Potential of Cactoblastis cactorum as a Vector for Fungi Pathogenic to Pricklypear, Opuntia inermis

In Australia, fungi associated with larvae of the biological control agent Cactoblastis cactorum may contribute to the control of the exotic weed pricklypear (Opuntia inermis). C. cactorum larvae were assessed for their ability to vector pathogenic fungi into O. inermis by the infestation of larvae with fungal suspensions. Six fungal isolates caused disease after being carried into the host on external surfaces of larvae, and propagules of one isolate (UQ5109) initiated disease after being transferred from the cladode epidermis into the host by larvae feeding on the plant. Scanning electron microscopy revealed extensive hyphal growth on the external surfaces of larvae infested with several of the isolates. Fungi isolated from field-grown O. inermis cladodes were tested for pathogenicity to this plant in an in vivo plant assay. In total, 152 isolates were screened, 22 of which infected the host in pathogenicity tests. Only 1 (UQ5115) infected undamaged host tissue, whereas the remainder required the host to be wounded before infection could proceed. The majority of isolates were only weakly pathogenic, even when inoculated via wounds, suggesting that most were either saprophytes or weak parasites. This study demonstrates that it is possible for larvae of C. cactorum to transmit fungal pathogens into O. inermis tissue and it has provided a sound basis for future field work to determine the contribution that fungi make to the control of O. inermis.     

Ultrastructural changes in the muscles,midgut, hemopoietic organ,imaginal discs and Malpighian tubules of the mosquito Aedes aegypti larvae infected by the fungus Coelomomyces stegomyiae

Fungi belonging to the genus Coelomomyces can infect mosquito larvae and develop within the larval hemocoel. To examine fungal development, Aedesaegypti larvae infected with Coelomomyces stegomyiae Keilin were fixed, embedded and sectioned for both light and electron microscopy. While fungal hyphae of C. stegomyiae did not invade cells other than the cuticular epithelial cells, they did penetrate a number of tissues including muscles, midgut, hemopoietic organ, imaginal discs, and Malpighian tubules. This revised version was published online in July 2006 with corrections to the Cover Date.     

The effect of a predatory leech,Nephelopsis obscura,on mortality,growth, and production of chironomid larvae in a small pond

Summary The effect of a predatory leech, Nephelopsis obscura, on survivorship, growth, and production of chronomid larvae was studied by enclosure experiments carried out in a small pond. The prey population was composed almost entirely of the tubiculous, microphagous chironomid larvae, Chironomus riparius and Glyptotendipes paripes. Nephelopsis significantly reduced chironomid survivorship within the enclosures, and accounted for most of the measured mortality of fourth instar larvae. The cropping by Nephelopsis was not significantly biased toward either prey species. In long-term experiments (66 d) chironomid biomass in enclosures without leeches reached much higher levels than in enclosures containing Nephelopsis. This increase in biomass was due to growth of surviving larvae, rather than recruitment, since emergence and oviposition were not going on during the course of the experiments. The enhanced survivorship of larvae within leech-free enclosures was eventually accompanied by reduced growth and specific production (daily production/biomass) for C. riparius, which made up about 90% of the larval population. Growth and specific production of G. paripes (10% of larval population) was not affected. Short-term experiments (25 d) involving manipulation of densities and species ratio (9:1 CR:GP and 1:9 CR:GP) of larvae revealed that growth of the majority species was strongly influenced by larval density, whereas growth of the minority species was not. The same pattern was observed both in the presence and in the absence of Nephelopsis and was a result of differences in resource utilization between the two species. In the shortterm experiments, growth rates estimated for larvae exposed to leeches were significantly less than those for larvae in leech-free enclosures. This could be due either to size-biased consumption of larvae by Nephelopsis, or possibly a disturbance factor leading to reduced larval food intake and/or increased metabolic costs.     

Pathogenicity, formulation and storage of insect pathogenic hyphomycetous fungi tested against Diabrotica speciosa

Studies were conducted tosearch for fungal strains with potentialpathogenicity against Diabrotica speciosa(Germar) (Coleoptera: Chrysomelidae).Among sixteen fungal isolates screenedthe most virulent was a Beauveria bassiana(Balsamo) Vuillemin isolate (FHD13) thatcaused 70% mortality of D. speciosathird instar larvae. The LC₅₀ value ofB. bassiana isolate FHD13 was3.48 × 10¹⁰ conidia/ml.Different temperatures (4, 17 and 26 °C)and vegetable oils (corn, sunflower and canola)used for storage did not significantly affectviability of conidia. A pathogenicity trialagainst D. speciosa larvae performed withthe corn oil formulation (1 × 10⁸ conidia/mlof oil) caused 65% of mortality.     

Lagenidium infection in eggs and larvae of mangrove crab (Scylla serrata) produced in Indonesia

A fungal infection occurred in the eggs and larvae of mangrove crab (Scylla serrata) in seed production in Bali, Indonesia. The causative fungus was classified as a member of the genusLagenidium (Oomycetes, Lagenidiales). After comparison of its biological and physiological characteristics with those ofL. callinectes ATCC 24973, a known parasite of various crustaceans, was concluded that the isolate is a new species ofLagenidium, L. thermophilum, because of its rapid and thermotolerant growth and unique discharge process. Fungal growth was observed on PYG agar containing 0–5.0% (w/v) NaCl and 0–2.5% (w/v) KCI. Similar pathogenicity toward the zoeae of swimming crab (Portunus trituberculatus) was demonstrated.     

In vivo development of the entomogeneous hyphomycetePaecilomyces farinosus in hostSpodoptera exigua (beet armyworm) larvae

The in vivo development of the entomogenous hyphomycetePaecilomyces farinosus inSpodoptera exigua (beet armyworm) larvae was examined using light and electron microscopic techniques. Blastospores injected into larval hemocoels (500 blastospores/larva) were immediately ingested by phagocytic hemocytes, and no fungal cells were detected in the hemolymph until 36 h post-injection. As indicated by immunocytochemical methods, the in vivo-produced blastosopres, in contrast to in vitro blastospores, lacked a galacto-mannan surface layer required for opsonization by aS. exigua humoral lectin. Therefore, these in vivo cells were not recognized by phagocytic granulocytes and were freely-circulating in the hemolymph. Hyphae differentiating from the blastospores were recognized by the hemocytes and induced formation of multicellular hemocytic nodules. By 72 h post-injection, mycelia were observed emerging from the nodules and by 96 h, larvae had become mummified due to extensive proliferation of the fungus throughout host tissues. Neither phagocytosis of the initially injected in vitro-produced blastospores nor nodule formation around hyphal cells later in the infection process was effective in stopping fungal growth. The in vivo development ofP. farinosus was similar to that of another hyphomycete,Beauveria bassiana except that in the latter case, extensive nodule formation was inhibited by the production of fungal metabolites.     

The life-history,distribution, and production of Chironomus riparius and Glyptotendipes paripes in a prairie pond

C. riparius and G. paripes exhibited univoltine life-cycles in Stephenson Pond; pupation, emergence and oviposition occurred mainly during May, and both species overwintered as mature fourth instar larvae. The marjority of larval growth for both species took place during the fourth instar stage (August–October), and growth and production were very low during late May to mid July when only young instars were present. Low production occurred during an interval when sestonic chlorophyll a concentration was very low, and the high production period corresponded to the Aphanizomenon bloom (August) and the autumn diatom pulse. None of the growth and production parameters investigated were correlated with temperature at the mud-water interface. Tube structure and behavior of the larvae indicate that G. paripes larvae are filter-feeders, whereas, C. riparius larvae are deposit-feeders.     

Dissemination of entomopathogenic fungi using Busseola fusca male as vector

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

Role of symbiotic and non-symbiotic bacteria in carbon dioxide production from hosts infected with Steinernema riobrave

Entomopathogenic nematodes of the family Steinernematidae and their mutualistic bacteria (Xenorhabdus spp.) are lethal endoparasites of insects. We hypothesized that growth of the nematode’s mutualistic bacteria in the insect host may contribute to the production of cues used by the infective juveniles (IJs) in responding to potential hosts for infection. Specifically, we tested if patterns of bacterial growth could explain differences in CO₂ production over the course of host infection. Growth of Xenorhabdus cabanillasii isolated from Steinernema riobrave exhibited the characteristic exponential and stationary growth phases. Other non-nematode symbiotic bacteria were also found in infected hosts and exhibited similar growth patterns to X. cabanillasii. Galleria mellonella larvae infected with S. riobrave produced two distinct peaks of CO₂ occurring at 25.6–36 h and 105–161 h post-infection, whereas larvae injected with X. cabanillasii alone showed only one peak of CO₂, occurring at 22.8–36.2 h post-injection. Tenebrio molitor larvae infected with S. riobrave or injected with bacteria alone exhibited only one peak of CO₂ production, which occurred later during S. riobrave infection (41.4–64.4 h post-infection compared to 20.4–35.9 h post-injection). These results indicate a relationship between bacterial growth and the first peak of CO₂ in both host species, but not for the second peak exhibited in G. mellonella.     

Distribution,occurrence and characterization of entomopathogenic fungi in agricultural soil in the Palestinian area

The occurrence of entomopathogenic fungi was investigated in irrigated vegetable fields and citrus orchards soils, over a nine-month period (April-December 1999),using the Galleria bait method (GBM). Entomopathogenic fungi were found to occur in 33.6% of the soil samples studied, with positive samples yielding 70 fungal isolates, belonging to 20 species from 13 genera. Conidiobolus coronatus was the most frequent and abundant entomopathogenic species recovered, comprising 31.4% of the total number of isolates. Soil pH, soil moisture content and the geographical location had minor or no effect on the isolation of entomopathogenic fungi in the fields studied. On the other hand, organic matter content of soil, and vegetation type were found to significantly affect the occurrence of entomopathogenic fungi in soil habitats, with orchard fields yielding larger numbers of isolates than vegetable fields. Using Koch's postulates the pathogenicity of fungal isolates to Galleria larvae was found to range from 16–100% (mortality rate). Isolates of C. coronatus proved to be the most virulent isolates recovered. The effect of media and temperature on mycelial growth rate, conidial production and conidial germination of six entomopathogenic fungal species (C. coronatus, Entomophaga grylli, Erynia castrans, Hirsutella jonesii, Paecilomyces farinosus and Sporodiniella umbellata) was also studied. Mycelial growth rate, spore production and spore germination were significantly affected by media, temperature and isolates. In view of the present results, C. coronatus appears to be a good candidate for pest control in agricultural soils, as it has a wide tolerance to agricultural practices, has frequently been isolated from both vegetable and orchard fields, and is characterized by high mycelial growth rate, conidial production and conidial germination.This revised version was published online in October 2005 with corrections to the Cover Date.     

Microbial pathogens of the coconut pest Oryctes rhinoceros: influence of weather factors on their infectivity and study of their coincidental ecology in Kerala,India

The rhinoceros beetle, Oryctes rhinoceros L., is an economically important pest of the coconut palm. Management of this pest has been accomplished using microbial agents viz., Oryctes virus (OrV) and an entomofungal pathogen Metarhizium anisopliae. Recently an opportunistic bacterial pathogen Pseudomonas alcaligenes has also been noticed to cause septicaemia in the grubs when under stress. To unravel the influence of abiotic weather factors and the interactions amongst these microbial pathogens, a 3 year study was conducted from September 1996 to August 1999 in three of the southern districts of Kerala, India. Of the 6627 grubs and 307 adults collected from various breeding sites of the pest, 5% of the grubs and 22% of the adults had natural virus infection, 3% larvae died of M. anisopliae mycosis and 20% larvae succumbed to bacterial septicaemia. Oryctes virus infection in grubs and adults was negatively correlated to minimum temperature (correlation co-efficient, r = –0.4, and –0.6 respectively, sample size, n = 0). Increase in relative humidity increased the fungal activity (r = 0.8) whereas, maximum temperature had a negative impact (r = –0.7). Occurrence of virus infection in grubs and adults was positively correlated (r = 0.6), supporting the contention of active transmission of the virus pathogen between these two stages. The bacterial septicaemia in the grubs was marginally correlated with virus infection and P. alcaligenes undermined the efficiency of the virus pathogen.     

Susceptibility of the cattle tick Boophilus microplus (Acari: Ixodidae) to isolates of the fungus Beauveria bassiana

The susceptibility of the tick Boophilus microplus to Beauveria bassiana was evaluated by inoculating eggs, larvae and engorged females of the tick with five fungal isolates at concentrations of 10⁶, 10⁷ and 10⁸ conidia/ml. Tick eggs (0.25 g) were immersed in 1 ml of a suspension of the different conidial concentrations for 1 min. Similar exposure was performed by immersion of 2000 larvae and homogeneous groups of nine engorged females in 2 and 20 ml of conidial suspension, respectively. Treated eggs, larvae and adults were placed in an incubator at 27 ± 1 °C and relative humidity above 80% for evaluation of the fungal action. All fungal isolates applied at all conidial concentrations reduced the hatching rate of larvae from treated eggs by 1.36–65.58% and increased the mortality rate of inoculated larvae by 0.8–70.49%. In the bioassay with engorged females, oviposition period was reduced by 9.69–47.80%, egg mass weight by 4.71–53.87%, estimated reproduction by 8.3–60.62%, egg production index by 5.03–54.20%, percent larval hatching by 0.27–13.96%, and the mortality rate of treated females was increased by 96.60–100%. The reduction of the estimated reproduction obtained for the treated groups ranged from 8.37 to 64.52%. The sporulation of the pathogen on dead females ranged from 3.70 to 88.88% depending on the isolate and concentration used. Isolates AM 09, CB 7 and JAB 07 were the most effective and effectiveness increased with increasing concentrations of conidia in the suspensions.     

Use of the egg parasiteEdovum puttleri [Hym.: Eulophidae] in an IPM system developed for Colorado potato beetle [Col.: Chrysomelidae] control on potatoes,Beltsville, Maryland

Edovum puttleri Grissell in conjunction with the fungal pathogenBeauveria bassiana (Balsamo) Vuillimen, a β-exotoxin ofBacillus thuringiensis varthuringiensis Berliner, and the insect growth regulator triflumuron (Alsystin 4F) were evaluated in a pest management system to control Colorado potato beetle,Leptinotarsa decemlineata (Say). Soil treatments ofB. bassiana had no significant impact on emerging Colorado potato beetle adults. Foliar applications of the β-exotoxin and triflumuron significantly reduced 1 ^st larval generation. Releases ofE. puttleri resulted in 56 % egg mass parasitization, significant reduction of 2 ^nd generation larvae, and significantly higher potato yields.Leptinotarsa texana (Schaeffer) was successfully used as an alternate host for production ofE. puttleri.      

Evaluation of entomopathogenic nematodes against the olive fruit fly, Bactrocera oleae (Diptera: Tephritidae)

Infectivity of six entomopathogenic nematode (EPNs) species against Bactrocera oleae was compared. Similar infection levels were observed when third-instar larvae were exposed to infective juveniles (IJs) on a sand-potting soil substrate. When IJs were sprayed over naturally infested fallen olives, many larvae died within treated olives as well as in the soil; Steinernema feltiae caused the highest overall mortality of 67.9%. In addition, three laboratory experiments were conducted to optimize a time period for S. feltiae field application. (1) Abundance of fly larvae inside fallen olives was estimated over the 2006–2007 season with the highest number of susceptible larvae (3 mm and larger) per 100 olives being observed during December, 2006. (2) S. feltiae efficacy against fly larvae dropped to the soil post-IJ-application was determined. B. oleae added to the substrate before and after nematode application were infected at similar levels. (3) Effect of three temperature regimes (min–max: 10–27, 6–18, and 3–12 °C) corresponding to October through December in Davis, California on S. feltiae survival and infectivity was determined. After 8 weeks, the IJs at the 3–12 °C treatment showed the highest survival rate. However, the cold temperature significantly limited S. feltiae infectivity. Our results demonstrate that B. oleae mature larvae are susceptible to EPN infection both in the soil and within infested olives. Being the most effective species, S. feltiae may have the potential to suppress overwintering populations of B. oleae. We suggest that November is the optimal time for S. feltiae field application in Northern California.     

Epirrita autumnata induced VOC emission of silver birch differ from emission induced by leaf fungal pathogen

The production of volatile organic compounds (VOCs) through the activation of different signal-transduction pathways may be induced in various biotic and abiotic stress situations having importance e.g. in insect and disease resistance. We compared the emission of VOCs emitted from silver birch Betula pendula Roth (clones 4 and 80) twigs damaged either by larvae of Epirrita autumnata, or infected with pathogenic leaf spot causing fungus Marssonina betulae. We also analysed whether local herbivore damage can systemically induce the release of VOCs from the undamaged top of same sapling. The emissions of methylsalicylate (MeSA), (Z)-ocimene, (E)-β-ocimene, (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT) and linalool were induced from the twigs after 72 h feeding damage by E. autumnata larvae. However, 48 h feeding damage did not induce rapid systemic release of VOCs from undamaged top leaves of the same twigs. Pathogen-infected birch twigs had significantly greater emission of (Z)-ocimene and (E)-β-ocimene than intact control twigs. The emission of DMNT was not significantly induced and MeSA was not found at all after pathogen infection, both being significantly different from herbivore damaged twigs. According to our results leaf fungal pathogen induces VOC emission profile differs from that of arthropod herbivore-damaged leaves, suggesting that birch is able to transmit parasite-specific information via VOC emissions to conspecifics and natural enemies of herbivores. Handling editor: Yvan Rahbé     

Evaluation of the fungus Beauveria bassiana (Deuteromycotina: Hyphomycetes), a potential biological control agent of Lutzomyia longipalpis (Diptera, Psychodidae)

Visceral leishmaniasis is a zoonosis whose primary vector in Brazil is the sandfly Lutzomyia longipalpis Lutz & Neiva. Presently, efforts to control the vector have not been effective in reducing the prevalence of disease. A possible alternative to current strategies is the biological control of the vector using entomopathogenic fungi. This study evaluates the effects of the fungus, Beauveria bassiana (Bals.) Vuilleman, in different developmental stages of L. longipalpis. Five concentrations of the fungus were utilized ranging from 10⁴ to 10⁸ conidia/ml, with appropriate controls. The unhatched eggs, larvae and dead adults exposed to B. bassiana were sown to reisolate the fungus. The fungus was subsequently identified by polymerase chain reaction (PCR) and DNA sequencing. Exposure to B. bassiana reduced the number of eggs that hatched by 59% (P < 0.01). The longevity of infected adults was 5 days, significantly lower than that of the negative control which was 7 days (P < 0.001). The longevity of the adult sandfly exposed to the positive chemical (pyrethroid, cypermetherin) control was less than 1 day. The effects of fungal infection on the hatching of eggs laid by infected females were also significant and dose-dependent (P < 0.05). With respect to fungal post-infection growth parameters, only germination and sporulation were significantly higher than the fungi before infection (P < 0.001). The identity of the reisolated fungus was confirmed by automated DNA sequencing post-passage in all insect stages. These data show that B. bassiana has good pathogenic potential, primarily on L. longipalpis larvae and adults. Consequently, the use of this fungus in sandfly control programs has potential in reducing the use of chemical insecticides, resulting in benefits to humans and the environment.     

Lagenidium myophilum infection in the coonstripe shrimp,Pandalus hypsinotus

A fungal infection occurred in juvenile coonstripe shrimps,Pandalus hypsinotus, cultured at Hokkaido Institute of Mariculture, Hokkaido, Japan. The fungus was identified asLagenidium myophilum, the same fungus that had previously been isolated from the abdominal muscle of adult northern shrimps,Pandalus borealis, and larvae of the coonstripe shrimp. Histopathologically, numerous nonseptate hyphae were observed in the lesions, and melanized hemocytes were present within the blackened areas. The optimum temperature for growth of the present strain was 25–30°C, and the optimum NaCl concentration for growth was 0.5–1.0%. Its biological characteristics were compared with those ofLagenidium myophilum isolated from diseased larval coonstripe shrimp and adult northern shrimp. The fungus was pathogenic toward shrimps of the genusPandalus, which live in deep sea areas. The fungus could infect shrimps at various stages, from larva to adult.     

Isolation of Beauveria species from Lebanon and evaluation of its efficacy against the cedar web-spinning sawfly, Cephalcia tannourinensis

Larvae of the cedar web-spinning sawfly, Cephalcia tannourinensis Chevin (Hymenoptera: Pamphiliidae), infected with a white fungus were collected from the Tannourine-Hadath El-Jebbeh cedar forest. Macro- and micro-morphological data based on the examination of colonies, conidiophores, and conidial shape of the fungus suggested a Beauveria species. Sequence analysis of the internal transcribed spacer regions of the isolated fungus showed that it is most closely related to isolates of B. bassiana Clade C. The present study showed that the isolated B. bassiana is a naturally occurring entomopathogenic fungus parasitizing the larvae of C. tannourinensis in Lebanon. Laboratory bioassays showed that B. bassiana caused high mortality of eggs and larvae. The infected eggs turned brownish in color, while larvae of the first instar ceased feeding and showed immobility and rigidity within 5 days and before sporulating conidial mat appeared on their cuticle. Second and third larval instars took longer time to show fungal sporulation: mortalities ranged between 85 and 100% within 7 days when treated with different conidial concentrations. The efficacy of control of C. tannourinensis using B. bassiana was higher or equal to the reference insect growth regulator, diflubenzuron, suggesting the possibility of its success as a biological control agent.     

Influence of Dimilin on a microsporidian infection in the gypsy moth Lymantria dispar (L.) (Lepidoptera: Lymantriidae)

Bioassay studies were conducted to investigate the influence of Dimilin (diflubenzuron), a chitinsynthetase inhibitor used for insecticidal control of the gypsy moth, Lymantria dispar, on the development and viability of a microsporidian pathogen of L. dispar. Before or after an infection with a Nosema species, L. dispar larvae were fed Dimilin in sublethal dosages. Dimilin fed to L. dispar larvae at 0.65 ng/cm² diet surface resulted in a total larval mortality of 53%. Although the microsporidian infection alone did not cause high mortality rates (9%), mortality increased to 96% when L. dispar larvae were inoculated with both Dimilin and Nosema spores. When Dimilin was fed to the larvae 24 h before or 6 days after inoculation with the microsporidium, the number of mature spores produced was significantly reduced. When Dimilin was fed to the larvae 24 h after microsporidian inoculation, the number of spores produced was not significantly reduced. Spores that were produced in larvae after Dimilin had been ingested with the diet were less infectious than spores produced in control larvae; the experimental infection rate decreased from 94% when spores obtained from control larvae were used, to 48 or 10% when spores obtained from larvae fed Dimilin 24 h or 6 days after Nosema inoculation, respectively, were used. Mature microsporidian spores washed in Dimilin solution prior to oral inoculation, however, were as infectious as spores stored in liquid nitrogen. We have shown that Dimilin interferes with the establishment of the parasite in its host. In addition, when Nosema sp. succeeds in infecting the L. dispar host despite treatment with Dimilin, the microsporidium does not develop optimally and spore production is reduced.     

Larval Mortality Factors of <Emphasis Type="Italic">Spodoptera Littoralis</Emphasis> in the Azores

Mortality among larval developmental stages of Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae), was determined by weekly sampling on weeds in a pasture on São Miguel Island (Azores, Portugal), from August to December, over a 3-year period (1999–2001). In all the years surveyed, larvae of S. littoralis usually appeared in pastures after the third week of August, with higher abundances in September and the beginning of October. Three different factors causing larval mortality were identified: one fungal pathogen, Furia virescens (Thaxter) Humber (Zygomycetes: Entomophthoraceae), two nucleopolyhedroviruses and one larval parasitoid, Meteorus communis (Cresson) (Hymenoptera: Braconidae). The percentages of dead larvae infected by virus or fungus were significantly higher than the other causes of mortality, regardless of the year. Furthermore, the percentage of larvae that died due to virus contamination was generally higher than the percentage of larvae infected by fungus. Significant correlations between the environmental factors and the percentage of larvae infected by virus or by fungus, were only observed during 2001. In 2001, the prevalence of fungal infection was negatively correlated with that of viral infection although prevalences of these two agents were positively correlated in both 1999 and 2000. These results show that virus and fungus are potential biological control agents for S. littoralis in Azores.