Avocado Industry Research Articles

Avocadoes and Chinese cuisine

This paper presents the results of qualitative research undertaken in Singapore with consumers from various Asian ethnic backgrounds, with emphasis on Chinese-ethnic consumers. The study provides an understanding of consumers’ attitudes, behaviours and beliefs towards avocadoes Persea americana). It also presents the results of unstructured interviews conducted with representatives of the food service industry in Singapore. The study found that although avocados are gaining popularity in Asian markets consumption is still relatively low, with only a small portion of consumers purchasing them regularly. Avocados are not popular with Chinese consumers, as most find it hard to integrate the fruit in Chinese cooking. Avocados are not commonly used in Asian cuisine and are only used for entertaining guests during gatherings. Furthermore, as avocados are known as ‘butter fruit’ in Chinese, there are misconceptions as to the negative health aspects of the fruit. The Australian avocado industry is taking active steps to gain market access to the expanding Asian consumer market. As the phytosanitary protocol development process is time consuming, costly and resource intensive, the industry needs to ensure that such investment translates into trade success. Understanding consumer’s attitudes and interaction with avocados in the first step to plan market development activities and ensure export success. This study concludes that to increase avocado consumption with consumers from Chinese background, greater awareness of the different uses of avocados is needed and more consumer information is required to dispel any confusion about the health attributes of the fruit.

A review of the status of Avocado sunblotch viroid in Australia

Avocado sunblotch viroid (ASBVd) can seriously impact both the yield and quality of avocado fruit and is also a serious impediment to international trade because of quarantine conditions imposed by importing countries. The Australian avocado industry was among the first in the world to adopt control measures for ASBVd, an outcome of distinguished research done by Australian scientists during the 1970–80s. The status of ASBVd in Australia has not been recently reviewed and much information is either not published or difficult to find. In this review, this information has been collated and comment made on historical distribution and prevalence, in order to guide future surveys and to allow evaluation of the success of the control programs.

Exotic plant disease threats to the New Zealand avocado industry and climatic suitability: a review

The avocado industry was established in New Zealand from several importations dating back to 1907. Several serious pathogens found elsewhere in the world were not imported. A literature review and internet search were conducted to determine what serious avocado pathogens are not present in New Zealand and the potential impact they could have if they established. Relevant information was summarised for six pathogens determined to be the most serious of avocado and not known to be present in New Zealand: avocado sunblotch viroid (ASBVd); Pseudocercospora purpurea (cercospora spot); Raffaelea lauricola (laurel wilt); Fusarium sp. (fusarium dieback); Phellinus noxius (brown root rot); and Sphaceloma perseae (avocado scab). Laurel wilt, brown root rot, cercospora spot and fusarium dieback could become established in New Zealand if the climate here becomes warmer but establishment of ASBVd and avocado scab (which are not restricted to hot climates) is more likely.

Avocado fertilization: Matching the periodic demand for nutrients

Abstract The main objective of this study was to assess the seasonal nutrients requirement of ‘Hass’ avocado trees grown in lysimeters, especially during flowering and the early period of fruit development that may affect later on the fruitlet abscission and determine crop yield. The experimental design included three fertigation treatments applying a fixed nutrient solution at three different starting dates of fertigation: (a) T1 – continuous fertigation, including macro nutrients (N-P -K) and micronutrients application, all over the year; (b) T2 – no fertilization (only irrigation) until 15 March, and fertigation as T1 since then; (c) T3 - no fertilization (only irrigation) until 15 May, and fertigation as T1 since then. Absence of fertilization during the winter period induced leaf-chlorosis while healthy, dense and plenteously green leaves characterized the fertilized trees (T1). The beneficial effect of early fertigation on fruit yield was statistically significant, mostly because of higher fruit number. Leaf analyses are commonly used in the avocado industry as a guide for fertilization yet; fruits rather than leaves are the main products of avocado orchards. Consequently, fruit rather than leaf analyses should determine fertilization management. Based on fruit growth data and nutrient concentration in the fruit, the N, P and K quantities removed by ‘Hass’ avocado fruit yield of 30 t ha−1 were 120, 25 and 240 kg ha−1. Taking into account common efficiency consideration (nutrient quantities removed by fruit yield divided by quantities added), the annual quantities of N, P and K required for attaining high quality avocado yield are 250–300, 80–120 and 500–600 kg ha−1, respectively. Thus, fertilization rate together with nutrient combination should be modified in order to insure optimal fruit development.

Acoustic Detection ofMallodon dasystomus(Coleoptera: Cerambycidae) inPersea americana(Laurales: Lauraceae) Branch Stumps

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).

Spore Acquisition and Survival of Ambrosia Beetles Associated with the Laurel Wilt Pathogen in Avocados after Exposure to Entomopathogenic Fungi.

Laurel wilt is a disease threatening the avocado industry in Florida. The causative agent of the disease is a fungus vectored by ambrosia beetles that bore into the trees. Until recently, management strategies for the vectors of the laurel wilt fungus relied solely on chemical control and sanitation practices. Beneficial entomopathogenic fungi (EPF) are the most common and prevalent natural enemies of pathogen vectors. Laboratory experiments demonstrated that commercial strains of EPF can increase the mortality of the primary vector, Xyleborus glabratus, and potential alternative vectors, Xylosandrus crassiusculus, Xyleborus volvulus and Xyleborus bispinatus (Coleoptera: Curculionidae: Scolytinae). Our study provides baseline data for three formulated commercially-available entomopathogenic fungi used as potential biocontrol agents against X. crassiusculus, X. volvulus and X. bispinatus. The specific objectives were to determine: (1) the mean number of viable spores acquired per beetle species adult after being exposed to formulated fungal products containing different strains of EPF (Isaria fumosorosea, Metarhizium brunneum and Beauveria bassiana); and (2) the median and mean survival times using paper disk bioassays. Prior to being used in experiments, all fungal suspensions were adjusted to 2.4 × 106 viable spores/mL. The number of spores acquired by X. crassiusculus was significantly higher after exposure to B. bassiana, compared to the other fungal treatments. For X. volvulus, the numbers of spores acquired per beetle were significantly different amongst the different fungal treatments, and the sequence of spore acquisition rates on X. volvulus from highest to lowest was I. fumosorosea > M. brunneum > B. bassiana. After X. bispinatus beetles were exposed to the different suspensions, the rates of acquisition of spores per beetle amongst the different fungal treatments were similar. Survival estimates (data pooled across two tests) indicated an impact for each entomopathogenic fungus per beetle species after exposure to a filter paper disk treated at the same fungal suspension concentration. Kaplan–Meier analysis (censored at day 7) revealed that each beetle species survived significantly shorter in bioassays containing disks treated with EPF compared to water only. This study demonstrated that ambrosia beetles associated with the laurel wilt pathogen in avocados are susceptible to infection by EPF under laboratory conditions. However, the EPF needs to be tested under field conditions to confirm their efficacy against the beetles.

An Evaluation of Scent-discriminating Canines for Rapid Response to Agricultural Diseases

Laurel wilt disease, incited by Raffaelea lauricola, has resulted in the death of more than 300 million laurel trees (Lauraceae) in the United States. One such tree is the commercially important avocado (Persea americana), the second largest tree crop in Florida other than citrus (Citrus sp.). This disease affects the industry in South Florida and two larger avocado industries in Mexico and California have taken notice. Trees succumb soon after infection, and once external symptoms are evident, the disease is very difficult to control and contain as the pathogen can spread to adjacent trees via root grafting. Presently, there is no viable, cost-effective method of early diagnosis and treatment. This study was undertaken to evaluate the use of scent-discriminating canines (Canis familiaris) for the detection of laurel wilt–affected wood from avocado trees. Three canines, one Belgian Malinois and two Dutch Shepherds, were trained and studied for this ability. In addition, prevailing weather conditions were recorded and evaluated to determine their effect on canine performance. The results of this evaluation indicated that canines can detect laurel wilt–affected wood and the laurel wilt pathogen and may be useful in the detection of laurel wilt–diseased trees in commercial groves.

Proyecto de inversión de aguacate booth 8 en la huasteca veracruzana, una oportunidad de negocio para los productores como generador de divisas

La industria del aguacate en México, en los últimos años se ha incrementado notablemente, actualmente somos el primer país productor de aguacate, el fruto que es producido en nuestro país es destinado a mercados internacionales de gran valor como Estados Unidos, principal importador de aguacate que se produce en México, el aguacate es muy demandado tanto como en el mercado local, así como el internacional (SAGARPA, 2011). En este proyecto de inversión sobre la producción, comercialización y exportación del aguacate BOOTH 8 con las características de estudios como; mercado, técnico, organizacional y económico -financiero se dará a conocer un diagnostico situacional actual del aguacate en México y el mercado meta que será Estados Unidos, al cual se pretende exportar dicho fruto de la mejor manera. El proyecto de inversión para la producción, comercialización y exportación de aguacate de la variedad Booth 8, nos muestra que se cuenta con la información necesaria para producir, comercializar y exportarlo además se precisó el mercado meta donde arrojo que la parte del pacifico es donde hay más consumo del aguacate y que además prefieren de variedades verdes como lo son el Booth 8 y el Hass. Estados Unidos es un mercado amplio con más de 300 millones de habitantes casi el 45% consume el fruto del aguacate. El precio que se manejara en el mercado local será $15 por pieza y en el mercado meta elevara su costo a $35 por lo que concluimos que se puede decir que el proyecto de producción, comercialización y exportación de aguacate Booth 8 hacia el mercado meta, es factible y rentable.

Optimal Nutrient Concentration Ranges of ‘Hass’ Avocado Cauliflower Stage Inflorescences—Potential Diagnostic Tool to Optimize Tree Nutrient Status and Increase Yield

Optimizing ‘Hass’ avocado (Persea americana Mill.) tree nutrient status is essential for maximizing productivity. Leaf nutrient analysis is used to guide avocado fertilization to maintain tree nutrition. The goal of this research was to identify a ‘Hass’ avocado tissue with nutrient concentrations predictive of yields greater than 40 kg of fruit per tree. This threshold was specified to assist the California avocado industry to increase yields to ≈11,200 kg·ha−1. Nutrient concentrations of cauliflower stage inflorescences (CSI) collected in March proved better predictors of yield than inflorescences collected at full bloom (FBI) in April, fruit pedicels (FP) collected at five different stages of avocado tree phenology from the end of fruit set in June through April the following spring when mature fruit enter a second period of exponential growth, or 6-month-old spring flush leaves (LF) from nonbearing vegetative shoots collected in September (California avocado industry standard). For CSI tissue, concentrations of seven nutrients, nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg), sulfur (S), zinc (Zn), and copper (Cu) were predictive of trees producing greater than 40 kg of fruit annually. Conditional quantile sampling and frequency analysis were used to identify optimum nutrient concentration ranges (ONCR) for each nutrient. Optimum ratios between nutrient concentrations and yields greater than 40 kg per tree were also derived. The high nutrient concentrations characterizing CSI tissue suggest current fertilization practices (timing or amounts) might be causing nutrient imbalances at this stage of avocado tree phenology that are limiting productivity, a possibility that warrants further investigation. Because CSI samples can be collected 4–6 weeks before full bloom, nutritional problems can be addressed before they affect flower retention and fruit set to increase current crop yield, fruit size, and quality. Thus, CSI nutrient analysis warrants further research as a potential supplemental or alternative tool for diagnosing ‘Hass’ avocado tree nutrient status and increasing yield.

Quercivorol as a lure for the polyphagous and Kuroshio shot hole borers, Euwallacea spp. nr. fornicatus (Coleoptera: Scolytinae), vectors of Fusarium dieback.

The polyphagous shot hole borer and Kuroshio shot hole borer, two members of the Euwallacea fornicatus species complex (Coleoptera: Curculionidae: Scolytinae), are invasive ambrosia beetles that harbor distinct species of Fusarium fungal symbionts. Together with the damage caused by gallery construction, these two phytopathogenic Fusarium species are responsible for the emerging tree disease Fusarium dieback, which affects over 50 common tree species in Southern California. Host trees suffer branch dieback as the xylem is blocked by invading beetles and fungi, forcing the costly removal of dead and dying trees in urban areas. The beetles are also threatening natural riparian habitats, and avocado is susceptible to Fusarium dieback as well, resulting in damage to the avocado industries in California and Israel. Currently there are no adequate control mechanisms for shot hole borers. This paper summarizes efforts to find a suitable lure to monitor shot hole borer invasions and dispersal. Field trials were conducted in two counties in Southern California over a span of two years. We find that the chemical quercivorol is highly attractive to these beetles, and perform subsequent field experiments attempting to optimize this lure. We also explore other methods of increasing trap catch and effects of other potential attractants, as well as the deterrents verbenone and piperitone.

The role of Euwallacea nr. fornicatus (Coleoptera: Scolytinae) in the wilt syndrome of avocado trees in Israel

The polyphagous shot hole borer (PSHB), Euwallacea nr. fornicatus (Coleoptera; Scolytinae) has become a serious threat to the avocado industry and several shade tree species in Israel. Branch wilting and tree mortality is the outcome of PSHB galleries. Understanding the relationship between avocado trees and the PSHB is required for considering management strategies. In Israel, 52 tree species from 26 botanical families were attacked by the PSHB, but only 12 species were suitable for beetle reproduction. All examined avocado cultivars were attacked, but ‘Hass’ most severely. Large and medium diameter avocado branches were more resistant to PSHB, compared to thin branches. Effectively, gallery density increased as branch diameter decreased. Concomitantly, in large and medium diameter branches, extensive sugar exudation occurred and beetle attack rarely progressed to the formation of natal galleries, whereas minimal sugar exudation was observed in thin branches. This was more evident in those that were weakened by repeated attacks followed by successful beetle colonization. PSHB prefers and successfully colonized branches that had been previously attacked by its conspecifics, and reproduction was much higher in these branches, as opposed to initial attacks. Lesion frequencies increased from late spring (April) until late summer (September). Avocado branches at the early stages of beetle colonization may be identified by sugar exudation at the base of the thin branches. The main approach for reducing damage caused by the PSHB is sanitation, achieved by the removal of colonized branches and intact infested pruned slash.

Cold Disinfestation of "Hass" Avocado (Persia americana) of Three Species of Fruit Fly (Diptera: Tephritidae)-Ceratitis capitata, Ceratitis rosa, and Ceratitis cosyra.

The avocado industry is important in South Africa, but access to certain markets is impeded by the presence of phytosanitary pests. One of the ways of securing entry to these markets is to demonstrate that a mitigating treatment will result in there being a negligible chance of accidental importation. In cold treatment comparative studies at 0 °C and 2 °C of immature stages of Ceratitis capitata (Wiedemann), Ceratitis rosa Karsch, and Ceratitis cosyra (Walker) in "Hass" avocado, the third instar of C. cosyra was shown to be the most cold tolerant. This larval life stage was used in a large-scale trial to test treatment efficacy at 2 °C, a temperature known to be the better for fruit quality. There were no survivors from the 49,795 individual fruit fly larvae subjected to the cold treatment at 2 °C for 20 d. It is argued that, although this level of assessment falls short of the Probit 9 level normally required for fruit fly, they are rarely found in avocado fruit and that the level of disinfestation obtained is more than sufficient to achieve quarantine security.

The National Economic Benefits of Food Imports: The Case of U.S. Imports of Hass Avocados From Mexico

ABSTRACTImports of food products are often seen primarily as a threat to domestic producers while the broader economic impacts are ignored. Research on rapidly growing U.S. avocado imports has focused on the consequences for the U.S. avocado industry. This study conducts an economic impact analysis to measure the level and industry distribution of any benefits of U.S. imports of avocados from Mexico that may accrue to the U.S. national economy. We find that the US$1.5 billion in U.S. imports of Mexican avocados in 2015 had a positive and statistically significant effect on the U.S. economy in that year. Every dollar of avocado imports from Mexico in 2015 generated US$2.31 in U.S. output, US$1.41 in U.S. GDP, and US$0.79 in U.S. labor income. About 12.3 jobs were generated per US$1 million of imports. A separate econometric analysis corroborates the result. We conclude that imports of Mexican avocados are pro-growth for the U.S. economy.

Identification of preharvest factors determining postharvest ripening behaviors in ‘Hass’ avocado under long term storage

A major challenge for the global avocado industry is to provide a homogenous product in terms of fruit-ripening behavior, especially considering the significant variability in quality that can be found within a box or pallet of the fruit. The broad range of conditions under which trees are grown, particularly with regard to climate, soil and agronomical management, can influence this ripening variability. The aims of this study were (i) to determine the variability in fruit ripening among ‘Hass’ avocado grown under different conditions in Chile and (ii) to understand the postharvest fruit-ripening behavior of ‘Hass’ avocado due to the combined effect of several preharvest variables. Preharvest variables were evaluated at 42 experimental sites in Chile during three consecutive seasons. In addition, avocados with over 21% dry matter were collected at each site during each season and stored for 35d at 5°C under normal atmospheric conditions before being ripened at 20°C. Indicators of ripening behavior, such as the softening rate (SOFTRATE), change in peel color (COLO35) and days at 20°C necessary to reach the ready-to-eat stage (RTE35), were evaluated. As expected, high fruit variability in terms of ripening behavior was observed among the experimental sites and seasons. Multivariate analysis showed that the seasonal mean minimum air temperature, seasonal degree-days, trunk diameter and fruit firmness at harvest had a proportional relationship with postharvest SOFTRATE and COLOR35 during storage and a significant inverse relationship with RTE35. Conversely, the leaf area index, number of plants per hectare, and irrigation management at the bloom stage had a proportional relationship with RTE35 and an inverse relationship with SOFTRATE and COLOR35. Moreover, all of the three postharvest ripening behavior indicators were significantly (p<0.05) estimated by predictive models considering preharvest variables. Therefore, attempting to predict postharvest behavior by considering only a single preharvest variable could be a misleading simplification of reality because several factors, including climate/environmental, agronomic management and physiological variables, influence the ripening behavior of ‘Hass’ avocado fruit.

Recovery Plan for Laurel Wilt of Avocado, Caused by Raffaelea lauricola

Laurel wilt kills American members of the Lauraceae plant family, including avocado (Persea americana). The disease threatens commercial production in the United States and other countries, and currently impacts the avocado industry in Florida. As laurel wilt spreads, the National Germplasm Repository for avocado in Miami (USDA-ARS) and commercial and residential production in other states (e.g., California and Hawaii), U.S. protectorates (Puerto Rico), and other countries are at risk. In the United States, value-added production of avocado of more than $1.3 billion/year is threatened. This recovery plan was produced as part of the National Plant Disease Recovery System (NPDRS), called for in Homeland Security Presidential Directive Number 9 (HSPD-9) to insure that the tools, infrastructure, communication networks, and capacity required to mitigate the impact of high-consequence plant disease outbreaks are such that a reasonable level of crop production is maintained. It is intended to provide a brief primer on the disease, assess the status of critical recovery components, and identify disease management research, extension, and education needs.

Detection and Differentiation between Laurel Wilt Disease, Phytophthora Disease, and Salinity Damage Using a Hyperspectral Sensing Technique

Laurel wilt (Lw) is a fatal disease. It is a vascular pathogen and is considered a major threat to the avocado industry in Florida. Many of the symptoms of Lw resemble those that are caused by other diseases or stress factors. In this study, the best wavelengths with which to discriminate plants affected by Lw from stress factors were determined and classified. Visible-near infrared (400–950 nm) spectral data from healthy trees and those with Lw, Phytophthora, or salinity damage were collected using a handheld spectroradiometer. The total number of wavelengths was averaged in two ranges: 10 nm and 40 nm. Three classification methods, stepwise discriminant (STEPDISC) analysis, multilayer perceptron (MLP), and radial basis function (RBF), were applied in the early stage of Lw infestation. The classification results obtained for MLP, with percent accuracy of classification as high as 98% were better than STEPDISC and RBF. The MLP neural network selected certain wavelengths that were crucial for correctly classifying healthy trees from those with stress trees. The results showed that there were sufficient spectral differences between laurel wilt, healthy trees, and trees that have other diseases; therefore, a remote sensing technique could diagnose Lw in the early stage of infestation.

Distribution, Pest Status and Fungal Associates of Euwallacea nr. fornicatus in Florida Avocado Groves.

Members of a complex of cryptic species, that correspond morphologically to the ambrosia beetle Euwallacea fornicatus (Eichhoff) (Coleoptera: Curculionidae: Scolytinae), were recently found attacking avocado (Persea americana Mill.) in Israel and California. In early 2016, an outbreak of another member of this species complex was detected infesting approximately 1500 avocado trees in an avocado orchard at Homestead, Florida. An area-wide survey was conducted in commercial avocado groves of Miami-Dade County, Florida to determine the distribution and abundance of E. nr. fornicatus, to identify different populations of E. nr. fornicatus and their fungal associates, and to assess the extent of damage to avocado trees. Ewallacea nr. fornicatus were captured in 31 of the 33 sampled sites. A sample of 35 beetles from six different locations was identified as E. nr. fornicatus sp. #2, which is genetically distinct from the species causing damage in California and Israel. Eleven fungal associates were identified: an unknown Fusarium sp., AF-8, AF-6, Graphium euwallaceae, Acremonium sp. Acremonium morum, Acremonium masseei, Elaphocordyceps sp. and three yeast species. The unknown Fusarium isolates were the most abundant and frequently found fungus species associated with adult beetles and lesions surrounding the beetle galleries. In addition to fungal associates, three bacteria species were found associated with adult E. nr. fornicatus. Visual inspections detected significant damage in only two orchards. A large number of beetles were captured in locations with no apparent damage on the avocado trees suggesting that E. nr. fornicatus are associated with other host(s) outside the groves or with dead trees or branches inside the groves. More research is needed to determine the potential threat E. nr. fornicatus and its fungal associates pose to the avocado industry and agricultural and natural ecosystems in Florida.

Transcriptome responses of an ungrafted Phytophthora root rot tolerant avocado (Persea americana) rootstock to flooding and Phytophthora cinnamomi.

BackgroundAvocado (Persea americana Mill.) is a commercially important fruit crop worldwide. A major limitation to production is the oomycete Phytophthora cinnamomi, which causes root rot leading to branch-dieback and tree death. The decline of orchards infected with P. cinnamomi occurs much faster when exposed to flooding, even if flooding is only transient. Flooding is a multifactorial stress compromised of several individual stresses, making breeding and selection for tolerant varieties challenging. With more plantations occurring in marginal areas, with imperfect irrigation and drainage, understanding the response of avocado to these stresses will be important for the industry.ResultsMaintenance of energy production was found to be central in the response to flooding, as seen by up-regulation of transcripts related to glycolysis and induction of transcripts related to ethanolic fermentation. Energy-intensive processes were generally down-regulated, as evidenced by repression of transcripts related to processes such as secondary cell-wall biosynthesis as well as defence-related transcripts. Aquaporins were found to be down-regulated in avocado roots exposed to flooding, indicating reduced water-uptake under these conditions.ConclusionsThe transcriptomic response of avocado to flooding and P. cinnamomi was investigated utilizing microarray analysis. Differences in the transcriptome caused by the presence of the pathogen were minor compared to transcriptomic perturbations caused by flooding. The transcriptomic response of avocado to flooding reveals a response to flooding that is conserved in several species. This data could provide key information that could be used to improve selection of stress tolerant rootstocks in the avocado industry.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0893-2) contains supplementary material, which is available to authorized users.

Invasive Asian Fusarium – Euwallacea ambrosia beetle mutualists pose a serious threat to forests, urban landscapes and the avocado industry

Several species of the ambrosia beetle Euwallacea (Coleoptera: Curculionidae: Scolytinae) cultivate Ambrosia Fusarium Clade (AFC) species in their galleries as a source of food. Like all other scolytine beetles in the tribe Xyleborini, Euwallacea are thought to be obligate mutualists with their fungal symbionts. Published diversification-time estimates suggest that the Euwallacea – Fusarium symbiosis evolved once approximately 21 million years ago. Female Euwallacea possess paired oral mycangia within which foundresses transport their Fusarium symbiont vertically from their natal gallery to new woody hosts. During the past two decades, exotic Asian Euwallacea – Fusarium mutualists have been introduced into the United States, Israel and Australia. Because these invasive pests attack and can reproduce on living woody hosts, they pose a serious threat to native forests, urban landscapes and the avocado industry.

Temperature-Dependent Development ofXyleborus glabratus(Coleoptera: Curculionidae: Scolytinae)

Redbay ambrosia beetle, Xyleborus glabratus Eichhoff (Coleoptera: Curculionidae: Scolytinae), is a nonnative pest that transmits the pathogenic fungus Raffaelea lauricola T.C. Harr., Fraedrich & Aghayeva (Ophiostomatales: Ophiostomataceae), which causes laurel wilt disease in trees of the family Lauraceae. Laurel wilt is present in the commercial avocado (Persea americana Mill.; Laurales: Lauraceae) growing areas of Florida and poses a potential threat to the avocado industries of California and Mexico. The life cycle of X. glabratus was studied in avocado logs at 16, 20, 24, 28, and 32 °C. Xyleborus glabratus successfully completed its life cycle at 24, 28, and 32 °C, with the greatest oviposition and development rate at 28 °C. Development of the egg and pupal stages was studied at 12, 16, 18, 20, 24, 28, 32, and 36 °C. One linear and 7 nonlinear developmental models were used to estimate the temperature-dependent development of both stages. The linear model estimated the lower threshold temperatures for egg and pupal development to be 13.8 °C and 11.1 °C, respectively, and the degree-days (DD) for egg and pupal development to be 55.1 DD and 68.2 DD, respectively. The Brier-2, Ratkowsky, Logan, and polynomial models gave the best estimates for the temperature-dependent development of the egg stages, whereas the Brier-1, Logan, and polynomial models gave the best estimates of temperature-dependent development of the pupal stages. Our results suggested that the optimal temperature for development of X. glabratus was around 28 °C, and that temperature will play an important role in the spread and successful establishment of X. glabratus.