Neozygites abacaridis sp. nov. (Entomophthorales), a new pathogen of phytophagous mites (Acari,Eriophyidae)

A new entomopathogenic fungus, described here as Neozygites abacaridis n. sp. (Zygomycetes: Entomophthorales), has been found on the mites Abacarus hystrix, Aculodes dubius, and A. mckenziei (Acari: Eriophyidae). It differs from other Neozygites species affecting mites by its small, globose primary conidia, short-ovoid, smoky coloured capilliconidia, and very short capillary conidiophores-which are usually not longer than the spore length. This pathogen infected mite individuals in autumn (from mid-August until mid-November) on Lolium perenne, Agrostis stolonifera, and Festuca rubra. It caused 0.5-1% host's mortality in the vicinity of Siedlce (Eastern Poland) and up to 2-8%, on an average in Puszczykowo (Wielkopolski National Park near Poznań), where its prevalence on some plants reached 13%.     

Interactions of two idiobiont parasitoids (Hymenoptera: Ichneumonidae) of codling moth (Lepidoptera: Tortricidae) with the entomopathogenic nematode Steinernema carpocapsae (Rhabditida: Steinernematidae)

Simultaneous use of parasitoids and entomopathogenic nematodes for codling moth (CM) control could produce an antagonistic interaction between the two groups resulting in death of the parasitoid larvae. Two ectoparasitic ichneumonid species, Mastrus ridibundus and Liotryphon caudatus, imported for classical biological control of cocooned CM larvae were studied regarding their interactions with Steinernema carpocapsae. Exposure of M. ridibundus and L. caudatus developing larvae to infective juveniles (IJs) of S. carpocapsae (10 IJs/cm2; approximately LC(80-90) for CM larvae) within CM cocoons resulted in 70.7 and 85.2% mortality, respectively. However, diapausing full grown parasitoid larvae were almost completely protected from nematode penetration within their own tightly woven cocoons. M. ridibundus and L. caudatus females were able to detect and avoid ovipositing on nematode-infected cocooned CM moth larvae as early as 12h after treatment of the host with IJs. When given the choice between cardboard substrates containing untreated cocooned CM larvae and those treated with an approximate LC95 of S. carpocapsae IJs (25 IJs/cm2) 12, 24, or 48h earlier, ovipositing parasitoids demonstrated a significant preference for untreated larvae. The ability of these parasitoids to avoid nematode-treated larvae and to seek out and kill cocooned CM larvae that survive nematode treatments enhances the complementarity of entomopathogenic nematodes and M. ridibundus and L. caudatus.     

Susceptibility of lady beetles (Coleoptera: Coccinellidae) to entomopathogenic nematodes

We investigated differential susceptibility of lady beetles to entomopathogenic nematodes, for two reasons: (1) to estimate potential nontarget effects on natural lady beetle populations, (2) to compare the susceptibility of exotic versus native lady beetle species. We hypothesize that successful establishment of some exotically introduced arthropods may be due, in part, to a lower susceptibility relative to competing native species. In laboratory studies, we compared the pathogenicity, virulence, and reproductive capacity of Heterorhabditis bacteriophora and Steinernema carpocapsae among two native (Coleomegilla maculata and Olla v-nigrum) and two successfully established exotic (Harmonia axyridis and Coccinella septempunctata) lady beetles, and a known susceptible lepidopteran host, Agrotis ipsilon. After 1 and 2 days of exposure to either nematode species, mortality of A. ipsilon was higher than in all lady beetles. Thus, we predict that nematode field applications would have significantly less impact on lady beetle populations than on a susceptible target pest. Additionally, the impact of soil-applied nematodes may be lower on lady beetles than on soil-dwelling hosts because the former spends relatively less time on the soil. Exotic lady beetles were less susceptible to nematode infection than native species. Reproductive capacity data also indicated lower host suitability in H. axyridis, but not in C. septempunctata. Overall, the hypothesis that low susceptibility to pathogens in certain exotic lady beetles may have contributed to competitive establishment was supported (especially for H. axyridis). Additional studies incorporating different hosts and pathogens from various geographic locations will be required to further address the hypothesis.     

Sydowia polyspora associated with current season needle necrosis (CSNN) on true fir (Abies spp.)

Current season needle necrosis (CSNN) has been a serious foliage disorder on true fir Christmas trees and bough material in Europe and North America for more than 25 y. Approximately 2–4 weeks after bud break, needles develop chlorotic spots or bands that later turn necrotic. The symptoms have been observed on noble fir (Abies procera), Nordmann fir (A. nordmanniana) and grand fir (A. grandis) on both continents. CSNN was reported as a physiological disorder with unknown aetiology from USA, Denmark, and Ireland, but was associated with the fungus Kabatina abietis in Germany, Austria and Norway. In 2007, a fungus that morphologically resembled K. abietis was isolated from symptomatic needle samples from Nordmann fir from Austria, Denmark, Germany, Norway, and USA. Sequencing of the internal transcribed spacer (ITS) region of ribosomal DNA of these cultures, plus a K. abietis reference culture from Germany (CBS 248.93), resulted in Hormonema dematioides, the imperfect stage of Sydowia polyspora, and thus the taxonomy is further discussed. Inoculation tests on Nordmann fir seedlings and transplants with isolates of S. polyspora from all five countries resulted in the development of CSNN symptoms. In 2009, S. polyspora was also isolated from symptomatic needles from Nordmann fir collected in Slovakia.     

Interactions between imidacloprid and Metarhizium brunneum on adult Asian longhorned beetles (Anoplophora glabripennis (Motschulsky)) (Coleoptera: Cerambycidae)

Anoplophora glabripennis (Motschulsky) (Coleoptera: Cerambycidae), a longhorned beetle species native to Asia, has been introduced into several North American and European cities. Currently eradication and preventive measures are limited to identifying and destroying infested trees and protecting uninfested trees with trunk or soil-injections of the systemic insecticide imidacloprid. Because entomopathogenic fungi like Metarhizium brunneum Petch have been identified as virulent against these beetles we conducted several tests to determine the compatibility of the two agents in combination. Radial hyphal growth and the sporulation capacity of M. brunneum on Sabouraud dextrose agar with yeast were not significantly affected by the presence of imidacloprid. In a 2 × 3 factorial experiment investigating interactions between exposure to imidacloprid and M. brunneum we observed no effect of imidacloprid alone on beetle survival when beetles were given a single dose of 10 or 100 ppm compared to control insects. We observed a significant effect of exposure to M. brunneum, and a significant interaction between imidacloprid and M. brunneum representing a synergistic effect of dual treatment. Beetles exposed to the fungus alone lived significantly longer compared to insects treated with a single dose of 100 ppm imidacloprid (9.5 vs. 6.5 d). Consumption of striped maple twigs by beetles exposed to imidacloprid, across concentrations, was reduced 48% compared to control insects, where as consumption by M. brunneum-exposed beetles was reduced by 16% over the first 6-days of the test period. Beetles fed 100 ppm imidacloprid consumed 32% less over the first 3 d compared to beetles not exposed to imidacloprid and thereafter consumed as much as beetles not fed 100 ppm imidacloprid. M. brunneum-exposed beetles consumed significantly less food than control insects throughout the test period, and beetles treated with imidacloprid produced significantly fewer conidia compared to beetles not treated with imidacloprid.     

Increased pathogenicity against coffee berry borer, Hypothenemus hampei (Coleoptera: Curculionidae) by Metarhizium anisopliae expressing the scorpion toxin (AaIT) gene

Coffee berry borer (CBB) is the Worlds most devastating coffee pest causing an estimated US$500 million worth of losses annually through damage and control costs. Beauveria bassiana and Metarhizium anisopliae have been employed to control this pest but their low virulence (slow kill and large inoculums) is an important factor constraining their use. M. anisopliae (AaIT-Ma549) has been modified to express the scorpion toxin (AaIT) in insect hemolymph and this greatly increased pathogenicity against Manduca sexta and Aedes aegypti. Here, we demonstrate that AaIT-Ma549 was also dramatically more virulent against CBB, and we provide a much more comprehensive analysis of infection processes and post-mortality development than in the previous research. We evaluated several spore concentrations (10¹ through 10⁷ spores/ml) of both the wild type and recombinant strain. At concentrations of 10¹, 10² and 10³ spores/ml, the recombinant strain significantly increased mortality of CBB by 32.2%, 56.6% and 24.6%, respectively. The medial lethal concentration (LC₅₀) was reduced 15.7-fold and the average survival time (AST) was reduced by 20.1% to 2.98 ± 0.1 days with 10⁷ spores/ml. This is the first occasion that an entomopathogenic fungus has been found to kill CBB in less than 3 days. However, AaIT-Ma549 produces significantly fewer spores on cadavers than the parental strain.     

First host record for Anteon pilicorne (Ogloblin) (Hymenoptera: Dryinidae), a parasitoid of Cicadellidae, including the corn leafhopper (Hemiptera: Cicadellidae)

For the first time the dryinid wasp Anteon pilicorne (Ogloblin) is recorded as a parasitoid of two Macrostelini leafhoppers: Balclutha rosea (Scott) and the corn leafhopper Dalbulus maidis (DeLong & Wolcott). New distributional records are presented.     

Entomophthora ferdinandii (Zygomycetes: Entomophthorales) Causing Natural Infections of Musca domestica (Diptera: Muscidae) in Argentina

The identity and activity of an entomopathogenic fungus belonging to the Entomophthora muscae species complex and infecting Musca domestica in poultry houses from La Plata, Argentina, is reported. Entomophthora caused natural infections between September 2001 and September 2003. Primary conidia of this fungus were on average 29.5 ± 1.2 × 23.4 ± 2.4 μm and contained, on average, 10.5 ± 0.1 nuclei (range: 7–15) with an average diameter of 4.8 ± 0.1 μm. This fungus is identified as E. ferdinandii Keller (this specific epithet includes a nomenclaturally required spelling correction); this is a first record of E. ferdinandii in South America and of any member of the E. muscae species complex from flies in Argentina.     

(n-7) and (n-9) cis-Monounsaturated fatty acid contents of 12 Brassica species

cis-Vaccenic acid or cis-11-octadecenoic acid, a C18:1 (n-7) isomer of oleic acid (C18:1 (n-9)) has been found in several oilseeds. It is synthesized from palmitic acid (C16:0) via production of C16:1 (n-7) by a Delta9 desaturase and elongation by an elongase giving C18:1 (n-7). In this study, the fatty acid composition of 12 Brassica species was analyzed by GC-FID and confirmed by GC-MS. All species contained C18:1 (n-7), C20:1 (n-7) and C22:1 (n-7) fatty acid isomers, suggesting that C18:1 (n-7) was elongated. The levels of these fatty acids varied according to the species. C18:1(n-7)) represented from 0.4% to 3.3% of the total relative fatty acid contents of the seeds. The contents of C20:1(n-7) and C22:1(n-7) levels were lower than C18:1(n-7) contents; the relative fatty acid composition varied from 0.02% to 1.3% and from below the limit of detection to 1.3% for C20:1 (n-7) and C22:1 (n-7), respectively. The ratios of (n-7)/(n-9) ranged from 2.8% to 16.7%, 0.6% to 29.5% and 0% to 2.6% for C18:1, C20:1 and C22:2, respectively. Using statistical similarities or differences of the C18:1 (n-7)/(n-9) ratios for chemotaxonomy, the surveyed species could be arranged into three groups. The first group would include Brassica napus, B. rapa, and B. tournefortii with Eruca sativa branching only related to B. napus. The second group would include B. tournefortii, Raphanus sativus and Sinapis alba. The last group would include B. juncea, B. carinata and B. nigra with no similarity/relationship between them and between the other species. Results suggested that the level of C20:1 (n-7) influenced the levels of all monounsaturated fatty acids with chain length higher than 20 carbons. On the other hand, palmitoleic acid (C16:1) levels, C16:1 being the parent of all (n-7) fatty acids, had no statistically significant correlation with the content of any of the fatty acids of the (n-7) or (n-9) family.     

Insecticidal effect of Beauveria bassiana (Balsamo) Vuillemin (Ascomycota: Hypocreaes) in combination with three diatomaceous earth formulations against Sitophilus granarius (L.) (Coleoptera: Curculionidae)

The insecticidal effect of the entomopathogenic fungus Beauveria bassiana (Balsamo) Vuillemin (Ascomycota: Hypocreaes) in combination with three diatomaceous earth (DE) formulations against adults of the granary weevil, Sitophilus granarius (L.) (Coleoptera: Curculionidae) was tested in the laboratory. The three DEs were Insecto™, SilicoSec^® and PyriSec^®. The fungus was applied at 400 ppm alone, or in combination with 200 ppm of each of the three DEs. Mortality was measured after 7 d of exposure. Bioassays were conducted at three temperatures 20, 25 and 30 °C and two relative humidities (rh) 55% and 75%. On wheat treated with B. bassiana alone, mortality was higher at 55% than at 75% rh. Also, the fungus alone was less effective at 20 °C than at the other two temperatures tested, but mortality did not exceed 52% for any of the conditions tested. Similar mortality levels were also noted on wheat treated with each of the three DEs alone. The simultaneous presence of B. bassiana and DE increased weevil mortality. In this combination, mortality was higher at high temperatures and low rh, and this effect was similar for all DEs tested. Progeny production on wheat treated with B. bassiana was higher that the respective progeny counts in the DE-treated wheat. The results indicate that a combination of B. bassiana and DEs is effective against S. granarius, under a broad range of temperature and rh levels in stored wheat.     

Effect of the entomopathogenic fungus,Entomophthora muscae (Zygomycetes: Entomophthoraceae), on sex pheromone and other cuticular hydrocarbons of the house fly,Musca domestica

House fly (Musca domestica) males are highly attracted to dead female flies infected with the entomopathogenic fungus Entomophthora muscae. Because males orient to the larger abdomen of infected flies, both visual and chemical cues may be responsible for the heightened attraction to infected flies. Our behavioral assays demonstrated that the attraction is sex-specific-males were attracted more to infected females than to infected males, regardless of cadaver size. We examined the effect of E. muscae on the main component of the house fly sex pheromone, (Z)-9-tricosene, and other cuticular hydrocarbons including n-tricosane, n-pentacosane, (Z)-9-heptacosene, and total hydrocarbons of young (7 days old) and old (18 days old) virgin females. Young E. muscae-infected female flies accumulated significantly less sex pheromone and other hydrocarbons on their cuticular surface than uninfected females, whereas the cuticular hydrocarbons of older flies were unaffected by fungus infection. These results suggest that chemical cues other than (Z)-9-tricosene, visual cues other than abdomen size, or a combination of both sets of cues might be responsible for attraction of house fly males to E. muscae-infected females.     

An endosymbiotic conidial fungus, Scopulariopsis brevicaulis, protects the American dog tick, Dermacentor variabilis, from desiccation imposed by an entomopathogenic fungus

The functional role of an endosymbiotic conidial fungus (Scopulariopsis brevicaulis) prevalent within the integumental glands and hemocoel of the American dog tick (Dermacentor variabilis) was investigated to explore the nature of this tick/fungus association. D. variabilis is normally highly resistant to Metarhizium anisopliae, a widely-distributed entomopathogenic fungus, but when mature female ticks harboring S. brevicaulis were fed a solution containing a mycotoxin (Amphotericin B) to purge this mycobiont internally, the ticks inoculated with M. anisopliae displayed classic signs of pathogenicity, as evidenced by recovery of M. anisopliae from ticks by internal fungus culture, greatly accelerated net transpiration water loss rates (nearly 3x faster than ticks containing S. brevicaulis naturally) and elevation of critical equilibrium humidity (CEH) closer to saturation, implying a reduced capacity to absorb water vapor and disruption of water balance (water gain not equal water loss) that resulted in tick death. The presence of S. brevicaulis within the tick was previously puzzling: the fungus is transmitted maternally and there is no apparent harm inflicted to either generation. This study suggests that S. brevicaulis provides protection to D. variabilis ticks against M. anisopliae. Thus, the S. brevicaulis/tick association appears to be mutualistic symbiosis. Given that both organisms are of medical-veterinary importance, disruption of this symbiosis has potential for generating novel tools for disease control.     

First record of entomopathogenic nematodes (Steinernematidae and Heterorhabditidae) in Costa Rica

A survey of entomopathogenic nematodes was conducted in the north Pacific (Guanacaste Conservation Area) and southeast Caribbean (Gandoca-Manzanillo Natural Refuge) regions of Costa Rica. Out of a total of 41 soil samples, 5 were positive for entomopathogenic nematodes (20.5%), with 3 (12.3%) containing Steinernema and 2 (8.2%) Heterorhabditis isolates. Morphological and molecular studies were undertaken to characterize these isolates. The Heterorhabditis isolates were identified as Heterorhabditis indica and the three Steinernema isolates were identified as two new undescribed species. H. indica was recovered from a coastal dry forest. Steinernema n. sp. 1 was isolated from a rainforest valley, between volcanoes. Steinernema sp. n. 2 was isolated from sand dunes in the Caribbean Coast (Punta Uva) near the rainforest strip along the coast. Although limited to two geographic regions, this study suggests entomopathogenic nematodes may be diverse and perhaps widely distributed in Costa Rica. A more intensive survey, covering all geographic regions is currently undergoing.     

Evaluation of Metarhizium anisopliae (Metsch) Sorok. to target larvae and adults of Capnodis tenebrionis (L.) (Coleoptera: Buprestidae) in soil and fiber band applications

The aim of this work has been to evaluate in the laboratory the potential of entomopathogenic fungi against adults and larvae of Capnodis tenebrionis (L.) (Coleoptera: Buprestidae) through fiber band application and a potted plant bioassay with soil application, respectively. Our previous findings revealed that Metarhizium anisopliae EAMa 01/58-Su isolate was the most virulent against neonate larvae of the buprestid. In the present work, M. anisopliae EAMa 01/58-Su isolate has been also shown to be highly virulent against adult beetles by immersion in a conidial suspension; thus it was selected to accomplish our objectives. When adult beetles were stimulated to climb 100 x 200 mm non-woven commercial fiber bands impregnated with conidia of M. anisopliae EAMa 01/58-Su isolate, total mortality rates varied from 85.7% to 100.0%; whereas no significant correlation was detected between the time needed to cross the band (mean value 648.7+/-22.4s) and the time of death, with mean average survival time ranging between 10.3 and 16.0 days, compared to 28 days of the controls. Potted seedlings (5-6 months old) of cherry plum (Prunus myrobalana Lois.), a commonly used apricot rootstock, were used to study the efficacy of soil treatment with M. anisopliae EAMa 01/58-Su isolate against neonate C. tenebrionis larvae. The soil inoculation with M. anisopliae EAMa 01/58-Su isolate had a significant effect on the mean number of dead larvae recovered from the roots, with mean mortality ranging from 83.3% to 91.6%; whereas no significant differences were detected between the three fungal doses. In all cases, dead larvae found within roots exhibited external signs of fungal growth. Hence, it may be possible to use M. anisopliae EAMa 01/58-Su isolate in a biocontrol strategy targeting both adults and larvae of C. tenebrionis.     

The efficacy of two entomopathogenic biocontrol agents against adult Thrips palmi (Thysanoptera:Thripidae)

The efficacy of the two entomopathogenic biocontrol agents, Steinernema feltiae (Filipjev) and Lecanicillium muscarium (Petch), against juvenile Thrips palmi Karny in the laboratory situation is well documented. This study investigated the extrapolation of this knowledge to the control of adult stages. S. feltiae caused significantly higher mortality to juvenile T. palmi than to adult stages, whereas L. muscarium had a more significant impact on adult stages. The potential to develop an IPM strategy to control T. palmi utilising the two entomopathogens is discussed.     

Sublethal effects of Beauveria bassiana (Balsamo) Vuillemin (Deuteromycotina: Hyphomycetes) on the whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) under laboratory conditions

Sublethal effects were evaluated in subsequent generations of whiteflies Bemisia tabaci (Gennadius) arising from parental generations exposed in the four nymphal stages to the fungus Beauveria bassiana (Balsamo) Vuillemin. Examples of such effects include impaired fertility, production of malformations or external variations, and reduced survival of later generations. Malformations of the head, legs, wings or abdomen were not observed in adults derived from treated nymphs, nor were negative effects observed in the fecundity and fertility of the descendants of the whiteflies treated with the fungus. However, moulting problems were observed in insects descended from B. bassiana-treated whiteflies. This is the first time that such effects have been reported, with almost 30% of imagos resulting from treated nymphs unable to detach completely from the exuvia. A gradual reduction in mortality rates between subsequent generations was observed. The importance of these results is discussed in the light of findings from other studies into the effects of entomopathogenic fungi on pest insects.     

A Novel Strain of Steinernema riobrave (Rhabditida: Steinernematidae) Possesses Superior Virulence to Subterranean Termites (Isoptera: Rhinotermitidae)

Subterranean termites are major global pests of wood structures and wood products. Among the most economically important subterranean termite species in the US are Heterotermes aureus, Reticulitermes flavipes, and Coptotermes formosanus. In prior studies, the entomopathogenic nematode, Steinernema riobrave strain 355, exhibited a high level of virulence to H. aureus compared with other nematode species. However, S. riobrave 355 was reported to be poorly or only moderately virulent to R. flavipes and C. formosanus, respectively. We hypothesized that other strains of S. riobrave may possess a high level of virulence to all three termite species. Under laboratory conditions we compared three novel strains of S. riobrave (3-8b, 7-12, and TP) with the 355 strain for virulence to H. aureus, R. flavipes, and C. formosanus workers. H. aureus was very susceptible to all the S. riobrave strains, and termites in all nematode treatments were dead after 4 d. The TP strain of S. riobrave caused greater mortality in R. flavipes and C. formosanus compared to the other nematode strains. Specifically, the TP strain caused 75% and 91% mortality in R. flavipes and C. formosanus, respectively, which was more than 300% and 70% higher than the mortality caused by other strains. Additional studies are warranted to determine the ability of S. riobrave (TP) to control the targeted termite species under field conditions.     

Ecological characterization of Steinernema anatoliense (Rhabditida: Steinernematidae)

Our study describes the basic ecological characteristics of the entomopathogenic nematode Steinernema anatoliense including its response to temperature, moisture, and host range. The effect of temperature and soil moisture on the infection of Galleria mellonella larvae by S. anatoliense was determined. The temperature range for infectivity was greater than that for development. The optimal temperature for infection and development was 25 degrees C. Although S. anatoliense infected the hosts at 10 degrees C, no reproduction occurred at this temperature. This nematode species that was isolated from a cold region of Turkey exhibited warm-adapted temperature characteristics. Optimum water content of the soil for S. anatoliense to infect the host was 10%.     

Transmission of Pandora neoaphidis in the presence of co-occurring arthropods

Transmission of the entomopathogenic fungus Pandora neoaphidis to the nettle aphid Microlophium carnosum was assessed in the presence of arthropods that co-exist with the fungus within the habitat but do not compete for aphid hosts. The presence of a parasitoid significantly enhanced transmission, and transmission rates were similar for both enemy and non-enemy parasitoids. Although herbivory of nettle leaves by Peacock butterfly (Inchis io) caterpillars indirectly reduced the number of M. carnosum by >30% due to a reduction in leaf area for feeding, the addition of I. io significantly increased transmission of P. neoaphidis in the remaining aphids. It is likely that enhanced transmission in the presence of A. rhopalosiphii and I. io is due to disturbance and subsequent movement of the aphid, resulting in contact with conidia deposited on the leaf surface. The presence and impact of co-occurring arthropods should be taken into consideration when assessing the transmission of fungal entomopathogens.