Modeling analysis on sporulation capacity,storage and infectivity of the aphid-specific pathogen Conidiobolus obscurus (Entomophthoromycota: Entomophthorales)

Entomophthorales are important natural enemies against agroforestry pests. Conidiobolus obscurus in this order, a common obligate aphid pathogen, possesses features of rapid growth in vitro and ease to mass production. This study sought to evaluate the potential of C. obscurus in aphid biocontrol, by modeling analyzing on the sporulation capacity and storage of its alginate formulation and infectivity to Myzus persicae. The C. obscurus mycelia-entrapping alginate pellets discharges 0.12–18.26 × 10⁴ conidia per pellet at 4−32 °C. The optimal temperature for the fungal sporulation was computed as 23.3 °C. Each pellet could sporulated for 7 d, releasing 22.3-fold more conidia than a cadaver at 24 °C. Moreover, it had longevity of 8 mo at 4 °C, with half decline time of 2.3 mo. The infectivity of C. obscurus was assessed by multi-concentration bioassays at 10−28 °C and 8−16 h light per d. The median lethal concentration (LC₅₀) at each temperature-photoperiod regime was computed based on the morality-concentration trend. The LC₅₀ values reached the lowest one of 15 conidia per mm² at 28 °C and 16:8 L:D cycles. The total results suggest that C. obscurus mycelia-inclusive alginate pellets meet the requirement of aphid biocontrol in the high-temperature surroundings of 24–28 °C.     

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

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

A PCR-based tool for the cultivation-independent monitoring of Pandora neoaphidis

Pandora neoaphidis is one of the most important fungal pathogens of aphids and has a great potential for use in biocontrol. Little is known on how this fungus persists in an area and in particular on its overwintering strategies. It is hypothesized that natural areas play an important role for survival and that soil may serve as a source of inoculum for new aphid populations in spring. To test these hypotheses, a cultivation-independent PCR-based diagnostic tool was developed, that allows the detection of P. neoaphidis in the environment. Two P. neoaphidis specific PCR primer pairs were designed, targeting sequences in the ribosomal RNA gene cluster. Specificity of both primer pairs was demonstrated with P. neoaphidis and non-target close entomophthoralean relatives. Moreover, single amplicons of expected sizes were obtained with both primer pairs from various environmental sample types, including aphid cadavers, plant material, and soil. The PCR-based diagnostic tool was applied to investigate the persistence of P. neoaphidis in soil samples obtained in 2004/2005 from a nettle field harboring infected aphids in fall 2004. P. neoaphidis was detected in every sample collected in November 2004 and March 2005, suggesting an overwintering stage of P. neoaphidis in top soil layers. The developed cultivation-independent PCR-based tool will be valuable for further investigation of the ecology of P. neoaphidis and for the development and future implementation of management strategies against aphids involving conservation biocontrol.     

The Endosymbiont Arsenophonus Is Widespread in Soybean Aphid,Aphis glycines,but Does Not Provide Protection from Parasitoids or a Fungal Pathogen

Aphids commonly harbor bacterial facultative symbionts that have a variety of effects upon their aphid hosts, including defense against hymenopteran parasitoids and fungal pathogens. The soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), is infected with the symbiont Arsenophonus sp., which has an unknown role in its aphid host. Our research goals were to document the infection frequency and diversity of the symbiont in field-collected soybean aphids, and to determine whether Arsenophonus is defending soybean aphid against natural enemies. We performed diagnostic PCR and sequenced four Arsenophonus genes in soybean aphids from their native and introduced range to estimate infection frequency and genetic diversity, and found that Arsenophonus infection is highly prevalent and genetically uniform. To evaluate the defensive role of Arsenophonus, we cured two aphid genotypes of their natural Arsenophonus infection through ampicillin microinjection, resulting in infected and uninfected isolines within the same genetic background. These isolines were subjected to parasitoid assays using a recently introduced biological control agent, Binodoxys communis [Braconidae], a naturally recruited parasitoid, Aphelinus certus [Aphelinidae], and a commercially available biological control agent, Aphidius colemani [Braconidae]. We also assayed the effect of the common aphid fungal pathogen, Pandora neoaphidis (Remaudiere & Hennebert) Humber (Entomophthorales: Entomophthoraceae), on the same aphid isolines. We did not find differences in successful parasitism for any of the parasitoid species, nor did we find differences in P. neoaphidis infection between our treatments. Our conclusion is that Arsenophonus does not defend its soybean aphid host against these major parasitoid and fungal natural enemies.     

Wheat containing snowdrop lectin (GNA) does not affect infection of the cereal aphid <Emphasis Type="Italic">Metopolophium</Emphasis><Emphasis Type="Italic">dirhodum</Emphasis> by the fungal natural enemy<Emphasis Type="Italic">Pandora neoaphidis</Emphasis>

Studies were carried out to determine if susceptibility of the cereal aphid Metopolophium dirhodum to the fungus Pandora neoaphidis was affected by wheat expressing snowdrop lectin (GNA). Aphid infection did not differ significantly between the transgenic GNA and non-transformed lines (91 and 82%, respectively). Fecundity also did not differ between aphids on the two lines, and was ca. 18 nymphs adult⁻¹. Time to infection was ca. 5 days for M. dirhodum on both lines in two of three assays. Our results indicate that wheat expressing GNA would not compromise the efficacy of P. neoaphidis as a biocontrol agent.     

Prevalence of Pandora neoaphidis (Zygomycetes: Entomophthorales) infecting Nasonovia ribisnigri (Hemiptera: Aphididae) on lettuce crops in Argentina

Lettuce crops, Lactuca sativa, organically produced in La Plata, Argentina, were sampled in order to determine the prevalence of fungal diseased aphids. Nasonovia ribisnigri was the only aphid detected and its occurrence was highly variable. The fungal pathogen Pandora neoaphidis (Entomophthoromycotina: Entomophthorales) was the only pathogen detected. We recorded a maximum of 34.2 aphids per plant and the highest rate of fungal prevalence was 56.6% (n = 30) (aphids infected/total aphids). Infected aphids were observed in all sampling sites. No differences of infection rates were detected between the center and the edge of crops. Host density was an important factor determining infection. The majority of host population was comprised of nymphs which were the most infected in terms of individuals per habitat unit (lettuce plant), but considering the proportion of infected aphids per stage of development, the prevalence of infection in nymphs and adults was similar.     

Effect of three isolates of Pandora neoaphidis from a single population of Sitobion avenae on mortality,speed of kill and fecundity of S. avenae and Rhopalosiphum padi at different temperatures

We studied the effect of three Pandora neoaphidis isolates from one Sitobion avenae population, three temperatures, and two aphid species namely S. avenae and Rhopalosiphum padi on (i) aphid mortality, (ii) time needed to kill aphids, and (iii) aphid average daily and lifetime fecundity. A total of 38% of S. avenae and 7% of R. padi died and supported fungus sporulation. S. avenae was killed 30% faster than R. padi. Average daily fecundity was negatively affected only in S. avenae inoculated with, but not killed by, P. neoaphidis. Nevertheless, lifetime fecundity of both aphid species inoculated and sporulating with P. neoaphidis was halved compared to lifetime fecundity of surviving aphids in the control. Increased temperature resulted in higher mortality rates but did not consistently affect lethal time or fecundity. Results suggest that (i) temperature effects on virulence differ between isolates, even when obtained within the same host population, and (ii) even though an isolate does not kill a host it may reduce its fecundity. Our findings are important for the understanding of P. neoaphidis epizootiology and for use in pest-natural enemy modelling.     

Interference between parasitoids [Hym.: Aphidiidae] and fungi [Entomophthorales] attacking cereal aphids

In field populations of cereal aphids parasitism levels declined through the season as fungal infection increased. In laboratory trials the fungusErynia neoaphidis Remaudiere & Hennebert took 3 to 4 days to kill the rose-grain aphid,Metopolophium dirhodum (Walker), whereas the parasitoidAphidius rhopalosiphi De Stefani-Perez took 8 to 9 days at 20°C. When aphids were infected by the fungus less than 4 days after being parasitized the parasitoids were prevented from completing their development. Conversely, when infection occurred more than 4 days after parasitization development of the fungus was significantly impaired. There was no histological evidence that the fungus invaded the tissues of the parasitoid when both attacked the same aphid. Interference between parasitoids and fungal pathogens must be taken into account when estimating the impact of these mortality agents on pest populations.     

Method To Enhance Growth and Sporulation of Pelletized Biocontrol Fungi

The biocontrol fungi Trichoderma harzianum, used to control soilborne plant pathogens, and Beauveria bassiana, used to control insect pests, were formulated as mycelial biomass in alginate pellets with wheat bran added. After drying for 0, 4, or 16 h, pellets were placed in water or in aqueous solutions of polyethylene glycol (PEG) 8000 for 4 to 24 h and then allowed to continue drying. PEG-treated pellets containing T. harzianum showed significantly greater proliferation of hyphae in soil than untreated pellets or pellets treated with water. Production of conidia of T. harzianum from PEG-treated pellets was lower than production from untreated pellets after 4 days, although rates were equivalent after 7 days. In contrast, production of conidia of B. bassiana was significantly more rapid from PEG-treated pellets than from untreated pellets. Biocontrol of soilborne plant pathogens or insect pests may be enhanced by rapid hyphal growth of T. harzianum in soil or rapid sporulation of B. bassiana on foliage, respectively. Therefore, PEG treatment may improve the efficacy of these biocontrol agents.     

Effects of constant and fluctuating temperatures on sporulation and infection by the aphid-pathogenic fungus Pandora neoaphidis

Laboratory studies were performed to assess the importance of temperature on sporulation and infection by the aphid-pathogenic fungus Pandora neoaphidis (Remaudière and Hennebert) Humber. Numbers of primary conidia discharged from mycelium formulated as alginate granules and unformulated mycelial mats were assessed, as well as infection of the potato aphid, Macrosiphum euphorbiae (Thomas) (Homoptera, Hemiptera, Aphididae), using culture plugs as inoculum sources. Sporulation from experiments at constant temperatures indicated the optimum temperature range was 10–20°C for both mycelial preparations and there was no or very little sporulation at 30°C. Infection of aphids kept at 15°C was 34–50%, while infection at 25°C was 11–44%. At 20°C, 77–79% of aphids were infected. Under fluctuating temperature cycles, conidia numbers did not differ when mycelial preparations were maintained at 18–25°C compared with 18–20°C, but fewer conidia were recorded when preparations were exposed continuously to 18–30°C. Infections of inoculated aphids kept for varying numbers of days at 18–25°C varied between 24–47%, but only 3–32% of aphids were infected when exposed to a cycle of 18–30°C for various times. Unformulated mycelial mats of P. neoaphidis appear to be superior to forumlated alginate granules for use in experimental greenhouse and field trials, since temperature stability is similar for both materials but mycelial mats are much easier to produce.     

The relationship between conidial dose,moulting and insect developmental stage on the susceptibility of cotton aphid,Aphis gossypii,to conidia of Lecanicillium attenuatum,an entomopathogenic fungus

The cotton aphid is one of the most serious pests of greenhouse vegetable crops worldwide. It is difficult to control because field populations usually include simultaneously several insect developmental stages. The current research evaluated an isolate (CS625) of Lecanicillium attenuatum, a fungal pathogen of aphids, as to its virulence against different developmental stages of cotton aphid, Aphis gossypii. The influence on mortality of several other factors also was examined: (a) insect moulting, (b) the number of conidia attached to insect cuticles and (c) germination rates of conidia on cuticles of aphids at various developmental stages. Mortality of cotton aphids treated with L. attenuatum conidia varied according to the developmental stage of the host, i.e. the LT_50s with third-instar nymphs and adults was shorter than with first-instar nymphs. The number of spores attached to the surface of first-instar nymphs was approximately one-half of that on third-instar nymphs and adults. Also, the level of spore germination on the surface of first-instar nymphs was lower than on the surface of other stages of the aphid. After moulting, the numbers of conidia attached to new insect cuticles were less than on exuviae. These results suggest that early nymphal stages of cotton aphids may escape fungal disease due, at least in part, to a combination of three factors: low numbers of conidia attached to their cuticles; low levels of conidial germination and rapid ecdyses, which removed conidia before their germ tubes penetrated the host hemolymph.     

Alginate embedding and subsequent sporulation of in vitro-produced Conidiobolus thromboides hyphae using a pressurised air-extrusion method

Conidiobolus thromboides is an entomophthoralean fungus with potential as a biological control agent of aphids. However, its application in biological control is limited due to its formulation requirements. The objective of this study was to develop and optimise a novel air-extrusion method to embed C. thromboides hyphae at high density in alginate pellets. An orthogonal experimental design was used to investigate selected combinations of parameters known to affect hyphal density within pellets. The diameter of pellets produced, and the calculated density of hyphae within them, ranged from 0.18 ± 0.09 to 3.17 ± 0.06 mm and from 0.02 to 350.56 mg/mm³ respectively. These data were used to predict the optimal parameter combination to deliver the greatest density of hyphae of C. thromboides per pellet: 1% sodium alginate, a 1:2 ratio of hyphae to sodium alginate, an orifice diameter of 0.232 mm and an air pressure of 0.05 MPa. Pellets made under the optimal conditions predicted produced a mean total of 4.3 ± 0.6 × 10⁵ conidia per pellet at 100% relative humidity which was significantly greater than the mean total number of conidia produced from infected aphid cadavers of comparable size (9.35 ± 0.85 × 10⁴) (p < 0.001). In conclusion, air-extrusion embedding appears to be a promising method for formulating in vitro-produced hyphae of C. thromboides for use in biological control.     

Aphid Wing Induction and Ecological Costs of Alarm Pheromone Emission under Field Conditions

The pea aphid, Acyrthosiphon pisum Harris, (Homoptera: Aphididae) releases the volatile sesquiterpene (E)-β-farnesene (EBF) when attacked by a predator, triggering escape responses in the aphid colony. Recently, it was shown that this alarm pheromone also mediates the production of the winged dispersal morph under laboratory conditions. The present work tested the wing-inducing effect of EBF under field conditions. Aphid colonies were exposed to two treatments (control and EBF) and tested in two different environmental conditions (field and laboratory). As in previous experiments aphids produced higher proportion of winged morphs among their offspring when exposed to EBF in the laboratory but even under field conditions the proportion of winged offspring was higher after EBF application (6.84±0.98%) compared to the hexane control (1.54±0.25%). In the field, the proportion of adult aphids found on the plant at the end of the experiment was lower in the EBF treatment (58.1±5.5%) than in the control (66.9±4.6%), in contrast to the climate chamber test where the numbers of adult aphids found on the plant at the end of the experiment were, in both treatments, similar to the numbers put on the plant initially. Our results show that the role of EBF in aphid wing induction is also apparent under field conditions and they may indicate a potential cost of EBF emission. They also emphasize the importance of investigating the ecological role of induced defences under field conditions.     

Effects of hydrophilic and hydrophobic kaolin-based particle films on pea aphid (Homoptera: Aphididae) and its entomopathogen Pandora neoaphidis (Entomophthorales: Entomophthoraceae)

Hydrophobic and hydrophilic kaolin-based particle films are effective for control of insect pests in certain agricultural crops. How these products interact with potential biological control agents is not well documented. This study was conducted to evaluate the effects of the hydrophobic (M96-018) and hydrophilic (Surround WP) kaolin-based particle films (Engelhard Corporation, Iselin, NJ) on pea aphid, Acyrthosiphon pisum (Harris), on peas (Pisum spp.), and on the fungal aphid pathogen Pandora neoaphidis (Remaudière and Hennebert) Humber. Over two field seasons (2001 and 2002) in northern Idaho, applications of M96-018 significantly reduced the rate of pea aphid increase on pea, but Surround WP, tested only in 2001, did not reduce aphid population growth rate. Neither particle film treatment was as effective as a standard application of esfenvalerate (DuPont Asana). In the laboratory, particle films suppressed pea aphid populations by up to 30%. M96-018 seemed to have some repellent activity based on aphid distributions after treating plants. When applied along with P. neoaphidis conidia, M96-018 but not Surround WP caused higher percentage of infection mortality of pea aphids by P. neoaphidis than occurred on controls treated only with P. neoaphidis conidia. P. neoaphidis conidia deposited on glass slides coated with M96-018, produced more germ tubes and secondary conidia than those deposited on untreated glass slides or slides treated with Surround WP. This result suggests that greater infection of pea aphids on plants treated with M96-018 is in part a result of a direct enhancement of fungal germination by the particle film.     

Prospects for biopesticides for aphid control

Diseases form an important component of the natural enemy complex of aphids. The most common and obvious of these diseases are entomophthoran fungi such asErynia neoaphidis Remaudiere & Herbert,Entomophthora planchoniana Cornu,Zoophthora radicans (Brefeld) Batko andConidiobolus obscurus (Hall & Dunn) Remaudiere & Keller. The pest status of some aphids such as the pea aphid,Acyrthosiphon pisum (Harris), is considerably reduced by natural epizootics of fungal disease. However, disease may contribute little to practical control as it is mainly effective in high density populations when weather conditions are suitable. Introduction of exotic diseases for classical biological control is only rarely possible since most diseases, like their aphid hosts, are distributed world-wide. One exception was the successful introduction into Australia of a strain ofZ. radicans for control of spotted alfalfa aphid,Therioaphis trifolii (Monell) f.maculata in 1979. Attempts to manipulate entomophthoran fungi have had limited success because of problems with mass production, the fragility of the conidia and the need for suitably moist conditions. Hyphomycete fungi such asVerticillium lecanii (Zimm.) Viegas,Metarhizium anisopliae (Metsch.) Sorokin,Beauveria bassiana (Bals.) Vuill. andPaecilomyces spp. are more suitable for development as mycoinsecticides as they are cheap to mass produce and form stable conidia. “Vertalec?”, a formulation ofV. lecanii, has been sold in small quantities commercially in Britain and parts of Europe for many years and used mainly in glasshouses. Recently promising results have been obtained with use ofM. anisopliae for control of lettuce root aphid,Pemphigus bursarius (L.) in the UK. Laboratory studies on selected isolates ofB. bassiana andPaecilomyces spp. show a promising level of activity. Problems may occur with these species as they can kill aphid predators such as coccinelids. In addition, more research is needed on developing improved formulations which enable control to be achieved under low humidity conditions.     

Observations on the Occurrence of Entomophthorales Infecting Aphids (Aphidoidea) in Slovakia

The species spectrum of entomophthoralean fungi parasiting aphids was investigated in Slovakia. The surveys focused on aphid fauna occupying both agricultural crops and vegetation at non-crop sites. During the surveys, 15 different entomophthoralean species were identified from 66 aphid species. Of these 15 fungal species, eight had not previously been recorded in Slovakia and one species, Erynia erinacea (Ben-Ze’ev et Kenneth) Remaudière et Hennebert, had not been recorded previously in Central Europe. New hosts for some parasitic fungi were also recorded. The occurrence of fungal infection and the fungal species spectrum varied with sampling period and sampling area. In general, the fungi were observed parasiting aphid populations from April until November. Pandora neoaphidis (Remaudière et Hennebert) Humber was the predominant fungal pathogen and could effectively reduce aphid populations. Entomophthora planchoniana Cornu and Conidiobolus obscurus (Hall et Dunn) Remaudière et Keller were also common pathogens of aphids, but without an epizootic potential. On the other hand, Neozygites fresenii (Nowakowski) Remaudière et Keller had a strong tendency to establish epizootics in dense aphid colonies, especially in those of the black bean aphid. Other entomophthoralean species observed in the country were considered to be minor aphid pathogens on account of their low occurrence, lower specificity to aphids, or high specificity to a single aphid species. This is the first detailed report to date on the occurrence of Entomophthorales in Slovakia.     

Survival of Bifidobacterium longum Immobilized in Calcium Alginate Beads in Simulated Gastric Juices and Bile Salt Solution

Bifidobacterium longum KCTC 3128 and HLC 3742 were independently immobilized (entrapped) in calcium alginate beads containing 2, 3, and 4% sodium alginate. When the bifidobacteria entrapped in calcium alginate beads were exposed to simulated gastric juices and a bile salt solution, the death rate of the cells in the beads decreased proportionally with an increase in both the alginate gel concentration and bead size. The initial cell numbers in the beads affected the numbers of survivors after exposure to these solutions; however, the death rates of the viable cells were not affected. Accordingly, a mathematical model was formulated which expressed the influences of several parameters (gel concentration, bead size, and initial cell numbers) on the survival of entrapped bifidobacteria after sequential exposure to simulated gastric juices followed by a bile salt solution. The model proposed in this paper may be useful for estimating the survival of bifidobacteria in beads and establishing optimal entrapment conditions.     

Virulence of Hypocreales fungi to pecan aphids (Hemiptera: Aphididae) in the laboratory

There is need for efficacious biocontrol agents for aphids in commercial orchards. As a preliminary step to this end we determined the virulence of several Hypocreales fungi to pecan aphids. In the first experiment we tested the virulence of Isaria fumosorosea (ARSEF 3581) blastospores to three pecan aphids Monellia caryella, Melanocallis caryaefoliae, and Monelliopsis pecanis under laboratory conditions. Rates of 1 × 10⁷ or 1 × 10⁸ spores per ml were applied in 2 ml via a spray tower to 90 mm Petri dishes containing 10 aphids each. Mortality and mycosis were determined after 24, 48 and 72 h. Treatment effects were observed by 48 h post-application, and by 72 h the higher application rate caused >90% mortality and mycosis in M. caryella and M. caryaefoliae, whereas <70% was observed in M. pecanis.We conducted two subsequent experiments (Experiments 2 and 3), using the same methodology, to compare the virulence of several Hypocreales species and strains against the aphid of primary economic concern to most pecan growers, M. caryaefoliae. In Experiment 2, we compared blastospores and conidia of two I. fumosorosea strains (ARSEF 3581 and ATCC 20874 [= strain 97]). The blastospores of ARSEF 3581 and conidia of ATCC 20874 showed higher virulence than other treatments and thus were included in Experiment 3, which also compared the virulence of conidia of Beauveria bassiana (GHA strain) and Metarhizium anisopliae (F52 strain). Results in Experiment 3 indicated the highest virulence in I. fumosorosea 3581 blastospores and M. anisopliae (F52) followed by I. fumosorosea (20874) conidia. The detection of pathogenicity to pecan aphids establishes the potential for commercial usage and additional study. Results reported here will narrow treatments to test in future greenhouse and field trials.     

Impact of the entomopathogenic fungus Verticillium lecanii on development of an aphid parasitoid, Aphidius colemani

The parasitoid Aphidius colemani developed normally (approximately 90% adult emergence) when its cotton aphid (Aphis gossypii) host was treated with Verticillum lecanii conidia 5 or 7 days after parasitization. Fungus exposure 1 day before or up to 3 days after parasitization, however, reduced A. colemani emergence from 0 to 10%. Also, numbers of spores and mycelial fragments in aphid homogenates were much higher in aphids exposed to the fungus up to 3 days after parasitization than in aphids treated after 5 or 7 days. Our results suggest that the parasitoid and fungus may be used together for aphid biocontrol as long as fungus applications are timed to allow late-instar development of the parasitoid.     

Efficacy of Beauveria bassiana (Blas.) Vuill. against cabbage aphid Brevicoryne brassicae L. (Hem.: Aphididae) in laboratory condition

In order to replace the conventional chemical pesticides, extensive researches have been done on entomopathogenic fungi. Entomopathogenic fungus Beauveria bassiana is an important biocontrol agent against major economic pests and is being employed in Integrated pest management (IPM) along with synthetic pesticides. Cabbage aphid Brevicoryne brassicae L. is one of the important pests of Brassicaceae family. Therefore, in this research, the virulence isolate of B. brassicae (IRAN 429C) was investigated on adults of cabbage aphid under laboratory conditions. The experiments were conducted at 25 ± 2 °C, 60 ± 10 R. H. and a photoperiod of 16:8 (L: D). After preliminary experiments, the adult aphids were treated with fungal concentrations of 1 × 10³ to 1 × 10⁷ spores/ml. Probit analysis was conducted to calculate LC₅₀ and LC₉₅ values for the isolate. Positive correlation was observed between concentrations and pest mortality. LC₅₀ and LC₉₅ values calculated for IRAN 429C isolate are 2.04 × 10⁵ and 1.82 × 10⁸, respectively. The mortality was counted one day after the treatment and then continued for 14 days. Cumulative mortality for 14 days after treatment varied from 54% for IRAN 429C at low concentration (10³ conidia/ml) to 83% at high concentration (10⁷ conidia/ml). The lowest LT₅₀ was obtained at 7.67 days for IRAN 429C isolate at concentration 1 × 10⁷ spore/ml. According to the insecticidal activity of mentioned fungi on cabbage aphid, it can be used in biocontrol programmes of B. brassicae.