Susceptibility of the tobacco whitefly,Bemisia tabaci (Hemiptera: Aleyrodidae) biotype Q to entomopathogenic fungi

Recently, the Q biotype of tobacco whitefly has been recognized as the most hazardous strain of Bemisia tabaci worldwide because of increased resistance to some insecticide groups requiring alternative strategies for its control. We studied the susceptibility of this biotype of B. tabaci to 21 isolates of Beauveria bassiana, three isolates of Isaria fumosorosea, one isolate of I. cateni, three isolates of Lecanicillium lecanii, one isolate of L. attenuatum, and one isolate of Aschersonia aleyrodis. These isolates were evaluated on pruned eggplant seedlings, at a concentration of 10⁸ conidia/mL (deposited at 6000±586 conidia mm^?2). The mortality based on mycosis varied from 18 to 97% after 6 days. Isaria fumosorosea isolate Pf04, B. bassiana isolates Bb06, Bb12, and L. lecanii L14 were found the most effective. Furthermore, five isolates were chosen for concentration–mortality response assays and compared to B. bassiana GHA as a standard. The numbers of nymphs infected by fungi were correlated with the spore concentration. L. lecanii L14 and I. fumosorosea Pf04 had the shortest LT₅₀ at 3.5 and 3.3 days at 6000±586 conidia mm^?2. Mortality declined and LT₅₀ values were longer as the concentration of conidia was reduced. The LD₅₀ values were calculated as 87, 147, 191, 263, and 269 conidia mm^?2 for isolates L14, GHA, AS1260, Bb13, and Pf04, respectively. These results indicated that the Q biotype of sweetpotato whitefly was susceptible to the five isolates of entomopathogenic fungi and these isolates have potential to be developed as microbial pesticides for whitefly control.     

Physiological effects of nanosilver on vegetative mycelium,conidia and the development of the entomopathogenic fungus,Isaria fumosorosea

An assessment of the influence of water nanosilver suspension was made at a concentration of 10 mg·L^?1 on biological material (i.e., vegetative mycelium and conidia of Isaria fumosorosea entomopathogen) on a background of the silver nitrate ionic form used. Conidia of I. fumosorosea treated with silver nitrate for more than 168 h were completely deactivated. The application of nanosilver on Isaria hyphae resulted in a quantitative limitation of mycelium growth and its weaker sporulation after culturing compared to the control. The pathogenicity of a conidial suspension obtained from such culturing towards test insects did not diverge from that observed in the standard culture. No obvious toxic effects of nanosilver were observed on I. fumosorosea conidia. Isaria conidia, after exposure to nanosilver over a period between 1 and 800 h, initially demonstrated weaker vegetative mycelium formation in culture on solid medium and, as a consequence, this mycelium often sporulated in a poorer manner. In one case, there was a significant stimulation of the sporulation process for nanosilver treatment before culture for 168 h. Concurrently, conidial suspensions obtained from the culture after exposure of over 168 h to nanosilver exhibited enhanced pathogenicity towards test insects, which may be considered a beneficial phenomenon in terms of the function played by Isaria in the whole environment. The reaction of conidia with nanosilver indicates the deactivation of conidia cells in suspensions and a possibility of selection in increased pathogenicity.     

Insecticidal activity of entomopathogenic fungi (Hypocreales) for potato psyllid,Bactericera cockerelli (Hemiptera: Triozidae): Development of bioassay techniques,effect of fungal species and stage of the psyllid

The potato psyllid, Bactericera cockerelli (?ulc), is a pest of potato, tomato, and some other solanaceous vegetables and has also been incriminated in the transmission of a bacterial pathogen, Candidatus Liberibacter solanacearum, resulting in a serious disease known as ‘zebra chip’. Although there are several reports of fungal pathogens in psyllids, there are none from B. cockerelli, nor have any fungi been evaluated against it. Five isolates of fungi, one Beauveria bassiana, two Metarhizium anisopliae and two Isaria fumosorosea, were bioassayed against B. cockerelli on potato leaves under ideal conditions for the fungi. All applications were made with a Potter spray tower. With the exception of concentration-effect studies, all other applications were made using 10⁷ conidia/mL in a 2-mL aqueous suspension. All isolates except B. bassiana, produced 95–99% mortality, corrected for control mortality, in adults 2–3 days after application of conidia and 91–99% in nymphs 4 days after application. The corrected mortalities for adults and nymphs treated with B. bassiana were 53 and 78%, respectively, 4 days after application. I. fumosorosea Pfr 97 produced 95% corrected mortality in both first and late third instar nymphs. M. anisopliae (F 52) produced 96% corrected mortality in first and third instar nymphs. Pfr 97 and F 52 were evaluated for insecticidal activity against third instar B. cockerelli using 10⁵, 10⁶, and 10⁷ conidia per mL. Mortality produced by I. fumosorosea Pfr 97 ranged from 83 to 97% and that of M. anisopliae F 52 was 88 to 95% at these concentrations.     

Host plants influence susceptibility of whitefly Bemisia tabaci (Hemiptera: Aleyrodidae) to the entomopathogenic fungus Isaria fumosorosea (Hypocreales: Cordycipitaceae)

We quantified the tritrophic effect of host plant on the susceptibility of the sweetpotato whitefly Bemisia tabaci (Genn.) to a fungal pathogen in the laboratory. Second-instar whiteflies reared on cucumber, eggplant, tomato and bean plants for six generations were exposed to conidial suspensions of Isaria fumosorosea isolate IF-1106. Our results did not detect differences in response (proportional survival or median lethal time, LT₅₀ days) among insect populations derived from different plants that were treated with 10⁷ conidia/ml. However, at concentrations ≤ 5×10⁶ conidia/ml, whiteflies reared on bean and tomato died significantly more quickly (i.e. LT₅₀ of 4–5 days) compared with cucumber and eggplant reared populations (5–7 days). Bean and tomato-reared populations were also more susceptible to mycosis (LC₅₀ ≈ 6 × 10⁵ conidia/ml) compared with those reared on cucumber (1.9 × 10⁶ conidia/ml) and eggplant (1.5 × 10⁶ conidia/ml). A separate study confirmed that this differential response of whitefly populations to I. fumosorosea was not explained by differences in deposition rate of conidia on leaf surfaces (i.e. a dosage effect). Our findings show that host plants affect the pathogenicity and virulence of a herbivore pathogen, but depend on the rate of exposure (inoculum) applied.     

Mixing of Isaria fumosorosea with enhanced diatomaceous earth and bitterbarkomycin for control of Rhyzopertha dominica

The virulence of Isaria fumosorosea alone and integrated with an enhanced formulation of diatomaceous earth (diatomaceous earth + bitterbarkomycin, DEBBM) was tested against the lesser grain borer Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae) under laboratory conditions on stored wheat. The fungus was applied to wheat grains at various concentrations of 3.60 × 10⁶, 3.60 × 10⁸, and 3.60 × 10¹⁰ conidia/kg alone, or in combination with 15 and 30 ppm of DEBBM. R. dominica was held at 20, 25 and 30°C and two RH regimes (56 and 75%) and mortality was registered after 5, 10 and 15 d. Generally, I. fumosorosea was most effective at 25°C caused the highest mortality of R. dominica at 56% RH. The increase of temperature, concentration and exposure interval increased the insecticidal effect of DEBBM at low RH level. The DE alone suppressed the progeny emergence at higher dose rate as compared I. fumosorosea alone, but their simultaneous use further reduced the progeny production of R. dominica. The integrated use of both tested bio control agents synergized the effect of each other and caused the highest mortality at 25°C and 56% RH. The results clearly demonstrated that I. fumosorosea and new enhanced DEBBM can be integrated to be an effective control measure for R. dominica in stored wheat.     

Comparison of aerial conidia and blastospores from two entomopathogenic fungi against Diaphorina citri (Hemiptera: Liviidae) under laboratory and greenhouse conditions

This study compared the insecticidal activity of liquid culture-produced blastospores and solid substrate-produced aerial conidia of Beauveria bassiana GHA and Isaria fumosorosea ARSEF3581 strains against Diaphorina citri adults. Insects exposed to 10⁷ propagules/ml in a spray residue contact leaf bioassay died within 6 days at 25°C, with no significant differences between fungal treatments. At higher concentrations (10⁸ propagules/ml), I. fumosorosea conidia killed psyllids faster compared to its blastospore formulation, i.e. 4 versus 5 days, respectively. In greenhouse tests, the same treatments applied to infested citrus plants (2?×?10⁶ spores/ml) all significantly reduced the number of nymphs compared with the untreated controls over 3 weeks; however, only I. fumosorosea blastospores significantly reduced the number of F1 adult psyllids when compared with controls. Similar results were observed in the follow-up greenhouse test, where I. fumosorosea blastospores were the most effective treatment overall, reducing D. citri populations by about 60% after 21 days; by contrast, imidacloprid killed almost 100% of psyllids within a week in both tests. Fewer psyllids exhibited mycosis in the greenhouse (i.e. ≈20 versus?≥?87% in the laboratory). This is the first report comparing both conidial and blastospore formulations of B. bassiana and I. fumosorosea for the control of a psyllid pest. Field testing is required to determine how successful different spore formulations might be under various environmental conditions.     

New records of entomopathogenic fungi infecting Bemisia tabaci and Trialeurodes vaporariorum, pests of horticultural crops, in Argentina

The whiteflies Bemisia tabaci (Gennadius) and Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae) are major crop pests throughout the world. Although extensive research about biological control of whitefly by parasitoids and predators has been conducted, also entomopathogenic fungi can be considered as potential biological control agents. Surveys for entomopathogenic fungi were carried out in organic and conventional horticultural crops in greenhouses and open fields in Buenos Aires and Corrientes provinces, Argentina. These surveys resulted in the recovery and isolation of the following fungi from whiteflies: Lecanicillium lecanii (Zimmerm.) Zare & W. Gams, L. muscarium (Petch) Zare & W. Gams, L. longisporum (Petch) Zare & W. Gams, Isaria fumosorosea Wize and I. javanica (Frieder. & Bally) Samson & Hywel-Jones. Pathogenicity tests were conducted against T. vaporariorum nymphs using a conidial suspension (1 × 10⁷ conidia/ml) of the fungi. A mortality rate between 26.6% and 76.6% was obtained at 7 days post-infection. These are the first records of natural infections in the southernmost region of the South American continent of L. lecanii, L. muscarium, L. longisporum and Isaria javanica (Ascomycota: Hypocreales) on T. vaporariorum and also the first report of I. fumosorosea on B. tabaci.     

Conidia production by Isaria fumosorosea on solid substrates and its pathogenicity towards Bemisia tabaci

Large amounts of conidia must be recovered to use Isaria fumosorosea as a biological control agent. Aerial conidia are mass-produced in solid substrate culture. Conidia obtained from growth on different substrates must be similar in quantity and quality (viability, purity and virulence). In the present work, several solid substrates were evaluated: rice, sorghum, sugarcane, corncob, plantain and wheat (derived from the production of Trichogramma sp.) to find alternatives that are economical and available in different regions. The highest conidia production was obtained on rice, plantain and corncob substrates, which yielded 5.33 × 10⁹ conidia/g, 5.24 × 10⁹ conidia/g and 4.8 × 10⁹ conidia/g substrate, respectively. At concentrations of 1 × 10⁷ conidia/mL, the mortality rates obtained with conidia developed on rice, plantain and corncob substrates were 98%, 97% and 88%, respectively. The lethal concentration 50 (LC₅₀₎ values of conidia obtained from rice and plantain were 7.2 × 10⁴ conidia/mL and 5.1 × 10⁴ conidia/mL, respectively.     

Susceptibility of different life stages of the European cherry fruit fly,Rhagoletis cerasi,to entomopathogenic fungi

The effects of six fungus isolates on the mortality of different life stages of the European cherry fruit fly, Rhagoletis cerasi (Diptera: Tephritidae), were assessed in a series of laboratory experiments to find an isolate suitable for biological control. In a first step, the effects of fungus treatments on mortality, mycosis and fecundity of adult flies at a concentration of 10⁷ conidia/ml were evaluated. All fungus isolates caused mycosis but virulence varied considerably among the isolates. Beauveria bassiana and Isaria fumosorosea caused 90–100% mortality and had the strongest influence on fecundity. Metarhizium anisopliae also induced high rates of mortality, while the pathogenicity of Isaria farinosa was low. The effects of lower conidia concentrations and the influence of the age of flies were assessed in a second step. Higher conidia concentrations generally resulted in a higher mortality. B. bassiana was most efficient at low concentrations. Young flies showed lower mortality rates than older flies but, sub‐lethal effects on eclosion rate of eggs were greater in younger flies. Finally, the effects on L₃ larvae were tested: none of the fungus isolates induced mortality in more than 25% of larvae. As L₃ larvae and pupae are not susceptible to fungus infection, field control of R. cerasi should be focused on adult flies.     

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.     

Joint action of the entomopathogenic fungus Isaria fumosorosea and four chemical insecticides against the whitefly Bemisia tabaci

The strain IfB01 of Isaria fumosorosea (Paecilomyces fumosoroseus) is a promising myco-insecticide candidate for control of Bemisia tabaci. Joint action of strain IfB01 and four chemical insecticides [spirotetramat (Spi), acetamiprid (Ace), imidacloprid (Imi) and thiamethoxam (Thi)] against the whitefly B. tabaci was evaluated using the cooperative virulence index (c.f.). Substantial synergistic actions were found in the mixtures of IfB01 conidia with Spi, Imi and Thi 2–4 days after treatment. The greatest synergism was recorded in the mixture of IfB01 (2.5 × 10⁶ conidia/L) and Imi (12.5 mg/L), which had a c.f. value of 184 at day 3 after treatment. Furthermore, the shorter LT₅₀ values recorded in mixtures indicated that effectiveness improved when the conidia were applied with the chemical insecticides. However, no substantial synergisms were recorded with Ace and from day 5 onwards.     

Pathogenicity of individual isolates of entomopathogenic fungi affects feeding preference of red imported fire ants Solenopsis invicta

Seven isolates of entomopathogenic fungi, Isaria fumosorosea (IFCF-H and IFCF-L), Beauveria bassiana s.l. (Bb02 and Bb04) and Metarhizium anisopliae s.l. (Ma01, SM076 and M09), were selected for their pathogenicity against Solenopsis invicta as well as feeding preference of S. invicta. When ants were treated with a conidial suspension at a concentration of 1 × 10⁸ conidia/ml, the median lethal times (LT₅₀) of IFCF-H, IFCF-L, Bb02, Bb04, Ma01, SM076 and M09 were 3.4, 162.6, 7.3, 2.8, 3.8, 7.3 and 2.7 days, respectively, after 10 days. The median lethal concentrations (LC₅₀) on the 10th day after inoculation were 1.20 × 10⁷, 1.56 × 10¹⁰, 4.23 × 10⁷, 3.04 × 10⁶, 6.13 × 10⁶, 2.90 × 10⁷ and 9.90 × 10⁵ conidia/ml, respectively. Furthermore, S. invicta consumed significantly less solution flavoured with Bb04 conidia than the control, which was demonstrated by the lowest preference index (PREF = 0.09). S. invicta did not have a significant feeding preference for other fungal isolates. The pathogenicity (LC₅₀) of fungal isolates was not significantly correlated (R² = 0.013) with the PREF of S. invicta. However, in the paired-choice experiments between different virulent isolates belonging to the same genera, S. invicta tended to select the solution flavoured with conidia of relatively lower pathogenic isolates such as IFCF-L, Bb02 and SM076. We conclude that the pathogenicity of congeneric fungi may affect the feeding preference of S. invicta. Red imported fire ants might adjust their feeding response to entomopathogenic fungi based on the profile of microbial volatile organic compounds.     

The potential of Isaria spp. as a bioinsecticide for the biological control of Nasutitermes corniger

The termite Nasutitermes corniger is a serious pest infesting urban areas of Brazil and many other countries. Control largely depends on synthetic pesticides whose indiscriminate use can impact the environment and the health of humans and other animals. Alternative strategies against insect pests, such as biological control by entomopathogenic fungi, could be effective while minimising these deleterious effects. We analysed the actions of the entomopathogenic fungi Isaria farinosa, Isaria fumosorosea, and Isaria javanica against the insect N. corniger. Our results indicated that the fungi examined were pathogenic against N. corniger, with I. farinosa ESALQ1355 being the most efficacious strain, resulting in the death of 95% of the workers (LC₅₀ 6.66?×?10⁴ conidia/mL) and 85% of the soldiers (LC₅₀ 6.81?×?10⁴ conidia/mL). This is the first report of the pathogenicity of Isaria spp. on N. corniger. These in vitro results suggest that I. farinosa ESALQ1355 demonstrates a significant biological potential for controlling N. corniger.     

Diaphorina citri populations carrying the bacterial plant pathogen Candidatus Liberibacter asiaticus are more susceptible to infection by entomopathogenic fungi than bacteria‐free populations

相似文献   

A beauvericin hot spot in the genus Isaria

Beauvericin is a naturally occurring cyclohexadepsipeptide originally described from Beauveria bassiana but also reported from several Fusarium species as well as members of the genus Isaria. Twenty-six isolates of Isaria species and its Cordyceps teleomorph, and ten taxonomically close strains including Beauveria, Nomuraea and Paecilomyces species were sequenced and tested for beauvericin production. Trees using ITS rDNA and β-tubulin sequence data were constructed and used to infer the phylogenetic distribution of beauvericin production. A group comprising Isaria tenuipes and its known teleomorph Cordyceps takaomontana, Isaria cicadae and its Cordyceps teleomorph, Isaria japonica and Isaria fumosorosea, showed positive beauvericin production which correlated well with combined ITS rDNA and β-tubulin phylogenies. The results suggested that beauvericin can serve as a chemotaxonomic marker for these limited species of the I. tenuipes complex.     

Isolation and characterisation of Isaria farinosa and Purpureocillium lilacinum associated with emerald ash borer,Agrilus planipennis in Canada

Entomopathogenic fungi of the genera Isaria and Purpureocillium were recovered from infestation sites of emerald ash borer (EAB) in Southern Ontario, Canada. Isolates were identified using morphological characters and by sequencing the ITS1-5.8S-ITS2 ribosomal DNA gene and partial β-tubulin gene. Phylogenetic analysis and constructed trees based on the ITS and β-tubulin gene explicitly confirm isolates L66B, SY17-a and LHY46-a as Isaria farinosa and B3A, B59A and SY45B-a as Purpureocillium lilacinum. Pathogenicity was tested in the laboratory against adult EAB using a single concentration (2.0×10⁷ conidia/ml) applied topically to adults. Controls included three commercial isolates: Isaria fumosorosea LRC176, Metarhizium brunneum LRC187 and Beauveria bassiana strain GHA. The native isolates I. farinosa L66B and P. lilacinum SY45B-a killed 75 and 50% of the beetles 14 days post-inoculation. Although these indigenous entomogenous fungi were less virulent compared with the commercial isolates, yearly isolation from EAB populations suggests they are one of the natural mortality factors of EAB in Canada.     

The entomopathogenic fungi Isaria farinosa (formerly Paecilomyces farinosus) and the Isaria fumosorosea species complex (formerly Paecilomyces fumosoroseus): biology,ecology and use in biological control

The entomopathogenic fungi, Isaria farinosa and Isaria fumosorosea were known as Paecilomyces farinosus and Paecilomyces fumosoroseus, for more than 30 years. Both fungi have a worldwide distribution and a relatively wide host range. While I. farinosa currently is of minor importance in research and as biocontrol agent, I. fumosorosea is regarded as a species complex, and various strains are successfully used for biocontrol of several pest insects, mainly whiteflies. During the past 40 years, numerous scientific papers on both fungal species covering various research areas were published. This is the first monographic review on the biology, ecology and use of I. farinosa and I. fumosorosea as biocontrol agents. In the following compilation, data on the identity, natural occurrence and geographical distribution, host range, production of metabolites, effect of abiotic and biotic factors (temperature, relative humidity, solar radiation, fungus, host plant) and on the use of these species in biocontrol experiments against pest insects, plant pathogens and nematodes in the laboratory and the field are summarised. Sections on their effects on non-target organisms and safety issues are also included. The aim of this review is to increase our knowledge on these entomopathogenic fungi.     

Behavioral and electrophysiological responses of Coptotermes formosanus Shiraki towards entomopathogenic fungal volatiles

Termites adjust their response to entomopathogenic fungi according to the profile of fungal volatile organic compounds (VOCs). This study demonstrates the pathogenicity of Metarhizium anisopliae, Beauveria bassiana and Isaria fumosorosea (=Paecilomyces fumosoroseus) towards the Formosan subterranean termite, Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae). Using no-choice assays, M. anisopliae was found to be highly virulent (LT₅₀ 3.10 d) when compared to B. bassiana (LT₅₀ 6.62 d) and I. fumosorosea (LT₅₀ 12.39 d). Also using choice assays, the foraging behavior of C. formosanus was determined in the presence of pathogenic fungi. The highly pathogenic fungi (M. anisopliae) elicited a repellent response, causing most of the termites to forage in a safe zone farthest from the fungal source. This repellency resulted in relatively low mortality similar to the controls. The repellency of M. anisopliae conidia can be used to protect human belongings and timber from termites. While I. fumosorosea cultures were not repellent to C. formosanus workers, the termites were highly susceptible to infection. Electroantennographic responses of workers showed approximately 47% and 78% lower level of response to conidia of B. bassiana and I. fumosorosea, respectively, as compared to M. anisopliae. The VOC profile of repellent cultures of M. anisopliae mainly consisted of paraffins (60.97%), while the major proportion of the I. fumosorosea profile consisted of branched and cyclic alkanes (84.41%). From the above findings, we conclude that the incorporation of I. fumosorosea may increase the control potential of bait.     

Evaluation of Isaria fumosorosea (Hypocreales: Cordycipitaceae) for control of the Asian citrus psyllid,Diaphorina citri (Hemiptera: Psyllidae)

A laboratory bioassay was developed to evaluate strains of Isaria fumosorosea Wize, against Diaphorina citri. Up to 100% of adult psyllids were killed at concentrations between 10⁶ and 10⁷ blastospores/ml after 12 days, with derived LC₅₀ values (at 7 days post treatment) between 1.4 × 10⁵ and 2.0 × 10⁶ blastospores/ml for strains ARSEF 3581, FE 9901 and Apopka-97. A significantly higher value (1.5 × 10⁷) was obtained with a conidial formulation of Apopka-97. Average survival times were dosage dependent, i.e. between 10.2 days at 10³ blastospores/ml and 3.5 days at 10⁸ blastospores/ml. Rates of mycosis were also dosage dependent, with up to 100% sporulation on cadavers at 10⁸ blastospores/ml but declining at lower concentrations. The Apopka-97 strain (commercially available as PFR-97) was tested against established D. citri infestations in potted citrus in greenhouse cages. Treatments at label rates reduced psyllid populations by approximately 50% over 3 weeks. The combination of PFR-97 with emulsifiable oils (0.25% v/v) did not increase psyllid mortality compared with either agent alone. Imidacloprid applied as a drench killed 100% of psyllids within 3 weeks. Subsequent greenhouse tests during humid conditions were hampered by natural dissemination of I. fumosorosea to untreated psyllids, suggesting that this fungus is spread by air movement and may be highly effective under very humid conditions. In later tests, a Cladosporium sp. rapidly colonised psyllid cadavers and leaf surfaces, but was not pathogenic in laboratory tests. Our studies confirm the potential of I. fumosorosea to be used in IPM strategies for D. citri that rely on other tactics, such as insecticidal oils and native or introduced biological control agents.     

Biochemical analysis and pathogenicity of entomopathogenic fungi to Diaphorina citri Kuwayama (Hemiptera: Liviidae)

Asiatic citrus psylla, Diaphorina citri, Kuwayama (Hemiptera: Liviidae) is an economic pest of citrus groves and a vector of the bacterium, Candidatus Liberibacter spp., one of the causative agents of citrus greening. In order to estimate the infectivity of six different isolates of Beauveria bassiana, Metarhizium anisopliae and Isaria fumosorosea, fungal bioassay was performed on the adults of D. citri. Adults of D. citri were treated individually with 1 × 10⁵, 1 × 10⁶, 1 × 10⁷, 1 × 10⁸, 2 × 10⁸ spores/mL fungal concentrations by the immersion method. Subsequent to fungal bioassay, treated D. citri were used to determine the levels of esterase and glutathione S‐transferases (GST) enzymes over a period of 3–7 days. The mortality results suggest that I. fumosorosea isolates (If‐02) caused 82.2% mortality on the seventh day of treatment. However, B. bassiana isolate (Bb‐08) with lowest LC₅₀ (1.4 × 10⁷ spores/mL) proved to be highest potential isolate against D. citri. Biochemical determination of esterase and GST activity assay showed significant differences in activities after infection of fungi. Significantly high activity of esterase was observed by Bb‐01 (27.0 unit per mg protein) on the seventh day, while Ma‐11.1 and If‐2.3 (16.9 and 36.3 unit per mg protein) on the third day post treatment. However, maximum GST's activity was showen by isolates Bb‐08,Ma‐M₂ and If‐2.3 (37.6, 1.40 and 10.9 unit per mg protein) on the third day. The current investigation will help to explore the relations between the insect defense system and entomopathogenic fungi. Moreover, the determination of enzymatic activities will be useful for selecting the most pathogenic isolates.