Overwintering of Monilinia fructicola in Stone Fruit Orchards in Northern China

Survival of Monilinia fructicola on the surface of mummified fruit and in peduncles and shoots of stone fruit trees infected by M. fructicola in the previous season was studied from 2003 to 2006 in orchards in the agricultural region of Beijing. Viable conidia of M. fructicola were consistently detected on fruit mummies from mid‐March to the end of April. During flowering (in mid‐April), studies in five peach orchards showed that 33–87% of mummified fruit bore viable conidia. The germination rate of conidia on diseased fruit was about 64% in autumn. It decreased to 24% in mid‐winter when the fruit was completely mummified, and in the following year to 2–4% in early spring. Viable M. fructicola was consistently detected in peach and nectarine shoots collected in winter and spring. In general, viable M. fructicola in peduncles was detected from mummified fruit of 11–27% branches and from asymptomatic plant tissues of 3–20% branches. Sporulation of M. fructicola was observed on peduncles in seven of eight surveys, and the percentage of branches containing viable M. fructicola in peduncles in contact with mummified fruits ranged from 18% to 40%. This study demonstrates that the tree‐borne mummified fruit and the peduncles could be the parts of trees where M. fructicola can survive the winter in orchards in suburban Beijing.     

Survival of Neozygites cf. floridana (Zygomycetes: Entomophthorales) in mummified cassava green mites and the viability of its primary conidia

The survival of Neozygites cf. floridana (Weiser and Muma) as dry hyphal bodies in mummified cassava green mites, Mononychellus tanajoa (Bondar), at 5.0% RH in the dark was affected by storage temperature. Survival of the fungus in mummies kept at 24±1.0°C could be demonstrated for 6–7 months. When stored at 4°C, the fungus sporulated from 90% of the mummies liberating an average of 186.9 primary conidia per mummy even after a storage period of 16 months, when the experiment was terminated. The temperature, humidity and light condition significantly affected the viability of primary conidia. The percent viability across all factors dropped from 98.4% after 0 h (beginning of the experiment) to 23.4% after a 1 h exposure to the conditions tested. Lower temperatures maintained higher viabilities with 86.3% of the conidia surviving after 18 h at 18°C, whereas almost all conidia died after 12 h at 33°C. Conidia survived less than 1 h when exposed to SDs (saturation deficit) of 2.0 mm Hg or higher at any tested temperature.     

Interactions among the entomopathogenic fungus, Beauveria bassiana (Ascomycota: Hypocreales), the parasitoid, Aphidius matricariae (Hymenoptera: Braconidae), and its host, Myzus persicae (Homoptera: Aphididae)

The effect of the entomopathogenic fungus Beauveria bassiana on the biological characteristics and life table of Aphidius matricariae, a parasitoid of the green peach aphid, Myzus persicae, was studied under laboratory conditions. Aphids were first infected with twice the LC₉₅ of B. bassiana for third-instar M. persicae (2 × 10⁸ conidia/ml). Subsequently, at different intervals they were exposed to 1-day-old mated parasitoid females for 24 h. The number of mummies produced per female and the percentage emergence of the F1 generation differed significantly as a function of the time interval between application of the fungus and exposure to the parasitoid. The interference of B. bassiana on parasitoid development was also studied by first exposing the aphid hosts to the parasitoid for 24 h and subsequently applying B. bassiana. The number of mummies produced by a female A. matricariae varied from 11.8 to 24.8 and was significantly different when the aphids were first exposed to the parasitoids and then treated with B. bassiana 24, 48, 72, and 96 h after exposure. There were no significantly different effects of B. bassiana on net reproductive rate (R₀), mean generation time (T), intrinsic rate (r_m) and the finite rate of increase (λ) of A. matricariae as a result of development in hosts exposed to low or high conidial concentrations (1 × 10², 2 × 10⁸ conidia/ml). The parasitoids developed in infected hosts had lower r_m, λ, T and DT (doubling time) values compared with those that developed in uninfected hosts but no differences were observed in R₀ values. With proper timing, A. matricariae and B. bassiana can be used in combination in the successful biological control of M. persicae.     

Monilinia jezoensis sp. nov. in the Sclerotiniaceae, causing leaf blight and mummy fruit disease of Rhododendron kaempferi in Hokkaido, northern Japan

A new leaf blight and mummy fruit disease caused by a species of Monilinia was first found on Rhododendron kaempferi at the lakeside of Shikotsu-ko, Hokkaido, northern Japan, in 2002. Studies on morphology, life cycle, cultural characters, and gene analyses of the causal fungus enabled us to conclude that it is a new species of the genus. It is named M. jezoensis. Rhododendron is a new host genus for Monilinia fungi in Japan.     

Effects of mummy consumption on fitness and oviposition site selection on Harmonia axyridis

Intraguild predation (IGP) has been commonly reported between predators and parasitoids used as biological control agents as predators consuming parasitoids within their hosts. However, the effect of parasitoid–mummy consumption on the fitness of the predator and subsequent oviposition site selection have not been well studied. In our study, we conducted two laboratory experiments to examine the influence of Aphidius gifuensis Ashmead (Hymenoptera: Braconidae) mummies as prey on fitness and subsequently oviposition site selection of Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae). Results indicate that when H. axyridis was reared on A. gifuensis mummies only, its larval development was prolonged, and body weight of the 4th instar larvae and newly emerged adults, and fecundity decreased. Moreover, H. axyridis did not exhibit oviposition preference on plants infested with unparasitized aphids or aphids parasitized for shorter than 9 days. However, compared with plants with mummies (parasitized ≥9 days), H. axyridis laid more eggs on plants with unparasitized aphids. In contrast, H. axyridis previously fed with A. gifuensis mummies did not show a significant oviposition preference between plants with unparasitized aphids and those with mummies (parasitized ≥9 days). Overall, our results suggest that mummy consumption reduced the fitness of H. axyridis. Although H. axyridis avoided laying eggs on plants with A. gifuensis mummies, prior feeding experience on A. gifuensis mummies could alter the oviposition site preference. Thus, in biological control practice, prior feeding experience of H. axyridis should be carefully considered for reduction of IGP and increase of fitness of H. axyridis on A. gifuensis.     

Inhibition of phagocytic activity and nodulation in Galleria mellonella by the entomopathogenic fungus Nomuraea rileyi

Changes in phagocytic activity and nodulation in the greater wax moth, Galleria mellonella (L.) (Lepidoptera: Pyralidae), were examined after treatment with the culture fluid of the entomopathogenic fungus Nomuraea rileyi SH1. When isolated hemocytes of G. mellonella were incubated with the conidia of N. rileyi in vitro, the rates of phagocytosis increased at 4 h after incubation but decreased subsequently. On the contrary, the rates of phagocytosis of isolated hemocytes decreased by 80% after 24 h preincubation with the fungal culture fluid (1/200, 1/100 dilutions). Levels of inhibition of phagocytic activity by the culture fluid depended on dilutions used. Galleria mellonella larvae showed a peak of nodulation at 4 h after injection with conidia. The percentage of nodules in hemolymph did not decrease by preinjection with the culture fluid, whereas the percentage of nodule‐containing conidia decreased, depending on the injected fluid. However, phagocytosis and nodulation in G. mellonella did not change after treatment of the culture fluid with proteinase K, indicating that the culture fluid contained proteinaceous immunosuppressive factors. Electrophoretic analysis of the culture fluid and not the fresh medium without culturing the fungus exhibited protein bands. Therefore, N. rileyi possibly secretes toxic proteins that impair cellular immune responses in G. mellonella larvae.     

Effects of intraguild predation on aphid parasitoid survival

To assess the potential selection pressure caused by intraguild predation between predators and parasitoids of aphids an estimate was made of the predation risk to Aphis fabaeScop. mummified by Lysiphlebus fabarum(Marshall, 1896) on sugar beet. Mummified aphids were exposed to a natural community of predators. Their survival time was estimated during a 10-day field survey. Additionallythe role of alternative prey on parasitoid survival was investigated by adding unparasitised aphids to half of the mummy aggregations.The field data were evaluated by survival analysis. Two covariates were tested within a Cox proportional hazard model: (i) the presence of the alternative prey and (ii) the patch structure (number of proximal mummies attacked). Within 4–5 days after exposure predators destroyed approx. 50% of the mummies. The model with both covariates revealed a significant difference concerning survival of the mummies in the two treatments (Likelihood ratio test, ²=78.03, P=0.0001). Alternative prey reduced the predation risk on mummies by 29%, while a high level of predation on proximal mummies increased the individual predation risk by 4%. The results are discussed in the context of prey location by predators and the evolution of anti-predator mechanisms.     

Medium Selection and Effect of Higher Oxygen Concentration Pulses on <Emphasis Type="Italic">Metarhizium anisopliae</Emphasis> var<Emphasis Type="Italic">. lepidiotum</Emphasis> Conidial Production and Quality

Rice and oat flours were analyzed as media for the production of conidia by M. anisopliae var. lepidiotum. The presence of peptone increased conidia yield regardless of the substrate used; however, the highest yield was achieved on oat flour media. The effect of oxygen on conidia production using oat-peptone medium was also studied at two levels: Normal atmosphere (21% O₂) and Oxygen-rich pulses (26% O₂). Maximum conidia production (4.25 × 10⁷ conidia cm⁻²) was achieved using 26% O₂ pulses after 156 h of culture, which was higher than 100% relative to conidial levels under normal atmosphere. Conidia yield per gram of biomass was 2.6 times higher with 26% O₂ (1.12 × 10⁷ conidia mg⁻¹). Conidia quality parameters, such as germination and hydrophobicity, did not show significant differences (P < 0.05) between those treatments. Bioassays parameters, using Tenebrio molitor adults, were analyzed for conidia obtained in both atmospheres and data were fitted to an exponential model. The specific mortality rates were 2.22 and 1.26 days⁻¹, whereas lethal times for 50% mortality were 3.90 and 4.31 days, for 26% O₂ pulses and 21% O₂ atmosphere, respectively. These results are relevant for production processes since an oxygen increase allowed superior levels of conidia by M. anisopliae without altering quality parameters and virulence toward Tenebrio molitor adults.     

Postprocessing microflora of commercial attieke (a fermented cassava product) produced in the south of Côte d'Ivoire

The distribution and presence of hygiene indicator and pathogenic micro‐organisms in 375 samples of attieke marketed in Côte d'Ivoire, and their roles in the food poisoning were evaluated. Microbiological analyses were carried out, which included the total viable bacteria, coliforms, Escherichia coli, Staphylococcus aureus, Salmonella, Bacillus spores, fungi and Clostridium perfringens. The results revealed that the viable bacteria counts ranged from 2·2 ± 1·2 × 10⁵ to 3·4 ± 1·4 × 10⁶ CFU g^?1, while the yeasts and the moulds counts ranged, respectively, from 2·4 ± 0·12 × 10⁴ to 9·8 ± 0·4 × 10⁵ CFU g^?1 and 1·3 ± 0·7 × 10¹ to 1·7 ± 0·7 × 10² CFU g^?1. Bacillus subtilis, Bacillus cereus, Staphylococcus aureus, Citrobacter freundi, Enterobacter amnigenus, Citrobacter youngae, Enterobacter aerogenes, Klebsiella pneumoniae, Serratia marcescens, Enterobacter agglomerans and Klebsiella oxytoca were the bacteria isolated, and Rhizopus spp., Mucor spp., Thamnidium spp., Fusarium spp., Moniliella spp. the fungi. Escherichia coli, Clostridium perfringens and Salmonella spp. were not found. The occurrence of some bacteria and fungi illustrate that attieke collected in Côte d'Ivoire markets may act as a reservoir of pathogenic micro‐organisms for human.

Significance and Impact of Study

This study demonstrates the great need to carry out microbiological tests frequently on attieke and even more the need to apply correct HACCP system during the production. Attieke is especially a well‐known product in West Africa; hence, it is extremely important to ensure an adequate microbiological quality to guarantee consumers health. Overall, the study highlighted the need for effective communication on microbiological food risks, proper instruction and supervision in food‐handling procedures, greater education on food safety risks.     

Microencapsulating aerial conidia of Trichoderma harzianum through spray drying at elevated temperatures

Conidia of Trichoderma harzianum produced from either solid or liquid fermentation must be dried to prevent spoilage by microbial contamination, and to induce dormancy for formulation development and prolonged self-life. Drying conidia of Trichoderma spp. in large scale production remains the major constraint because conidia lose viability during the drying process at elevated temperatures. Moreover, caking must be avoided during drying because heat generated by milling conidial chunks will kill conidia. It is ideal to dry conidia into a flow-able powder for further formulation development. A method was developed for microencapsulation of Trichoderma conidia with sugar through spray drying. Microencapsulation with sugars, such as sucrose, molasses or glycerol, significantly (P < 0.05) increased the survival percentages of conidia after drying. Microencapsulation of conidia with 2% sucrose solution resulted in the highest survival percentage when compared with other sucrose concentrations and had about 7.5 × 10¹⁰ cfu in each gram of dried conidia, and 3.4 mg of sucrose added to each gram of dried conidia. The optimal inlet/outlet temperature setting was 60/31 °C for spray drying and microencapsulation. The particle size of microencapsulated conidia balls ranged from 10 to 25 μm. The spray dried biomass of T. harzianum was a flow-able powder with over 99% conidia, which could be used in a variety of formulation developments from seed coatings to sprayable formulations.     

The development and multiple uses of a standardised bioassay method to select hypocrealean fungi for biological control of aphids

A technically standardised bioassay method was designed, evaluated and used to assess virulence and host range of hypocrealean fungi against aphids. A track mounted sprayer was used to apply conidia because hand held versions of the same sprayer can be used for field applications, thereby allowing the outcome from laboratory experiments to predict activity in the field accurately. Eighteen fungal isolates were assessed in single concentration bioassays against the black bean aphid Aphis fabae Scopoli. Isolates comprised commercially available mycoinsecticides (based on Beauveria bassiana and Lecanicillium longisporum) and isolates of B. bassiana, Lecanicillium spp., Paecilomyces fumosoroseus and Metarhizium anisopliae. Aphid mortality was in excess of 80% for 15 isolates, and HRI 1.72 (L. longipsorum), Z11 (P. fumosoroseus), Mycotech strain GHA (B. bassiana) and ARSEF 2879 (B. bassiana) were studied further. Multiple concentration bioassays identified HRI 1.72 as the most virulent isolate against A. fabae with significantly smaller LC₅₀ and LT₅₀ values compared to other isolates. A precise LC₅₀ value (2.95 × 10² conidia ml⁻¹) was calculated for HRI 1.72 using a second multiple concentration assay with smaller concentrations of conidia. The four isolates were applied at a single concentration (1 × 10⁸ conidia ml⁻¹) against Myzus persicae, A. fabae, Acyrthosiphon pisum, Metopolophium dirhodum, Sitobion avenae and Rhopalosiphum padi. A ranking of aphid susceptibility was obtained, such that S. avenae > M. persicae, A. pisum, A. fabae > R. padi. Results indicate the importance of standardising bioassay methods to reduce bioassay variability without compromising the ability to use the bioassay to investigate fungus–host interactions under varying abiotic and biotic conditions.     

Cordyceps cateniannulata,a novel entomopathogenic fungus to control Stenoma impressella Busck (Lepidoptera: Elachistidae) in Colombia

Stenoma impressella is one of the most important defoliator pests in oil palm plantations in Colombia. To identify an alternative method for its control was characterized biologically and molecularly two strains of Cordyceps cateniannulata (CPIsp1201 and IPIsp1201) and three strains of Beauveria bassiana (CPBb0502; CPBb0411; CPBb0404) against S. impressella larvae. Virulence was evaluated under laboratory conditions. In an oil palm leaflet, individual larvae obtained from the insect colony were inoculated with 5 μl of a conidial suspension containing 1 × 10⁷ conidia/ml. The five strains were pathogenic against S. impressella larvae. CPIsp1201 and IPIsp1201 strains resulted in the highest mortality and were subsequently evaluated in two bioassays using a dose of 1 × 10¹³ conidia/ha. In the first bioassay, performed under shaded conditions, leaves of oil palms were infested with 75 larvae from the breeding/treatment. The second bioassay was performed in the field using natural populations. No differences were found between strains in both bioassays and the different dosages (5 × 10¹², 1 × 10¹³, and 1.5 × 10¹³ conidia/ha). Finally, the two strains were evaluated under oil palm plantation conditions at a dose of 1 × 10¹³ conidia/ha in 126 naturally infested palms. Larval mortality caused by the strains IPIsp1201 and CPIsp1201 (79.5% and 70.5%, respectively) was higher than the natural mortality registered in the control (37.3%). Cordyceps cateniannulata used at 1 × 10¹³ conidia/ha was effective at controlling S. impressella.     

Hydrophobicity-Related Protein Contents and Surface Areas of Aerial Conidia are Useful Traits for Formulation Design of Fungal Biocontrol Agents

To clarify the potential use of hydrophobicity-related traits of aerial conidia in formulation design of fungal biocontrol agents, hydrophobicity rates (H _r) and surface areas (S _a) of aerial conidia were assessed with 48 strains of Beauveria bassiana, Isaria fumosorosea and Metarhizium spp. Inter- or intra-specific variation was large in H _r (59.7–92.2%) and S _a (7.9–25.3 μm² conidium⁻¹) measurements, which were significantly correlated (r ² = 0.55). Six isolates of the three fungi with distinguished H _r and S _a were further studied. Conidial wall proteins of these isolates were sequentially extracted with sodium dodecyl sulfate (SDS), formic acid (FA) and trifluoroacetic acid (TFA). Their H _r values were significantly correlated to the contents (P _c) of TFA-soluble, but FA-insoluble, proteins (2.7–44.8 μg per 10⁷ conidia; r ² = 0.79) and reduced drastically by the FA/TFA treatments, which eliminated the hydrophobin-based rodlet layers of conidial surfaces. However, the SDS treatments had no effect on either H _r or rodlet layers. The dispersancy of a tested emulsifier to oil formulations of the six isolates in water was adversely correlated to their H _r (r ² = 0.94). The results indicate that both P _c and S _a are inherent hydrophobicity-related traits and can be utilized to select fungal biocontrol candidates for improved formulation and application.     

Bioaccumulation and biosorption efficacy of Trichoderma isolate SP2F1 in removing copper (Cu(II)) from aqueous solutions

In our study, we isolated the isolate Trichoderma SP2F1 from sediment samples from the Penchala River, heavily contaminated with effluents from nearby industrial areas. Qualitative and quantitative screening using plate and broth assay, respectively, supplemented with various concentrations of Cu(II) showed the isolate was able to tolerate 6 mM CuSO₄, although growth was also detected in broths with 10 mM CuSO₄. Trichoderma spp. was able to remove Cu(II) in aqueous solutions in both viable and non-viable cell forms. Bioaccumulation capacity of viable SP2F1 cells removed 19.60 mg g⁻¹ of Cu(II) after 168 h incubation, while the maximum Cu(II) biosorption capacity for non-viable SP2F1 cells was 28.75 mg g⁻¹ of Cu(II). Results here showed that Trichoderma spp isolate SP2F1 has good potential for application in Cu(II) removal, can be used to treat sewage waste by applying either in viable or non-viable cell forms.     

Relationships between photosystem II efficiency and photochemical reflectance index under different levels of illumination: comparison among species grown at high- and low elevations through different seasons

Previously, we found a significant association between photosystem II efficiency (ΦPSII) and photochemical reflectance index (PRI) measured at predawn among different species at different elevations and throughout several seasons. However, this relationship has not been evaluated under varied levels of illumination. Here, we used the Taiwan species Pinus taiwanensis (a conifer distributed at 750–3,000 m a.s.l.), Stranvaesia niitakayamensis (an evergreen tree, 1,700–3,100 m) and two Miscanthus spp. (perennial C₄ Gramineae, coastline–3,200 m) to elucidate the ΦPSII–PRI relationship. We studied six levels of photosynthetic photon flux density (PPFD) (0, 200, 400, 800, 1,200 and 2,000 μmol m⁻² s⁻¹) over several growth seasons at high (2,600 m a.s.l.) and low (800 m a.s.l.) elevation sites. In comparing the same species or genus, ΦPSII and PRI were closely correlated in darkness or under the same level of PPFD, with data obtained from different seasons and elevations pooled for regression analysis. Because both the intercept and slope of the ΦPSII–PRI equation showed a negative curvilinear correlation with PPFD, we could fit an empirical regression model, ΦPSII = c + d·ln(PPFD) + e·[ln(PPFD)]² + f·PRI + g·PRI·ln(PPFD) + h·PRI·[ln(PPFD)]², for multiple regression analysis. Using this model, we found a close correlation between the estimated and measured ΦPSII (r ² = 0.842−0.937, P < 0.001) for all four species examined and for mango (Mangifera indica) measured under both artificial illumination and sunlight (data from Weng et al. 2010). This empirical regression model could simulate both seasonal and diurnal variations of leaf-scale photosynthetic efficiency at high and low elevations.     

The effects of spacing on growth, morphology and biomass production and allocation in two hybrid poplar clones growing in the boreal region of Canada

Intra-clonal competition was studied in young hybrid poplar plantations to assess the effects of spacing on growth, biomass production and allocation, and morphological characteristics of above- and below-ground tree parts. Three spacings were used as whole-plots (1 × 1 m, 3 × 3 m and 5 × 5 m), with two hybrid poplar clones as subplots (BT747, Populus balsamifera L. × P. trichocarpa Torr. & Gray; MB915, P. maximowiczii A. Henry × P. balsamifera L.) in a split-plot design. After six growing seasons, diameter at breast height (dbh) increased by about 120% from the 1 × 1 m to the 5 × 5 m spacing for clone MB915, while there was no significant change in dbh for the other clone. The effect of spacing on height growth was opposite for the clones; it increased by about 175% from the narrowest to the widest spacing for clone MB915, while it decreased by about 27% for clone BT747. Estimates of above-ground biomass production after six growing seasons were significantly reduced with increasing spacing, with 29.6, 4.9 and 3.2 MgDM ha⁻¹ on average from the narrowest to the widest spacing. Branch traits and the vertical distribution of leaf area were the most affected by spacing for both clones, while live crown ratio and percentage of syllepsis did not change. Spacing also affected proportions of biomass allocated to stem, leaves, and branches, but allocation to roots did not change.     

Increased heat tolerance afforded by oil-based conidial formulations of Metarhizium anisopliae and Metarhizium robertsii

The thermotolerance of oil-based conidial formulations of Metarhizium anisopliae s.l. (IP 46) and Metarhizium robertsii (ARSEF 2575) were investigated. Conidia of IP 46 or ARSEF 2575 were suspended in different adjuvants and exposed to 45?±?0.2°C for 4, 6, 8 or 24?h; their viability was then assessed after 48?h incubation at 27?±?1°C. Conidia heated in pure mineral or vegetable oil exhibited mean relative viability exceeding 70% after 8?h of heat exposure, whereas low germination (≤20%) was observed when conidia were heated in water (Tween 80^® 0.01%), carboxymethyl cellulose gel or emulsifiable oils (Graxol^® or Assist^®) and exposed to heat for 6 or 8?h. In addition, conidia of IP 46 suspended in either pure mineral or canola oil and exposed to heat for 48?h had moderate viability, 57% or 41%, respectively. Unstable oil-in-water emulsions showed a higher percentage of conidia incorporated into oil micellae, while the stable emulsions had higher percentage of conidia outside the oil micellae. The thermotolerance of conidia formulated in stable emulsions, however, did not differ from that of conidia formulated in unstable emulsions. The present study highlights possibilities to alleviate the deleterious effects of heat stress towards Metarhizium spp. conidia applied for controlling arthropod pests and vectors through oil-based formulations.     

Biological control of the pinewood nematode <Emphasis Type="Italic">Bursaphelenchus xylophilus</Emphasis> by application of the endoparasitic fungus <Emphasis Type="Italic">Esteya vermicola</Emphasis>

Esteya vermicola (Ophiostomataceae) is the first reported endoparasitic fungus of the pinewood nematode (PWN), Bursaphelenchus xylophilus (Nematoda: Aphelenchoidoidea). It has high in vitro infectivity. In this study, the nematocidal effect of E. vermicola in logs was investigated and evaluated. Two months after inoculation of pine wilt-killed Pinus densiflora logs with E. vermicola conidia suspensions of 3 × 10⁸ and 3 × 10⁶ ml⁻¹, the density of nematodes decreased by approximately 79% and 47%, respectively. When the fungus was sprayed on to four-year-old pine seedlings one month before PWN inoculation, the survival index of seedlings reached 0.67 compared with only 0.067 for control seedlings without fungal spraying. These results suggest that conidia spraying of E. vermicola can, to some extent, protect pine trees from wilt disease. Moreover, infected nematodes and hyphae of E. vermicola were observed in the treated wood sections.     

Defoliation of wild native box trees (Buxus sempervirens): Does box rust (Puccinia buxi) infection influence herbivory,survival and growth of the invasive Cydalima perspectalis?

The invasive box‐tree moth Cydalima perspectalis causes damage to horticultural box trees (Buxus spp.) in private gardens and parks in Europe and defoliation of large areas of European native box trees Buxus sempervirens, which grow in the understorey of deciduous forests. In some parts of their distribution area, wild native box trees are infected by the box rust Puccinia buxi, a fungus which does not occur in the native range of C. perspectalis. We examined whether the infection of P. buxi deters grazing by C. perspectalis in 31 wild box‐tree stands in forests in north‐western Switzerland and south‐western Germany. On average, 82.4% of the box trees were infested by P. buxi (among‐site variation 20%–100%), or 18.5% of their leaves. Linear mixed‐effect (LME) models revealed that the percentage of rust‐infected leaves was influenced by the local box‐tree density and the slope aspect of the forest site. 9.5% of the leaves showed grazing damage by C. perspectalis. LME showed that the percentage of leaves with grazing damage was affected by the elevation of the site and the percentage of rust‐infected leaves. The effect of box rust infection on food choice and larval performance (survival and growth rate) was examined in two experiments. In food‐choice tests, larvae of C. perspectalis did not show any preference for uninfected or rust‐infected box‐tree leaves and consumed similar amounts of leaf tissue of either type. However, when larvae were reared on leaves with three different degrees of P. buxi‐infection (and uninfected leaves as control), both survival and growth rate decreased with increasing degree of rust infection. This indicates that larval performance of C. perspectalis is reduced by the box rust. In the case of an outbreak of C. perspectalis, however, larvae may indiscriminately defoliate wild box trees.     

Cultivar‐specific plant odour preferences of a generalist aphid parasitoid Aphidius colemani and a possible mechanism for maternal priming of resistance to toxic plant chemistry

Aphidius colemani Viereck, emerging from Myzus persicae (Sulzer) mummies on the Brussels sprout cultivar ‘Bedford Winter Harvest’ (BWH), responds positively in the olfactometer to the odour of that cultivar in comparison with air. Responses to the odours of other sprout cultivars, cabbage and broad bean could be explained by the humidity from plant leaves. In a choice between BWH and other sprout cultivars, the BWH odour is preferred, or that of cv. ‘Red Delicious’ (RD) if the parasitoids are reared on RD. This confirms previous work showing that the secondary chemistry of a cultivar is learnt from the mummy cuticle during emergence. Adults emerging from pupae excised from the mummy show a similar but less pronounced preference. Parasitoids developing in aphids on an artificial diet do not discriminate between the odours of BWH and RD, unless allowed contact with a mummy from the same cultivar that the mother develops on. This suggests a cultivar‐specific maternal cue. This cue is speculated to consist of a small amount of the secondary chemistry (probably glucosinolates in the present study) that are left in or on the egg at oviposition, which subsequently induces enzymes that detoxify plant‐derived toxins in the aphid host. Indeed, when parasitoids emerging from diet‐reared aphids are released on aphid‐infested sprout plants, fewer mummies are produced than by parasitoids emerging from mummies of plant‐reared aphids or from excised pupae. Only parasitoids that emerge from mummies of plant‐reared aphids prefer the cultivar of origin as shown by the number of mummified hosts.