Mulching with coffee husk and pulp in strawberry affects edaphic predatory mite and spider mite densities.

Mulching of soil beds of strawberry fields is usually done with polyethylene film in southern Minas Gerais state, Brazil. This material is relatively expensive and difficult to discard after use. In some countries, mulching is done with the use of organic material that could have an advantage over the use of plastic for its easier degradation after use, and for favoring edaphic beneficial organisms. Predatory mites (especially Gamasina, Mesostigmata) may be abundant in the soil and could conceivably move to the soil surface and onto the short-growing strawberry plants at night, helping in the control or pest arthropods. The two-spotted spider mite, Tetranychus urticae Koch, is considered an important strawberry pest in that region, where the fungus Neozygites floridana (Weiser and Muma) has been found to infect it. Different mulching types could affect the incidence of this pathogen. Dehydrated coffee husk and pulp (DCHP) is a byproduct readily available in southern Minas Gerais, where could be used as organic mulching in strawberry beds. The temporary contact of that material with the soil of a patch of natural vegetation could facilitate its colonization by edaphic predatory mites helpful in the control of strawberry pests. The objective of this work was to study the effect of mulching type on the population dynamics of the two-spotted spider mite, associate mites and N. floridana, in a greenhouse and in the field. The use of DCHP increased the number of edaphic Gamasina on strawberry plants-Proctolaelaps pygmaeus (Müller) (Melicharidae) and Blattisocius dentriticus (Berlese) (Blattisociidae) were observed on strawberry leaflets, mainly in nocturnal samplings, indicating their possible daily migration from soil to plants. Lower levels of two-spotted spider mite occurred on plants from pots or soil beds mulched with DCHP instead of polyethylene film, possibly because of the slightly higher levels of mites of the family Phytoseiidae and infection by N. floridana. Adding DCHP onto the floor of natural vegetation did not result in higher diversity or levels of gamasine mites on DCHP. Complementary studies should be conducted to find ways to increase diversity and density of those organisms in strawberry beds, in an attempt to improve biological control of strawberry pests. The decision to use DCHP for mulching should also take into account other factors such as strawberry yield, costs and efficiency of weed management, to be evaluated in subsequent studies.

Pandora bullata (Entomophthoromycota: Entomophthorales) affecting calliphorid flies in central Brazil.

Fungi are where one finds them, and if one seeks fungal pathogens affecting flies, then a garbage dump may be an ideal place to find both persistent, abundant fly populations and their fungal pathogens. An obvious fungal epizootic affecting the oriental latrine fly, Chrysomya megacephala (Diptera: Calliphoridae), was observed over several days in mid-February 2015 at the local garbage dump adjacent to the city of Cavalcante, northern Goiás. This site harbored large populations of both C. megacephala and a Musca sp. (Diptera: Muscidae) but only the population of oriental latrine fly was affected by any fungal pathogen and presented unusually dense populations of fresh cadavers. The fungus was identifiable as Pandora bullata (Entomophthorales: Entomophthoraceae) only after a very small number of characteristically decorated resting spores were found in these flies two months later; this represents the first Brazilian (and South American) record of this species. P. bullata is known previously from a small number of North American, European and Australian collections, all of which have included relatively abundant production of resting spores. We cannot dismiss the possibility that the extremely sparse formation of resting spores at this Brazilian site may be due to abiotic factors such as latitude (13°46'40.53″S), day length, ambient temperatures, or even the precipitation patterns in this mid-tropical montaine site. Epizootic events affecting calliphorids in Brazil strengthen the interest in entomophthoran pathogens for biological control of flies.

Prevalence of entomophthoralean fungi (Entomophthoromycota) of aphids in relation to developmental stages.

BACKGROUND: Transmission of fungal pathogens of aphids may be affected by the host developmental stage. Brassica and Lactuca sativa L. crops were sampled in Santa Fe, Argentina, to determine the prevalence of fungal-diseased aphids and investigate the differences between developmental stages of aphids. RESULTS: The fungal pathogens identified were Zoophthora radicans (Bref.) A. Batko, Pandora neoaphidis (Remaud. & Hennebert) Humber and Entomophthora planchoniana Cornu. Their prevalence on each crop was calculated. The numbers of infected aphids were significantly different between the different developmental stages on all crops except B. oleracea var. botrytis L. CONCLUSIONS: The entomophthoralean fungi identified are important mortality factors of aphids on horticultural crops in Santa Fe. The numbers of infected nymphs and adults were significantly different, nymphs being the most affected developmental stage. © 2015 Society of Chemical Industry.

Two-spotted spider mite and its natural enemies on strawberry grown as protected and unprotected crops in Norway and Brazil.

Cultivation of strawberry in plastic tunnels has increased considerably in Norway and in southeastern Brazil, mainly in an attempt to protect the crop from unsuitable climatic factors and some diseases as well as to allow growers to expand the traditional production season. It has been hypothesized that cultivation under tunnels could increase the incidence of one of its major pests in many countries where strawberry is cultivated, including Norway and Brazil, the two spotted spider mite, Tetranychus urticae. The objective of this study was to evaluate the effect of the use of tunnels on the incidence of T. urticae and on its natural enemies on strawberry in two ecologically contrasting regions, Norway (temperate) and southeastern Brazil (subtropical). In both countries, peak densities of T. urticae in tunnels and in the open fields were lower than economic thresholds reported in the literature. Factors determining that systematically seem to be the prevailing relatively low temperature in Norway and high relative humidity in both countries. The levels of occurrence in Norway and Brazil in 2010 were so low that regardless of any potential effect of the use of tunnel, no major differences were observed between the two cropping systems in relation to T. urticae densities. In 2009 in Norway and in 2011 in Brazil, increase in T. urticae population seemed to have been restrained mainly by rainfall in the open field and by predatory mites in the tunnels. Phytoseiids were the most numerous predatory mite group of natural occurrence on strawberry, and the prevalence was higher in Brazil, where the most abundant species on strawberry leaves were Neoseiulus anonymus and Phytoseiulus macropilis. In Norway, the most abundant naturally occurring phytoseiids on strawberry leaves were Typhlodromus (Anthoseius) rhenanus and Typhlodromus (Typhlodromus) pyri. Predatory mites were very rare in the litter samples collected in Norway. Infection rate of the pest by the fungus Neozygites floridana (Neozygitaceae) was low. The results of this work suggest that in Norway the use of tunnels might not affect the population densities of T. urticae on strawberry in years of lower temperatures. When temperature is not a limiting factor for the development of T. urticae in that country (apparently always the case in southern Brazil), strawberry cultivation in the tunnels may allow T. urticae to reach higher population levels than in open fields (because of the provided protection from the direct impact of rainfall), but natural enemies may prevent higher levels from being reached.

Confirmation of Neozygites floridana azygospore formation in two-spotted spider mite (Tetranychus urticae) in strains from tropical and temperate regions.

Neozygites floridana is an obligate fungal pathogen of mites in the family Tetranychidae and is an important natural enemy of the two-spotted spider mite (Tetranychus urticae). Until now, information about the formation of azygospores remained to be fully confirmed. In this study, we document the formation of azygospores by a Brazilian N. floridana strain and the formation of azygospores and zygospores by a Norwegian N. floridana strain, both in the host T. urticae. Evidence of both zygosporogenesis and azygosporogenesis was also found in the same individual in the Norwegian stains. Further we report the presence of immature azygospores with 1-3 nuclei for the Norwegian strains, immature resting spores (probably azygospores) with 1-8 nuclei for the Brazilian strain, and mature resting spores with 2 nuclei for both the Norwegian and the Brazilian strains (azygo- or zygospores). Our observations suggest that the immature resting spore (prespore) of both strains begins in a multinucleate condition but that the nuclear number is reduced during maturation until mature resting spore is binucleate regardless of its origin as a zygospore or azygospore.

Competition between isolates of Zoophthora radicans co-infecting Plutella xylostella populations.

Interactions between Zoophthora radicans isolates were studied in vitro and in vivo during infection of Plutella xylostella larvae. We distinguished between isolates within infected hosts using PCR-RFLP. Isolates obtained from P. xylostella larvae (NW386 and NW250) were more virulent than isolates from other insect hosts. Isolate NW250 was most virulent at 27°C and isolate NW386 was most virulent at 22°C. In vitro growth of all isolates except NW386 was affected by the presence of other isolates. During in vivo interactions between NW250 and NW386, the isolate with the greatest conidial concentration at inoculation infected more larvae than its competitor. Dual infected larvae were only found in treatments where inoculation concentrations of conidia were high for both isolates. Where concentrations of conidia at inoculation were low for both isolates, only NW250 caused successful infection. The implications of these results for the ecology of Z. radicans are discussed.

Natural occurrence of Zoophthora radicans (Entomophthorales: Entomophthoraceae) on Thaumastocoris peregrinus (Heteroptera: Thaumastocoridae), an invasive pest recently found in Brazil.

Occurrence of Zoophthora radicans infecting nymphs and adults of Thaumastocoris peregrinus Carpintero and Dellape, 2006 is reported in Brazil. This is a new record of host for this fungal species and the first fungal pathogen associated with this pest worldwide. Infection of Z. radicans on T. peregrinus populations on commercial Eucalyptus plantation (Eucalyptus spp.) reached up to 100%, and low insect densities were associated with high levels of fungal infection in three out of seven plots. This pathogen seems to be virulent against T. peregrinus and may play an important role in population regulations of this invasive pest through naturally induced epizootics.

The effect of host plants on Tetranychus evansi, Tetranychus urticae (Acari: Tetranychidae) and on their fungal pathogen Neozygites floridana (Entomophthorales: Neozygitaceae).

In a series of tritrophic-level interaction experiments, the effect of selected host plants of the spider mites, Tetranychus evansi and Tetranychus urticae, on Neozygites floridana was studied by evaluating the attachment of capilliconidia, presence of hyphal bodies in the infected mites, mortality from fungal infection, mummification and sporulation from fungus-killed mite cadavers. Host plants tested for T. evansi were tomato, cherry tomato, eggplant, nightshade, and pepper while host plants tested for T. urticae were strawberry, jack bean, cotton and Gerbera. Oviposition rate of the mites on each plant was determined to infer host plant suitability while host-switching determined antibiosis effect on fungal activity. T. evansi had a high oviposition on eggplant, tomato and nightshade but not on cherry tomato and pepper. T. urticae on jack bean resulted in a higher oviposition than on strawberry, cotton and Gerbera. Attachment of capilliconidia to the T. evansi body, presence of hyphal bodies in infected T. evansi and mortality from fungal infection were significantly higher on pepper, nightshade and tomato. The highest level of T. evansi mummification was observed on tomato. T. evansi cadavers from tomato and eggplant produced more primary conidia than those from cherry tomato, nightshade and pepper. Switching N. floridana infected T. evansi from one of five Solanaceous host plants to tomato had no prominent effect on N. floridana performance. For T. urticae, strawberry and jack bean provided the best N. floridana performance when considering all measured parameters. Strawberry also had the highest primary conidia production. This study shows that performance of N. floridana can vary with host plants and may be an important factor for the development of N. floridana epizootics.

Molecular detection of establishment and geographical distribution of Brazilian isolates of Neozygites tanajoae, a fungus pathogenic to cassava green mite, in Benin (West Africa).

Diagnostic PCR with two specific primer pairs (NEOSSU and 8DDC) were used to monitor the establishment and geographical distribution of Brazilian isolates of Neozygites tanajoae Delalibera, Hajek and Humber (Entomophthorales: Neozygitaceae) released in Benin for the biological control of the cassava green mite, Mononychellus tanajoa (Bondar) (Acari: Tetranychidae). A total of 141 cassava fields were visited and samples of M. tanajoa suspected to be infected by N. tanajoae were collected in 60 fields distributed between the coastal Southern Forest Mosaic (SFM) and the Northern Guinea Savanna (NGS) zones of Benin, West Africa. Analysis of DNA samples of dead mites using the species specific NEOSSU primers revealed the presence of N. tanajoae in 46 fields. The second country specific pair of primers 8DDC revealed the presence of Brazilian isolates of N. tanajoae in 36 fields, representing 78.3% of fields positive for N. tanajoae. Brazilian isolates occurred from SFM to NGS zones in Benin, however, they were concentrated in fields located within former release zones (e.g. Department of Ouémé in the South and Borgou in the North). In contrast, the indigenous African isolates of N. tanajoae were evenly distributed in the sub-humid and humid savannah zones of the country. The mean infection rate of M. tanajoa with indigenous isolates of N. tanajoae was relatively low (5.3%) compared to Brazilian isolates (28%), indicating a higher biocontrol potential of the latter. This first post-release monitoring using PCR techniques showed that the Brazilian strains of N. tanajoae is well established in Benin and spread effectively in this area.

Effect of temperature on sporulation of Neozygites floridana isolates from different climates and their virulence against the tomato red spider mite, Tetranychus evansi.

The fungal pathogen Neozygites floridana Weiser and Muma has been evaluated as a classical biological candidate for introduction into Africa against the invasive tomato red spider mite Tetranychus evansi Baker and Pritchard. In this study, the effect of temperature on sporulation, germination and virulence of three isolates of N. floridana collected from T. evansi in three climatically distinct regions of Brazil and Argentina was determined. Six constant temperatures of 13 degrees C, 17 degrees C, 21 degrees C, 25 degrees C, 29 degrees C and 33 degrees C were tested for their effect on the ability of the three fungal isolates to sporulate, germinate and kill the mites. Six alternating-temperature regimes of 17-13 degrees C, 21-13 degrees C, 29-13 degrees C, 33-13 degrees C, 33-23 degrees C, 33-28 degrees C under a 12h photophase were also tested to estimate virulence of the three isolates against T. evansi. The Vipos isolate discharged more conidia than isolates from Recife or Piracicaba at all temperatures and sporulation was strongly temperature dependent. Optimal sporulation rates were observed at 25 degrees C while optimal germination rates were observed at 25 degrees C and 29 degrees C. At 29 degrees C, the shortest mean survival time of T. evansi (3.16 days, 95% CI of 3.05-3.27) was observed for the isolate from Vipos, while the longest LT(50) (3.47 days, 95% CI 3.34-3.59) was observed for the isolate from Piracicaba. Mortality of mites increased as the differences between alternating day and night temperatures increased from 8 degrees C (21-13 degrees C), to 10 degrees C (33-23 degrees C), to 16 degrees C (29-13 degrees C), with smallest and highest temperature differences of 4 degrees C (17-13 degrees C) and 20 degrees C (33-13 degrees C), both producing low mortalities. The overall results suggest that the Vipos isolate is better adapted to a wider range of temperatures than the other isolates tested.

Host range of Neozygites floridana isolates (zygomycetes: entomophthorales) to spider mites.

Neozygites floridana (Weiser & Muma) (Zygomycetes: Entomophthorales) has been reported infecting naturally at least 18 species of tetranychids worldwide. However, the host range of N. floridana is unknown. Epizootics caused by this pathogen to tetranychid populations indicate that N. floridana has the potential to be used as a biological control agent. However, the virulence and specificity of species and strains of Neozygites need to be assessed in the laboratory to reveal its potential as a biological control agent. N. floridana isolates are currently been investigated in Brazil as biological control agents against the tomato red mite, Tetranychus evansi Baker & Pritchard, and the two-spotted spider mite, Tetranychus urticae Koch. The pathogenicity of five strains of N. floridana obtained from T. urticae, T. evansi and T. ludeni Zacher was assessed against populations of Mononychellus tanajoa (Bondar), Schizotetranychus sacharum Flechtmann & Baker, Tetranychus abacae Baker & Pritchard and Tetranychus armipenis Flechtmann & Baker, in addition to the species from which the fungus was obtained. Mummified mites were placed on leaf discs of the host plant of each tetranychid to promote fungal sporulation, and after 24h the mites were transferred to the leaf discs. Contamination, infection and mummification were evaluated daily for seven days after confinement. Each isolate was pathogenic to three or four out of the six spider mite species tested. However, except for isolate ESALQ1421, all isolates caused higher levels of infection and significant mummification only to the tetranychid species from which they were collected. None of the isolates was pathogenic to S. sacharum and only one isolate infected T. abacae. Alternative hosts may be important for N. floridana survival in tropical regions where resting spores are rarely found.

Failure of the mite-pathogenic fungus Neozygites tanajoae and the predatory mite Neoseiulus idaeus to control a population of the cassava green mite, Mononychellus tanajoa.

Monitoring of a population of the phytophagous cassava green mite, Mononychellus tanajoa (Bondar), and its natural enemies was undertaken in central Bahia, Brazil, in mid-1996. In spite of the presence of extremely high densities of the predatory phytoseiid mite Neoseiulus idaeus Denmark & Muma, the phytophagous mite population reached such high densities itself that there was total overexploitation of the cassava plants, leading to total leaf loss. Meanwhile, the mite-pathogenic fungus Neozygites tanajoae Delalibera, Humber & Hajek did not affect the M. tanajoa population in its growth phase as there was no inoculum present, even though we predict from a simple regression model that there was the potential for epizootics at that time. Soon after the M. tanajoa population crashed due to defoliation, there could have been an epizootic but there were simply no mite hosts to infect. These data demonstrate the ineffectiveness of one natural enemy (the predator) in terms of prey population regulation and demonstrate the importance of timing in the possible effectiveness of the other (the pathogen). For the pathogen, this probably explains its sporadic effect on host populations as previously reported. We conclude that the fungus is likely to be most useful as an adjunct to biological control with predatory mites other than N. idaeus.

Does methyl salicylate, a component of herbivore-induced plant odour, promote sporulation of the mite-pathogenic fungus Neozygites tanajoae?

Blends of volatile chemicals emanating from cassava leaves infested by the cassava green mite were found to promote conidiation of Neozygites tanajoae, an entomopathogenic fungus specific to this mite. Methyl salicylate (MeSA) is one compound frequently present in blends of herbivore-induced plant volatiles (HIPV) as well as that of mite-infested cassava. Here, we investigated the effect of methyl salicylate in its pure form on the production of pre-infective spores (conidia), and the germination of these spores into infective spores (capilliconidia), by a Brazilian isolate and a Beninese isolate of N. tanajoae. Mummified mites previously infected by the fungal isolates were screened under optimal abiotic conditions for sporulation inside tightly closed boxes with or without methyl salicylate diffusing from a capillary tube. Production of conidia was consistently higher (37%) when the Beninese isolate was exposed to MeSA than when not exposed to it (305.5 +/- 52.62 and 223.2 +/- 38.13 conidia per mummy with and without MeSA, respectively). MeSA, however, did not promote conidia production by the Brazilian isolate (387.4 +/- 44.74 and 415.8 +/- 57.95 conidia per mummy with and without MeSA, respectively). Germination of the conidia into capilliconidia was not affected by MeSA for either isolate (0.2%, 252.6 +/- 31.80 vs. 253.0 +/- 36.65 for the Beninese isolate and 4.2%, 268.5 +/- 37.90 vs. 280.2 +/- 29.43 for the Brazilian isolate). The effects of MeSA on the production of conidia were similar to those obtained under exposure to the complete blends of HIPV for the case of the Beninese isolate, but dissimilar (no promoting effect of MeSA) for the case of the Brazilian isolate. This shows that MeSA, being one compound out of many HIPV, can be a factor promoting sporulation of N. tanajoae, but it may not be the only factor as its effect varies with the fungal isolate under study.

The role of resting spores in the survival of the mite-pathogenic fungus Neozygites floridana from Mononychellus tanajoa during dry periods in Brazil.

Survival of pathogens during long periods of unfavorable conditions can be critical to their ecology and to their use in biological control. In northeastern Brazil, the mite pathogen Neozygites floridana must survive hot and dry conditions between wet seasons when it infects the cassava green mite Mononychellus tanajoa. We report on large numbers of mite cadavers bearing resting spores towards the end of epizootics in mid-1995. High within-leaf variability indicated that local factors may be important in determining resting spore formation. These spores remain in the host cadaver on a leaf until the cadaver breaks up, whereupon the spores fall freely to the soil, there to remain dormant. Laboratory simulation of field conditions led to ca. 25% of mycosed individuals bearing resting spores. Mummies (without resting spores) kept in hot and dry conditions showed little or no viability within 2 months, implying no role for survival over extended dry periods. It is proposed that resting spores form the principal means by which this pathogen survives the dry season in the study area. This has implications for its introduction to new areas in classical biological control.