Order of Inoculation Affects the Success of Co-Invading Entomopathogenic Fungi

The effect of order of inoculation of Pandora blunckii and Zoophthora radicans co-infecting Plutella xylostella (L.) (Lepidoptera: Plutellidae) was investigated. After co-inoculation, the proportion of larvae infected by either species was greatly reduced compared to when they were inoculated singly. The order of inoculation influenced the final outcome; the isolate inoculated last always killed more larvae than the isolate inoculated first.     

Effect of temperature on the in vitro radial growth of Zoophthora radicans and Pandora blunckii, two co-occurring fungal pathogens of the diamondback moth Plutella xylostella

The effect of four different temperatures (15, 20, 25 and 30°C) on the in vitro growth of 19 isolates of Pandora blunckii and 14 isolates of Zoophthora radicans from Plutella xylostella larvae was investigated. Both species grew more at 20 and 25°C than the other two temperatures. However, Z. radicans grew more than P. blunckii at 20 and 25°C. Within each species there were differences amongst: all isolates regardless of geographical origin, isolates from different countries and isolates from Mexico. No relationship was found between optimal growth temperature and geographical origin. This represents the first report of the relationship between temperature and the in vitro growth of P. blunckii. The ecological role of this large variability amongst isolates within each species is discussed.     

Competition and co-existence of Zoophthora radicans and Pandora blunckii, two co-occurring fungal pathogens of the diamondback moth, Plutella xylostella

The entomopathogenic fungi Zoophthora radicans and Pandora blunckii co-occur in field populations of Plutella xylostella and, therefore, are likely to interact during the infection process. We have investigated the possible outcomes of these interactions in the laboratory. Using four isolates, two of each fungal species, inter-specific interaction experiments were done in Petri dishes and on intact plants. In Petri dish experiments, larvae were inoculated directly using sporulating mats of mycelium, both species had the same opportunity to infect and only the relative concentration of conidia of each pathogen species applied was manipulated. In the intact plant experiments, larvae were placed onto fungus-contaminated plants, inoculation was passive and the probability of infection by either or both species of fungi depended on larval activity and proximity to inoculum. In the Petri dish experiment, the species with the largest concentration of conidia out-competed the other regardless of virulence, and results were similar in the intact plant experiment. The ecological implications for competition or co-existence of these two pathogens in the field are discussed.     

Horizontal Transmission of Entomopathogenic Fungi by the Diamondback Moth

The relative potential of the pathogenic fungi Beauveria bassiana and Zoophthora radicans for use as autodisseminated biological control agents of the diamondback moth (Plutella xylostella) was compared. The LC₅₀ of B. bassiana conidia to third instar larvae was 499 conidia/mm² of leaf surface and individual cadavers of mycosed fourth instar larvae yielded a mean of 67.5 × 10⁶ (±7.5 × 10⁶) conidia. All concentrations of B. bassiana tested in inoculation chambers (0.24, 2.4, and 6.2 μg/mm²) induced 100% mortality in adult male moths within 7 days. The times to death and sporulation were concentration and exposure duration dependent. A standard procedure for inoculating male moths resulted in >85% mortality from Z. radicans and >93% mortality from B. bassiana. Pairing of inoculated males with clean moths of both sexes yielded higher rates of passive transmission of B. bassiana than Z. radicans, but there was no evidence for sexual transmission of either pathogen. Similarly, B. bassiana was more effectively transmitted from inoculated male moths to larvae foraging on whole plants. Single sporulating cadavers producing B. bassiana or Z. radicans conidia placed on plants infested with larvae resulted in a similar rate of transmission for both pathogens. However, an increase of the density of sporulating cadavers from one to three/plant increased Z. radicans transmission (greater than fourfold) but had no effect on B. bassiana transmission. Simultaneous inoculations of larvae with conidia of both fungi reduced the mortality induced by each pathogen, the reduction being most acute for B. bassiana-induced mortality. Inoculation of adults with both fungi showed that, at concentrations required for effective passive transmission to larvae, B. bassiana severely inhibited Z. radicans mycosis in adults.     

Initiation of fungal epizootics in diamondback moth populations within a large field cage: proof of concept for auto-dissemination

Adult diamondback moths (DBM), Plutella xylostella L. (Lepidoptera: Plutellidae), inoculated with the fungus Zoophthora radicans, were released within a large field cage containing DBM‐infested potted broccoli plants. Larvae and pupae on exposed and caged control plants were examined on five occasions over the next 48 days for evidence of Z. radicans infection. Infected larvae were first detected on exposed plants 4 days after the initial release of adults, and after 48 days the infection level reached 79%. Aerially borne conidia were a factor in transmission of the fungus. Infection had no effect on possible losses of larval and adult cadavers due to scavengers in field crops. In a trial to measure the influence of infection on dispersal, twice as many non‐infected as infected males were recaptured in pheromone traps, although the difference in cumulative catch only became significant 3 days after release of the males. In a separate experiment, when adult moths were inoculated with Beauveria bassiana conidia and released into the field cage, DBM larvae collected from 37 of 96 plants sampled 4 days later subsequently died from B. bassiana infection. The distribution of plants from which the infected larvae were collected was random, but the distribution of infected larvae was clustered within the cage. These findings suggest that the auto‐dissemination of fungal pathogens may be a feasible strategy for DBM control, provided that epizootics can be established and maintained when DBM population densities are low.     

Etiology and symptomatology of chalkbrood in the alfalfa leafcutting bee,Megachile rotundata

Aseptically reared larvae of the alfalfa leafcutting bee, Megachile rotundata, are susceptible to infection by spores but not mycelial cultures of Ascosphaera aggregata when introduced per os. The symptoms and signs of chalkbrood vary, depending upon host age at inoculation. Larvae inoculated early in life did not undergo the internal color changes after death that characterized larvae inoculated later. A longer time to death was also evident among larvae inoculated at an early age. Changes in the aerobic state of the host gut at the molt to the fourth instar may account for the difference in average time to death.     

Quantifying horizontal transmission of Nosema lymantriae, a microsporidian pathogen of the gypsy moth, Lymantria dispar (Lep., Lymantriidae) in field cage studies

Nosema lymantriae is a microsporidian pathogen of the gypsy moth, Lymantria dispar that has been documented to be at least partially responsible for the collapse of L. dispar outbreak populations in Europe. To quantify horizontal transmission of this pathogen under field conditions we performed caged-tree experiments that varied (1) the density of the pathogen through the introduction of laboratory-infected larvae, and (2) the total time that susceptible (test) larvae were exposed to these infected larvae. The time frame of the experiments extended from the early phase of colonization of the target tissues by the microsporidium to the onset of pathogen-induced mortality or pupation of test larvae. Upon termination of each experiment, the prevalence of infection in test larvae was evaluated. In the experiments performed over a range of pathogen densities, infection of test larvae increased with increasing density of inoculated larvae, from 14.2 ± 3.5% at density of 10 inoculated per 100 larvae to 36.7 ± 5.7% at 30 inoculated per 100 larvae. At higher densities, percent infection in test larvae appeared to level off (35.7 ± 5.5% at 50 inoculated per 100 larvae). When larval exposure to the pathogen was varied, transmission of N. lymantriae did not occur within the first 15 d post-inoculation (dpi) (11 d post-exposure of test larvae to inoculated larvae). We found the first infected test larvae in samples taken 20 dpi (16 d post-exposure). Transmission increased over time; in the cages sampled 25 dpi (21 d post-exposure), Nosema prevalence in test larvae ranged from 20.6% to 39.2%.     

Effects of Heliothis virescens ascovirus (HvAV-3e) on a novel host, Crocidolomia pavonana (Lepidoptera: Crambidae)

Ascoviruses are double-stranded DNA viruses which cause fatal disease in lepidopteran host larvae. They induce a unique pathology, causing cleavage of host cells into virion-containing vesicles. With the single exception of Diadromus pulchellus ascovirus, all ascoviruses have been exclusively reported from the Noctuidae. To investigate whether Heliothis virescens AV (HvAV-3e) has a broader host range at the family level, larvae of Crocidolomia pavonana F. (Lepidoptera: Crambidae), a major pest of brassica crops in tropical and sub-tropical regions of the Old World and Australasia, were inoculated with HvAV-3e. Larvae were readily infected by the ascovirus and feeding, growth and survival were significantly affected. However, the milky white discolouration of the haemolymph which is characteristic of ascovirus infection in noctuid hosts was not apparent. In further contrast to infected noctuid host larvae that do not develop to the pupal stage, a significant proportion of infected C. pavonana larvae pupated but all were killed at this stage. Thus, C. pavonana appears to be a semi-permissive host of the ascovirus, the presence of such hosts in the field might be an explanation for the conundrum for the ascovirus-noctuid-wasp relationship, helping explain the persistence of the ascovirus.     

Soybean leaf consumption by Nomuraea rileyi (Fungi: Deuteromycotina)-infected Plathypena scabra (Lepidoptera: Noctuidae) larvae

To determine the impact of Nomuraea rileyi on consumption by the green cloverworm, Plathypena scabra, larvae were reared from eggs obtained from field-collected moths, inoculated with conidia, and placed individually in separate plastic vials with a piece of surface-sterilized soybean leaflet. No significant differences in consumption rates were found between N. rileyi-inoculated and control larvae until after 144 hr post-treatment. After this period, consumption by larvae inoculated as first, second, third, or fourth instars was significantly less than that of control larvae because of mortality. First or second instars inoculated with N. rileyi conidia had significantly longer subsequent stadia than did control larvae. The average LT₅₀ of all inoculated instar groups was 6.5 days, and there was little evidence of significantly different N. rileyi susceptibility among instar groups. In general during the N. rileyi infection period leading to their deaths, inoculated P. scabra larvae had consumption patterns that were very similar to those of healthy larvae.     

Nematospiroides dubius: arrested development of larvae in immune mice.

When immune NIH mice were killed 10 days after a challenge infection with Nematospiroides dubius, approximately 10% of the inoculated larvae were recovered from the intestinal lumen, irrespective of the dose administered. When such mice were treated with cortisone from Day 10 for a period of 8 to 14 days and were subsequently killed for worm counts, it was found that they had significantly more worms than the immune control mice killed on Day 10. During the week following the beginning of treatment with cortisone there was little change in the low worm burdens in immune mice. However, 9 to 11 days after this treatment worm counts indicated that worms were accumulating in the intestinal lumen, and concurrently eggs were recorded in the feces of the mice. These observations indicated that a period of 9 to 11 days was required after the initiation of cortisone treatment on Day 10 for the worms in immune mice to complete their development to the adult lumen-dwelling stage. It is suggested that the larvae in the challenge infection became arrested early in their development in the intestinal wall and that growth resumed only after cortisone treatment. When treatment with cortisone was initiated later after challenge, it was still effective in reactivating arrested worms, but the lower worm recoveries in these mice indicated that the arrested larvae were being slowly rejected by the host. In subsequent experiments it was established that the arrested larvae of N. dubius were insusceptible to the activity of pyrantel embonate, an anthelmintic which is 99% effective against adult worms in the intestinal lumen. The mechanism whereby the larvae of N. dubius became arrested in immune mice and subsequently resumed their development after cortisone treatment is discussed.     

Kinetics of primary and secondary infections with Taenia crassiceps metacestodes (Zeder, 1800) rudolphi, 1810 (cestoda: cyclophyllidea)

Siebert A. E. Jr., Good A. H. & Simmons J. E. 1978. Kinetics of primary and secondary infections with Taenia crassiceps metacestodes (Zeder, 1800) Rudolphi, 1810 (Cestoda: Cyclophyllidea). International journal for Parasitology8: 39–43. When three T. crassiceps metacestodes were inoculated intraperitoneally in mice as a primary infection, approximately 50% of the larvae recovered during the first 4 weeks after inoculation were found to be dead, while in mice primed by previous subcutaneous inoculation, about 85% of the larvae died. Larvae which survived the first 4 weeks following primary intraperitoneal inoculation reproduced asexually by exogenous budding and produced viable infections within the host mice. But larvae in secondary infections were encapsulated by host granulomata, failed to reproduce asexually, and did not produce viable infections. In mice given intraperitoneal inoculations of seven, ten and twenty metacestodes, fewer larvae were killed and little encapsulation response was noted, though host cells were common at the budding region of the larvae. Such a biphasic host-response to the infection has not previously been reported for larval cestode infections, and the reduction in host response associated with increased worm burdens may indicate possible depression of the host immune system.     

Dirofilaria immitis: fate and immunogenicity of irradiated infective stage larvae in beagles

Experiments were conducted on the fate of irradiated infective larvae of Dirofilaria immitis in dogs, and on the effect of these infections on a challenge dose of nonirradiated larvae administered at a later date. Six dogs were inoculated with 200 to 296 irradiated larvae; in no case was a patent infection established. No living worm was recovered beyond 66 days. Eight dogs inoculated with 200 to 2401 irradiated larvae over varying periods of time were exposed 57 to 190 days after the final inoculation of irradiated larvae, to a challenge infection of 200 to 250 nonirradiated (normal) larvae. The results showed that the number of worms which developed to maturity in these dogs was sharply reduced compared to that in the 5 controls (dogs inoculated with normal larvae only). The most striking effect was seen in “vaccinated” dogs which were challenged 3 months or more after the final administration of irradiated larvae.     

Host genotype overrides endophyte infection effects on growth,physiology, and nutrient content of a native grass,Achnatherum sibiricum

The effect of infection by the fungal endophyte Neotyphodium, host genotype, and their interaction on growth and physiology, as well as photosynthesis, was investigated in the native grass Achnatherum sibiricum. We artificially inoculated the endophyte into mature tillers of endophyte-free A. sibiricum. Plants were clipped to 5 cm height after recording growth traits, and analyzed for total nonstructural carbohydrates (TNC %), the percentage of nitrogen (N %), and carbon (C %) in leaves before and after clipping. In our study, the prominent host genotype–endophyte infection interactions detected in A. sibiricum indicates that, for many growth and storage traits, endophyte infection can impact a little change. However, there is no overriding consistently positive effect of the endophyte on growth or storage in A. sibiricum before or after clipping. Our study showed that the interaction between endophyte and host grasses was highly contingent on plant genotypes. We found host genotype overrode fungal endophyte infection in influencing tiller number and photosynthetic properties of A. sibiricum before clipping. After clipping, host genotype accounted for more of the variation in regrowth and above-ground biomass of A. sibiricum than endophyte infection. Our study showed that host genotype affected the total nonstructural carbohydrates of A. sibiricum before and after clipping, whereas endophyte infection increased the carbon content after clipping. Genotype by infection interactions for plant height, leaf mass, total nonstructural carbohydrates, and photosynthetic characteristics indicated genotype-specific effects of endophytes on A. sibiricum physiology and photosynthetic capacity. The host genotype–endophyte infection interactions detected in A. sibiricum suggest that host genotype overrides fungal endophyte infection on growth, physiology, and nutrient content of this native grass. In contrast, endophyte effects did not appear to positively affect growth, physiology, or photosynthetic capacity before or after clipping.     

Effect of temperature on distribution and success of introduction of an Empoasca fabae (Homoptera: Cicadellidae) isolate of Erynia radicans (Zygomycetes: Entomophthoraceae)

Empoasca fabae is a serious leafhopper pest of agriculturally important crops in the midwestern and northeastern United States. The geographic distribution of Erynia radicans, a fungal pathogen of E. fabae, led us to examine the effects of temperature on tn vitro and in vivo growth and conidial germination of E. radicans. In addition, we examined the effects of temperature on the establishment of E. radicans in the field. E. radicans grew at constant temperatures of 28°C and below, both in vivo and in vitro, but did not grow at 30°C or above. Conidial germination followed a similar pattern; however, E. radicans survived exposure periods of up to 24 hr at 32°C in vivo. E. radicans did not cycle through a caged population of E. fabae in a growth chamber at 22°C despite the occurrence of infections immediately following fungal release. E. radicans did not become established after introduction into field populations of E. fabae at three sites in Illinois. We observed initial infections of leafhoppers at two of these sites and evidence suggests that horizontal transmission occurred at one of them. Epizootics, however, did not occur despite high populations of leafhoppers. Temperatures exceeded the laboratory thresholds for growth of E. radicans at each of the three sites during the first week after release, but for different durations.     

Conflicts between a fungal entomopathogen, Zoophthora radicans, and two larval parasitoids of the diamondback moth

Zoophthora radicans (Zygomycetes: Entomophthorales), Diadegma semiclausum (Hymenoptera: Ichneumonidae), and Cotesia plutellae (Hymenoptera: Braconidae) are all natural enemies of the diamondback moth, Plutella xylostella (Lepidoptera: Yponomeutidae). Adult C. plutellae are not susceptible to Z. radicans infection but the pathogen can infect and kill adult D. semiclausum. Infection of adult D. semiclausum prior to exposure to P. xylostella host larvae significantly reduced the number of parasitoid cocoons subsequently developing from the host larvae. Although Z. radicans infection of P. xylostella larvae prior to parasitism by D. semiclausum or C. plutellae always resulted in the death of the immature parasitoids, neither species discriminated between healthy and Z. radicans-infected host larvae in an oviposition choice experiment. However, host larvae recently killed by Z. radicans were always rejected by D. semiclausum but sometimes accepted by C. plutellae. At 20 degrees C, egg to pupa development took 6.7 and 7.8 days for D. semiclausum and C. plutellae, respectively. C. plutellae parasitism significantly increased host instar duration but D. semiclausum parasitism did not. Cadavers of P. xylostella larvae parasitized 1 day prior to fungal infection showed no reduction in Z. radicans conidia yield. However, cadavers of larvae parasitized 3 days prior to fungal infection demonstrated a marked decrease in Z. radicans conidia yield. Z. radicans infection of P. xylostella larvae < or = 4 days after parasitism resulted in 100% parasitoid mortality; thereafter, the reduction in parasitoid cocoon yield decreased as the time between parasitism and initiation of fungal infection increased. The extended duration of the host larval stage induced by C. plutellae parasitism increased the availability of the parasitoid to the pathogen. Estimates of interspecific competition indicated a similar pattern for the interaction between Z. radicans and each species of parasitoid.     

Strongyloides stercoralis: Hyperinfection in immunosuppressed dogs

Hyperinfective strongyloidiasis involving the threadworm, Strongyloides stercoralis, is well known in humans and primates. Although this nematode also frequently parasitizes dogs, canine hyperinfective strongyloidiasis has not been reported. To determine whether a fulminant pattern of nematode development can occur in dogs, and to test the S. stercoralis/dog system for suitability as a model for human hyperinfective and disseminated strongyloidiasis, five canine infections with a dog-derived strain of S. stercoralis were monitored by the quantitative recovery of larvae from feces. Even 3-month-old pups controlled their initial infections successfully, the number of larvae excreted declining to near zero in 90 days. Immunosuppressive treatment with prednisolone, prednisolone and azathiaprine, or niridazole resulted in a rapid return to former or greater intensities of infection, as judged by larval output. Only first stage (rhabditiform) larvae were passed in the feces, although third stage (filariform) larvae occurred in the intestinal contents of dogs when they were examined at necropsy. In 3 of the 5 dogs, the adult worm recovery exceeded the inoculated dose greatly and, in one of these, adults and rhabditiform larvae were found in distant, extraintestinal sites. In the remaining 2 of the 5 dogs, the adult worm population was less than the inoculated dose, but, in both, the infection was terminated by the host's death before hyperinfection could have developed. The observations demonstrate that autoinfection occurs in dogs infected with S. stercoralis and that, if it is allowed to continue for a sufficiently long time in immunosuppressed hosts, massive hyperinfection, and even disseminated infection, may occur. This spectrum of increasingly invasive parasitism closely resembles strongyloidiasis in humans. Therefore, the S. stercoralis/dog system has excellent potential as a model for human hyperinfective and disseminated strongyloidiasis.     

Effect of Inoculation and Leaf Litter Amendment on Establishment of Nodule-Forming Frankia Populations in Soil

High-N₂-fixing activities of Frankia populations in root nodules on Alnus glutinosa improve growth performance of the host plant. Therefore, the establishment of active, nodule-forming populations of Frankia in soil is desirable. In this study, we inoculated Frankia strains of Alnus host infection groups I, IIIa, and IV into soil already harboring indigenous populations of infection groups (IIIa, IIIb, and IV). Then we amended parts of the inoculated soil with leaf litter of A. glutinosa and kept these parts of soil without host plants for several weeks until they were spiked with [¹⁵N]NO₃ and planted with seedlings of A. glutinosa. After 4 months of growth, we analyzed plants for growth performance, nodule formation, specific Frankia populations in root nodules, and N₂ fixation rates. The results revealed that introduced Frankia strains incubated in soil for several weeks in the absence of plants remained infective and competitive for nodulation with the indigenous Frankia populations of the soil. Inoculation into and incubation in soil without host plants generally supported subsequent plant growth performance and increased the percentage of nitrogen acquired by the host plants through N₂ fixation from 33% on noninoculated, nonamended soils to 78% on inoculated, amended soils. Introduced Frankia strains representing Alnus host infection groups IIIa and IV competed with indigenous Frankia populations, whereas frankiae of group I were not found in any nodules. When grown in noninoculated, nonamended soil, A. glutinosa plants harbored Frankia populations of only group IIIa in root nodules. This group was reduced to 32% ± 23% (standard deviation) of the Frankia nodule populations when plants were grown in inoculated, nonamended soil. Under these conditions, the introduced Frankia strain of group IV was established in 51% ± 20% of the nodules. Leaf litter amendment during the initial incubation in soil without plants promoted nodulation by frankiae of group IV in both inoculated and noninoculated treatments. Grown in inoculated, amended soils, plants had significantly lower numbers of nodules infected by group IIIa (8% ± 6%) than by group IV (81% ± 11%). On plants grown in noninoculated, amended soil, the original Frankia root nodule population represented by group IIIa of the noninoculated, nonamended soil was entirely exchanged by a Frankia population belonging to group IV. The quantification of N₂ fixation rates by ¹⁵N dilution revealed that both the indigenous and the inoculated Frankia populations of group IV had a higher specific N₂-fixing capacity than populations belonging to group IIIa under the conditions applied. These results show that through inoculation or leaf litter amendment, Frankia populations with high specific N₂-fixing capacities can be established in soils. These populations remain infective on their host plants, successfully compete for nodule formation with other indigenous or inoculated Frankia populations, and thereby increase plant growth performance.     

The elimination of supernumerary larvae of the gregarious egg-parasitoidTrichogramma embryophagum [Hym.: Trichogrammatidae] in eggs of the hostEphestia kuehniella [Lep.: Pyralidae]

Larvae ofTrichogramma embryophagum Htg., the gregarious parasitoid of eggs of Lepidoptera, ingest the ooplasm of the host by pharyngeal sucking. In the case of a supernumerary number of larvae, some die shortly after all the food has been ingested, although all larvae are still at an early stage of development. The food previously swallowed by the dead animals flows back into the host chorion, and this is ingested by the surviving larvae. As a result of this, there is no wastage of food, and in eggs ofEphestia kuehniella Z. up to 3 larvae always survive to the adult stage.     

Experimental Infections with Mycoplasma agalactiae Identify Key Factors Involved in Host-Colonization

Mechanisms underlying pathogenic processes in mycoplasma infections are poorly understood, mainly because of limited sequence similarities with classical, bacterial virulence factors. Recently, large-scale transposon mutagenesis in the ruminant pathogen Mycoplasma agalactiae identified the NIF locus, including nifS and nifU, as essential for mycoplasma growth in cell culture, while dispensable in axenic media. To evaluate the importance of this locus in vivo, the infectivity of two knock-out mutants was tested upon experimental infection in the natural host. In this model, the parental PG2 strain was able to establish a systemic infection in lactating ewes, colonizing various body sites such as lymph nodes and the mammary gland, even when inoculated at low doses. In these PG2-infected ewes, we observed over the course of infection (i) the development of a specific antibody response and (ii) dynamic changes in expression of M. agalactiae surface variable proteins (Vpma), with multiple Vpma profiles co-existing in the same animal. In contrast and despite a sensitive model, none of the knock-out mutants were able to survive and colonize the host. The extreme avirulent phenotype of the two mutants was further supported by the absence of an IgG response in inoculated animals. The exact role of the NIF locus remains to be elucidated but these data demonstrate that it plays a key role in the infectious process of M. agalactiae and most likely of other pathogenic mycoplasma species as many carry closely related homologs.     

The impact of arbuscular mycorrhizal fungi on tomato plant resistance against Tuta absoluta (Meyrick) in greenhouse conditions

The symbiotic relationship between plants and arbuscular mycorrhizal fungi (AMF) improves plant growth and increases its resistance to pests and diseases. Mycorrhizal fungi are among the specialized fungi associated with the rhizosphere and are completely dependent on plant organic carbon. In this research tomato, Solanum lycopersicum L. was used as the host plant to evaluate the interaction effects between inoculation of tomato plant with AMF and feeding of tomato leaf miner, Tuta absoluta (Meyrick). In addition, plant growth parameters and growth rate of insect were assessed. The mycorrhizal treatment included a mixture of four fungal species (Funneliformis mosseae, Rhizophagus intraradices, R. irregularis and Glomus iranicus). The results of the experiment showed that tomato plant roots were well colonized (66.29%) by AMF and there was a significant mutual relationship between the insects feeding on the plants and the fungi. Feeding by the insects on plants inoculated with the fungus increased percentage of colonization by AMF in plants infested with the insect as compared to the control plants. The results also indicated that growth parameters and phosphorus content of the plants inoculated with fungi significantly increased compared to the control group. Moreover, significantly lower growth rate and consumption index observed in the T. absoluta larvae were fed on the leaves of plants treated with AMF compared to leaves of plants not inoculated with AMF.