In vitro compatibility of Beauveria bassiana strain ATCC 74040 with copper fungicides

Copper fungicides and mycoinsecticides based on entomopathogenic fungi Beauveria spp. are the most common pesticides used in organic crop production systems. The in vitro effects of the copper fungicides copper oxide, copper hydroxide, copper oxychloride, copper sulphate, dicopper chloride trihydroxide and tribasic copper sulphate were investigated for mycelial growth, sporulation and conidial germination of the ATCC 74040 commercial strain of Beauveria bassiana. Mycelial growth was evaluated on potato dextrose agar plates with 100%, 75%, 50%, 25%, 12.5%, 6.25% and 0% of the recommended application rates of each fungicide at 15 and 25°C. Sporulation and conidial germination were determined at the recommended field doses of each fungicide at 25°C. All copper fungicides had fungistatic or fungicidal effects on B. bassiana that varied according to the dose. Only in two cases, copper oxide at 15°C and copper hydroxide at 25°C, at the lowest concentration of 6.5%, was mycelial growth not statistically significantly inhibited. Inhibition of mycelial growth depended both on the fungicide and its concentration, and partly on temperature. Both sporulation and conidial germination of B. bassiana were significantly inhibited by all fungicides. All fungicides inhibited the sporulation in a similar way (99.8%–100%). With the exception of copper oxychloride (inhibition, 13.6%), the other fungicides showed high detrimental effects on conidial germination (inhibition, 91.7%–100%). The fungus was strongly affected by some fungicides even at the lowest doses. The biological index used for the B. bassiana with copper fungicides ranged from 0.6 (copper sulphate) to 18.1 (copper oxychloride). Therefore, the tested fungicides were classified into the upper half of the highly toxic (T) category and are considered incompatible with the entomopathogenic fungus B. bassiana strain ATCC 74040 under in vivo experimental conditions. These results need to be further verified in vitro under both greenhouse and open-field conditions.     

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.     

Entomogenous Fungi as Promising Biopesticides for Tick Control

When ticks were sealed in nylon tetrapacks and infected with the entomogenous fungi, Beauveria bassiana and Metarizium anisopliae and maintained in potted grass in the field, the fungal oil formulations (10⁹ conidia per ml) induced 100% mortality in larvae of Rhipicephalus appendiculatus and Amblyomma variegatum, whereas mortalities in nymphs varied between 80–100% and in adults 80–90%. The aqueous formulations (10⁹ conidia per ml) induced mortalities of 40–50% and reductions in egg hatchability of 68% (B. bassiana) and 48% (M. anisopliae) when sprayed on Boophilus decoloratus engorging on cattle. The strains of B. bassiana and M. anisopliae isolated from naturally infected ticks were also found to induce high mortalities in both R. appendiculatus and A.variegatum in tetrapacks placed in potted grass. Both aqueous and oil-based formulations were found to be effective, although the latter induced higher mortalities. These fungal strains in aqueous formulation (10⁸ conidia per ml) suppressed on-host populations of adult R. appendiculatus by 80% (B. bassiana) and 92% (M. anisopliae) when sprayed on tick-infested grass once per month for a period of 6 months. The feasibility of using entomogenous fungi for tick control in the field is discussed.     

<Emphasis Type="Italic">Beauveria bassiana</Emphasis> pathogenicity to the cherry slugworm, <Emphasis Type="Italic">Caliroa cerasi</Emphasis> (Hymenoptera: Tenthredinidae) larvae

The cherry slugworm Caliroa cerasi is a significant destructive pest of sour cherries (Prunus cerasus) in Turkey. The potential of entomopathogenic fungi for controlling C. cerasi was evaluated. The effects of exposure methods and conidial concentrations (1 × 10⁶, 1.5 × 10⁶, 1 × 10⁷ and 1.5 × 10⁷ conidia/ml) on mature larvae of C. cerasi infected by Beauveria bassiana were investigated under laboratory conditions. Larvae sprayed directly with B. bassiana conidial suspensions and larvae exposed to B. bassiana-treated leaves resulted in 100% mortality within 2.90 and 2.77 days, respectively. The median lethal time (LT₅₀) and days to mortality were highest in the 1.0 × 10⁷ concentrations of conidia for both direct spray and leaf exposure. The present study suggests that B. bassiana has good potential for control of the cherry slugworm, C. cerasi.     

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.     

Evaluation of Beauveria bassiana and B. brongniartii strains and four wild-type fungal species against adults of Bactrocera oleae and Ceratitis capitata

The virulence of two isolates of the hyphomycete fungi, Beauveria bassianaand B. brongniartii, and additional fungal species isolated from diseased Bactrocera oleae pupae and Sesamia nonagrioideslarvae were assessed against adults of the olive fruit fly B. oleae and the Mediterranean fruit fly Ceratitis capitata (Diptera: Tephritidae). Contact and oral bioassays revealed that moderate to high mortality rates for the olive fruit fly occurred when the adults were exposed to conidia of Mucor hiemalis, Penicillium aurantiogriseum, P. chrysogenum and B. bassianaisolates. A strain of M. hiemalis isolated from S. nonagrioides larvae was the most toxic resulting in 85.2% mortality to the olive fruit fly adults. B. brongniartiiand B. bassiana were the most pathogenic to the C. capitataadults causing 97.4 and 85.6% mortality. Metabolites collected from the M. hiemalis and P. chrysogenum isolates were toxic to adults of both species.     

Effect of different isolates of Beauveria bassiana on field populations of Lygus hesperus

Lygus hesperus (Knight) (Hemiptera: Miridae) is a particularly damaging pest of many crops in the Western United States. Current control tactics are chemically based and there is some concern over resistance building up in populations. Based on previous laboratory studies conducted in California and Mississippi, USA, two new isolates of the entomopathogenic fungus Beauveria bassiana (Balsamo) Vuillemin (Deuteromycotina: Hyphomycetes) were selected for field-testing against L. hesperus in California. Alfalfa plots were treated with one of three isolates of B. bassiana (a commercial isolate, an isolate from CA (WTPB2) or an isolate from MS (TPB3)) or the chemical pesticide Warrior T. More than 75% of the adults collected from plots 3 days after application with B. bassiana were infected but no differences in percentage infection occurred among fungal treatments. In addition, approximately 30% of the insects collected from control plots or plots treated with Warrior T were also infected. PCR analysis using SSR markers revealed that the isolate causing most of the infections in fungus treated plots was the isolate applied. A mix of infections was found in control plots and plots treated with Warrior T. Despite high levels of infection, no significant reductions of adult populations occurred until 10–14 days after application when plots treated with Warrior T or B. bassiana had about half the numbers of adult L. hesperus as the control plots.     

Effects of inoculation method on efficacy of wettable powder and oil dispersion formulations of Beauveria bassiana against Colorado potato beetle larvae under low-humidity conditions

The effects of inoculation method on efficacy of two formulations of Beauveria bassiana strain GHA against Colorado potato beetle larvae were investigated. Under dry greenhouse conditions, ca. 58% mortality was observed among second-instar larvae exposed directly to sprays of B. bassiana conidia, whereas mortality among larvae exposed to similarly treated foliage (either leaf dorsal or ventral surfaces) was <10%. Mortality was ca. 64% among larvae exposed to both direct sprays and foliar spray deposits. Equivalent rates of mortality were observed among larvae treated with a clay-based wettable powder versus an emulsifiable oil-based formulation of B. bassiana conidia; however, this was observed despite application of an approximately 40% greater dose of WP-formulated conidia, indicating greater efficacy of the emulsifiable oil formulation. These results suggest that, under dry conditions, potato beetle larvae do not readily acquire an effective dose of conidia from treated foliage and that development of improved application technologies to more effectively target the larvae may ultimately prove more beneficial than development of formulations with greater foliar persistence.     

Establishment of Beauveria bassiana as a fungal endophyte in potato plants and its virulence against potato tuber moth,Phthorimaea operculella (Lepidoptera: Gelechiidae)

The potato tuber moth, Phthorimaea operculella, is the most damaging potato pest in the world and is difficult to control as the larvae are internal feeders in the foliage and tubers. Entomopathogenic fungi that colonize plants as endophytes have lethal and sublethal pathological effects on insect pests. We show that Beauveria bassiana colonizes the aerial parts of potato plants endophytically after inoculation through soil drenching. Endophytic B. bassiana persisted in potato foliage for more than 50 days postinoculation. Bioassays indicated that foliage of B. bassiana-inoculated potato plants were pathogenic against larvae of P. operculella. Sublethal experiments indicated that B. bassiana negatively affected the growth, development, and reproduction of P. operculella. Development experiments showed that the weight of P. operculella pupae reared on B. bassiana-colonized potato plants (4.25 mg) was significantly less than that of those reared on uninoculated control plants (8.89 mg). Compared with newly eclosed larvae fed on control plants, those fed on B. bassiana-inoculated plants had significantly lower survivorship, with only 17.8% developing to the adult stage. Oviposition of P. operculella females reared on B. bassiana endophytically colonized plants was significantly lower (35 eggs/female) than of those reared on uninoculated plants (115 eggs/female). This study demonstrates that endophytic B. bassiana can be a potential biological control agent for the control and management of P. operculella. Comparing pupal weights of P. operculella reared on potato plants inoculated with the B. bassiana strain GZGY-1-3 and on untreated control plants, pupae from the control plants were significantly heavier than those from treated plants.     

Response of the Wasp Cephalonomia tarsalis (Hymenoptera: Bethylidae) to Beauveria bassiana (Hyphomycetes: Moniliales) as Free Conidia or Infection in Its Host, the Sawtoothed Grain Beetle, Oryzaephilus surinamensis (Coleoptera: Silvanidae)

Cephalonomia tarsalis, an ectoparasitoid, and Beauveria bassiana, an entomopathogenic fungus, are potential biological control agents for the sawtoothed grain beetle, Oryzaephilus surinamensis. Several experiments were conducted to determine whether the two beneficial organisms are compatible. Wasps exhibited little avoidance behavior toward the fungus. Adult wasps oviposited on B. bassiana-infected larvae up to within 1 day of the host's death and the appearance of red fungal pigment. Wasp larvae are susceptible to the fungus and die within 1 day of oviposition on host larvae with mycosis. A 3-h exposure of adult wasps to 100 mg of B. bassiana/kg of wheat resulted in 52.7% mortality. Nevertheless, the wasps entered into grain containing B. bassiana conidia as freely as they entered into conidia-free grain. The mean prevalence of B. bassiana in 46 samples of pooled wheat representing 276 locations was 7.5 colony-forming units/g of wheat. Natural C. tarsalis exposure to B. bassiana in untreated stored wheat is likely to be below lethal quantities, and the introduction of the fungus in insecticidal quantities would have a negative impact on C. tarsalis populations.     

Simulated acid rain reduces the susceptibility of the European pine sawfly (Neodiprion sertifer) to its nuclear polyhedrosis virus

Summary The study dealt with the effect of simulated acid rain (both H₂SO₄ and HNO₃; acidities of pH 4 and pH 3) on the susceptibility of the larvae of Neodiprion sertifer to its nuclear polyhedrosis virus. Scots pines growing in a subarctic area with low ambient pollution levels were irrigated with simulated acid rain during two summers. Neodiprion larvae fed with foliage from the experimental trees were infected with a dilute virus suspension. The acid treatment of host trees had a significant effect on the proportion of virus-treated larvae alive 16 days after the virus application: there were almost no differences between the controls and the pH 4 irrigation group, but on the needles of pH 3-treated trees larval survival was twice as high as with other treatments. The direct spraying of acid water on the needles before they were fed to the larvae did not significantly affect the survival of virus infected larvae. Our results suggest that acid rain may reduce the susceptibility of Neodiprion larvae to virus disease via changes in the quality of pine foliage.     

Spruce budworm growth,development and food utilization on young and old balsam fir trees

Laboratory rearing of spruce budworm, Choristoneura fumiferana, in conjunction with field rearing, gravimetric analyses, a transfer experiment, and foliage chemical analyses at six dates during the period of budworm feeding activity indicated that the age of balsam fir, Abies balsamea, trees (70-year-old mature trees or 30-year-old juvenile trees) affected tree suitability for the spruce budworm via the chemical profile of the foliage. Insects reared on old trees had greater survival and pupal weight, shorter development times, and caused more defoliation than those reared on young trees. Young trees were more suitable for the development of young larvae (instars 2–5), while old trees were more suitable for the development of older, sixth-instar larvae. These results were confirmed by the laboratory transfer experiment. Young larvae fed foliage from young trees had higher relative growth rates (RGR), digestibility (AD), and efficiency of conversion of ingested foliage (ECI) than those fed foliage from old trees. These differences appeared to be related to the high N:tannins ratio, and the high contents of P present in young trees during the development of the young larvae. Old larvae fed foliage from old trees had higher relative growth rates, relative consumption rates (RCR), and digestibility of the foliage than those fed foliage from young trees. The high digestibility of the foliage of old trees was compensated for by a lower efficiency of conversion of digested food (ECD), which in turn resulted in no significant effect of tree age on the efficiency of conversion of ingested foliage by old larvae. The low relative consumption rate of old larvae fed foliage from young trees appeared to be related to the low N:tannins ratio, and the high contents of bornyl acetate, terpinolene, and °-3-carene present in young trees during the budworm sixth instar. Variations in these compounds in relation to tree age may serve as mechanisms of balsam fir resistance to spruce budworm by reducing the feeding rate of sixth instar larvae.     

Season long intraplant epizootics of entomopathogens,Beauveria bassiana andNosema pyrausta,in a corn agroecosystem

Intraplant epizootics of entomopathogens,Beauveria bassiana (Balsamo) Vuillemin, andNosema pyrausta (Paillot) were studied in a corn,Zea mays L., agroecosystem. Egg masses of the European corn borer,Ostrinia nubilalis (Hübner), infected withN. pyrausta were placed on midwhorl-stage corn plants. Conidia ofB. bassiana were applied in an aqueous suspension. Frass from the initial insects remaining within the plants was contaminated with sufficientN. pyrausta spores to infest 80% of the filial generation in each year of a 2-yr study. Viability ofN. pyrausta within the frass was monitored throughout the winter. Potential for impact of this inoculum on the filial generation is discussed. Conidia from cadavers of the European corn borer that were killed by the initial inoculum ofB. bassiana and/or conidia from the initial inoculum ofB. bassiana significantly reduced tunneling by the filial generation of the European corn borer. However, neither the concentration ofB. bassiana nor the age of the larvae exposed toB. bassiana, had any significant (P<.05) effect on tunneling by the 2nd-generation larvae. This paper reports the results of research only. Mention of a pesticide in this paper does not constitute a recommendation for use by the U.S. Department of Agriculture or cooperators, nor does it imply registration under FIFRA as amended.     

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.     

Observations on the vapour phase activity of some foliage fungicides

By means of a Botrytis fabae/Vicia faba bio-assay technique it has been demonstrated that phenyl mercury chloride, maneb, mancozeb, dichlo-fluanid and oxythioquinox protect areas of leaf beyond the visible limits of the fungicide deposits. The evidence suggests that the extended areas of protection are due to the release of fungicidal vapours. For a given dose of mancozeb the area of protection was related to the number of conidia of B. fabae dusted on to the leaves and for a given inoculum density it extended with increasing fungicide dose applied in standard drop sizes. When the same dose of fungicide was applied in increasing volumes of water, producing widening areas of deposit, the area of protection also increased. Fungicide deposits aged on leaves for up to 4 weeks continued to release toxic vapours. Contact between the fungicides and leaves or between fungicides and spores was not necessary for the demonstration of the phenomenon since vapours diffused from deposits on glass and inhibited the germination of spores in water droplets placed at a distance from the fungicide source. For a given distance separating the fungicide and the spores inhibition increased with increasing fungicide dose. For a standard fungicide dose, inhibition decreased with increasing distances between the fungicide and the spores. The fungicidal vapours inhibited the germination of spores of test fungi other than B. fabae. The practical implications of these observations are examined in the light of evidence that vapour phase protection can occur on leaves incubated in large cabinets; on leaves pre-incubated at unsaturated humidities; and on leaves incubated in a moving stream of air.     

Pathogenicity of Beauveria bassiana (Deuteromycotina: Hypomycetes) to Larvae of the Small Poplar Longhorn Beetle, Saperda populnea (Coleoptera: Cerambycidae)

The small poplar longhorn beetle, Saperda populnea is an important pest of Lombardy poplars (Populus nigra L.) in Turkey. A survey for natural entomopathogenic fungi of S. populnea larvae was made in Erzurum, Turkey, during the period 2004–2005. Larvae (13.5%) infected with a strain of the fungus Beauveria bassiana were found. The pathogenicity of B. bassiana strain 46 was conducted with different concentrations of conidia (10⁶, 10⁷ and 10⁸ conidia/ml) of this isolate on S. populnea larvae. The lowest concentration (10⁶ conidia/ml) caused about 56% mortality within 6 days. One hundred percent mortality was achieved after median lethal time (LT₅₀) of 4.6 and 4.4 days for 10⁷ and 10⁸ conidia/ml, respectively. There were no significant differences between median lethal times. This is the first record of natural infection of S. populnea larvae by B. bassiana.     

Effect of Bt-cotton expressing Cry1A(c) on the survival and fecundity of two hymenopteran parasitoids (Braconidae, Encyrtidae) in the laboratory

We examined the effect of Bt-cotton (Event 531) plants expressing the Bacillus thuringiensis δ-endotoxin CryIA(c) on two hymenopteran endoparasitoids, Cotesia marginiventris and Copidosoma floridanum. In the laboratory, parasitized and unparasitized Pseudoplusia includens larvae were reared on foliage from a conventional soybean cultivar (Pioneer 97B61), a conventional cotton cultivar (DPL 5415), or a Bt-cotton cultivar (NuCotn 33B). C. marginiventris developed significantly faster within P. includens larvae feeding on Pioneer 97B61 and DPL 5415 compared to those feeding on NuCotn 33B. C. marginiventris that developed inside P. includens larvae feeding on NuCotn 33B suffered reduced longevity, and females had fewer ova. NuCotn 33B also affected the growth and development of P. includens parasitized with C. floridanum and life history parameters of adult C. floridanum. Parasitized and unparasitized P. includens developed more slowly when they were fed NuCotn 33B and the prepupae weighed less. Survival of parasitized and unparasitized P. includens was lower when larvae were fed NuCotn 33B and some evidence points to higher susceptibility of parasitized caterpillars to intoxication by NuCotn 33B. Fewer C. floridanum adults emerged from hosts fed NuCotn 33B, but pupal weight and adult longevity were unaffected. Analysis comparing the two experiments conducted with C. floridanum suggests that older NuCotn 33B plants (90–120 days after planting) may affect parasitoid development and adult survival less than younger NuCotn 33B plants (60–90 days after planting). Feeding on NuCotn 33B by P. includens affected the survival and development of the two hymenopteran endoparasitoids studied here, and the degree of the effect was similar to that observed with natural resistance found in soybean plants. It remains to be determined if the effects demonstrated here are less than, equal to, or greater than the impact of conventional insecticide applications used in conventional, non-transgenic, cotton.     

A larval hunger signal in the bumblebee Bombus terrestris

Larvae of Bombus terrestris, a pollen-storing bumblebee, are dependent on progressive provisioning by workers. We test the hypothesis that larval cuticular chemicals can act as a hunger signal. We first show with a new classical conditioning experiment, using a Y-shaped tube, that workers can be trained to prefer the extracts of normally fed larvae over those of starved larvae. This proves the ability of workers to discriminate between larval extracts. Second, we show in a bioassay that workers also use these perceived differences to feed larvae according to their nutritional status. Larval broods sprayed with the extracts of the starved larvae were fed significantly more than larval broods sprayed with the extracts of normally fed larvae or with the solvent (n-pentane) only. We therefore conclude that B. terrestris larvae signal their need for food via their cuticular chemicals, and discuss the extent to which this form of communication could give larvae some control over their development. Received 2 September 2005; revised 11 April; accepted 24 April 2006.     

Effect of fungicides on survival of Rhizobium on seeds and the nodulation of bean (Phaseolus vulgaris L.)

The survival of Rhizobium leguminosarum biovar phaseoli on seeds of bean was tested, using the cultivar Carioca. The seeds were treated seven days before inoculation with Benlate, Vitavax, Banrot, Difolatan or Ridomil fungicides. The rhizobial strains used were: CIAT 899, CPAC 1135 and CIAT 652. Strain CIAT 899 showed greater survival on the seed with fungicide than the other strains. Two hours after the contact with fungicides strains CIAT 652 and CPAC 1135 had significantly lower numbers of rhizobia than the treatment without fungicide. The Benlate and Banrot fungicides had the greatest effect on survival of rhizobial strains. There was a drastic mortality of the two strains, CIAT 652 and CPAC 1135, on seeds treated with Benlate and Ridomil. Under field conditions, granular inoculation produced fewer nodules, but a similar total nodule weight as seed inoculation. Serological tests (ELISA) showed that seed treatment with Benlate in connection with seed inoculation reduced drastically the occurrence of inoculated strains in nodules, while the same fungicide treatment and inoculation applied in the seed furrow did not affect the survival of the inoculated strain.     

Nematicidal activity of culture filtrate of <Emphasis Type="Italic">Beauveria bassiana</Emphasis> against <Emphasis Type="Italic">Meloidogyne hapla</Emphasis>

Culture filtrates of Beauveria bassiana at different concentrations were evaluated for nematicidal activity against the northern root knot nematode (Meloidogyne hapla); bioassays included egg hatching, mortality and infectivity on tomato plants in pots under glasshouse conditions. The percentage mortality and inhibition of hatching of root-knot nematode were directly proportional to the concentration of culture filtrates of B. bassiana. Soil drenching with culture filtrate of B. bassiana significantly reduced nematode population densities in soil and in the roots and subsequent gall formation and egg-mass production by M. hapla under glasshouse conditions.