Isolates Of Metarhizium Anisopliae Research Articles

INFECTION PROCESS OF ENTOMOPATHOGENIC FUNGI Metarhizium anisopliae IN THE Tetranychus kanzawai (KISHIDA) (TETRANYCHIDAE: ACARINA)

The importance of fungal attack to acarina has been observed but not yet on Tetranychus kanzawai . When infected mite, either within in a same species or even in a different species of entomopathigenic probably have similar signs and simptoms to mites. Characteristic of entomopathogenic fungus to Tetranychus kanza-wai was investigated. Three selected isolates of Metarhizium anisopliae , from Philippines and Indonesia were evaluated. The following aspects were investigated: (1) Bioassay tes of virulence, (2) Koch Postulate and (3) Infection process on each fungus against mite. Virulence of Metarhizium anisopliae was 1.4 X 10 3 , 7.2 X 10 2 , 5 X 10 2 PIB per ml on Ma4, Ma5 and Ma6, respectively. On Koch Postulates, Reinoculation and reisolation of all seven isolates from infected T. kanzawai showed definite signs of infection. This demonstrated its entomopathogenic capacity. In this experiment, adult mites were sprayed with 10 8 per ml concentrations of conidia observed under light microscope and Scanning Electron Microscopy (SEM). The result found T. kanzawai was very susceptible to three isolates M . anisopliae . In the end of the trials, fungal growth was detectable as early as 2 until 4 days of observation. Infection process with microphoto-graph and Scanning Electro Microscopy showed attachment, germination and penetration, extrusion and conidiogenesis fungal form. Keywords: Infection, Tetranychus kanzawai , Metarhizium anisopliae , Light micros-copy, Scanning Electro Microscopy (SEM) Normal 0 false false false EN-US X-NONE X-NONE Normal 0 false false false EN-US X-NONE X-NONE

Effects of interactions among Metarhizium anisopliae, Bacillus thuringiensis and chlorantraniliprole on the mortality and pupation of six geographically distinct Helicoverpa armigera field populations

A local isolate of Metarhizium anisopliae (Hypocreales: Clavicipitaceae), Bacillus thuringiensis subsp. kurstaki and chlorantraniliprole were assessed against six field populations of tomato fruitworm Helicoverpa armigera Hubner (Lepidoptera: Noctuidae) in a series of laboratory bioassays. Two dose rates of B. thuringiensis (0.5, 1 μg g−1), one of both M. anisopliae (1.3 × 106 conidia ml−1) and chlorantraniliprole (0.01 ppm) were applied alone and in combination with each other against 2nd, 3rd, 4th and 5th larval instars. The mortality was observed every 24 h until pupation. The bioassays were carried out at 25°C and 75% r.h. The highest mortality was observed in Rawalpindi with the lowest pupation rate by applying the combined concentrations of B. thuringiensis and chlorantraniliprole. The lowest mortality was observed in population from Gujranwala among all the tested populations. The antagonistic interaction was noted where the high dose rate of B. thuringiensis was combined with M. anisopliae; however, the remaining interactions enhanced the mortality and reduced the percent pupation. The overall results demonstrated that all the treatments gave significant control of the larval instars of H. armigera. The population from Gujranwala proved least susceptible whereas the one from Rawalpindi was highly susceptible.

Evaluation of entomopathogenic fungi against the sycamore lace bug, Corythucha ciliata (Say) (Hemiptera: Tingidae)

The sycamore lace bug, Corythucha ciliata (Say) (Hemiptera: Tingidae), is one of the most destructive pests of plane trees (Platanus spp.) worldwide. This pest is a major nuisance in Europe since plane trees are very popular in parks. Thirteen entomopathogenic fungal strains including 4 isolates of Beauveria bassiana, 2 isolates of Beauveria pseudobassiana, 6 isolates of Metarhizium anisopliae, and 1 isolate of Isaria fumosorosea were screened against adults and nymphs of C. ciliata under controlled laboratory conditions in order to test their efficacy and search for an effective and safe biocontrol agent strategy. Each isolate was applied with a conidial concentration of 1 × 107 conidia mL-1 to adults and nymphs of the pest. B. bassiana isolate KTU - 24 showed the highest mortality for both adults and nymphs with 86% within 2 weeks after inoculation. This isolate also caused the highest mycosis for adults and nymphs with 83% and 80%, respectively. Mortalities of the other fungal isolates ranged from 43% to 86% and from 36% to 73% for adults and nymphs. Therefore, B. bassiana KTU - 24 was selected for further dose mortality tests based on its high virulence and mycosis value. Dose-response mortality bioassays using 5 different concentrations (1 × 104, 1 × 105, 1 × 106, 1 × 107, and 1 × 108 conidia mL-1) were performed to determine the lethal concentration (LC50) of this isolate. Based on probit analysis, the LC50 values of isolate B. bassiana KTU - 24 were calculated as 5.51 × 105 and 3.96 × 105 conidia mL-1 against adults and nymphs, respectively. Consequently, B. bassiana KTU - 24 appears to be a promising candidate for further investigations as a biocontrol agent against C. ciliata.

Use ofMetarhizium anisopliaeChitinase Genes for Genotyping and Virulence Characterization

Virulence is the primary factor used for selection of entomopathogenic fungi (EPF) for development as biopesticides. To understand the genetic mechanisms underlying differences in virulence of fungal isolates on various arthropod pests, we compared the chitinase genes, chi2 and chi4, of 8 isolates of Metarhizium anisopliae. The clustering of the isolates showed various groups depending on their virulence. However, the analysis of their chitinase DNA sequences chi2 and chi4 did not reveal major divergences. Although their protein translates have been implicated in fungal virulence, the predicted protein structure of chi2 was identical for all isolates. Despite the critical role of chitin digestion in fungal infection, we conclude that chi2 and chi4 genes cannot serve as molecular markers to characterize observed variations in virulence among M. anisopliae isolates as previously suggested. Nevertheless, processes controlling the efficient upregulation of chitinase expression might be responsible for different virulence characteristics. Further studies using comparative “in vitro” chitin digestion techniques would be more appropriate to compare the quality and the quantity of chitinase production between fungal isolates.

Characterization of Metarhizium anisopliae using amplifed ribossomal DNA restriction analysis (ARDRA) and internal transcribed spacer (ITS) sequence analysis

Molecular methods have revolutionized systematic entomology in the genus Metarhizium . In Brazil, the importance of these entomopathogenic fungi in agriculture is critical to the control of the sugar cane spittlebug ( Mahanarva posticata ) ( Homoptera: Cercopidae ). Other important factors for the selection of isolates of Metarhizium anisopliae for use in the biological control of particular pests are virulence, reproductive characteristics and the media of artificial cultures. In addition, the genetic variability of these entomopathogenic fungi indicates a great potential for pest control and a lack of a link between isolates from specific host sites and fungal virulence. We studied five Metarhizium hosts including the sugar cane spittlebug (IPA213, IPA215, IPA219 and IPA216) and the grasshopper (IPA217). It is noteworthy that these five isolates are used as biological control for growing sugar cane on an industrial scale for the Brazilian Northeast. Hence, the importance to genetically characterize these isolates of Metarhizium cannot be over emphasized. Amplifed ribossomal DNA restriction analysis (ARDRA) did not differentiate any of the isolates that were studied following digestion with three endonuclease namely; HindIII, HinfI and HpaI . The data that were generated using ITS1 and ITS4 markers revealed that although these isolates infect the same host, they are genetically distinct perhaps due to the unknown origin of the hosts. However, the isolate IPA217, which was isolated from the grasshopper, did not behave differently from the others. These results show that the M. anisopliae complex is monophyletic and it was concluded that the use of markers and morphological studies yielded results that may corroborate the idea that investigation of the phenotypic and molecular characteristics of this genus may indentify a new species of Metarhizium . Key words : Cordyceps brittebankisoides, genetic identity, ITS1, ITS4, phylogeny, sugar cane spittlebug.

Virulence and mycotoxic effects of Metarhizium anisopliae on Mahogany shoot borer, Hypsipyla robusta (Lepidoptera: Pyralidae)

Developing appropriate control measures for the Mahogany shoot borer, Hypsipyla robusta Moore has become increasingly important due to the severe damaging effect of the pest on the establishment of the saplings of Swietenia mahagoni Jacq (Sapindales: Meliaceae). Existing management methods are largely limited to silvicultural practices and spraying of chemical insecticides. To identify a potential fungal biocontrol agent, we compared the virulence of six native and two standard ARSEF isolates of Metarhizium anisopliae Metsch. against this pest. The average survival time and conidial yield of IWST-Ma7 was higher (6.2 to 7.3 days and 4.9 to 4.7×105 conidia/ml) than the standards. Significant difference in sporulation on the cadavers between isolates, doses and incubation periods were substantiated for the selection of potential strain. The mycotoxic effects of crude soluble protein extract when incorporated in the artificial diet, the ARSEF 2596 and ARSEF 3603 showed LD50 value of 3.7% and 5.6%. However, IWST-Ma7 was highly lethal with significant lowest LD50 value of 2.6%. The enzyme activity of IWST-Ma7 was highest for chitinase, CDA, protease and lipase viz., 1.90 U/mg, 1.80 U/mg, 0.98 U/mg and 0.80 U/mg respectively. However the enzyme activity of chitinase and Chitin deacetylase assay for all the isolates was significantly higher than protease and lipase activity. The ITS regions (5.8S rDNA and 28S rDNA) of seven isolates of M. anisopliae were amplified using the ITS1 and ITS4 primers which was a unique fragment of approximately 550 bp. Based on ITS regions, phylogenetic tree have been constructed and the isolates have been grouped in to 5 clades. The virulence and mycotoxic effects of different isolates could rationally be used to employ them for the management of the mahogany borer.

Comparison of Volatile Blends and Nucleotide Sequences of Two Beauveria Bassiana Isolates of Different Virulence and Repellency Towards the Termite Macrotermes Michealseni

Isolates of the fungus Beauveria bassiana have different levels of virulence and repellency against the termite Macrotermes michaelseni. In the present study, we compared the volatile profiles and gene sequences of two isolates of the fungus with different levels of virulence and repellence to the termite. Gas chromatography-mass spectrometric analyses showed quantitative and qualitative differences in the composition of volatiles of the two isolates. The repellencies of synthetic blends of 10 prominent components that mimicked the volatiles of each of the two isolates were significantly different. Subtractive bioassays showed that the repellency of each isolate was due to synergistic effects of a few constituents. As previously reported for isolates of Metarhizium anisopliae, some differences also were found in the nucleotide sequences of the two isolates of B. bassiana, suggesting a genetic basis for the observed intra-specific differences in their repellency and virulence against the termite.

Laboratory evaluation of virulence of Chinese Beauveria bassiana and Metarhizium anisopliae isolates to engorged female Rhipicephalus (Boophilus) microplus ticks

Rhipicephalus (Boophilus) microplus, an important ectoparasite that can transmit Babesia and Anaplasma, has caused inestimable economic losses around the world. Traditionally, acaricides are used for the control of ticks. However, drawbacks of chemical control, such as resistance, environmental pollution, and traces in food promote alternative strategies to pesticides. Microbial control is one option to reduce tick populations. In this study, we investigated the pathogenicity of thirteen Beauveria bassiana isolates and seven Metarhizium anisopliae isolates to the engorged female R. (B.) microplus ticks using different conidial concentrations of 107, 108 and 109conidiamL–1. Fourteen days after treatment, three B. bassiana isolates (B.bAT01, B.bAT03, B.bAT13) and one M. anisopliae isolate (M.aAT04) resulted in 100% mortality of engorged female ticks with conidial concentrations of 108 and 109conidiamL–1. Isolates of B.bAT01, B.bAT03, B.bAT13 and M.aAT04 at all conidial concentrations could reduce the reproductive efficiency index (REI) of R. (B.) microplus ticks.

Selection of promising fungal biological control agent of the western flower thrips Frankliniella occidentalis (Pergande)

Larval stages of Frankliniella occidentalis are known to be refractory to fungal infection compared with the adult stage. The objective of this study was to identify promising fungal isolate(s) for the control of larval stages of F. occidentalis. Ten isolates of Metarhizium anisopliae and eight of Beauveria bassiana were screened for virulence against second-instar larvae of F. occidentalis. Conidial production and genetic polymorphism were also investigated. Metarhizium anisopliae isolates ICIPE 7, ICIPE 20, ICIPE 69 and ICIPE 665 had the shortest LT(50) values of 8.0-8.9 days. ICIPE 69, ICIPE 7 and ICIPE 20 had the lowest LC(50) values of 1.1 × 10(7), 2.0 × 10(7) and 3.0 × 10(7) conidia ml(-1), respectively. Metarhizium anisopliae isolate ICIPE 69 produced significantly more conidia than M. anisopliae isolates ICIPE 7 and ICIPE 20. Internally transcribed spacers sequences alignment showed differences in nucleotides composition, which can partly explain differences in virulence. These results coupled with the previous ones on virulence and field efficacy against other species of thrips make M. anisopliae isolate ICIPE 69 a good candidate. Metarhizium anisopliae isolate ICIPE 69 can be suggested for development as fungus-based biopesticide for thrips management.

Compatibility of Metarhizium anisopliae isolate ICIPE 69 with agrochemicals used in French bean production

The compatibility of the Metarhizium anisopliae (Metschnikoff) Sorokin isolate ICIPE 69, which is being developed as a biopesticide for the control of Frankliniella occidentalis Pergande, was assessed under laboratory conditions with 12 agrochemicals including 5 insecticides (thiamethoxam, L-cyhalothrin, imidacloprid, chlorpyrifos, diazinon), 1botanical insecticide (azadirachtin), 2 acaricides (abamectin, spiromesifen), and 3 fungicides (carbendazim, copper hydroxide, probineb) used in French bean production. The insecticides abamectin and imidacloprid were highly compatible with M. anisopliae; thiamethoxam was compatible, whereas azadirachtin and L-cyahalothrin were toxic to the fungus, adversely affecting vegetative growth and sporulation. The acaricide spiromesifen was moderately toxic, while the fungicides carbendazim, probineb, and copper-hydroxide were very toxic to the fungus. The combination of the M. anisopliae isolate ICIPE 69 with imidacloprid or thiamethoxam did not result in any synergistic or antagonistic effects to larvae of F. occidentalis. However, the combination of lower concentrations of the fungus with thiamethoxam resulted in a shorter lethal time (LT50) compared with individual treatments. Our results suggest that application of the fungus with agrochemicals has to be assessed carefully prior to any field intervention.

Pathogenicity of Beauveria bassiana and Metarhizium anisopliae against Galleria mellonella

The greater wax moth Galleria mellonella L. (Lepidoptera: Pyralidae) is occasionally found in beehives and is a major pest of stored wax. Entomopathogenic fungi have recently received attention as possible biocontrol elements for certain insect pests. In this study, 90 isolates of Beauveria bassiana and 15 isolates of Metarhizium anisopliae were screened for proteases and lipases production. The results showed significant variations in the enzymatic action between the isolates. In the bioassay, the selected isolates evinced high virulence against the 4th instar of the G. mellonella larvae. The isolates BbaAUMC3076, BbaAUMC3263 and ManAUMC3085 realized 100% mortality at concentrations of 5.5 × 106 conidia ml−1, 5.86 × 105 conidia ml−1, and 4.8 × 106 conidia ml−1, respectively. Strong enzymatic activities in vitro did not necessarily indicate high virulence against the tested insect pest. The cuticle of the infected larvae became dark and black-spotted, indicating direct attack of fungus on the defense system of the insects. The LC50 values were 1.43 × 103, 1.04 × 105 and 5.06 × 104 for Bba3263AUMC, Bba3076AUMC and Man3085AUMC, respectively, and their slopes were determined by computerized probit analysis program as 0.738 ± 0.008, 0.635 ± 0.007 and 1.120 ± 0.024, respectively.

Comparison of bioassay responses to the potential fungal biopesticide Metarhizium anisopliae in Rhipicephalus(Boophilus) microplus and Lucilia cuprina

Quantal response bioassays were conducted with cattle ticks and sheep blowflies with three different isolates of Metarhizium anisopliae and different methods of inoculation. Ticks were either topically dosed with 2μl or immersed in the conidial preparations. Blowflies were either topically dosed with 2μl of the conidial preparation or fed on conidia mixed with sugar. Probit analyses were carried out on the mortality data to compare the virulence of these isolates to ticks and blowflies and look for indications of different virulence mechanisms employed by M. anisopliae isolates when invading these hosts. One isolate (ARIM16) showed high virulence to both hosts killing 95% of ticks after 2 days and 88 (±2)% of blowflies after 4 days. Strikingly different mortality patterns indicated that virulence is dependent on different mechanisms in ticks and blowflies. The pattern of mortality seen with ticks suggested that the number of conidia adhering per unit area of the cuticle was more important for rapid tick death than the total number of conidia contacting the entire tick surface. Blowflies fed conidia mixed with food died rapidly after an initial lag phase regardless of dose.

Investigation of native isolates of entomopathogenic fungi for the biological control of three citrus pests

The pathogenicity of 15 isolates of Beauveria bassiana (Balsamo) Vuillemin, five isolates of Metarhizium anisopliae (Metschnikoff) Sorokin and one isolate of M. flavoviride (Gams and Rozsypal) were tested under laboratory conditions against the subterranean life stages of the citrus pests, Ceratitis rosa Karsch, C. capitata Wiedemann (Diptera: Tephritidae) and Thaumatotibia leucotreta Meyrick. (Lepidoptera: Tortricidae). When these citrus pests were treated with a concentration of 1×107 conidia mL−1, fungal isolates had a significantly greater effect on the adults of C. rosa and C. capitata than they did on the puparia of these two fruit fly species. Further, C. rosa and C. capitata did not differ significantly in their response to entomopathogenic fungi when adult and pupal mycosis were considered. Depending on fungal isolate, the percentage of T. leucotreta adults which emerged from fungal treated sand ranged from 5 to 60% and the percentage of pupae with visible signs of mycosis ranged from 21 to 93%. The relative virulence of the four most promising fungal isolates, as well as the commercially available B. bassiana product, BroadBand® (Biological Control Products, South Africa), were compared against one another as log-probit regressions of mortality against T. leucotreta which exhibited a dose-dependent response. The estimated LC50 values of the three most virulent B. bassiana isolates ranged from 6.8×105 to 2.1×106 conidia mL−1, while those of the least pathogenic ranged from 1.6×107 to 3.7×107 conidia mL−1.

Dissemination of entomopathogenic fungi using Busseola fusca male as vector

The stem borer, Busseola fusca (Fuller), is an important pest of maize Zea mays L. and sorghum Sorghum bicolor (L.) in eastern and southern Africa. To control this pest, biological control methods including the use of entomopathogenic fungi are being considered. The pathogenicity of one isolate of Metarhizium anisopliae (Metsch.) Sorok. and one isolate of Beauveria bassiana Bals. (Vuill.) were first tested on different developmental stages of B. fusca including eggs, neonate, 2nd and 3rd-instar larvae. Both fungal isolates were pathogenic to all the stages tested. However, differences in mortality were observed among larvae that hatched from treated egg masses. Experiments were conducted thereafter to test whether B. fusca males could serve as a vector for fungal conidia to contaminate B. fusca females and subsequently eggs and larvae. Results demonstrated that B. fusca males successfully transferred inoculum to females during copulation, which in turn transmitted it to the eggs they laid on maize plants, resulting in the decrease of leaf damages.

Laboratory evaluation of entomopathogenic fungi against the white grubs, Holotrichia oblita and Anomala corpulenta (Coleoptera: Scarabaeidae) from the field of peanut, Arachis hypogaea

We evaluated the pathogenicity of nine isolates of entomopathogenic fungi, including six isolates of Metarhizium anisopliae, one of Beauveria bassiana, and two of Beauveria brongniartii, against eggs and various larval instars of two scarab-beetle species, Holotrichia oblita and Anomala corpulenta, under laboratory conditions. The fungal isolates differed in pathogenicity. Generally, the isolates were more pathogenic to A. corpulenta than to H. oblita. Some of the isolates prevented egg hatching and caused larval death. Isolates M2-2 and Br5-8 caused 39 and 27% egg mortality, respectively, and produced 23 and 24% viewable fungal-infection rates in H. oblita. Three isolates had no significant effect on egg hatchability. Three isolates (Br5-8, Br232818, and M200614) caused about 40% mortality in H. oblita first instars. In A. corpulenta, all isolates except M200614 caused more than 60% egg mortality, and M2-2, Br232818 and Br5-8 caused egg-infection rates greater than 50%. M2-2 caused 47% infection and 100% mortality in first-instar larvae of A. corpulenta, while Br5-8 and Br232818 yielded over 80% mortality of the larvae. The three most virulent isolates, M2-2, Br232818 and Br5-8, were selected for further bioassays against second- and third-instar larvae. In addition, seven graduated concentrations of a Br5-8 conidial suspension were assayed against H. oblita second instars. Larval mortality was positively correlated with fungal dosage, and the LC50 was 4.49×106 conidia/mL. These three virulent isolates may be used to prevent H. oblita and A. corpulenta larval infestations in field crops.

Cellular and humoral immune defenses of Oxya japonica (Orthoptera: Acrididae) to entomopathogenic fungi Metarhizium anisopliae

AbstractOne Indonesian isolate of the fungus Metarhizium anisopliae, named Majalengka strain, was evaluated not only for its virulence but also for the immune response of rice grasshopper Oxya japonica (Orthoptera: Acrididae) as a target organism. Five aqueous suspensions with different conidia concentrations in logarithmic series were prepared. The fungus showed high virulence as it caused 100% mortality at low conidia concentration (1.5 × 102 conidia/mL). Remarkable changes in the cellular and humoral responses were also observed when adult grasshoppers were infected with the fungus. The number of hemocytes decreased significantly within 12 h after infection. In addition, the total number of granulocytes increased rapidly in the first 12 h then gradually decreased 24 and 48 h after infections, while the number of coagulocytes fluctuated over time. The infection influenced the humoral response by increasing the phenoloxidase activity.

Identification and Selection of Entomopathogenic Fungi as Biocontrol Agents for Aphis gossypii from South Sumatra

Aphid, Aphis gossypii is a vector of curly virus disease. The damage of chili due to its feeding is only 35% and it can achieved 100% if the damage caused by the aphid as a vector. The objectives of this research were to explore, to isolate, to identify, and to select entomopathogenic fungi as biocontrol agents for A. gossypii. The fungi were explored using insect bait in soil and collected infected insects from South Sumatra, Indonesia. Then, the fungi were isolated and identified, and finally the bioefficacy tests were done using 1 x 10 6 conidia mL -1 against the third instar of A. gossypii. The explorations found 25 isolates of enthomopathogenic fungi consisting 10 isolates of Beauveria bassiana and 15 isolates of Metarhizium anisopliae. Selection of the fungi isolates on the aphid nymphs showed that isolate BPM isolated from Pseudoplusia chalcites caused the highest mortality rate (80.80%), while the lowest (47.20%) was caused by the isolate BAgTb isolated from A. gossypii. The shortest time needed to produce 50% mortality (Lethal Time 50) was 2.54 days (isolate of Chrysodeixis chalcites from Muarasiban). The longest time (3.66 days) was produced by isolate of Tenebrio molitor from Tanjung Raja.

Identification and Selection of Entomopathogenic Fungi as Biocontrol Agents for Aphis gossypii from South Sumatra

Aphid, Aphis gossypii is a vector of curly virus disease. The damage of chili due to its feeding is only 35% and it can achieved 100% if the damage caused by the aphid as a vector. The objectives of this research were to explore, to isolate, to identify, and to select entomopathogenic fungi as biocontrol agents for A. gossypii. The fungi were explored using insect bait in soil and collected infected insects from South Sumatra, Indonesia. Then, the fungi were isolated and identified, and finally the bioefficacy tests were done using 1 x 106 conidia mL-1 against the third instar of A. gossypii. The explorations found 25 isolates of enthomopathogenic fungi consisting 10 isolates of Beauveria bassiana and 15 isolates of Metarhizium anisopliae. Selection of the fungi isolates on the aphid nymphs showed that isolate BPM isolated from Pseudoplusia chalcites caused the highest mortality rate (80.80%), while the lowest (47.20%) was caused by the isolate BAgTb isolated from A. gossypii. The shortest time needed to produce 50% mortality (Lethal Time 50) was 2.54 days (isolate of Chrysodeixis chalcites from Muarasiban). The longest time (3.66 days) was produced by isolate of Tenebrio molitor from Tanjung Raja.

Pathogenicity of Entomopathogenic FungiMetarhizium anisopliaeandBeauveria bassiana(Hypocreales: Clavicipitaceae) Isolates to the Adult Pea Leafminer (Diptera: Agromyzidae) and Prospects of an Autoinoculation Device for Infection in the Field

Seventeen isolates of Metarhizium anisopliae (Metschnikoff) Sorokin and three isolates of Beauveria bassiana (Balsamo) Vuillemin (Hypocreales: Clavicipitaceae) were evaluated for their pathogenicity to the adult pea leafminer, Liriomyza huidobrensis (Blanchard) (Diptera: Agromyzidae), in the laboratory. Flies were contaminated with dry conidia through a velvet material wrapped around the inner side of a cylindrical plastic tube. All the isolates were pathogenic to the pea leafminer, causing mortality between 40 and 100% at 5 d after exposure. The lethal time for 50% mortality (LT(50)) ranged from 2.6 to 5.4 d, whereas the LT(90) values varied between 3.2 and 9.1 d depending on the isolate. An autoinoculation device was evaluated in cage field experiments using only one of the virulent isolates, M. anisopliae ICIPE 20. The device was loaded with 2-3 g of dry conidia. Mortality of up to 100% was observed in flies captured from fungus-treated cages held under laboratory conditions. The average number of spores picked up by a single fly visiting the device increased with days after inoculation. One day after the inoculation, adults picked up an average of 4.1 +/- 0.7 x 10(5) conidia and 39.6 +/- 4.0 x 10(5) conidia 5 d after inoculation. Depending on the sampling date, the LT(50) varied between 1.8 and 3.4 d. Results indicate that some isolates of B. bassiana and M. anisopliae are highly pathogenic to L. huidobrensis, suggesting a potential for their use in the control of this pest. They also suggest the possibility of L. huidobrensis suppression with fungi using an autoinoculation device.

Evaluation of the biocontrol potential of various Metarhizium isolates against green peach aphid Myzus persicae (Homoptera: Aphididae)

Twenty-three isolates of Metarhizium anisopliae (Metschnikof) Sorokin and M. acridum (Driver & Milner) JF Bischoff, Rehner & Humber from non-aphid host insects around the globe were evaluated for their aphid biocontrol potential, which is not well known. The apterous adults of green peach aphid Myzus persicae (Sulzer) were exposed to the fungal sprays of 11.5, 99 and 1179 conidia mm(-2) and blank control in three leaf-dish bioassays. All the tested isolates except one were proven to be infective to the aphid species at 21 +/- 1 degrees C and 14:10 h light:dark photoperiod, causing corrected mortalities of 10.1-95.3% at the high spore concentration. The data from ten isolates causing > 50% mortality at the high concentration were found to fit a time-concentration-mortality model well, yielding parameters for the estimates of their LC(50) and LT(50) that vary with post-spray time and spore concentration respectively. Four isolates of M. anisopliae (ARSEF 759, 4132, 2080 and 576) had LC(50) values of 44-80 conidia mm(-2) on day 8 and LT(50) values of 4.9-6.8 days at 100 conidia mm(-2), with 91-98% of the killed aphids being well mycotised after death. The Metarhizium infectivity to M. persicae differs greatly among the tested isolates. The four mentioned isolates with desired virulence and sporulation potential are excellent candidates for microbial control of aphids.