles likeX. bispinatuscan partner with different ambrosia fungi, their symbiosis under natural conditions is modulated by their mycangium and possibly other environmental factors. However, exposure to symbionts of invasive beetles can result in stable partnerships with these fungi and affect the population dynamics of ambrosia beetles and their symbionts.

In the last decade in South Florida, approximately 200,000 avocado trees have succumbed to laurel wilt (LW), a fungal disease vectored by ambrosia beetles. Sanitation (e.g., pruning, stumping, and removal of LW–affected trees) and replanting with young trees are cultural practices currently used by avocado growers to reduce the incidence of LW. Surveillance in these managed orchards suggests a decline in ambrosia beetle abundance, and previous research determined that female flight activity is influenced by light intensity. Therefore, we investigated the effect of three canopy covers (i.e., full canopy, topworked, and new planting) on ambrosia beetle abundance. A total of 28,184 individuals, representing 15 species within Scolytinae and Platypodinae, were captured passively in three LW–affected avocado orchards over a one-year period. Full canopy cover exhibited the highest number of beetles and the lowest light intensity. The opposite was found for topworked and new planting covers. Additionally, we documented the effect of meteorological factors on the flight dispersal of five species known to vector the LW pathogen. The flight activity of Xylosandrus crassiusculus and Xyleborinus saxesenii was highly influenced by abiotic factors (R² > 0.50), especially solar radiation, whereas the flight of Xyleborus affinis, Xyleborus volvulus, and Xyleborus bispinatus was only partially explained by climatic variables (0.20 < R² < 0.30). Our results indicate that reducing canopy cover, thereby increasing light intensity, suppresses ambrosia beetle abundance, especially for species associated with the LW pathogen. Abiotic factors play a critical role in the dispersal of invasive species (X. crassiusculus and X. saxesenii), but their effect is less pronounced on native species (X. affinis, X. volvulus, and X. bispinatus). Canopy management alters the microclimatic conditions in avocado orchards, affecting ambrosia beetle abundance and flight activity.

Mallodon dasystomus Say (Coleoptera: Cerambycidae: Prioninae) is a pest of hardwood trees in the southern United States that recently began attacking trees in avocado groves in Miami-Dade County, Florida. The larvae feed hidden inside the tree, and adult attractants have not been commercialized; consequently, this species is difficult to find in field environments. It was of interest to consider the potential use of insect acoustic detection devices to help survey the magnitude and locations M. dasystomus populations in commercial avocado groves so that the extent of their economic damage could be estimated. An insect acoustic detection system was tested in 2 avocado groves on 11 trees suspected of harboring infestations. Four infested trees were identified and 6 were correctly classified as uninfested. One uninfested tree was classified as infested, possibly due to the occurrence of wind during signal recording. The use of acoustic methods to detect M. dasystomus can be of benefit in estimating its economic damage to the Florida avocado industry already facing losses from laurel wilt, caused by Raffaelea lauricola, Harrington, Fraedrich, and Aghayeva (Ophiostomataceae), vectored by redbay ambrosia beetle Xyleborus glabratus Eichhoff (Coleoptera: Curculionidae) (Ploetz et al. 2017), and Fusarium (Hypocreaceae) dieback, vectored by Euwallacea nr. fornicatus (Coleoptera: Curculionidae) (Carrillo et al. 2016; Kendra et al. 2017). Mallodon dasystomus Say es una plaga de árboles de madera dura en el sur de los Estados Unidos que recientemente comenzó a atacar árboles en las plantaciones de aguacate en el condado de Miami-Dade, FL. Las larvas se alimentan de manera oculta dentro del árbol y los atrayentes adultos no se han comercializado; en consecuencia, esta especie es difícil de encontrar en ambientes de campo. Fue de interes considerar el uso potencial de los aparatos de detección acústica de insectos para ayudar a estudiar la magnitud y la ubicación de las poblaciones de M. dasystomus en las plantaciones comerciales de aguacate, de manera que se pueda estimar el alcance de su daño económico. Se probó un sistema de detección acústica de insectos en dos plantaciones de aguacate con 11 árboles sospechosos de tener infestaciones. Se identificaron cuatro árboles infestados y 6 se clasificaron correctamente como no infestados. Un árbol no infestado se clasificó como infestado, posiblemente debido al viento que sucedió durante el registro de la señal. El uso de métodos acústicos para detectar M. dasystomus puede ser beneficioso para estimar su daño económico a la industria del aguacate de la Florida que ya enfrenta pérdidas por marchitez de laurel, causada por Raffaelea lauricola Harrington, Fraedrich y Aghayeva, transmitido por Xyleborus glabratus Eichhoff, el escarabajo descortezador de “redbay” (Persea borbonia) (Ploetz et al., 2017), y muerte regresiva por Fusarium, transmitida por Euwallacea cr. fornicatus (Carrillo et al., 2016; Kendra et al., 2017).

Like other members of the tribe Xyleborini, Xyleborus bispinatus Eichhoff can cause economic damage in the Neotropics. X. bispinatus has been found to acquire the laurel wilt pathogen Raffaelea lauricola (T. C. Harr., Fraedrich & Aghayeva) when breeding in a host affected by the pathogen. Its role as a potential vector of R. lauricola is under investigation. The main objective of this study was to evaluate three artificial media, containing sawdust of avocado (Persea americana Mill.) and silkbay (Persea humilis Nash.), for rearing X. bispinatus under laboratory conditions. In addition, the media were inoculated with R. lauricola to evaluate its effect on the biology of X. bispinatus. There was a significant interaction between sawdust species and R. lauricola for all media. Two of the media supported the prolific reproduction of X. bispinatus, but the avocado-based medium was generally more effective than the silkbay-based medium, regardless whether or not it was inoculated with R. lauricola. R. lauricola had a neutral or positive effect on beetle reproduction. The pathogen was frequently recovered from beetle galleries, but only from a few individuals which were reared on inoculated media, and showed limited colonization of the beetle’s mycangia. Two media with lower water content were most effective for rearing X. bispinatus.