Formulation and optimisation of various nuclear polyhedrosis virus isolates and assessment of their insecticidal activity against Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) larvae

Helicoverpa armigera (Hubner) is a pest that poses serious threat to the tomato crop in India. Larvae of this species are susceptible to the nucleopolyhedrovirus (NPV), which has attracted interest as a potential biocontrol agent. Rearing of larvae in natural diet resulted in less number of pupae, while in artificial diet more pupae and healthy adults were obtained. The NPV was tested for its insecticidal action against H. armigera in natural and artificial diets. The bioassay results of inoculated H. armigera nucleopolyhedrosis virus (HaNPV) with different concentrations indicate that the 4.0 g/l dosage caused maximum mortality (70.3% and 60.54%), and minimum mortality 46.83% and 44.08% was recorded in the 0.5 g/l dosage under laboratory and pot culture conditions, respectively. Polyhedral inclusion bodies (PIBs) were estimated using a standard haemocytometer. According to the estimate, purified PIBs were found at a concentration of 1 × 10⁹/ml. The different formulation of NPV, i.e. wettable fine powder with a hue of white, had a particle size of 100 μm with a concentration of 1 × 10⁸/ml. The encapsulated product was found to be in the form of beads and was red in colour with a concentration of 1 × 10⁸ PIBs/ml. The effectiveness of NPV against H. armigera larvae was noted at maximum LC₅₀ values at a concentration of 1 × 10⁹/ml. Qualitative analysis estimates showed that protein polyhedrin and enzyme chitinase had a molecular weight of 33 and 45 kDa, respectively. Viral DNA was isolated from NPV-infected larvae and was then separated using SDS-PAGE. The estimated polyhedrin with a molecular weight of 33 kDa, which is responsible for the increased mortality percent of larvae, was confirmed by the bioassay. Hence it was concluded that NPV is ecofriendly in the management of pests on tomato and other crops.     

Comparative bioassay of different isolates of Bacillus thuringiensis subsp. kurstaki on the third larval instars of diamondback moth,Plutella xylostella (L.) (Lep.: Plutellidae)

The diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae) is one of the most important pests of cruciferous plants throughout the world. In recent years, this insect has been a serious pest for cabbage fields in Tehran province. Resistance of P. xylostella to all main groups of insecticides has been recorded and it is ranked in the 20 most resistant pest species reported up to now. According to many researchers, to eliminate the problem of pest resistance to chemical pesticides, an integrated pest management programme should be used. In line with this, the uses of microbial control agents (MCAs) are discussed. The bacterium, Bacillus thuringiensis (Bt) is one of microbial control agents of pests. It is characterised by its ability to produce proteic crystalline inclusions during sporulation. Cry1 protein has insecticidal activity and is highly specific to certain insects and not toxic to unrelated insects, plants or vertebrates. In this work, the pathogenicity of some Bt isolates, including Dipel, 20, 29, 79 and 87, was tested against P. xylostella and the lethal concentrations (LC₅₀) of their crystal proteins to P. xylostella third larval instar was determined. The experiment was designed in factorial in randomised complete design with 5 treatments (different concentrations including 10⁴, 10⁵, 10⁶, 10⁷, 10⁸ CFU/ml and 5 replications and with 10 third larval instars. Spore–crystal complex was applied to the surface of natural diets (cabbage leaves) and the mortality of P. xylostella larvae was assessed 120?h after exposure of Bt toxin in each treatment. Results showed that percentage of survival was significantly higher for control treatment. Results also showed that after 5?days, LC₅₀ for isolates of Dipel, 20, 29, 79 and 87 were equal to 1?×?10⁶, 1?×?10⁵, 5?×?10⁵, 4?×?10⁵ and 1?×?10⁴ CFU/ml, respectively. LT₅₀ were equal to 93.71, 48.04, 71, 40.49 and 75.28?h. Of and most the percentage larval mortality relate to attendance 87 and also at least percentage mortality is related to the groom Dipel.     

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.     

Entomopathogenic fungus as a biological control agent against Rhyzopertha dominica F. (Coleoptera: Bostrychidae) on stored wheat

To evaluate the pathogenicity of Metarhizium anisopliae (Metschinkoff) Sorokin (Deuteromycotina: Hyphomycetes) a bioassay was designed under laboratory conditions against Rhyzopertha dominica F. (Coleoptera: Bostrychidae) on stored wheat. The fungus was applied at the dose rates of 8 × 10³, 8 × 10⁵, 8 × 10⁷ and 8 × 10⁹ conidia/kg of wheat and the bioassay was conducted at 25°C with 60% relative humidity. The data regarding the mortality was recorded after 7 and 14 days exposure intervals. All the treatments gave the significant mortality of R. dominica and M. anisopliae of 8 × 10⁹ conidia/kg was found to be the most effective after a 14-day exposure interval. There was greater production of progeny when the low rate of M. anisopliae was applied to wheat. Overall, our study showed that M. anisopliae is vigorous when applied at a high dose rate which revealed an effective control of R. dominica and also played a pivotal role in the integrated pest management program (IPM) of stored wheat insect pests.     

Insecticidal efficacy of two isolates of Beauveria bassiana (Bals.) (Vuill.), on the second larval stage of Leptinotarsa decemlineata (Say) (Col.: Chrysomelidae)

Leptinotarsa decemlineata is a serious potato pest throughout the world that has developed resistance to many insecticides. This study investigated the virulence of two indigenous isolates of Beauveria bassiana, consisting of DEBI007 and IR1217C. Five different concentrations of each isolate, 1 × 10⁷, 3.1 × 10⁷, 1 × 10⁸, 3.1 × 10⁸ and 1 × 10⁹ conidia ml^?1, were applied in bioassay using dipping method on second instar larvae. Control insects were treated with distilled water containing 0.01% Tween-80 (Sigma, Germany) as surfactant. The results showed that mortality percentages due to DEBI007 and IR1217C isolates in the highest concentration were 60% and 57.77%, respectively. There was a significant difference between efficacies of different conidial concentrations; therefore, with rise in conidial concentration, the mortality percentage was increased. The DEBI007 isolate that was previously isolated from the soil was more effective than IR1217C isolate. Calculated LC₅₀ for this effective isolate was 1.4 × 10⁷ conidia ml^?1, which, respectively, is the highest concentration.     

Development of Beauveria bassiana (Ascomycota: Hypocreales) as a mycoinsecticide to control green peach aphid,Myzus persicae (Homoptera: Aphididae) and investigation of its biocontrol potential

Long-term and intensive use of synthetic insecticides to control the green peach aphid, Myzus persicae (Homoptera: Aphididae) in agricultural production in the world has resulted in pest resistance and environmental pollution. The aim of the study was to develop an environmentally-friendly and effective mycoinsecticide from a local fungal isolate against M. persicae. According to the results of the screening experiments using 15 isolates (6 × Metarhizium, 5 × Beauveria, 2 × Isaria, 2 × Lecanicillium) at 1 × 10⁷ conidia ml^?1 concentrations and the dose–response experiments at 1 × 10⁵ –1 × 10⁹ conidia ml^?1 concentrations against M. persicae nymphs, Beauveria bassiana (KTU-24) was identified as the most promising isolate. The strain KTU-24 is also had tolerance to ecological conditions such as temperature, and UV-B. KTU-24 with advantageous and superior properties was used to develop a test mycoinsecticide. Mass production of spores by KTU-24 was conducted out by liquid-state fermentation using liquid medium. Spores harvested from the sporulated biomass were used to develop an oil-based mycoinsecticide, and the product was designated as AFIDISIDAL-OD Bbas-TR61. The product had lethal effect on M. persicae nymphs at a concentration of 1 × 10⁸ conidia ml^?1 in leaf-disc (82.5%) and pot (84.33%) experiments in a climate chamber. The oil-based mycoinsecticide developed in this study could be profitable when used in aphid-IPM prgrams by reducing crop loss and synthetic pesticides use.     

Effect of entomopathogenic Aspergillus strains against the pea aphid,Acyrthosiphon pisum (Hemiptera: Aphididae)

Aphids (Homoptera: Aphididae) are sap-sucking insect pests that feed on several plants of agronomical importance. Entomopathogenic fungi are valuable tools for potential aphid control. As part of a selection process, laboratory bioassays were carried with five different concentrations of Aspergillus clavatus (Desmazières), Aspergillus flavus (Link) and Metarhizium anisopliae ((Metschnikoff) Sorokin) spores against the pea aphid, Acyrthosiphon pisum (Harris). Aspergillus isolates induced higher mortalities than M. anisopliae, which is a well-known entomopathogen in the literature. Lethal concentrations (LC₅₀ and LC₉₀) were 1.23 × 10³ and 1.34 × 10⁷ spores/ml for A. flavus, 4.95 × 10² and 5.65 × 10⁷ spores/ml for A. clavatus, and 3.67 × 10³ and 9.71 × 10⁷ spores/ml for M. anisopliae 5 days after treatment. Mycelia development and sporulation on adult cadavers were observed 48 h after incubation. The intrinsic growth rate of A. pisum decreased with increased spore concentration for all fungal strains, suggesting an increase in pathogen fitness related to a consumption of host resources. In conclusion, Aspergillus species could be useful in aphid control as pest control agents despite their saprophytic lifestyle. This is also to our knowledge the first report of A. clavatus and A. flavus strains pathogenic to aphids.     

Fipronil enhanced natural occurrence of Fusarium solani (Hypocreales: Nectriaceae) on building infesting termite Heterotermes indicola Wasmann (Blattodea: Rhinotermitidae)

The Southeast Asian subterranean termite, Heterotermes indicola Wasmann (Blattodea; Rhinotermitidae), is recognized as a building infesting lower termite species in urban environment. The extensive use of chemical termiticides against aerial mud tubes and underground nests of H. indicola beneath the buildings could not suppress its infestation; however, it enhanced the environmental contamination and insecticide resistance. In the present study, we tried to control termites using naturally occurring entomopathogenic fungi Fusarium solani (Mart.) Sacc., along with sublethal concentrations of termiticide fipronil in no-choice feeding pathogenecity bioassay for 20?days. Termite mortality after 20?days of continuous exposure to highest fungal treatment 1?×?10⁹?conidia/mL was 10% exclusively, whereas 100% mortality was calculated just after 16?days of concurrently exposure to 5?ppm of fipronil and highest rate of fungus 1?×?10⁹?conidia/mL. These results indicated that insecticidal stress declined the immune response of termites and reduced the repellency of termites against fungal conidia by breaching the primary defense mechanism (allogrooming). This co-application of F. solani at suitable sublethal concentrations of fipronil showed the promising potential against termites that may reduce the selection pressure of pesticides and resistance risk by targeted pests, but further investigations are necessary for developing field trials.     

Studies on the application of a nuclear polyhedrosis virus to control populations of the Egyptian cottonworm, Spodoptera littoralis

Variations in the resistance to nuclear polyhedrosis virus (NPV) were found in three populations of Spodoptera littoralis. The LD₅₀ for the most resistant population was 1.07 × 10⁴ PIB/5th instar larva as compared to 8.4 × 10² and 5.8 × 10² PIB/larva in the other two populations. The effect of NPV persisted in larvae which survived and pupated. Some of the pupae died, and those which survived produced normally shaped adults. While fecundity was sharply reduced in the less resistant populations, the effect on the most tolerant population was less pronounced. A 3-year-old inoculum, stored unprotected from daylight and without cooling, was much less effective even against the most sensitive larval population as compared to a relatively fresh and refrigerated batch. Larvae in their 6th instar proved to be approximately 10-fold more resistant to the NPV than 5th instar ones, while the difference in weight was only about twice. These variations in resistance to NPV are also discussed from the point of view of applying S. littoralis NPV in pest control schemes.     

Effects of soil-treatment with fungal biopesticides on pupation behaviors,emergence success and fitness of tea geometrid,Ectropis grisescens (Lepidoptera: Geometridae)

Ectropisgrisescens Warren (Lepidoptera: Geometridae) is one of the most severe defoliating pests of tea plants. Synthetic pesticides have been widely applied to control this pest in tea plantations, but pesticide residues may decrease the quality and safety of tea products. In the present study, we hypothesized that soil treatment with the two commercial biopesticides (Shuiguxin^®) based on Metarhizium anisopliae (Metchnikoff) Sorokin and Beauveria bassiana (Balsamo) could reduce the survivorship and fitness of E. grisescens. Wandering larvae of E. grisescens were allowed to pupate in soil treated with each biopesticide, and the concentrations of M. anisopliae (Shuiguxin^®) and B. bassiana (Shuiguxin^®) that produced the 50% mortality values (LC₅₀) were 2.9 × 10⁶ and 1.6 × 10⁷ conidia/g soil, respectively. Artificial burying the pupae using soil treated with M. anisopliae (Shuiguxin^®) and B. bassiana (Shuiguxin^®) (1 × 10⁸ or 1 × 10⁹ conidia/g soil for both biopesticides) also significantly reduced emergence success of E. grisescens. In addition, choice tests showed that soil treated with the high concentration of M. anisopliae (Shuiguxin^®) or B. bassiana (Shuiguxin^®) had repellent effects on pupating E. grisescens. However, sublethal concentrations (LC₂₅ and LC₅₀) of both biopesticides did not significantly affect fecundity, fertility and longevity of post-emerged adults. Our study showed that soil treatment with the two commercial biopesticides caused direct mortality of pupating E. grisescens, but may not effectively suppress E. grisescens populations at sublethal concentrations. The realistic application of the fungal dosage in fields should be determined in future studies     

Cordyceps cateniannulata,a novel entomopathogenic fungus to control Stenoma impressella Busck (Lepidoptera: Elachistidae) in Colombia

Stenoma impressella is one of the most important defoliator pests in oil palm plantations in Colombia. To identify an alternative method for its control was characterized biologically and molecularly two strains of Cordyceps cateniannulata (CPIsp1201 and IPIsp1201) and three strains of Beauveria bassiana (CPBb0502; CPBb0411; CPBb0404) against S. impressella larvae. Virulence was evaluated under laboratory conditions. In an oil palm leaflet, individual larvae obtained from the insect colony were inoculated with 5 μl of a conidial suspension containing 1 × 10⁷ conidia/ml. The five strains were pathogenic against S. impressella larvae. CPIsp1201 and IPIsp1201 strains resulted in the highest mortality and were subsequently evaluated in two bioassays using a dose of 1 × 10¹³ conidia/ha. In the first bioassay, performed under shaded conditions, leaves of oil palms were infested with 75 larvae from the breeding/treatment. The second bioassay was performed in the field using natural populations. No differences were found between strains in both bioassays and the different dosages (5 × 10¹², 1 × 10¹³, and 1.5 × 10¹³ conidia/ha). Finally, the two strains were evaluated under oil palm plantation conditions at a dose of 1 × 10¹³ conidia/ha in 126 naturally infested palms. Larval mortality caused by the strains IPIsp1201 and CPIsp1201 (79.5% and 70.5%, respectively) was higher than the natural mortality registered in the control (37.3%). Cordyceps cateniannulata used at 1 × 10¹³ conidia/ha was effective at controlling S. impressella.     

A new biopesticide from a local <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis> var. <Emphasis Type="Italic">tenebrionis</Emphasis> (Xd3) against alder leaf beetle (Coleoptera: Chrysomelidae)

Use of chemical pesticides in agriculture harms humans, non-target organisms and environments, and causes increase resistance against chemicals. In order to develop an effective bio-pesticide against coleopterans, particularly against Agelastica alni (Coleoptera: Chrysomelidae) which is one of the serious pests of alder leaf and hazelnut, we tested the insecticidal effect of 21 Bacillus isolates against the larvae and adults of the pest. Bacillus thuringiensis var. tenebrionis-Xd3 (Btt-Xd3) showed the highest insecticidal effect based on screening tests. For toxin protein production and high sporulation of Xd3, the most suitable medium, pH and temperature conditions were determined as nutrient broth medium enriched with salts, pH 7 and 30?°C, respectively. Sporulated Btt-Xd3 in nutrient broth medium enriched with salts transferred to fermentation medium containing soybean flour, glucose and salts. After fermentation, the mixture was dried in a spray dryer, and spore count of the powder product was determined as 1.6?×?10¹⁰ c.f.u. g^?1. Moisture content, suspensibility and wettability of the formulation were determined as 8.3, 86% and 21 s, respectively. Lethal concentrations (LC₅₀) of formulated Btt-Xd3 were determined as 0.15?×?10⁵ c.f.u. ml^?1 for larvae at laboratory conditions. LC₅₀ values were also determined as 0.45?×?10⁶ c.f.u. ml^?1 at the field condition on larval stage. Our results showed that a new bio-pesticide developed from B. thuringiensis tenebrionis (Xd3) (Btt-Xd3) may be valuable as a biological control agent for coleopteran pests.     

Pathogenicity of Beauveria bassiana ANU1 to the red imported fire ant,Solenopsis invicta workers in Korea

The red imported fire ant (RIFA), Solenopsis invicta, is one of the globalized invasive pests. This study focused on pathogenicity and virulence of entomopathogenic fungi as one of the biological control agents to RIFA workers under different temperatures. The fungal pathogen, Beauveria bassiana ANU1 was isolated from Korea in 2015 and showed the pathogenicity to RIFA workers. A conidial suspension (1 × 10⁷ conidia/ml) induced a low mortality from day 2 after treatment and reached to 100% mortality at day 7 and day 8 after treatment for major and minor workers, respectively. The median lethal concentrations of B. bassiana ANU1 were calculated as 3.9 × 10³ for major and 4.6 × 10³ for minor workers at day 7 after treatment. Low temperatures decreased a virulence of B. bassiana ANU1 (1 × 10⁷ conidia/ml) to RIFA and showed mortality of 26.6% for major and 20% for minor workers. Based on bioassay results, this study provides one of possibilities of effective and successful strategy for controlling RIFA by entomopathogenic fungi.     

A novel alphabaculovirus isolated from the cotton bollworm, <Emphasis Type="Italic">Helicoverpa armigera</Emphasis> (Hubner) (Lepidoptera: Noctuidae): characterization and pathogenicity

The cotton bollworm, Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) is a polyphagous pest that exist all over the world. It is also very destructive in Turkey on various agricultural products. In this study, we have detected an alphabaculovirus from Helicoverpa armigera larvae collected from cotton field. The virus isolate was named as Helicoverpa armigera nucleopolyhedrovirus (HearNPV-O1) based on morphological and molecular properties. This is the first record of baculovirus from H. armigera in Eurasia region. Scanning electron microscopy examinations of polyhedral inclusion bodies (PIBs) showed their irregular morphology with average diameter of 0.85 to 1.25 μm. Transmission electron microscopy studies revealed that the nucleocapsids were multiple enveloped and bacilliform shaped. The size of nucleocapsid was found as 279 nm with a width of 56 nm. Digestion of viral genome by PstI generated 8 fragments with total size of 130.9 kbp. According to the phylogenetic analysis of the partial polyhedrin (polh), late expression factor 8 (lef8) and late expression factor 9 (lef9) genes, HearNPV-O1 isolate is very close to H. armigera MNPV Indian isolate-443. Five different concentrations of HearNPV-O1 between 10³ and 10⁷ were used in dose-response test on neonate, 3rd and 5th instars larvae of H. armigera. The highest dose (10⁷) showed 92%, 88% and 57% mortality, respectively within 14 days. LC₅₀ values of HearNPV-O1 isolate were calculated as 6?×?10⁴, 7?×?10⁴ and 8?×?10⁶ PIBs/mL^?1 against neonate, 3rd and 5th instars larval stages, respectively. These results demonstrate that HearNPV-O1 isolate may be a potential biocontrol agent to be utilized against H. armigera.     

Virulence of entomopathogenic fungi against Culex pipiens: Impact on biomolecules availability and life table parameters

Culex pipiens mosquitoes considered as vectors for many arboviruses such as the West Nile virus and encephalitis virus showing a global impact on human health. The natural management of the aquatic stages of this pest is crucial for maintaining an insecticide-free and sustained environment. The present work focused on studying the biological and biochemical effects of the entomopathogenic fungi: Metarhizium anisopliae, Beauveria bassiana, and Paecilomyces lilicanus, against 3^rd instar larvae of Culex pipiens laboratory colony. The results revealed that M. anisopliae showed maximum larval mortality (88%) with the lowest lethal time (LT₅₀) (22.6 hrs) at 10⁸ spores/ml followed by B. bassiana (73.33%) with LT₅₀ (38.35 hrs), while P. lilicanus showed minimum percent mortality (65%) with highest LT₅₀ (51.5 hrs). The median lethal concentration (LC₅₀) values were found to be 1.027 × 10⁵ spores/ml for M. anisopliae, 1.24 × 10⁶ spores/ml for B. bassiana, while it was 8.453 × 10⁶ spores/ml for P. lilicanus. A reduction in female fecundity, number of hatched eggs, pupation and adult emergence percentage were recorded. The biochemical analysis of the treated larvae revealed different quantitative decrease in total soluble proteins, lipids, and carbohydrate hydrolyzing enzymes compared to control. Histopathological effects of fungal infection upon insect cuticles, muscles, and midgut were investigated. Based on the obtained results, M. anisopliae proved its superior virulent effect as a bio-control agent against Cx. pipiens.     

Role of cuticle-degrading enzymes of Beauveria bassiana and Metarhizium anisopliae in virulence on Plodia interpunctella (Lepidoptera,Pyralidae) larvae

Entomopathogenic fungi (EPF) are important biological control agents in pest management programs in agroecosystems against insect pests. EPF such as Beauveria bassiana (Bals.) Vuillemin and Metarhizium anisopliae (Metchn.) Sorokin produce a wide range of extracellular enzymes involved in disturbance of the first barrier in the insect cuticle comprising proteins, chitin, and lipids. Realizing relationships between the expression of these enzymes and fungal virulence might aid in development of effective mycoinsecticides. The virulence of B. bassiana (isolates TV and OZ1) and M. anisopliae (isolate CS1) were investigated on Plodia interpunctella (Hübner) larvae in this study. The third instar larvae were immersed in a suspension containing 1 × 10⁸ conidia mL^?1 of fungal conidial inoculum. The results revealed that all three fungal isolates caused mortality in larvae, but there was a considerable variation in their virulence. Total proteinase, exochitinase and lipase assays were done for these isolates. The TV isolate with the highest mortality with 41.7%, had the highest level of specific activity of exochitinase, protease, and lipase with 0.148, 0.654, and 0.190 U. mg^?1 protein, respectively. In the current study, a positive correlation was determined between the virulence of fungal isolates and the activities of protease and lipase, but this link was not significant for exochitinase. Our results demonstrated that extracellular enzymes, particularly protease and lipase, may play a crucial role in the virulence of these fungal isolates against P. interpunctella larvae.     

Infectivity of Steinernema mushtaqi (Rhabditida: Steinernematidae) against insect pests and their mass production

The infectivity of entomopathogenic nematode (EPN), Steinernema mushtaqi was tested against legume pod borer, Maruca vitrata, tobacco caterpillar, Spodoptera litura, blue butterfly, Lampides boeticus, red hairy caterpillar, Amsacta moorei, brown bug, Clavigralla gibbosa, mealy bug, Centrococcus somatics, fruit borer, Earias vittella and green bug, Nezara viridula larvae and in vivo mass production of the above-tested species of EPN have been carried out during 2008. S. mushtaqi was found to be more pathogenic to A. moorei, as it brought about 100% mortality within 48 h, than to S. litura, L. boeticus, N. viriduala and E. vittella, as mortality occurred within 72 h; whereas this level of mortality was recorded in C. somatis, C. gibbosa and M. vitrata within 144 h. No mortality was observed in the control treatment. Multiplication of S. mushtaqi and the yield of infective juveniles (IJs) on these insects was the highest (0.94 × 10⁵ IJs/cadaver) from N. viriduala, followed by S. litura (0.76 × 10⁵ IJs/cadaver), L. boeticus as also C. gibbosa (0.31 × 10⁵ IJs/cadaver) and M. vitrata (0.20 × 10⁵ IJs/cadaver). Very poor populations of IJs were found from A. moorei (0.15 × 10⁵ IJs/cadaver) and C. somatics (0.01 × 10⁵ IJs/cadaver). No multiplication of IJs was found from the cadaver of E. vittella. This opens a new hope of utilising S. mushtaqi in the insect pests management programme.     

Efficacy of Beauveria bassiana against the strawberry pests, Lygus lineolaris, Anthonomus signatus and Otiorhynchus ovatus

There are several insect species causing serious economic losses in strawberry, Fragaria vesca L., productions. In Quebec, Canada, the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), the strawberry bud weevil clipper, Anthonomus signatus (Say) and the strawberry root weevil, Otiorhynchus ovatus (L.) are the most important pests. We tested the susceptibility of these pests to the entomopathogenic fungus Beauveria bassiana under laboratory conditions. Sixteen isolates were evaluated for their insecticide potential against these insects. Adults of each species were infected by the immersion method. All isolates were pathogenic to adults of all three species, causing mortality rates between 23.3% and 100% at a concentration of 1 × 10⁷ conidia/ml. Based on the screening results, isolate INRS‐CFL was selected for its insecticide potential and then used for further analyses against L. lineolaris, A. signatus and O. ovatus adults. Bioassays were performed to evaluate the lethal concentration (LC₅₀) and the average survival time (AST) of this isolate against both insect species. Results of dose–response mortality bioassays using four concentrations – 1 × 10⁴, 1 × 10⁶, 1 × 10⁸ and 1 × 10⁹ conidia/ml – indicated a LC₅₀ values of 5.3 × 10⁵, 1.8 × 10⁷ and 9.9 × 10⁷ conidia/ml at 7 days after inoculation for L. lineolaris, A. signatus and O. ovatus respectively. Using a dose of 1 × 10⁸ conidia/ml, the AST values were estimated at 4.41, 7.56 and 8.29 days, respectively, at a concentration of 1 × 10⁸ conidia/ml. This study demonstrated the potential of B. bassiana for the management of L. lineolaris, A. signatus and O. ovatus. Results also suggest that the heteropteran species is more susceptible than coleopteran species to B. bassiana.     

Toxin Gene Contents and Activity of <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis> Strains Against Two Sugarcane Borer Species, <Emphasis Type="Italic">Diatraea saccharalis</Emphasis> (F.) and <Emphasis Type="Italic">D. flavipennella</Emphasis> (Box)

Bacillus thuringiensis (Berliner) bears essential characteristics in the control of insect pests, such as its unique mode of action, which confers specificity and selectivity. This study assessed cry gene contents from Bt strains and their entomotoxicity against Diatraea saccharalis (F.) and Diatraea flavipennella (Box) (Lepidoptera: Crambidae). Bioassays with Bt strains were performed against neonates to evaluate their lethal and sublethal activities and were further analyzed by PCR, using primers to identify toxin genes. For D. saccharalis and D. flavipennella, 16 and 18 strains showed over 30% larval mortality in the 7th day, respectively. The LC₅₀ values of strains for D. saccharalis varied from 0.08 × 10⁵ (LIIT-0105) to 4104 × 10⁵ (LIIT-2707) spores + crystals mL^?1. For D. flavipennella, the LC₅₀ values of strains varied from 0.40 × 10⁵ (LIIT-2707) to 542 × 10⁵ (LIIT-2109) spores + crystals mL^?1. For the LIIT-0105 strain, which was the most toxic to D. saccharalis, the genes cry1Aa, cry1Ab, cry1Ac, cry1B, cry1C, cry1D, cry1F, cry1I, cry2Aa, cry2Ab, cry8, and cry9C were detected, whereas for the strain LIIT-2707, which was the most toxic to D. flavipennella, detected genes were cry1Aa, cry1Ab, cry1Ac, cry1B, cry1D, cry1F, cry1I, cry2Aa, cry2Ab, and cry9. The toxicity data and toxin gene content in these strains of Bt suggest a great variability of activity with potential to be used in the development of novel biopesticides or as source of resistance genes that can be expressed in plants to control pests.     

First record of an entomopathogenic fungus of tomato leafminer,Tuta absoluta (Meyrick) in Tanzania

Tuta absoluta (Meyrick) is a destructive pest causing adverse environmental and economic effects globally. Management of T. absoluta by synthetic chemicals is of diminutive achievement due to resistance trick of the pest. Harnessing of biocontrols is currently fascinating and efficient for management of the tremendous pests. This study isolated an entomopathogenic fungus from dead larvae of T. absoluta on tomato leaves from farmer’s field Tanzania. Two Aspergillus fungal isolates were isolated and tested against larvae and adults of T. absoluta under conditions of 19.5°C and 50%RH, 30.4°C and 70% RH, respectively, in the laboratory. Sequence analysis of Aspergillus isolates that we referred as A-Tz1 and A-Tz2 were analysed with the BLAST program available at the National Center for Biological Information (NCBI). The two isolates (A-Tz1 and A-Tz2) showed 100% similarity with Aspergillus oryzae of GeneBank accession numbers EF121337.1 and MG519722.1. Such similarity implied that both A-Tz1 and A-Tz2 isolates were A. oryzae. To confirm pathogenicity, bioassays were conducted against the larvae, pupa and adults of T. absoluta. Results showed that at 1.0?×?10⁸?conidia/mL, fungal isolates caused up to 70% larval mortality 3 days post inoculation and consequently inhibited pupation by 84.5% and adult emergence by 74.4%. The identified A. oryzae reduced the life span of adult T. absoluta up to 5 days post inoculation at 1.0?×?10⁸?conidia/mL whereas in control T. absoluta survived up to 25 days. This study found that isolates of Aspegillus species have the potential to be used as active ingrediennt for the formulation of a new bioinjections for application by farmers to control the pest in fields.