Bassiana Isolates Research Articles

ISOLATION AND IDENTIFICATION OF THREE ENTOMOPATHOGENIC FUNGI

Entomopathogenic fungi used in the present study were Metarhizium anisopliae, Beauveria bassiana and Paecilomyces fumosoroseus. The first fungus was isolated from the Rhynhophorus ferruginens in Ismailiya governorate, the second from the white fly in the Sharkia and the third from Aphis gossypii in Al-Fayoom governorate. Beauveria colonies are usually slow growing, downy, at first white but later often becoming yellow. The spores as balls represent dense clusters of large numbers of conidiogenous cells and conidia. Paecilomyces colonies are usually slow growing, at first white but later often becoming rosy-tan to smoky-pink (or Grey) in mass. Ovoid to elongate. Metarhizium colonies are usually strong growing, olivaceous green with yellowish color in reverse. yellowished green in mass. RAPD amplified DNA products using 5 primers differentiated 3 isolates of entomopathogenic fungi belonging to different genera collected from different locations and host insects. Total of 91 amplified fragments generated 81 polymorphic bands can be used as RAPD markers. There are 81 specific markers out of 137 total amplified fragments. RAPD markers were found to be useful as isolate specific marker. The results showed the specific markers for the 3 entomopathogenic fungi isolates resulting from RAPD-PCR analysis. B. bassiana isolate exhibit 18 positive amplified fragments and 9 negative, while P. fumosoroseus isolate generated 22 positive amplified fragments as a highest number of specific positive markers and 12 negative amplified fragments. As well M. anisopliae isolate showed 15 positive amplified fragments and 8 negative. The proteins of three entomopathogenic isolates were extracted from their mycelium and fractionated by SDS-PAGE. The proteins of B. bassiana, P. fumosoroseus and M. anisopliae were separated into 11, 4 and 5 bands respectively.

English

Three newly isolated and two existing isolates of M. anisopliae and B. bassiana were tested against aphids, whiteflies and beneficials, individually and with chitin synthesis inhibitor. Hundred percent of aphids have died of fungal treatments 7 days post inoculation, but number of individuals that developed mycosis varied depending on the isolate used. Whiteflies, however, were slightly more resistant. All tested isolates appeared to be fast killing fungi requiring only one or two days for reducing aphid population by half and needing 4 to 6 days for 50% of whiteflies to succumb to the disease. Both, aphid and whitefly, mortalities increased with increasing dose. The estimated LC50 values against M. persicae were 10 3.88 and 10 4.75 conidia ml -1 , respectively. These results were comparable with values obtained for the same isolates tested against whitefly Bemisia tabaci. Hundred precent of parasitized aphids by whitefly parasitoid demonstrated the emergence hole in the controls and in the individuals treated with new M. anisopliae isolate and 87% of emergence holes in the individuals treated with new B. bassiana. Exposure of mealybug predator to new isolates resulted in high mortalities. Native B. bassiana isolate in combination with diflubenzuron significantly reduced population of 1 st instar larvae of whiteflies under greenhouse conditions 14 days post treatment.

EFFICACY OF FUNGAL ENTOMOPATHOGENS AGAINST RED COTTON STAINER, DYSDERCUS CINGULATUS FABRICIUS (HEMIPTERA: PYRRHOCORIDAE)

ABSTRACT The efficacy of entomopathogenic fungi [Beavueria bassiana (Bb08, Bb10) and Isaria fumosorosea (Ifr)] isolated from different regions of Southern Tamil Nadu, India was assessed against red cotton stainer, Dysdercus cingulatus. All the tested isolates showed 100% mortality. The B. bassiana isolates such as Bb08, Bb10 and an I. fumosorosea isolates exemplified the significant mortality among the isolates tested. LC50, LC90 and correlation coefficient were calculated for mortality. Bb08, Bb10 and Ifr isolates unveiled the lowest LC50 (5.9 x 105 , 6.6 x 105 and 2.6 x 105) and LC90 (1 x 109 , 7.3 x 108 and 3.9 x 108) value compared to the isolates tested. Highly significant correlation coefficient was observed in the isolates Bb08, Bb10 and Ifr

Diversity, prevalence and virulence of fungal entomopathogens in colonies of the ant Formica selysi

The richness of the parasitic community associated with social insect colonies has rarely been investigated. Moreover, understanding how hosts and pathogens interact in nature is important to interpret results from laboratory experiments. Here, we assessed the diversity, prevalence and virulence of fungal entomopathogens present around and within colonies of the ant Formica selysi. We detected eight fungal species known to be entomopathogenic in soil sampled from the habitat of ants. Six of these entomopathogens were found in active nests, abandoned nests, and corpses from dump piles or live ants. A systematic search for the presence of three generalist fungal entomopathogens in ant colonies revealed a large variation in their prevalence. The most common of the three pathogens, Paecilomyces lilacinus, was detected in 44% of the colonies. Beauveria bassiana occurred in 17% of the colonies, often in association with P. lilacinus, whereas we did not detect Metarhizium brunneum (formerly M. anisopliae) in active colonies. The three fungal species caused significant mortality to experimentally challenged ants, but varied in their degree of virulence. There was a high level of genetic diversity within B. bassiana isolates, which delineated three genetic strains that also differed significantly in their virulence. Overall, our study indicates that the ants encounter a diversity of fungal entomopathogens in their natural habitat. Moreover, some generalist pathogens vary greatly in their virulence and prevalence in ant colonies, which calls for further studies on the specificity of the interactions between the ant hosts and their fungal pathogens.

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.

Generating thermotolerant colonies by pairing Beauveria bassiana isolates

Low thermotolerance in entomopathogenic fungi is the main impediment to their industrialization. This research, for the first time, describes the generation of a thermotolerant colony by pairing and subculturing (cycling) two Beauveria bassiana isolates without sexual reproduction. A mixture of B.bassiana ERL1578 and ERL1576 was inoculated on quarter-strength Sabouraud dextrose agar with yeast extract (¼SDAY). The paired culture (ERL1578+1576) was cycled three times to increase the frequency of possible hyphal fusion at the first cycle (c.5/5×10(5) conidia), followed by a heat treatment as a selection pressure. Two non-paired isolates served as controls. Two morphologically different colonies (BbHet1 and BbHet2) were isolated from the pairing. BbHet1 colony had the highest conidial yield. BbHet2 had the most rapid mycelial growth and produced sponge-like mycelial masses (the others were flat), and its conidia were darker than the non-paired colonies under a microscope (400×). BbHet2 conidia had 60.7% germination after exposure to 45°C for 60min (the others had <15%) without significant loss of virulence against Western flower thrips, Frankliniella occidentalis; however, there was a slight decrease in conidial yield. The new phenotypes formed suggested that a genetic variation happened as a result of heterokaryosis and/or recombination, more than environmental adaptation, when mixing different conidia. This methodology seems to be very useful for enhancing thermotolerance in fungi.

Use of a multiple logistic regression model to determine the effects of soil moisture and temperature on the virulence of entomopathogenic fungi against pre-imaginal Mediterranean fruit fly Ceratitis capitata

Last-instar larvae of the Mediterranean fruit fly, Ceratitis capitata, were exposed to Beauveria bassiana and Metarhizium anisopliae isolates in sterile soil under controlled conditions. A multiple logistic regression model for mycosis was applied, and different temperature and moisture patterns for each of the four isolates were observed (Bb-1333, EABb 01/33-Su, EAMa 01/58-Su, EAMa 01/158-Su). In general, B. bassiana isolates were less virulent than M. anisopliae isolates. For all of the fungal isolates, lower mycosis values were observed under extreme moisture conditions (1% and 17% wt.:wt.). For the most virulent isolate, M. anisopliae EAMa 01/58-Su, higher mycosis values were observed at intermediate temperatures. Conversely a direct relationship between temperature and puparia mortality was observed for M. anisopliae isolate EAMa 01/158-Su. Both B. bassiana isolates displayed a parabolic relationship with moisture, and mycosis was observed at low temperatures (15–20.1 °C). This work provides additional evidence on the fact that for each fungal species, each isolate is an independent biological entity with different responses to environmental conditions; therefore, entomopathogenic fungal isolates for pest control should have a range of temperatures and humidities that can be matched to the desired environment.

Susceptibility of Sitophilus zeamais (Mostch.) (Coleoptera: Curculionidae) to Beauveria bassiana and Metarhizium anisopliae

Evaluation of eleven Metarhizium anisopliae and six Beauveria bassiana isolates against the maize weevil Sitophilus zeamais was conducted under laboratory with the objectives of identifying the most virulent locally available fungal isolates, and determining the dose mortality response. The pathogenicity (virulence) of the entomopathogenic fungi was determined using LT50 and percent mortality at the conidial concentration of 1 x 108 ml-1. The most virulent isolates of M. anisopliae (PPRC-2, PPRC-14 and PPRC-51) and B. bassiana (PPRC-GG and PPRC-HH) caused 84.4% to 98.3% mortality to S. zeamais. These isolates had LT50 ranging from 3.8 to 4.3 days. The dose response study with the isolates PPRC-2, PPRC-14 and PPRC-51 at doses ranging from 1x 104 to 1x 108 conidia ml-1 revealed susceptibility of the S. zeamais with mortality ranging from 25 to 95.5%. There was an increase in the resulting LT50 from 4.0 to 11.9 days with a decrease in conidial concentration from 1x 108 to 1x 104 conidia ml-1. PPRC-2 showed the lowest LC50 (1.46x 10 conidia ml-1) followed by PPRC-14 and PPRC-51 (3.5x 105 and 3.9x 105 conidia ml-1, respectively). In conclusion, the isolates PPRC-2, PPRC-14, PPRC-51, PPRC-GG and PPRC-HH, can be considered as a potential candidates in the development of mycoinsectisdes against S. zeamais.

Improving photoprotection of Beauveria bassiana conidia for biological control of the cactus pest Dactylopius opuntiae in the semiarid region northeast of Brazil

A technical grade conidial preparation of the entomopathogenic fungus Beauveria bassiana isolate LCB63 was exposed to ultraviolet light (UV) from artificial and natural sources in the presence of various photoprotectants to develop a viable formulation to control Dactylopius opuntiae, a limiting pest of forage cacti in the Brazilian semiarid region. In the first experiment, Conidial viability was assessed in preparations containing water and liposoluble photoprotectants at a concentration of 1% and exposed to solar radiation for 0, 60, and 120 min. In another experiment, preparations containing different concentrations of the selected photoprotectants were exposed to natural and artificial UV radiation for 120 and 5 min, respectively. Insecticide activity of technical grade conidial preparations containing selected photoprotectants were evaluated against first instar nymphs of D. opuntiae. In general, no evaluated compounds showed deleterious effects on conidial germination, and they provided a strong degree of protection over a short period of time. One-percent concentrations of starch and skim milk resulted in low photoprotection over a longer irradiation period, while 1% Neo Heliopan AV, Neo Heliopan E1000 and Oxybenzone provided a moderate degree of protection. Increasing the concentration of Oxybenzone increased germination rate to 70%, while treatment with 1% Neo Heliopan E1000 maintained germination at 50%. A technical grade conidial preparation containing 1% Oxybenzone was effective in promoting D. opuntiae nymph mortality. These results suggested that addition of liposoluble photoprotectants could provide better photoprotection for B. bassiana LCB63 conidia in bioinsecticide formulations.

An intensive search for promising fungal biological control agents of ticks, particularly Rhipicephalus microplus

Entomopathogenic fungi have been investigated worldwide as promising biological control agents of the cattle tick Rhipicephalus microplus. The current study evaluates the virulence of several fungal isolates to R. microplus larva in the laboratory as part of an effort to identify isolates with promise for effective biocontrol of R. microplus in the field. Sixty fungal isolates, encompassing 5 Beauveria spp. and 1 Engyodontium albus (=Beauveria alba), were included in this study. In addition to bioassays, the isolates were characterized morphologically and investigated as to their potential for conidial mass production. These findings were correlated with previous reports on the same fungal isolates of their natural UV-B tolerance (Fernandes et al., 2007), thermotolerance and cold activity (Fernandes et al., 2008), and genotypes (Fernandes et al., 2009). R. microplus larvae obtained from artificially infested calves were less susceptible to Beauveria bassiana infection than ticks acquired from naturally infested cattle from a different location. Isolates CG 464, CG 500 and CG 206 were among the most virulent Beauveria isolates tested in this study. All fungal isolates presented morphological features consistent with their species descriptions. Of the 53 B. bassiana isolates, five (CG 481, CG 484, CG 206, CG 235 and CG 487) had characteristics that qualified them as promising candidates for biological control agents of R. microplus, viz., mean LC50 between 107 and 108conidiaml−1; produced 5000 conidia or more on 60mm2 surface area of PDAY medium; and, in comparison to untreated (control) conidia, had the best conidial tolerances to UV-B (7.04kJm−2) and heat (45°C, 2h) of 50% or higher, and conidial cold (5°C, 15d) activity (mycelial growth) higher than 60%. The current study of 60 Beauveria spp. isolates, therefore, singles out a few (five) with high potential for controlling ticks under field conditions.

Characterization of a newly discovered Beauveria bassiana isolate to Franklimiella occidentalis Perganda, a non-native invasive species in China

In this study, a new virulent Beauveria bassiana isolate ( B. bassiana-CYT5) had been identified as a new member of the species B. bassiana. The B. bassiana-CYT5 isolate was compared with four other virulent B. bassiana isolates and found to be highly infectious and virulent against the Franklimiella occidentalis Perganda. The B. bassiana-CYT5 could approximately 93.08% mortality of F. occidentalis 6 days post inoculation in the concentration of 1 × 10 8 conidia/mL. The phylogenetic tree based on ITS and partial sequence of elongation factor 1-alpha (EF1-alpha) indicated that B. bassiana-CYT5 isolate was in a cluster of B. bassiana. Furthermore, B. bassiana-CYT5 isolate demonstrated high heat tolerance (60–100% relative germination) between 1-h and 2-h exposure at 37 °C, 38 °C, 39 °C and 40 °C, respectively. So our results suggested that B. bassiana-CYT5 isolate could be a new efficient biocontrol agent against F. occidentalis.

Effect of culture substrates on virulence of Beauveria bassiana (Ascomycota: Cordycipitaceae) conidia against the browntail moth, Euproctis chrysorrhoea (Lepidoptera: Lymantriidae)

We studied the effect of different solid substrates on virulence of two Beauveria bassiana isolates against the browntail moth, Euproctis chrysorrhoea (L.) (Lep.: Lymantriidae). Conidia produced on wheat grains, wheat flour, wheat bran, rice flour, rice bran, rice paddy, corn flour, millet, and Sabouraud's dextrose agar with 1% yeast extract (SDAY) as control were compared. There were significant differences among these substrates for their effects on the virulence of produced conidia. Applying 107 conidia/mL of B. bassiana EUT105, produced on rice bran caused the highest (84.9%) and on rice flour, the lowest (57.6%) mortalities. Bioassay on fifth-instar larvae using aerial conidia harvested from wheat grains, rice paddy, and SDAY indicated that conidia from wheat grains had the highest virulence while those from rice paddy, the lowest.

Genetic analyses place most Spanish isolates of Beauveria bassiana in a molecular group with word-wide distribution

BackgroundThe entomopathogenic anamorphic fungus Beauveria bassiana is currently used as a biocontrol agent (BCA) of insects. Fifty-seven Beauveria bassiana isolates -53 from Spain- were characterized, integrating group I intron insertion patterns at the 3'-end of the nuclear large subunit ribosomal gene (LSU rDNA) and elongation factor 1-alpha (EF1-α) phylogenetic information, in order to assess the genetic structure and diversity of this Spanish collection of B. bassiana.ResultsGroup I intron genotype analysis was based on the four highly conserved insertion sites of the LSU (Ec2653, Ec2449, Ec2066, Ec1921). Of the 16 possible combinations/genotypes, only four were detected, two of which were predominant, containing 44 and 9 members out of 57 isolates, respectively. Interestingly, the members of the latter two genotypes showed unique differences in their growth temperatures. In follow, EF1-α phylogeny served to classify most of the strains in the B. bassiana s.s. (sensu stricto) group and separate them into 5 molecular subgroups, all of which contained a group I intron belonging to the IC1 subtype at the Ec1921 position. A number of parameters such as thermal growth or origin (host, geographic location and climatic conditions) were also examined but in general no association could be found.ConclusionMost Spanish B. bassiana isolates (77.2%) are grouped into a major phylogenetic subgroup with word-wide distribution. However, high phylogenetic diversity was also detected among Spanish isolates from close geographic zones with low climatic variation. In general, no correlation was observed between the molecular distribution and geographic origin or climatic characteristics where the Spanish B. bassiana isolates were sampled.

Biological control of engorged female Haemaphysalis qinghaiensis (Acari: Ixodidae) ticks with different Chinese isolates of Beauveria bassiana

Seven isolates of the fungus Beauveria bassiana (B.b) were assessed for their lethality against Haemaphysalis qinghaiensis, a prevalent tick species in China. Fourteen days after exposure to the isolates B.bAT1, B.bAT5, and B.bAT7 (at 10(8) conidia mL(-1)), the mortality rate had reached 100%. The results indicated that these three B. bassiana isolates were highly virulent against the engorged female H. qinghaiensis ticks. The present study suggests that B. bassiana has potential for biocontrol applications to eradicate H. qinghaiensis.

Natural occurrence of soil-borne entomopathogenic fungi in the Moroccan Endemic forest of Argania spinosa and their pathogenicity to Ceratitis capitata

The occurrence and abundance of entomopathogenic fungi were analysed in 203 soil samples of the Moroccan endemic forests of Argania spinosa, the world main refuge of the Mediterranean fruit fly, Ceratitis capitata. Using the Galleria baiting method and selective media, entomopathogenic fungi were isolated from 186 of the 203 (91.62%) soil samples, with only three species found: Beauveria bassiana (Balsamo) Vuillemin, Metarhizium anisopliae (Metschnikoff) Sorokin and Paecilomyces lilacinus (Thom.) Samson. B. bassiana was the most widespread entomopathogenic fungi (90.64%) in the Argan forest whereas M. anisopliae was less common (15.27%) and P. lilacinus was very rare (1.48%). This is the first report of natural occurrence of M. anisopliae and P. lilacinus in Morocco. Furthermore, 118 Moroccan B. bassiana isolates were studied for their pathogenicity to C. capitata and thermotolerance. Most of these autochtonous B. bassiana isolates were virulent (86.44%) to Medfly pupae and tolerant (55.08%) to temperature stress at 45°C for 2 h. Only 60.17% of Moroccan B. bassiana isolates might be considered as highly entomopathogenic and will serve as a source of potential biological control agents to C. capitata. The percentage of thermotolerant and pathogenic B. bassiana to C. capitata were shown to decrease significantly at winter time characterized by low temperatures and absence of any noticeable medfly in the Argan forest. The occurrence, thermotolerance and virulence of B. bassiana isolates to C. capitata seemed to be related to the sampling periods and location. Our data are discussed with respect to fungal ecology and biocontrol potential of B. bassiana isolates in relation to their habitat.

Utilization of Carbohydrates by Beauveria Bassiana Isolates Obtained from Forest Pests

Carbohydrate utilization profiles of ten isolates of the entomopathogenic fungus Beauveria bassiana (Bals.-Criv.) Vuillemin were studied and compared to assist in determining their phenotypic characterization. Isolates were obtained in pure cultures from dead individuals of several forest pests collected from different regions in Bulgaria. Studies on utilization profiles were based on the acidification of twenty carbohydrates. The results indicate that sucrose, maltose and trehalose were assimilated at a high degree compared to esculin, arabinose and dul- citol. According to the results of a cluster analysis of the carbohydrate utilization profiles, the B. bassiana isolates were divided into two larger groupings. All isolates in the first larger cluster were obtained from the coleopteran insects - Stenomax aeneus, Ips typographus, I. sexdentatus and Dryocoetes autographus. Isolates from the other cluster were obtained from the lepidopteran larvae of Thaumetopoea pityocampa and Lymantria dispar, and from an adult of the coleopteran species Hylurgops palliatus. We determined that each B. bassiana isolate exhibited a different and specific carbohydrate utilization profile but differences at the p-level < 0.05 were significant among some of them. The most distinguishable was the isolate 560Bb obtained from T. pityocampa. Differences between the isolate 560Bb and the other nine B. bassiana isolates were highly significant at the p-level < 0.005. Isolate 433Bb obtained from a dead adult of I. typogra- phus was significantly different from five of the studied isolates at the p-level < 0.05.

Pathogenicity of Three Entomopathogenic Fungi against Helicoverpa armigera

The agricultural pests and pathogens known so far include 2,000 species of insects and 800 fungi. Among the insect pests Helicoverpa armigera, a lepidopteran insect causes more than 50% loss in yield of important crops such as cotton, pulses, vegetables and sunflower in India. In recent years, agricultural production of pulses repeatedly have suffered average yield loss of about 67% due to high levels of insecticide resistance in H.armigera. In the present study, Metarhizium anisopliae, Beauveria bassiana, and Nomuraea rileyi are used to control the insect pest. The mass production of cell wall was carried out by two stage fermentation for the production of various enzyme and its inhibitors. The M. anisopliae and B. bassiana isolates from fields showed greater than 70% mortality of H. arimgera in the bioassay the percentage mortality declined; there was a decrease in the enzyme activities of B. bassiana. N. rileyi isolates did not exhibit detectable chitinase levels even up to 120 h.

Beauveria bassiana: quercetinase production and genetic diversity

Beauveria bassiana genetic diversity and ability to synthesize quercetin 2,3-dioxygenase (quercetinase) were analyzed. B. bassiana isolates, obtained from Brazilian soil samples, produced quercetinase after induction using 0.5 g/L quercetin. B. bassiana ATCC 7159 (29.6 nmol/mL/min) and isolate IP 11 (27.5 nmol/ml/min) showed the best performances and IP 3a (9.5 nmol/mL/min) presented the lowest level of quercetinase activity in the culture supernatant. A high level of polymorphism was detected by random amplified polymorphic DNA (RAPD) analysis. The use of internal-transcribed-spacer ribosomal region restriction fragment length polymorphism (ITS-RFLP) did not reveal characteristic markers to differentiate isolates. However, the ITS1-5.8S-ITS2 region sequence analysis provided more information on polymorphism among the isolates, allowing them to be clustered by relative similarity into three large groups. Correlation was tested according to the Person's correlation. Data of our studies showed, that lower associations among groups, level of quercetinase production, or geographical origin could be observed. This study presents the production of a novel biocatalyst by B. bassiana and suggests the possible industrial application of this fungal species in large-scale biotechnological manufacture of quercetinase.

Occurrence of entomopathogenic fungi from agricultural and natural ecosystems in Saltillo, México, and their virulence towards thrips and whiteflies.

Entomopathogenic fungi were collected from soil in four adjacent habitats (oak forest, agricultural soil, pine reforestation and chaparral habitat) in Saltillo, México using the insect bait method with Tenebrio molitor (L.) (Coleoptera: Tenebrionidae) larvae as bait. Overall, of the larvae exposed to soil, 171 (20%) hosted Beauveria bassiana (Balsamo) Vuillemin (Hypocreales: Cordycipitaceae), 25 (3%) hosted Metarhizium anisopliae (Metschnikoff) Sorokin (Hypocreales: Clavicipitaceae) and 1 (0.1%) hosted lsaria (=Paecilomyces) sp. (Hypocreales: Cordycipitaceae). B. bassiana was significantly more frequent on larvae exposed to oak forest soil. M. anisopliae was significantly more frequent on larvae exposed to agricultural soil. From the infected bait insects, 93 isolates of B. bassiana and 24 isolates of M. anisopliae were obtained. Strains were tested for their infectivity against Cuban laurel thrips, Gynaikothrips uzeli Zimmerman (Thysanoptera: Phlaeothripidae) and the greenhouse whitefly, Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae). B. bassiana isolates caused the highest mortality on thrips (some causing 88% mortality after 6 days); both fungal species caused similarly high mortality levels against whiteflies (75%) after 6 days. Large amounts of germplasm of entomopathogenic fungi, fundamentally B. bassiana and M. anisopliae, exist in the habitats sampled; pathogenicity varied among strains, and some strains possessed significant virulence. Soils in these habitats are reservoirs of diverse strains with potential for use in biocontrol.

Efficiency of entomopathogenic fungi Beauveria bassiana and Verticillium lecanii for biological control of whitefly, Bemisia tabaci

A study was conducted under field conditions to evaluate the efficiency of two entomopathogeaic fungi: Beauveria bassiana and Verticillium lecanii to parasitize whitefly nymphs and adults. Results revealed that V. lecanii showed the highest perecentage of parasitism (73.4%) on adults and nymphs on egg plant under field conditions at AL-Nehrawn compared with B. bassiana isolate 1 and 2 (56.7 and 50.4% respectively) after 10- days of treatment. When used conidia suspension of V. lecanii with 0.02% triton caused the highest parasitism (90%) after 10 days of treatment. In a field experiment at AL-Tuwaitha, the results indicated that V. lecanii showed that highest percentage of parasitism (90 and 80.66%) compared with B. bassiana isolate 1 and 2 (68.66, 60 and 53.33, 48%) when used 0.02% triton and 0.2% corn oil resectively after 10 days of treatment . While in a green house experiment , the results showed the use of V. lecanii and B. bassiana isolate 1 together was more effective in parasitizing (90%) than use of either one alone (70.3 and 81% for V. lecanii and B. bassiana isolate 1 respectively) on adults and nymphs after 15 das of treatment . There was a clear reduction in the number of colony forming units (CFU) viability of V. lecanii and B. bassiana isolate 1 and 2 with time of storage, for the fungal viability storage at room temperature was less efficient than storage at 4 0C .