Use of entomopathogenic fungi combined with biorational insecticides to control Dichroplus maculipennis (Orthoptera: Acrididae: Melanoplinae) under semi-field conditions

Grasshoppers are among the invertebrate herbivores that cause most economic losses in grasslands throughout Argentina’s Pampas and parts of Patagonia. Chemical insecticides remain the sole option for grasshopper control in this area, despite being of significant environmental concern. Our aim was to evaluate the efficacy of combinations between three entomopathogenic fungi strains (Beauveria bassiana LPSc 1067 and LPSc1082), and Metarhizium anisopliae (LPSc 907), two biorational insecticides (luphenuron and methoxyfenozide), and a new synthetic chemical pesticide (rynaxypyr) in the control of the pest grasshopper Dichroplus maculipennis under field cage conditions. Fungal strains used were adjusted to 1 × 10⁸, 1 × 10⁶ and 1 × 10⁴ conidia/ml. Insecticides were tested at three concentrations: the average concentration recommended for application in the field (100%), 50% of that level and finally 25%. Combinations of the insecticides with B. bassiana (LPSc 1067, LPSc 1082) and M. anisopliae (LPSc 907) caused higher mortality to D. maculipennis nymphs than any of the individual agents used alone. The three insecticides tested did not negatively affect the isolates of the two species of entomopathogenic fungi employed.     

Infectivity,viability and effects of Paranosema locustae (Microsporidia) on juveniles of Dichroplus maculipennis (Orthoptera: Acrididae: Melanoplinae) under laboratory conditions

Infectivity and effects on host of a long-term stored aqueous suspension of Paranosema locustae on juveniles of Dichroplus maculipennis, a pest grasshopper in parts of the Pampas and Patagonia, were evaluated. Infections developed in 90–97.8% of treated individuals. Mortality increased with time, reaching highest values at 30–40 days post-inoculation (79.5–100%). Infected nymphs showed significantly slower development.     

Susceptibility of Bufonacris claraziana (Orthoptera: Tristiridae) to Beauveria bassiana (Ascomycota: Hypocreales) under controlled conditions

Bufonacris claraziana outbreaks, an endemic grasshopper of Argentinian Patagonia, are a recurrent phenomenon in that region, causing severe damage to forage. The aim of this study was to evaluate the susceptibility of B. claraziana to different strains of the entomopathogenic fungus Beauveria bassiana under laboratory conditions. The strains tested were LPSc 1225, LPSc 1226, and LPSc 1227. Percentage of mortality was 100% for all three strains, a significant difference was registered with the control where mortality was from 26.66?±?2.76%. Results obtained represent a first contribution on the use of an entomopathogenic microorganism as a potential biocontrol agent of this species.     

Isolation and characterization of microsatellite loci from the entomopathogenic fungus Beauveria bassiana (Ascomycota: Hypocreales)

Beauveria bassiana, an entomogenous fungus used for the biological control of pest insects, comprises a globally‐distributed species complex of regionally endemic lineages. In order to study the population genetics of B. bassiana, detail species boundaries, conduct ecological studies of natural populations and track fates of experimentally‐released strains, sensitive genetic markers are required. We describe the isolation and characterization of eight microsatellite loci that amplify successfully from strains representative of the phylogenetic diversity in the B. bassiana complex.     

Effect of host plant on susceptibility of whitefly Bemisia tabaci (Homoptera: Aleyrodidae) to the entomopathogenic fungus Beauveria bassiana (Ascomycota: Hypocreales)

We determined host plant effect on susceptibility of whitefly Bemisia tabaci to the entomopathogenic fungus Beauveria bassiana under controlled conditions. Insects were reared on cucumber, eggplant, tomato or cabbage. Fungal suspensions of 1×10⁴, 10⁵, 10⁶, 10⁷ and 10⁸ conidia/mL were applied on second-instar nymphs. Nymphal survival significantly differed among different host plant species on which the nymphs were reared. Ten days after inoculation with 1×10⁸ conidia/mL, percent survival was 4.2±0.7, 9.6±0.4, 13.4±0.8, and 24.3±0.9% on cucumber, eggplant, tomato and cabbage, respectively. Average survival times of nymphs were also significantly influenced by host plant species. After inoculation with 1×10⁸ conidia/mL, survival times were 4.8±0.15, 6.0±0.11, 5.7±0.13, and 6.2±0.08 days for nymphs reared on cucumber, eggplant, tomato, and cabbage, respectively. Virulence also differed depending on host plant species; 10 days after inoculation, LC₅₀ values were 4.6×10⁴, 1.6×10⁵, 4.2×10⁵ and 2.1×10⁶ conidia/mL on cucumber, eggplant, tomato and cabbage, respectively. Nymphs on cucumber showed highest susceptibility.     

Efficiency of food utilization by Dichroplus maculipennis (Orthoptera: Acrididae: Melanoplinae) on four crop plants under controlled conditions

The aim of this study was to analyze the food utilization efficiencies and the relative growth and consumption rates of different developmental stages and sexes of D. maculipennis under controlled conditions on wheat, oat, corn, and soybean plants, important crops in the Pampas region of Argentina. As expected from a polyphagous species, D. maculipennis was observed to consume all four of the plant species offered. Nevertheless, the consumption of both nymphs and adults was differentiated. Oat and wheat were more consumed than corn and soybean. Females presented higher consumption rates (384.6 ± 30.64 mg/individual/day) than males (278.71 ± 24.26 mg/individual/day). Adult females had the highest growth rate, followed by nymphs of the same sex, and then adult males. The highest values of ECI and ECD were obtained in soybean; females had higher values of food efficiencies than males, and nymphs had greater values than adults. In relation to this, soybean was the highest quality food; the amount of nitrogen present in soybean was approximately twice that found in the other species. The nutritional needs of D. maculipennis might have been satisfied by feeding on low quantities of soybean, which is, among the food offered, the most “nutritionally balanced food”.     

Postembryonic development and food consumption of Dichroplus elongatus Giglio-Tos and Dichroplus maculipennis (Blanchard) (Orhtoptera: Acrididae: Melanoplinae) under laboratory conditions

Dichroplus maculipennis (Blanchard) and D. elongatus Giglio-Tos are two of the most important melanoplines in Argentina, both ecologically and economically. The postembryonic development and forage loss (consumption of Bromus brevis Ness + fallen material) caused by older nymphs (instars IV, V, VI) and adults of both species were studied under controlled conditions (30oC, 14L:10D, 40% RH). Five nymphal instars were recorded in D. elongatus, and six in D. maculipennis. Total nymphal development was similar in both species (D. elongatus: 32 ± 0.70 days; D. maculipennis: 34.5 ± 0.37 days). Daily consumption increased from nymphal instars to pre-reproductive adult stage. In both species, pre-reproductive females had higher consumption rates than other stages considered (D. elongatus: 30.6 ± 0.56 mg dry weight/day; D. maculipennis: 48.7 ± 0.74 mg dry weight/day). In the reproductive stage, consumption decreased significantly in both sexes. When feeding, D. maculipennis let some plant material to drop, increasing total loss. The percentage of fallen material was greater in reproductive adults, representing 3.9% and 2.9% of the total daily loss for males and females, respectively. Females and males of D. maculipennis were heavier than those of D. elongatus (P < 0.05), and daily consumption was significantly higher (P < 0.05). Regardless sex and reproductive status, adults of D. maculipennis consumed 29.1 ± 0.64 mg dry weight/day on average, while one of D. elongatus 20.0 ± 0.3 mg dry weight/ day.     

First record of Beauveria bassiana (Ascomycota: Clavicipitaceae) infecting Cerambyx welensii (Coleoptera: Cerambycidae) and pathogenicity tests using a new bioassay method

The pathogenicity of Beauveria bassiana on Cerambyx welensii is first reported. Three native fungal isolates from Badajoz (Spain) were bioassayed on neonates using cork oak disks and LC₅₀s were 1.16–1.76 × 10⁵ and 0.30–0.61 × 10⁵ spores/ml on the 7th and 14th day post-inoculation. The fungus is potentially a biocontrol agent of C. welensii.     

Effect of combination treatment with entomopathogenic fungi Beauveria bassiana and Nomuraea rileyi (Hypocreales) on Spodoptera litura (Lepidoptera: Noctuidaeae)

In biocontrol of insect pests, efficacy of treatment with multiple pathogens has not been frequently investigated but may have potential for effective management. The possible advantage of a combination treatment with two entomopathogenic fungi - Beauveria bassiana and Nomuraea rileyi - was assessed in laboratory bioassays on second instar Spodoptera litura. From among the fungal isolates of an epizootic population, two isolates of each fungus differing in virulence to S. litura were chosen, one highly virulent and the other with low virulence. The bioassays were carried out at either a continuous temperature of 25±1°C or at a temperature cycle of 32±2°C 8 h/21±2°C 16 h to mimic the field temperatures during the epizootic. Treatments with the two fungi were done both simultaneously and sequentially. In combination treatments at 25±1°C, in all isolate combinations, a majority of the larvae showed N. rileyi induced mycosis; the percentage mortality and speed of kill of insects in these treatments was similar to the N. rileyi isolate used in the combination treatments. At the temperature cycle of 32±2°C 8 h/21±2°C 16 h, in all combination treatments, all the dead insects exhibited B. bassiana mycosis; the mortality pattern was similar to the B. bassiana isolate used in the combination treatments. The adverse effect of high temperature on virulence of N. rileyi was however, not evident in in vitro growth assays. Combination treatment with both fungi did not have a synergistic effect on insect mortality.     

Endophytic colonisation of tobacco,corn, wheat and soybeans by the fungal entomopathogen Beauveria bassiana (Ascomycota,Hypocreales)

We demonstrate the effectiveness of three inoculation methods (foliar spray, seed immersion and root immersion) in establishing fungal the entomopathogen Beauveria bassiana as an endophyte in tobacco, corn, wheat and soybean. Colonisation of leaves by B. bassiana was assessed 7, 14, 21 and 28 days post-inoculation. There were significant differences (p < 0.001) in endophytic colonisation among the different inoculation techniques.     

马来西亚蝗科及一新种记述（直翅目：蝗总科）

记述了采自马来西亚的蝗科6亚科22属30种,包括一新种Vitalisia bangiensus sp. nov.。 并首次发现和描述了Sedulia perakensis Willemse的雄性及Eucoptacra minima Ramme和Pagdenia rufipes Miller的雌性。还发现Meltripata bolivari Willemse 和Pagdenia rufipes Miller具二型：全翅型和退化翅型。提供了马来西亚已记录属和种的检索表。     

Biocontrol of almond bark beetle (Scolytus amygdali Geurin-Meneville, Coleoptera: Scolytidae) using Beauveria bassiana (Bals.) Vuill. (Deuteromycotina: Hyphomycetes)

AIMS: To formulate the entomopathogenic fungus Beauveria bassiana in invert emulsion, then apply it against adults of almond bark beetle (Scolytus amygdali) under laboratory and field conditions. METHODS AND RESULTS: The effect of formulated B. bassiana in invert emulsion against S. amygdali adults was shown by comparing the mortality percentage of adults exposed to the formulated fungus using a Petri dish treatment method and by field applications to infested peach trees with mortality of adults exposed to the unformulated fungus or the untreated control. Results obtained from both exposure methods have indicated that treatment of S. amygdali adults with the formulated fungus resulted in a significantly higher mean mortality percentage (P < 0.05) when compared with the treatment with the unformulated fungus or the untreated control. This mortality ranged from 81.2 to 100%, 10 days after treatment with the formulated fungus when compared with 6.7 to 49.6% mortality, 10 days after treatment with the control or the unformulated fungus, respectively. Viability of the fungus conidia in invert emulsion was assessed by calculating the germination percentage of the conidia over time. Results indicated a high storage stability shown by a small loss of germination percentage for the formulated conidia of both strains (5.8 to 8.4% over a 12-week period) vs a low storage stability shown by a high loss of germination percentage for the unformulated conidia of the same strains (58.9 to 61.0% over the same period). The presence of B. bassiana in the galleries of beetles following the treatment of infested trees was shown in the present research. CONCLUSIONS: The results obtained have demonstrated a significantly higher level of efficacy of formulated B. bassiana in invert emulsion against S. amygdali adults under laboratory and field conditions. The ingredients of invert emulsion used in the formulation of the fungus had a negligible effect on the viability of formulated conidia when compared with the unformulated. SIGNIFICANCE AND IMPACT OF THE STUDY: Results obtained in the present research are promising and may be exploited commercially to control S. amygdali adults on various species of stone fruit trees, especially peach trees. This type of biocontrol of this insect may be used as an alternative means to chemical control for management of the insect. No adverse environmental impacts of the fungus or its formulation have been observed during application.     

Susceptibility of apple clearwing moth larvae,Synanthedon myopaeformis (Lepidoptera: Sesiidae) to Beauveria bassiana and Metarhizium brunneum

Apple clearwing moth larvae, Synanthedon myopaeformis (Lepidoptera: Sesiidae) were found to be susceptible to infection by two entomopathogenic fungi: an indigenous fungus isolated from S. myopaeformis cadavers and identified as Metarhizium brunneum (Petch); and Beauveria bassiana isolate GHA. In laboratory bioassays, larvae exhibited dose related mortality after exposure to both the M. brunneum and Beauveria bassiana with 7 day LC₅₀'s of 2.9×10⁵ and 3.4×10⁵ spores/mL, respectively. Larval mortalities caused by the two isolates at 1×10⁶ spores/mL were not significantly different and 73% of the M. brunneum-treated, and 76% of the B. bassiana-treated larvae were dead 7 days post treatment, with LT₅₀'s of 5.5 and 5.1 days, respectively.     

Efficacy of entomopathogenic fungi Beauveria bassiana and Metarhizium anisopliae against Thaumetopoea pityocampa Shiff. (Lepidoptera: Thaumatopoeidae)

Abstract

In this study, Metarhizium anisopliae TR 106 and Beauveria bassiana TR 217 was tested against fourth instar larvae of Thaumetopoea pityocampa. The LT₅₀ and LT₉₀ of 1?×?10⁶ concentration of M. anisopliae against T. pityocampa were 3.60 and 4.11 for direct application, while these were 2.87 and 3.60?days, respectively in leaves application. The LT₅₀ and LT₉₀ of the 1?×?10⁸ concentration of the same isolate were 2.50 and 2.95?days for direct application, and 2.98 and 3.74?days for leaves application. The LT₅₀ of insect and leaves application for 1?×?10⁶ of B. bassiana were 3.75 and 3.49?days, respectively. The LT₉₀ of same concentration for insect application was 4.48?days, while LT₉₀ for leaves application was 4.63?days. Similarly, LT₅₀ of insect and leaves application for 1?×?10⁸ of B. bassiana were 3.03 and 3.31?days, while LT₉₀ were 3.68 and 4.29?days, respectively. Approximate 100% mycosis was observed in all treatments.     

Endophytic colonisation of squash by the fungal entomopathogen Beauveria bassiana (Ascomycota: Hypocreales) for managing Zucchini yellow mosaic virus in cucurbits

We investigated the potential of endophytic Beauveria bassiana to provide protection against Zucchini yellow mosaic virus (ZYMV), one of the most economically important viral diseases in cucurbits. Four selected B. bassiana strains were able to successfully colonise squash plants following foliar inoculation with the conidial suspension of each respective strain. However, no significant difference in percentage colonisation was observed among the tested B. bassiana strains. Disease incidence (percentage of plants showing ZYMV symptoms) and severity (rating based on a 5-point scale), sampled weekly for four weeks following the challenge inoculation of plants with ZYMV, were significantly lower in B. bassiana-inoculated plants as compared to control plants, regardless of the inoculated strain. This is, to our knowledge, the first report on the potential of endophytic B. bassiana to confer protection against plant viruses. Further studies should be conducted to determine whether such endophytic B. bassiana-mediated protection against ZYMV in squash extends to other cucurbits.     

Simulated aerial sprays for field cage evaluation of Beauveria bassiana and Metarhizium brunneum (Ascomycetes: Hypocreales) against Anabrus simplex (Orthoptera: Tettigoniidae) in Montana

Field efficacy of the entomopathogenic Ascomycetes Beauveria bassiana strain GHA and Metarhizium brunneum strain F52 was evaluated against nymphs of the Mormon cricket, Anabrus simplex. Fungi were applied with a new apparatus that allows simulated aerial sprays to 0.1-m² areas in the field. The Mormon crickets were then individually housed in cylindrical, metal hardware cloth cages on treated grass. Both fungi demonstrated only marginal success in reducing immature Mormon cricket survival in the field cages. After 28 days, the field mortality of insects, corrected for control deaths, was 28 and 45% for B. bassiana and M. brunneum, respectively. Field-exposed but laboratory-incubated insects, however, suffered 90–100% mortality within 12 days with initial deaths occurring on Day 6 (Beauveria) or Day 5 (Metarhizium), indicating a lethal rate was applied and acquired by the crickets in the field. Potential daily body temperatures were determined for the entire post-treatment observation period using special thermal surrogates. High ambient temperatures and/or thermoregulation by Mormon crickets, in excess of the upper thermal limits of both fungi, prevented higher mortality from being expressed in the field. Thermal surrogates were used to develop models for predicting onset of mortality from infections. The surrogate data indicated mortality should begin between 8 and 26 days after treatment with M. brunneum and 11 and 33 days after treatment with B. bassiana. The timing of mortality in field cages was consistent with the upper boundaries of the temporal models developed from the thermal surrogates, i.e., at or after 28 days after treatment.     

Persistence of Beauveria bassiana sensu lato and Metarhizium anisopliae sensu lato in Vermont (USA) forest soil

Persistence of granular formulations of Beauveria bassiana sensu lato, strains GHA726 and ERL1170, and Metarhizium anisopliae sensu lato, strains ERL824 and ERL701, applied to forest soil was documented. One formulation was prepared by producing fungi on millet and at application adding cooked, dried millet to provide additional nutrients for fungal growth. The other was made by producing fungi on corn starch ‘packing peanuts’, a biodegradable packaging material, adding additional packing peanuts as a nutrient base. The trial was conducted in three sites in a forest predominating in sugar maple (Acer saccharum) in Underhill, VT, USA. In each site, 33 dominant sugar maples were randomly selected. A 1-m² plot located 1 m from the bole of the tree was established. Soil samples were collected before application, and 1 h, 2, 4, 8, 12 and 16 wk post-application. Fungal levels were estimated based on number of colony-forming units (CFUs). A significant increase in CFUs was observed 2 wk post-application in plots treated with isolates GHA726, ERL1170 and ERL824 as a result of fungal reproduction on nutrients in the formulations. Evidence of greater persistence for the B. bassiana than the M. anisopliae isolates was observed, based on CFU levels over time. Isolates formulated with millet proliferated more than those on packing peanuts. Use of entomopathogenic fungi in forest soil has potential for managing soil-dwelling insect pests such as pear thrips, Taeniothrips inconsequens, and the black vine weevil, Otiorhynchus sulcatus, though the type of formulation and the specific isolate used must be selected carefully.     

Postembryonic development, fecundity and food consumption of Dichroplus exilis (Orthoptera: Acrididae) under controlled conditions

Dichroplus exilis is a widely distributed species in Southern South America. Although there have been reports of D. exilis as an agricultural pest, some recent observations suggest that the damage attributed to D. elongatus may actually have been caused by D. exilis. This study was conducted to determine the postembryonic life cycle stages, fertility and food consumption of this species under controlled conditions (30 degrees C, 14L-10D, 40% RH). Individuals employed belong to the laboratory-hatched first generation (F1), from adults (n = 64, female = 28, male = 36) collected in natural grasslands near Rafaela, Santa Fe province in North-Eastern Argentina. Three cohorts of 16, 17 and 20 individuals were monitored independently in acetate tubes on a daily basis, until death of the last insect. Average fecundity was 381.84, 38.54 eggs per female. Egg-pod incubation time was 14.4, 1.08 days and six nymphal instars were recorded. Nymphal development time was 41.38, 0.71 days (I = 8.73, 0.20; II = 6.38, 0.24; III = 5.64, 0.33; IV = 7.15; 0.43; V=9.76, 0.54; IV = 7.85, 0.95). The recorded food consumption was 9.89, 1.08 (mg/ind/day) for nymphs IV, 18.04, 0.73 (mg/ind/day) for nymphs V-IV, 16.76, 1.06 (mg/ind/day) for pre-reproductive males, 28.09, 1.81 (mg/ind/day) for pre-reproductive females, 7.71,0.91 (mg/ind/day) for reproductive males and 13.06, 0.71 (mg/ind/day) for reproductive females, while the average adult food consumption, regardless of sex and reproductive status, was 16.41, 4.32 mg/day. Average food consumption of adult females was 17.47, 1.15 mg, and was significantly higher than that of males (10.83, 0.91mg). Data obtained in this study showed that D. exilis exhibits at least some of the biological attributes needed to configure an actual or potential agricultural pest, albeit not yet recognized as such. Field monitoring of grasshopper communities in areas where damage by D. exilis is suspected is envisaged in order to determine its possible status as a pest.     

Response of grasshoppers (Orthoptera: Acrididae) to livestock grazing in southeastern Arizona: differences between seasons and subfamilies

Summary Grasshopper densities were compared between grazed and ungrazed semidesert grassland sites in southeastern Arizona. Bouteloua-dominated perennial grass cover was about 1.5 times greater on the livestock exclosure. Grasshoppers were 3.7 times more abundant on the protected area in the summers of 1983 and 1984, when dominant species were grass-feeding members of the subfamily Gomphocerinae. In fall 1984, grasshoppers were 3.8 times more common on the grazed site, when dominants were mainly herb-feeders in the subfamily Melanoplinae. These results indicate important seasonal and taxonomic differences in the responses of grasshoppers to the activities of vertebrate grazers.