<Emphasis Type="Italic">Colletotrichum acutatum</Emphasis> occurs asymptomatically on apple leaves

Fungi within the Colletotrichum acutatum species complex occur asymptomatically on plant parts of many different plant species. Leaves from apple orchards in southern Norway were sampled, frozen for five hours and incubated for six days to reveal presence of asymptomatic infections of C. acutatum. Number of leaves (incidence) and leaf area covered (severity) with conidial masses of C. acutatum were assessed biweekly on cv. Aroma from late May to late September during three growing seasons. The first finding of conidial masses occurred in the second half of July, and there was a higher incidence occurring in August and September. Sampling of leaves from fruit spurs and vegetative shoots of cvs. Aroma and Elstar showed that conidial masses of C. acutatum developed on leaves on both shoot types, and there was no difference in incidence between these two types. The fungus was detected on leaves from six of eight commercial orchards of cv. Aroma over three years, with a mean incidence of 5.5 %. After storage, bitter rot was found on apple fruit from all eight orchards. There was no correlation between incidence of conidial masses of C. acutatum on leaves and on fruit. In all orchards and seasons investigated, incidence and severity on leaves varied from 0 to 67 % and 0 to 85 %, respectively. The discovery of apple leaves containing conidial masses of C. acutatum clearly indicate for leaves as a potential source of inoculum for fruit infections.     

Quantitative detection of <Emphasis Type="Italic">Colletotrichum godetiae</Emphasis> and <Emphasis Type="Italic">C. acutatum sensu stricto</Emphasis> in the phyllosphere and carposphere of olive during four phenological phases

A duplex qPCR detection method was developed to detect and quantify Colletotrichum godetiae and C. acutatum sensu stricto (s.s.) in olive tissues. The method proved highly specific and sensitive with a detection limit of 10 pg for each pathogen. The analysis of green and senescent leaves, fertilized fruitlets with floral residues, green fruit and symptomatic and asymptomatic fruit collected in May, June, October and December revealed a high incidence of both C. godetiae and C. acutatum s.s. in Calabria, southern Italy. In comparison with previous reports, these results highlighted an ongoing population shift from C. godetiae to C. acutatum s.s. Interestingly, C. godetiae was slightly more abundant in terms of number of infected samples, yet the quantity of C. acutatum in infected samples was always higher, suggesting greater aggressiveness and/or sporulation ability of the latter pathogen. The populations of both C. godetiae and C. acutatum s.s. increased sharply in December even though both pathogens were detected widely in asymptomatic samples in May, June and October, confirming an important role of latent infections in the disease cycle. A large quantity of both C. godetiae (1.7 × 10⁸ cells/mg of tissue) and C. acutatum s.s. (7.5 × 10⁸ cells/mg of tissue) was estimated in symptomatic fruit, presenting an enormous inoculum potential for secondary infections. Two other important observations were a high incidence and quantity of both pathogens in senescent leaves and in fertilized fruitlets with floral residues as compared to green leaves.     

Epidemiology of apple bitter rot caused by <Emphasis Type="Italic">Colletotrichum acutatum sensu lato</Emphasis>

Apple bitter rot caused by Colletotrichum acutatum sensu lato results in fruit decay before and after harvest. We investigated the epidemiology of the disease in terms of conidial formation and dispersal as well as the change in susceptibility of fruits in Iwate, Japan. Conidia of C. acutatum were detected in rainwater collected from inside the tree canopy from May to August with peaks in production in mid-May to early June and mid- to late July. The first peak corresponded to the most conidia being produced on fruit scars, but the second peak was due to conidiation on mummified fruitlets and peduncles collected in July. Inoculation experiments revealed that fruits were susceptible to the pathogen between 20 and 90 days after petal fall and that immature fruits infected as early as 20 days after petal fall frequently developed lesions on the lower fruit half as growth progressed. These results suggest that C. acutatum sporulates on infested fruit scars to infect immature fruits, resulting in bitter rot and that the fungus also colonizes mummified fruitlets and peduncles, contributing to survival of the pathogen on fruit scars. Thus, infested fruit scars represent the primary source of inoculum.     

Assessment of the baseline sensitivity and resistance risk of <Emphasis Type="Italic">Colletotrichum acutatum</Emphasis> to fludioxonil

Anthracnose, which is caused by Colletotrichum acutatum, is a destructive disease of pepper. A preliminary study demonstrated that fludioxonil (a phenylpyrrole fungicide) has good activity against C. acutatum and thus has potential to be used as an alternative fungicide for the management of pepper anthracnose. However, there is no information regarding the baseline sensitivity and resistance risk of C. acutatum to fludioxonil. Thus, the sensitivities of 205 isolates of C. acutatum to fludioxonil were determined. The results showed that the frequency distributions of the EC₅₀ values were unimodal, and the mean EC₅₀ values for the inhibition of mycelial growth and spore germination were 0.031 μg/mL and 0.035 μg/mL, respectively. Three stable mutants with high resistance to fludioxonil were obtained in the laboratory. Two parameters, namely in vitro sporulation and the in vitro and in vivo germination of spores, showed significant difference (P < 0.01) when the mutants were compared to the sensitive isolates. Moreover, the mutants were more sensitive to osmotic stress compared to the parents. No significant differences (P ≥ 0.05) were detected in colony diameter, mycelia weight, pathogenicity or sporulation in vivo between the fludioxonil-resistant mutants and their corresponding parents. Cross-resistance occurred between fludioxonil, iprodione and procymidone. Overall, resistance risk of C. acutatum to fludioxonil was low to medium, and thus resistance management should be considered.     

Characterization of <Emphasis Type="Italic">Phaeoacremonium</Emphasis> isolates associated with Petri disease of table grape in Northeastern Brazil,with description of <Emphasis Type="Italic">Phaeoacremonium nordesticola</Emphasis> sp. nov.

Severe outbreaks of Alternaria leaf blotch and fruit spot were recently observed in cv. Pink Lady apples in northern Israel, especially on fruit. Such severe outbreaks have not been reported from other countries. Symptoms involved cracks and rot around the calyx and external rot of the fruit body. Up to 80 % of the fruit in some orchards were affected by the disease. Microscopic examinations, fulfillment of Koch’s postulates and molecular (genetic) analyses confirmed the causal agent as Alternaria alternata f. sp. mali. The incidence of Alternaria increased as the degree of calyx cracking increased, or if fruit were both cracked and rotted. Injecting spore suspensions into the fruit produced typical rot symptoms. Injection assays of detached fruit of eight apple cultivars showed that cvs. Pink Lady and Golden Delicious were susceptible whereas cv. Jonathan was resistant. Pink Lady and Golden Delicious produced more fruit rot as the inoculum concentration increased. Rot in all three cultivars was moderate close to the skin but more severe close to the seed locule. Aqueous extracts taken from Jonathan fruit peel inhibited germ tube elongation of A. alternata f. sp. mali in vitro. This is the first report on heavy infection of Pink Lady fruit in Israel caused by A. alternata f. sp. mali.     

Identification and characterization of <Emphasis Type="Italic">Colletotrichum</Emphasis> spp. associated with chili anthracnose in peninsular Malaysia

Anthracnose fruit rot caused by Colletotrichum spp. is a serious post-harvest disease of chili fruits (Capsicum spp.). One hundred-thirty isolates of Colletotrichum spp. were isolated from anthracnose of green and red cayenne pepper (Capsicum annuum) and bird’s eye chili (Capsicum frutescens). The isolates were morphologically identified as Colletotrichum acutatum sensu lato (62 isolates), Colletotrichum truncatum (54 isolates), and Colletotrichum gloeosporioides sensu lato (14 isolates). Molecular identification and phylogenetic analyses were based on internal transcribed spacer regions, β-tubulin, actin, and glyceraldehyde-3-phosphate dehydrogenase genes, and the isolates were re-identified as C. scovillei (58 isolates), C. truncatum (54 isolates), C. siamense (11 isolates), C. fioriniae (four isolates), and C. fructicola (3 isolates). Maximum likelihood trees using combined sequences showed that isolates of the same species grouped in the same main clade with the isolates used for comparison. Pathogenicity testing showed that the tested isolates from each species were pathogenic towards green and red Capsicum annuum and Capsicum frutescens upon treatment of wounded fruit, using both the mycelial plug and conidial suspension methods. Only five isolates of C. truncatum and seven isolates of C. scovillei were found to be pathogenic upon treatment of unwounded fruit. The occurrence of five Colletotrichum spp. (C. siamense, C. fructicola, C. scovillei, C. fioriniae, and C. truncatum) associated with chili anthracnose in Peninsular Malaysia indicates that correct species identification is important to formulate not only effective disease management, but also effective quarantine policy.     

A climatic risk analysis of the threat posed by the South American leaf blight (SALB) pathogen <Emphasis Type="Italic">Microcyclus ulei</Emphasis> to major rubber producing countries

In 2010, symptoms of cobweb disease were observed on cultivated Pleurotus eryngii crops in Spain. Based on morphological and genetic analyses, the causal agent of cobweb was identified as Cladobotryum mycophilum. Pathogenicity tests on fruit bodies were performed using conidial suspensions of three C. mycophilum isolates. The causal agent was re-isolated in 80–85 % of the fruit bodies inoculated internally and 15–40 % of those fruit bodies inoculated on the cap surface. The results pointed to a certain resistance of the P. eryngii cap surface to the mycelium of C. mycophilum. Two cropping trials inoculated with C. mycophilum were set up to evaluate the pathogenicity of the causal agent of cobweb in two casings. At the end of the growth cycle, 50–60 % of the inoculated blocks cased with mineral soil, and 20–33 % of the inoculated blocks cased with black peat showed cobweb symptoms. This difference in the appearance of the disease and its aggressiveness may be partly explained by different electrical conductivity values of the casing materials used. In vitro sensitivity of the C. mycophilum isolates and P. eryngii strains against four fungicides (chlorothalonil, prochloraz-Mn, thiabendazole and thiophanate-methyl) was assessed in radial growth experiments on fungicide-amended media. The most effective fungicides for inhibiting the in vitro growth of C. mycophilum were prochloraz-Mn and chlorothalonil, while prochloraz-Mn was also the most selective fungicide between P. eryngii and C. mycophilum, and chlorothalonil was the most toxic fungicide against the P. eryngii mycelium.     

Factors affecting <Emphasis Type="Italic">Neofuscicoccum ribis</Emphasis> infection and disease progression in blueberry

Botryosphaeria stem blight is an economically important disease of blueberry worldwide. In this study, factors affecting inoculum production, infection and disease progression of Neofusicoccum spp. in blueberries were investigated. Under laboratory conditions conidia of the main three Neofusicoccum species (N. australe, N. parvum and N. ribis) were released from pycnidia at 15–30 °C and under relative humidities (RHs) of 80–100%, with greatest numbers released by N. parvum. The greatest numbers of oozing pycnidia and conidial release occurred at higher temperatures (25–30 °C) and RHs (92–100%). Inoculation of green shoots with different N. parvum and N. ribis conidial concentrations (50 μL of 5 × 10⁴?5 × 10⁶ conidia/ mL) caused 100% incidence but lesion lengths increased with increasing concentrations. Wound age affected N. ribis lesion development, with lesions only observed for 0–7-day-old wounds in soft green shoots and 0–4-day-old wounds for both hard green shoots and trunks. Colonisation length decreased with increasing wound age. Lesions developed on wounded shoots when plants were exposed to 20 or 25 °C and 90 or 100% RH during the early infection processes; and in non-wounded shoots spot-like lesions were observed although N. ribis colonised the stem tissue. Seasons (summer, autumn and winter) had no effect on susceptibility of wounded plants to N. ribis. External lesions only developed in summer-inoculated plants and colonisation length was lower in winter-inoculated plants. Information on host and environmental factors that affect disease development determined by the study will be used to inform the development of control strategies.     

Phylogenetic relationship and fungicide sensitivity of members of the <Emphasis Type="Italic">Colletotrichum gloeosporioides</Emphasis> species complex from apple

The members of the Colletotrichum gloeosporioides species complex (CGSC), the dominant pathogens of apple bitter rot in Nagano prefecture, Japan, were reidentified and the relationship between the species and fungicide sensitivity was revealed. Based on phylogenetic analysis of the ApMat locus with the neighbor-joining (NJ) method, isolates from apple contained three species of the CGSC; C. fructicola, C. aenigma, C. siamense, and three clades of the CGSC: Clade V, S and K. Colletotrichum fructicola and Clade S dominated in Nagano Prefecture. Isolates of C. siamense, C. aenigma and Clade V, S and K remained sensitive to benomyl and quinone outside inhibitor (QoI) fungicides, while C. fructicola often developed resistance to benomyl and QoI fungicides. These results suggest that the development of fungicide resistance differs among members of the CGSC.     

<Emphasis Type="Italic">Fibulorhizoctonia psychrophila</Emphasis> is the causal agent of lenticel spot on apple and pear fruit in the Netherlands

In a survey for postharvest diseases of apples and pears in the Netherlands, an unknown postharvest fruit rot was observed. The disease appeared to originate from infected lenticels. A fungus was consistently isolated from the decayed fruits. The fungal pathogen was isolated on potato dextrose agar, and at low temperatures development of a fast-growing whitish mycelium was observed. Growth of this fungus was observed between 1 and 20 °C with an optimum at 15 °C, while incubation of mycelium at 25 °C resulted in no growth. The isolates did not produce asexual or sexual spores. The isolates were characterized and identified by morphology and molecular phylogenetic analysis. Genomic DNA was isolated and amplified using ITS1-ITS4, EF1 and RPB2 primers, and BLAST searches in GenBank placed the fungus taxonomically in the genus Fibulorhizoctonia, with the highest matches to F. psychrophila. Pathogenicity of representative isolates from apple and pear fruit was confirmed under laboratory conditions. To the best of our knowledge this is the first report of F. psychrophila causing lenticel spot on apple and pear, and also the cause of a whitish mould on storage bins.     

Environmental effects on growth and sporulation of <Emphasis Type="Italic">Fusarium</Emphasis> spp. causing internal fruit rot in bell pepper

Internal fruit rot in bell pepper (Capsicum annuum L.) is mainly caused by members of the Fusarium lactis species complex (FLASC) and to a lesser extent by Fusarium oxysporum and Fusarium proliferatum. Despite the importance of the disease, there is hardly no information about growth, sporulation and germination dynamics of FLASC. In order to understand the dominance of FLASC as main pathogen of internal fruit rot, the effects of temperature (5 °C – 35 °C), water activity (a_w 0.76–0.96), pH (pH 3 - pH 9) and oxygen concentration (2.5% - 20%) on growth and sporulation of all three Fusarium species were compared. In addition, germination kinetics were also investigated. FLASC showed optimal mycelium growth and sporulation in the narrow range of 25 °C, while both other strains were also tolerant for higher temperatures to 30 °C. FLASC was also characterized by a broad pH optimum from pH 3–7 while F. oxysporum (pH 4–7) and F. proliferatum (pH 5–8) were more demanding concerning pH. In addition, optimal sporulation occurred in the acid region for FLASC (pH 3) whilst neutral and alkaline pH were more favourable for the other species. Germination kinetics revealed that FLASC did not benefit from an earlier and/or faster germination process. A thorough understanding of the growth characteristics and dominance of FLASC as main pathogen for internal fruit rot is inevitable to develop sustainable control measures for the disease.     

Parasitism of <Emphasis Type="Italic">Psytallia concolor</Emphasis> (Hymenoptera: Braconidae) on <Emphasis Type="Italic">Bactrocera oleae</Emphasis> (Diptera: Tephritidae) infesting different olive varieties

Psytallia concolor (Szépligeti) is a koinobiont endoparasitoid of many Tephritidae larvae, including Bactrocera oleae (Rossi), and has been used in Mediterranean areas for biological control of olive fruit fly by inundative release. The present study evaluates the influence of olive fruit variety (Amfissis, Arbequina, Branquita de Elvas, Carolea, Kalamon, Koroneiki, Leccino, Manzanilla, Mastoidis, Moroccan Picholine and Picholine) on P. concolor parasitism efficiency and performance in the field during two successive years. The results showed that the percentage of parasitism was significantly higher (>30%) in Mastoidis and Koroneiki (light-weight varieties <1.5 g) than Leccino which has a medium fruit weight, followed by Amfissis, Moroccan Picholine, Picholine and Branquita de Elvas. Only Manzanilla among large weight varieties, exhibited high percentage of parasitization (42.72%) during 2013. The mean weight of the pupae (>4.21 mg) as well as the length of the developed adult parasitoids (>3.5 cm) in Mastoidis and Manzanilla were significantly higher than these individuals developed from other varieties such as Koroneiki and Kalamon. Finally, the optimal host fruit for P. concolor development seems to be Mastoidis variety with great biological parameters and percentage of parasitism.     

Resistance to root-knot nematodes on passion fruit genotypes in Brazil

With the expansion of passion fruit cultivation in Brazil, phytosanitary problems have increased, among them, the occurrence of root-knot nematodes. This research aimed to study the response of passion fruit genotypes to Meloidogyne incognita, M. javanica and M. enterolobii in addition to evaluating the life cycle of M. enterolobii in the passion fruit genotype ‘FB 200’. The genotype response was carried out in a greenhouse. Each pot’s soil was inoculated with 5000 eggs. Gall index, egg mass index and nematode reproduction factors were evaluated at 120 days after inoculation. All genotypes studied were resistant to M. incognita, M. javanica and M. enterolobii, except ‘Roxinho do Kênia’, which was susceptible to the three nematode species. The life cycle of M. enterolobii in “FB 200” passion fruit was studied in a growth chamber at 26 °C with a photoperiod of 12 h. Seven days after transplantation, each plant was inoculated with approximately 400 second-stage juveniles. Evaluations were done at 7, 14, 21, 28, 35, 42 and 49 days post inoculation. The nematode did not complete its life cycle.     

Development of a method for detection of latent European fruit tree canker (<Emphasis Type="Italic">Neonectria ditissima</Emphasis>) infections in apple and pear nurseries

Fruit tree canker caused by Neonectria ditissima is a serious problem in apple-producing regions with moderate temperatures and high rainfall throughout the year; especially in northwestern Europe, Chile, and New Zealand. Control measures are applied to protect primary infection sites, mainly leaf scars, from invasion by external inoculum. However, latent infections may occur when young apple trees are infected symptomlessly during propagation. This study aimed to develop a method for detection of latent fruit tree canker infections. Inoculations with conidiospore suspensions of N. ditissima were carried out in tree nurseries on the main stems of two-year-old trees of three apple cultivars and one pear cultivar. The inoculations were carried out during the natural abscission period in the autumn. No visible lesion or canker formations were present at the time when the inoculated trees were uprooted. It appeared that the infections may remain latent during the period from infection to uprooting (2 months) and during the subsequent 4 months of cold storage of the trees. Nevertheless, symptoms were generally induced within 8 weeks after transfer of infecting planting material from the nursery field into a climate chamber with high temperature and high relative humidity. The methodology presented is developed to detect latent infections of N. ditissima in nursery trees, prior to planting in the orchards, and it may contribute in reducing the problem with European fruit tree canker in commercial production.     

Long-term dynamics of causative agents of stem base diseases in winter wheat and reaction of Czech <Emphasis Type="Italic">Oculimacula</Emphasis> spp. and <Emphasis Type="Italic">Microdochium</Emphasis> spp<Emphasis Type="Italic">.</Emphasis> populations to prochloraz

Trichoderma aggressivum is an aggressive contaminant mould in the cultivation of Agaricus bisporus leading to severe reductions in mushroom yields. Production of fully colonised A. bisporus substrate in Europe is commonly carried out in large tunnels (Phase III), after which the substrate undergoes several bulk handling (mixing) operations before ending up on shelves in mushroom growing facilities. The work presented here studied the effect of Trichoderma aggressivum inoculum, substrate mixing and supplementation on Agaricus bisporus yields and evaluated four methods to detect T. aggressivum in bulk handled substrate. Inoculum dilution level was shown to correlate well with mushroom yield (P < 0.0001) with reductions of 2–6 % at the most dilute level (10^?4) and 60–100 % at the most concentrated level (10^?1), depending on the experiment. Supplementation, with or without T. aggressivum, had no significant effect on mushroom yield (P ≥ 0.85) but a high degree of substrate mixing was shown to significantly increase (P < 0.0001) T. aggressivum-associated crop losses. Four T. aggressivum detection methods were evaluated and a quantitative polymerase chain reaction (qPCR) method gave the most consistent and least variable results. Cycle threshold (CT) values ranged from 24 to 40, depending on the experiment and the inoculum dilution level, and false negatives (CT = 40) were reported on one occasion with the most dilute samples. The results indicate that Phase III mushroom substrate is vulnerable to infection by T. aggressivum when the fully colonised substrate is broken up and mixed during bulk handling operations, identifying a previously unidentified risk for Phase III substrate producers.     

Environmental and inoculum effects on epidemiology of bacterial spot disease of stone fruits and development of a disease forecasting system

Bacterial spot disease of stone fruits, caused by Xanthomonas arboricola pv. pruni, is of high economic importance in the major stone-fruit-producing areas worldwide. A better understanding of disease epidemiology can be valuable in developing disease management strategies. The effects of weather variables (temperature and wet/dry period) on epiphytic growth of X. arboricola pv. pruni on Prunus leaves were analyzed, and the relationship between inoculum density and temperature on disease development was determined and modeled. The information generated in this study, performed under controlled environmental conditions, will be useful to develop a forecasting system for X. arboricola pv. pruni. Optimal temperature for growth of epiphytic populations ranged from 20 to 30 °C under leaf wetness. In contrast, multiplication of epiphytic populations was not only interrupted under low relative humidity (RH) (< 40%) at 25 °C, but also resulted in cell inactivation, with only 0.001% initial cells recovered after 72 h incubation. A significant effect of inoculum density on disease severity was observed and 10⁶ CFU/ml was determined as the minimal infective dose for X. arboricola pv. pruni on Prunus. Infections occurred at temperatures from 15 to 35 °C, but incubation at 25 and 30 °C gave the shortest incubation periods (7.7 and 5.9 days respectively). A model for predicting disease symptom development was generated and successfully evaluated, based on the relationship between disease severity and the accumulated heat expressed in cumulative degree day (CDD). Incubation periods of 150, 175 and 280 CDD were required for 5, 10 and 50% of disease severity, respectively.     

Incidence and etiology of postharvest fungal diseases of loquat fruit (<Emphasis Type="Italic">Eriobotrya japonica</Emphasis> (Thunb.) Lindl. cv. ‘Algerie’) in Alacant province (Spain)

‘Algerie’ is currently the most important loquat cultivar in Spain. The incidence and etiology of postharvest diseases affecting this cultivar were determined under local conditions. Latent and wound pathogens were evaluated for two consecutive seasons on commercially grown loquats from two orchards. Healthy loquats were either surface-disinfected or artificially wounded in the rind and placed in humid chambers at 20 °C for up to 5 weeks. Additionally, decay was assessed on commercially-handled loquats stored at 5 °C for up to 20 weeks. The most frequent disease was caused by Alternaria alternata, followed by Penicillium expansum. These two pathogens were present on fruit assessed for all types of infection. Moreover, decay caused by Botrytis cinerea was abundantly observed on both wounded and cold-stored fruit, while Colletotrichum gloeosporioides was frequently found on surface-disinfected fruit. Other pathogens that were observed causing latent infection to a lesser extent included Pestalotiopsis clavispora and Diplodia seriata. Common isolates were identified by macroscopic and microscopic morphology and/or DNA amplification and sequencing. Pathogenicity of selected isolates was demonstrated by fulfilling Koch’s postulates and disease development was assessed on artificially inoculated loquats stored at either 20 or 5 °C.     

Genetic structure of <Emphasis Type="Italic">Pyrenophora teres</Emphasis> f. <Emphasis Type="Italic">teres</Emphasis> and <Emphasis Type="Italic">P. teres</Emphasis> f. <Emphasis Type="Italic">maculata</Emphasis> populations from western Canada

Infection by Pyrenophora teres f. teres (Ptt) or P. teres f. maculata (Ptm), the causal agents of the net and spot forms of net blotch of barley, respectively, can result in significant yield losses. The genetic structure of a collection of 128 Ptt and 92 Ptm isolates from the western Canadian provinces of Alberta (55 Ptt, 27 Ptm), Saskatchewan (58 Ptt, 46 Ptm) and Manitoba (15 Ptt, 19 Ptm) were analyzed by simple sequence repeat (SSR) marker analysis. Thirteen SSR loci were examined and found to be polymorphic within both Ptt and Ptm populations. In total, 110 distinct alleles were identified, with 19 of these shared between Ptt and Ptm, 75 specific to Ptt, and 16 specific to Ptm. Genotypic diversity was relatively high, with a clonal fraction of approximately 10 % within Ptt and Ptm populations. Significant genetic differentiation (PhiPT = 0.230, P = 0.001) was found among all populations; 77 % of genetic variation occurred within populations and 23 % between populations. Lower, but still significant genetic differentiation (PhiPT = 0.038, P = 0.001) was detected in Ptt, with 96 % of genetic variation occurring within populations. No significant genetic differentiation (PhiPT = 0.010, P = 0.177) was observed among Ptm populations. Isolates clustered in two distinct groups conforming to Ptt or Ptm, with no intermediate cluster. The high number of haplotypes observed, combined with an equal mating type ratio for both forms of the fungus, suggests that P. teres goes through regular cycles of sexual recombination in western Canada.     

Thermal effects on the development of <Emphasis Type="Italic">Bactrocera dorsalis</Emphasis> (Hendel) (Diptera: Tephritidae) and model validation in Taiwan

The oriental fruit fly, Bactrocera dorsalis (Hendel), is a major polyphagous insect pest with a worldwide distribution. The effects of temperature on stage-specific development in B. dorsalis were investigated at eight constant temperatures (13.0 °C, 14.4 °C, 16.2 °C, 19.5 °C, 23.8 °C, 27.7 °C, 31.8 °C and 34.8 °C). B. dorsalis developed successfully from the egg stage to the adult stage at all the tested temperatures, except at the lowest temperatures (13.0 °C and 14.4 °C). Stage-specific lower developmental thresholds and thermal constants were determined using linear regression. The lower and higher temperature threshold (TL and TH, respectively) were estimated using the Sharpe-Schoolfield-Ikemoto model. The lower developmental threshold and thermal constant from egg to adult emergence were 9.8 °C and 325.5 degree-days, respectively. The intrinsic optimum temperatures of the egg, larval, pupal and egg to pupal stage were 20.7 °C, 21.8 °C, 21.1 °C, and 22.4 °C, respectively. The temperature range of the B. dorsalis total immature stage from TL to TH was 20.4 °C (13.8 °C - 34.2 °C). The stage-specific developmental completion of B. dorsalis was determined using a two-parameter Weibull function. The daily adult emergence frequency of B. dorsalis was estimated in relation to adult age and temperature using non-linear developmental rate functions and the Weibull function. The date of cumulative 50% adult emergence estimated using non-linear functions was approximately one day earlier than the experimentally observed date. Thermal performance was compared among B. dorsalis populations from different locations.