Entomopathogenic fungi detection and avoidance by mole crickets (Orthoptera: Gryllotalpidae)

A chamber to monitor mole cricket behavior was designed using two different soil-filled containers and photosensors constructed from infrared emitters and detectors. Mole crickets (Scapteriscus spp.) were introduced into a center tube that allowed them to choose whether to enter and tunnel in untreated soil or soil treated with Beauveria bassiana (Balsamo) Vuillemin. Each time the cricket passed through the photosensor located near the entrance of soil-filled containers, the infrared light was blocked and the exact moment that this occurred was logged onto a computer using custom-written software. Data examined included the first photosensor trigger, total number of sensor triggers, presence of tunneling, and final location of the cricket after 18 h. These behaviors were analyzed to discern differences in mole cricket behavior in the presence of different treatments and to elucidate the mechanism that mole crickets use to detect fungal pathogens. The first study examined substrate selection and tunneling behavior of the southern mole cricket, Scapteriscus borellii Giglio-Tos, to the presence of five strains of B. bassiana relative to a control. There were no differences between the first sensor trigger and total number of triggers, indicating the mole crickets are not capable of detecting B. bassiana at a distance of 8 cm. Changes in mole cricket tunneling and residence time in treated soil occurred for some strains of B. bassiana but not others. One of the strains associated with behavioral changes in the southern mole cricket was used in a second experiment testing behavioral responses of the tawny mole cricket, S. vicinus Scudder. In addition to the formulated product of this strain, the two separate components of that product (conidia and carrier) and bifenthrin, an insecticide commonly used to control mole crickets, were tested. There were no differences in mole cricket behavior between treatments in this study. The differences in behavioral responses between the two species could suggest a more sensitive chemosensory recognition system for southern mole crickets.     

Biocontrol of Acanthoscelides obtectus and Sitophilus oryzae with diatomaceous earth and Beauveria bassiana on stored grains

Combined treatment with Beauveria bassiana, and diatomaceous earth (DE) was evaluated against the bean weevil Acanthoscelides obtectus and rice weevil Sitophilus oryzae. DE from Argentina was screened both alone or in combination with water or dry fungal formulations. DE killed 100% of A. obtectus and 68% of S. oryzae showing a significantly higher insecticidal effect than the fungal dust. For A. obtectus, median lethal time (MLT) with the DE-dry fungus was significantly lower than with a fungal aqueous-suspension. In S. oryzae, powder formulations with either of B. bassiana or DE showed a MLT significantly higher than the wet treatments.     

Aptness of Beauveria bassiana and enhanced diatomaceous earth (DEBBM) for control of Rhyzopertha dominica F.

A diatomaceous earth formulation enhanced with bitterbarkomycin (DEBBM) combined with Beauveria bassiana (Balsamo) Vuillemin was evaluated against lesser grain borer Rhyzopertha dominica F. (Coleoptera: Bostrychidae) under laboratory conditions. DEBBM was applied at the rates of 15 and 30 ppm alone as well as in combination with 6.69 × 10⁶, 6.69 × 10⁸ and 6.69 × 10¹⁰ conidia/kg of wheat. Mortality of treated adults was recorded after 5, 10 and 15 days of exposure. Bioassays were carried out at 20, 25 and 30°C with 55 and 75% relative humidity. The emergence of progeny was also assessed 60 days post exposure. The combined use of DEBBM and B. bassiana considerably increased adult mortality especially at increasing temperatures and longer exposure intervals compared with DEBBM and B. bassiana alone. Progeny production was less in wheat treated with high dose rates of DEBBM +B. bassiana. The per cent mycosis in the cadavers was maximum where B. bassiana was applied at low dose rates. The results of the present study indicated that a combination of DEBBM and B. bassiana may provide effective control of R. dominica.     

Euryconema brevicauda n. sp. (Oxyurida: Thelastomatidae) a parasite of the mole cricket Neocurtilla claraziana (Orthoptera: Gryllotalpidae) in Argentina

Euryconema brevicauda n. sp. parasitizing the mole cricket Neocurtilla claraziana found in Buenos Aires province, Argentina, is described and illustrated. This species is characterized by the male having 3 pairs of genital papillae, 1 pair preanal and 2 pairs postanal, and a short, conical-shaped tail.     

The complete nucleotide sequence and gene organization of the mitochondrial genome of the oriental mole cricket, Gryllotalpa orientalis (Orthoptera: Gryllotalpidae)

The complete nucleotide sequences of the mitochondrial genome (mitogenome) of the oriental mole cricket, Gryllotalpa orientalis (Orthoptera: Gryllotalpidae), were determined. The 15,521-bp-long G. orientalis mitogenome contains typical gene complement, base composition, and codon usage found in metazoan mitogenomes. The G. orientalis mitogenome contains the third lowest A+T content (70.5%) among the complete insects mt genome sequences. The initiation codon for the G. orientalis COI gene appears to be ATG, instead of the tetranucleotides, which have been postulated to act as initiation codon for Locusta migratoria and some lepidopteran COI genes. The initiation codon for ND2 appears to be GTG, which is rare, but has been designated as an initiator of Tricholepidion gertschi ND2. All anticodons of G. orientalis tRNAs were identical to Drosophila yakuba and L. migratoria. The tRNA(Ser)(AGN) could not form a stable stem loop structure in the DHU arm as shown in many other insect tRNA(Ser)(AGN). Phylogenetic analysis of nucleotide sequence information from all mt genes supported a monophyletic Diptera, a monophyletic Lepidoptera, a monophyletic Coleoptera, a monophyletic Mecopterida (Diptera+Lepidoptera), and a monophyletic Endopterygota (Diptera+Lepidoptera+Coleoptera), suggesting that the complete insect mitogenome sequence has a resolving power to the diversification events within Endopterygota. However, the relationships of ancient insect orders were unstable, indicating the limited use of mitogenome information at deeper phylogenetic depth.     

Effect of irrigation on the efficacy of insecticides for controlling two species of mole crickets (Orthoptera: Gryllotalpidae) on golf courses

Effects of irrigation regimen, quantity, and timing on the efficacy of three insecticides for controlling nymphs of the southern mole cricket, Scapteriscus borellii Giglio-Tos, and the tawny mole cricket, Scapteriscus vicinus Scudder, were studied on golf courses in 1997, 1998, and 1999. Two irrigation regimen tests using two rates of bifenthrin and lambda-cyhalothrin produced inconclusive results. Mole cricket damage ratings after the applications of bifenthrin (60 g [AI]/ha) and lambda-cyhalothrin (76 g [AI]/ha) were not significantly different among the four irrigation regimens (non-irrigation, irrigation before treatment, irrigation after treatment, and irrigation before and after treatment). Mole cricket damage rating after the application of bifenthrin (120 g [AI]/ha) under irrigation before and after irrigation was significantly better than those under other irrigation regimens at 14 and 21 d after treatment (DAT). Different irrigation quantity and irrigation timing (after insecticide treatment) did not significantly affect the performance of imidacloprid (434 g [AI]/ha) in the 1998 tests. However, the results from the 1999 test indicated that mole cricket damage ratings from the imidacloprid-treated plots were significantly different between 2 and 0.5 cm irrigation water after treatment at 21 and 28 DAT. Application of bifenthrin at a rate of 120 g (AI)/ha with 0.5 cm of irrigation water after treatment resulted in significantly lower mole cricket damage ratings than those of 1.0 and 2.0 cm of irrigation water after treatment at 30 DAT only in the 1998 test. Bifenthrin with irrigation at 1 h after insecticide treatment provided better mole cricket control than that of irrigation at 5 min after treatment at 30 DAT only in the 1998 test. Mole cricket damage ratings after application of bifenthrin were not significantly different between either irrigation quantity treatment or irrigation timing treatment in the 1999 tests. Possible effects of application timing, environmental conditions, irrigation practice, and insecticide physical properties on the results are discussed.     

Interaction effects between Beauveria bassiana and imidacloprid against Thrips tabaci (Thysanoptera: Thripidae)

The onion thrips, Thrips tabaci Lindeman is a major pest of many horticultural crops in many parts of the world. The entomopathogenic fungus Beauveria bassiana (Balsamo) Vuillemin and imidacloprid are used for the control of the onion thrips. The potential interactions between the fungus and the chemical against the onion thrips adults were evaluated in a laboratory and two greenhouse bioassays. The laboratory bioassay was a leaf dip bioassay for a mixture of B. bassiana and imidacloprid. The first greenhouse bioassay was a topical application of a mixture of the fungus and the chemical while the second bioassay was a drenching application of imidacloprid and a topical application of B. bassiana. In all bioassays, the combined application resulted in higher percentage mortalities than either B. bassiana or imidacloprid alone. In the laboratory bioassay, the highest mortality of 97% was achieved by using B. bassiana at the field rate with imidacloprid at 1/10th the field rate relative to 88%, 94%, 21% for B. bassiana alone, imidacloprid alone and the control, respectively. In the first greenhouse bioassay, the highest mortality of 80% resulted from the combined application of B. bassiana and imidacloprid at field rates compared with 55%, 75%, and 22% for B. bassiana alone, imidacloprid alone and the control, respectively. In the second greenhouse bioassay, the combined application of both control agents at field rates resulted in 85% mortality compared with 52%, 83%, and 18% for B. bassiana alone, imidacloprid alone and the control, respectively. The interaction effect between the two control agents was additive except when B. bassiana at 1/2 field rate was mixed with imidacloprid at 1/10th field rate in the laboratory bioassay, where the interaction was antagonistic. The above results indicate that combining imidacloprid with B. bassiana might reduce the rate of the insecticide application while enhancing the efficacy of the biological control agent.     

Learning and solar orientation in the mole cricket Gryllotalpa gryllotalpa (Orthoptera: Gryllidae)

The ecologically efficient escape direction assumed by Gryllotalpa gryllotalpais learned by the larvae after they leave the maternal nest. Nonetheless, larvae hatched in the laboratory are innately capable of using the sun to maintain a set escape direction. The species can also modify the set point of its sun compass to conform to topographical changes encountered during its wanderings.     

Antagonism between Beauveria bassiana and imidacloprid when combined for Bemisia argentifolii (Homoptera: Aleyrodidae) control

Imidacloprid and the entomopathogenic fungus Beauveria bassiana (Balsamo) Vuillemin are both used to control the whitefly Bemisia argentifolii Bellows & Perring. We tested whether the two control strategies acted additively, synergistically, or antagonistically when combined for whitefly control. We found antagonism in that B. bassiana inhibited the effectiveness of imidacloprid. When B. bassiana was combined with imidacloprid, insect response was either less than or similar to (depending on B. bassiana rates) that when imidacloprid was used alone. Adding imidacloprid to B. bassiana treatments always increased mortality, but the increase was less than additive. Beauveria bassiana spore germination and colony formation were not inhibited by imidacloprid in vitro, and B. bassiana did not adsorb or degrade imidacloprid in a tank mix. We hypothesize that B. bassiana caused a behavioral response that reduced insect feeding and uptake of imidacloprid.     

Integration of insect parasitic nematodes (Rhabditida steinernematidae) with insecticides for control of pest mole crickets (Orthoptera: Gryllotalpidae: Scapteriscus spp.)

To develop a successful integrated pest management program for pest mole crickets (Orthoptera: Gryllotalpidae: Scapteriscus spp.), it is important to ascertain the compatibility of infective juveniles of insect parasitic nematodes and chemical insecticides. Aqueous solutions of five pesticides (acephate, bifenthrin, deltamethrin, fipronil, and imidacloprid) used in turfgrass to control mole crickets were tested for compatibility with Steinernema scapterisci Nguyen & Smart (Rhabditida: Steinernematidae) in the laboratory. Survival of S. scapterisci was >95% in solutions of acephate, bifenthrin, and imidacloprid. Infectivity of S. scapterisci in adult Scapteriscus vicinus Scudder was >60% in acephate and bifenthrin; however, infectivity was <40% in imidacloprid. The entomopathogenic nematode was compatible with most insecticides tested without significantly reduced survival or infectivity.     

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.     

Insecticidal effect of the combined application of spinosad,Beauveria bassiana and diatomaceous earth for the control of Tribolium confusum

Laboratory bioassays were carried out to evaluate the insecticidal effect of Beauveria bassiana (Balsamo) Vuillemin (Ascomycota: Hypocreales) germinated conidia, a commercial formulation of diatomaceous earth and a liquid formulation of spinosad, applied alone or in all possible combinations on wheat, against adults of the confused flour beetle, Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae). Diatomaceous earth was applied at one (200 ppm), the fungus at two (100 and 300 ppm) and spinosad at three (0.01, 0.1 and 0.5 ppm) dose rates, whereas all combinations of two or three of the insecticide concentrations were also tested. Insect mortality was determined after 2, 7 and 14 d of exposure. The simultaneous use of B. bassiana germinated conidia with diatomaceous earth notably increased mortality of T. confusum adults by sixfold 7 d after exposure, as compared with either B. bassiana or diatomaceous earth alone. When diatomaceous earth and spinosad were combined, diatomaceous earth did not increase the efficacy of spinosad. In general, the combination of all three agents did not differ from either the application of the agents tested alone, or their binary combinations, in most treatments examined.     

Trials of Beauveria bassiana, Paecilomyces fumosoroseus and imidacloprid for management of Trialeurodes vaporariorum (Homoptera: Aleyrodidae) on greenhouse grown lettuce

Mineral oil-based emulsifiable preparations of Beauveria bassiana (Bb) and Paecilomyces fumosoroseus (Pfr) conidia were separately applied alone or together with low rates of imidacloprid 10% WP at 4.7% (Im 1), 14.0% (Im 2), and 23.3% (Im 3) of its recommended application rate, respectively, against the greenhouse whitefly, Trialeurodes vaporariorum, on lettuce grown in the greenhouse. Besides eight fungal treatments, the three low application rates of imidacloprid in the oil-based carrier and a blank control (CK) were also included as treatments of the trials conducted in 2002 and 2003. For the 12 treatments of each trial with three replicates, 1,000-fold aqueous dilutions were sprayed twice on transplanted lettuce at a 15-day interval at a rate of ∼1.43×10¹³ conidia ha^-1 for each fungal treatment or at one of the low rates of imidacloprid using a backpack hand-operated hydraulic sprayer. Based on whitefly densities, mortalities, relative efficacies and percent density declines estimated from whitefly counts made at 5-day intervals, all B. bassiana and P. fumosoroseus sprays were highly effective against T. vaporariorum compared to CK and Im 1-3 in both trials. In trial 1, the estimates of whitefly density decline and relative efficacy ranged from 44 and 72% (Bb) to 79 and 90% (Pfr+Im 2-3) on day 10 after the first spray and exceeded 94% for all fungal treatments 10 days after the second spray. Similar trends in whitefly control were also achieved in the corresponding treatments of trial 2. A more desirable and faster control resulted from fungal sprays containing more imidacloprid, but none of the three low imidacoprid rates alone suppressed the whitefly population more effectively than any fungal treatment despite a varying degree of efficacy. Moreover, P. fumosoroseus tended to be more effective against T. vaporariorum than B. bassiana when applied alone or together with the same low rate of imidacloprid but the difference in whitefly control eventually achieved was not significant between the two fungal agents. Thus, the emulsifiable preparations of both fungal agents can be considered as alternatives for whitefly management and for a slightly faster control can be applied together with imidacloprid at around 15% of its common application rate. An economic balance between the efficacy of whitefly control and the ease and cost of conidial production is needed when both fungi are incorporated into whitefly management.     

中国蝼蛄属一新种记述(直翅目:蝼蛄科)

记述蝼蛄属GryllotalpaLatreille1新种:武当蝼蛄Gryllotalpa wudangensis,sp.nov.。模式标本保存于陕西师范大学动物研究所标本室。     

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.     

Survival and fecundity of Dichroplus maculipennis and Ronderosia bergi (Orthoptera: Acrididae: Melanoplinae) following infection by Beauveria bassiana (Ascomycota: Hypocreales) under laboratory conditions

This study examined the effects of strain Beauveria bassiana (LPSC 1067) on nymphal development time, fecundity and adult survival in Dichroplus maculipennis and Ronderosia bergi under laboratory conditions. It was observed that infection with 1×10³ conidia/ml altered nymphal development time, fecundity and adult survival in both species. Mortality of D. maculipennis during third through the last instar (sixth) was significantly higher among treated nymphs (66±3.8%) than in controls (15±1.7%). Similarly, mortality in R. bergi during third through the last instar (fifth) was higher in treated nymphs (71±2.8%) than in controls (19±1.5%). Nymphal development times of both infected D. maculipennis and R. bergi were longer than controls. On the other hand, among survivors of both the species, control adults lived longer than infected adults. Finally, control grasshoppers of both species were much more successful reproductively than infected grasshoppers.     

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.     

Effect of Beauveria bassiana on the ovarian development and reproductive potential of Anastrepha ludens (Diptera: Tephritidae)

We investigated the virulence of a native strain of Beauveria bassiana on the mortality, ovarian development, oogenesis, survival, fecundity and fertility of 4-, 8- and 12-day-old Anastrepha ludens females. In the first study, this strain caused 85% mortality in 8-day-old treated females, with a median lethal concentration (LC₅₀) of 3.1×10⁸ (2.1×10⁸–4.7×10⁸) conidia/mL and a median lethal time (LT₅₀) of 6.5 days. In the second study, the ovarian development and oogenesis of A. ludens females treated with 1×10⁹ conidia/mL were monitored daily in sacrificed flies. The fungus infection did not significantly affect ovarian development of the treated females, although there was a delay in vitellogenesis and a reduction in the quantity of mature basal oocytes and oviposition index in these flies. Moreover, the lowest net fecundity was found in 4-, 8- and 12-day-old treated females, and reduced fertility was observed in 4-day-old treated females. An application to test the potential use of this strain under field conditions is discussed.