The potential of some adjuvants in promoting infection with Verticillium lecanii: laboratory bioassays with Myzus persicae

The potential of 14 adjuvants, including mineral oils, vegetable oils, stickers, spreaders, surfactants and nutrients, in promoting the virulence of the entomopathogenic fungus Verticillium lecanii were compared relative to a commercial formulation of the pathogen. The rate of infection over time with each adjuvant relative to the commercial formulation was tested using the peach potato aphid Myzus persicae. The proportion of infected aphids was modelled binomially with a logistic rate function assumed for the proportion infected over the time period of the experiment. Four of the adjuvant treatments, Codacide, skimmed milk, glycerol and Cutinol together with the commercial control had similar logistic slope parameters and were modelled using parallel regressions. The parallel regressions model showed significant differences between the intercepts with both glycerol and Cutinol significantly better than V. lecanii alone. Glycerol had a more positive intercept than Cutinol but the difference was not statistically significant. Although highly variable, the numbers of progeny produced by the treated aphids were significantly reduced by all the treatments relative to untreated control aphids. Glycerol and Cutinol were the only treatments that significantly reduced the number of progeny relative to the V. lecanii control.     

Control of glasshouse whitefly, Trialeurodes vaporariorum, by an 'aphid' strain of the fungus Verticillium lecanii

Heavy infestations of whitefly on glasshouse cucumber plants were controlled below the level of economic crop damage by fortnightly or monthly sprays of Verticillium lecanii spores. The fungus did not spread from glasshouse to glasshouse, or from plant to plant, and often not from diseased whitefly scales bearing fungal spore heads to nearby healthy scales. Some scales survived and the resulting adults laid eggs on new leaves bearing no infected scales, creating another, healthy, generation. This makes regular spraying of new leaves essential. Blastospores were as effective as conidia in controlling scales when sprayed to ‘run off’ at concentrations near 10⁷ spores ml^-1 sprayed on to the undersurfaces of leaves. A fivefold increase in spore concentration at levels near 10⁷ spores ml^-1 usually caused significant improvement in mortality, but increase above this concentration is likely to be unrewarding. Thorough coverage of leaves was found to be vital. Control was impaired by dry conditions and by prolonged air temperatures above 25 °C. The fungicide dimethirimol, used against cucumber mildew, did not impair whitefly control by V. lecanii.     

Effects of the fungus <Emphasis Type="Italic">Lecanicillium lecanii</Emphasis> on survival and reproduction of the aphid <Emphasis Type="Italic">Schizaphis graminum</Emphasis>

This study investigated the effects of a strain of the fungus Lecanicillium lecanii (Zimm.) Zare and Gams (Hypocreales: Ascomycota) on the aphid Schizaphis graminum (Rondani) (Hemiptera: Aphididae). The fungus was administered to fourth instar nymphs and to alate and apterous adult morphs as a ground rice-kernel formulation. This study showed that L. lecanii formulation affected the survival of the aphids and interacted differently with the studied morphs, the Lethal Time values being lower for alate compared to apterous morphs and nymphs. The treatment also caused a significant reduction in the fecundity of the three treated aphid groups. Histological analysis revealed that the hyphae invaded the host hemocoel of a limited number of alate and apterous morphs: the fungus only entered through the spiracles. Scanning Electron Microscope observations revealed that L. lecanii adhered to the body surface of both adults and nymphs without differentiation. In conclusion, the present study suggests that this strain might be a good candidate for a programme of biological control of S. graminum and other aphid species.     

Untersuchungen über die in Lagerhäusern der DDR Trockenfäule an Kartoffeln verursachenden Fusarium-Arten

The virulence of two strains of the entomopathogenic fungus Verticillium lecanii to the aphids Myzus persicae, Aphis gossypii and Brevicoryne brassicae was bioassayed. The strain (V24 and V18) tested were capable of infecting all three aphids species, but their virulence determined by LC50 and LT50 varied. The strain (V24) originally isolated from M. persicae showed the highest virulence against the homologous aphid species, but the whitefly (Trialeurodes vaporariorum) derived strain (V18) showed also the highest virulence against an aphid species. The variability of the bioassay results and the impossibility of defining clearly traits associated with the virulence of a fungus strain toward a specific insect species are discussed. Effect of additives (glycerin, soyflour and rape oil) was studied for strain improvement. Considerable improvement of the strains virulence was not observed with glycerin and soyflour. The results are discussed in conjunction with the non-convincing results published earlier.     

Hoverfly oviposition response to aphids in broccoli fields

The oviposition response of predacious hoverflies (Diptera: Syrphidae) to Brevicoryne brassicae L. and Myzus persicae (Sulzer) (Homoptera: Aphididae) in commercial broccoli, Brassica oleracea var. italica L., Plenck (Brassicaceae), fields was investigated at two sites over the course of a growing season. The hoverfly oviposition responses to these aphid species on different parts of the broccoli plant canopy were also examined. There were no hoverfly eggs on broccoli plants without aphids, egg numbers were very low on plants with fewer than 50 aphids, and no peak in oviposition relative to aphid numbers was observed. Within individual plants that were colonized by aphids, there was some oviposition on individual leaves without aphids, and no hoverfly eggs were seen on leaves that had more than 400 aphids. Leaves in the broccoli plant canopy, and the datasets associated with them, were divided into three sections vertically, ‘upper’, ‘middle’, and ‘lower’. Brevicoryne brassicae was more abundant in the upper and middle canopy sections, while M. persicae was found mostly in the lower section. The rate of hoverfly oviposition per aphid was higher in the upper section than in the two other sections. Modeling of the oviposition response using logistic regression showed that the presence of hoverfly eggs was positively correlated with numbers of each aphid species and sampling date.     

The use of visual cues in host evaluation by aphidiid wasps

We examined host evaluation behaviour in three species of aphid parasitoids, Ephedrus californicus Baker, Monoctonus paulensis (Ashmead), and Praon pequodorum Viereck (Hymenoptera: Aphidiidae). Mated females were provided with pairwise choices among three kinds of hosts in the laboratory: (green) pea aphid, Acyrthosiphon pisum (Harris), and a green and a pink colour morph of alfalfa aphid, Macrosiphum creelii Davis. Patterns of attack and host acceptance were species-specific. Females of E. californicus did not respond to the presence of aphids prior to making antennal contact. Variations in rates of parasitization (pea aphid>green alfalfa aphid>pink alfalfa aphid) were consistent with differences in aphid defensive behaviours; no ‘preference’ for any host type was evident when aphids were anaesthetized with carbon dioxide. In M. paulensis, the order of preference (pea aphid>green alfalfa aphid>pink alfalfa aphid) did not vary when aphids were immobilized, or presented in the dark, or both. Host movement did not influence the rate of attack by M. paulensis. In contrast, the ranked order of preference in P. pequodorum varied with circumstance. In the light, females attacked pea aphid and green alfalfa aphid with equal frequency, but parasitized significantly more of the former; both kinds of aphids were attacked and parasitized at higher rates than pink alfalfa aphid. In the dark, P. pequodorum females parasitized green and pink alfalfa aphids equally and at higher rates than pea aphids. Whereas E. californicus was more successful ovipositing in immobilized hosts, P. pequodorum females attacked and laid more eggs in normal than anaesthetized aphids. Patterns of host recognition and evaluation are compared across six species representing four genera in the family Aphidiidae.     

Application ofVerticillium lecanii for the control ofAphis gossypii by a low-volume electrostatic rotary atomiser and a high-volume hydraulic sprayer

Verticillium lecanii (Fungi: Deuteromycete) blastospores were applied to a chrysanthemum crop by an ULV electrostatically charged rotary atomiser (APE-80). The deposition of spores and subsequent control ofAphis gossypii were compared to high volume hydraulic application. A full rate treatment (2×10¹³ blastospores per ha.) was applied by the APE-80 at week 1 and reduced spore rates of 1/6^th and 1/12^th applied by both the APE-80 and the hydraulic sprayer once and twice a week respectively for weeks 1 to 6. Untreated plots served as controls. Initial deposits of spores were higher with the electrostatic sprayer and better distributed with respect to the position of the target aphids. Significantly lower aphid populations were recorded on the electrostatically treated plots in week 4. The single full rate treatment had significantly fewer aphids than the untreated plots from week 3 and all treatments had significantly fewer aphids than the untreated plots from week 5 onwards. The proportion of the aphid population killed byV. lecanii was higher on the electrostatically treated plots until week 6.      

Behavioural responses of the seven‐spot ladybird Coccinella septempunctata to plant headspace chemicals collected from four crop Brassicas and Arabidopsis thaliana,infested with Myzus persicae

1 Insects using olfactory stimuli to forage for prey/hosts are proposed to encounter a ‘reliability–detectability problem’, where the usability of a stimulus depends on its reliability as an indicator of herbivore presence and its detectability. 2 We investigated this theory using the responses of female seven‐spot ladybirds Coccinella septempunctata (Coleoptera: Coccinellidae) to plant headspace chemicals collected from the peach‐potato aphid Myzus persicae and four commercially available Brassica cultivars; Brassica rapa L. cultivar ‘turnip purple top’, Brassica juncea L. cultivar ‘red giant mustard’, Brassica napus L. cultivar ‘Apex’, Brassica napus L. cultivar ‘Courage’ and Arabidopsis thaliana. For each cultivar/species, responses to plants that were undamaged, previously infested by M. persicae and infested with M. persicae, were investigated using dual‐choice Petri dish bioassays and circular arenas. 3 There was no evidence that ladybirds responded to headspace chemicals from aphids alone. Ladybirds significantly preferred headspace chemicals from B. napus cv. Apex that were undamaged compared with those from plants infested with aphids. For the other four species/cultivars, there was a consistent trend of the predators being recorded more often in the half of the Petri dish containing plant headspace chemicals from previously damaged and infested plants compared with those from undamaged ones. Furthermore, the mean distance ladybirds walked to reach aphid‐infested A. thaliana was significantly shorter than to reach undamaged plants. These results suggest that aphid‐induced plant chemicals could act as an arrestment or possibly an attractant stimulus to C. septempunctata. However, it is also possible that C. septempunctata could have been responding to aphid products, such as honeydew, transferred to the previously damaged and infested plants. 4 The results provide evidence to support the ‘reliability–detectability’ theory and suggest that the effectiveness of C. septempunctata as a natural enemy of aphids may be strongly affected by which species and cultivar of Brassica are being grown.     

Competitive interaction between strains of Verticillium lecanii on two insect hosts

Differences were observed in the pathogenicities of two strains of Verticillium lecanii (strain numbers 1.72 and 19.79) to the whitefly Trialeurodes uaporariorum and the aphid Macrosiphoniella sanborni. The mean pathogenicity of a mixture of the two strains was intermediate to that of the individual strains, attributable to a competitive interaction during infection. Differences between strains were observed in the production of conidia in vitro and on host insect cadavers. When hosts were infected with the dual-strain suspension, conidia of strain 19.79 only were recovered from T. vaporariorum whereas conidia from both strains were recovered from M. sanborni.     

Direct and Indirect Impacts of Infestation of Tomato Plant by Myzus persicae (Hemiptera: Aphididae) on Bemisia tabaci (Hemiptera: Aleyrodidae)

The impacts of infestation by the green peach aphid (Myzus persicae) on sweetpotato whitefly (Bemisia tabaci) settling on tomato were determined in seven separate experiments with whole plants and with detached leaves through manipulation of four factors: durations of aphid infestation, density of aphids, intervals between aphid removal after different durations of infestation and the time of whitefly release, and leaf positions on the plants. The results demonstrated that B. tabaci preferred to settle on the plant leaves that had not been infested by aphids when they had a choice. The plant leaves on which aphids were still present (direct effect) had fewer whiteflies than those previously infested by aphids (indirect effect). The whiteflies were able to settle on the plant which aphids had previously infested, and also could settle on leaves with aphids if no uninfested plants were available. Tests of direct factors revealed that duration of aphid infestation had a stronger effect on whitefly landing preference than aphid density; whitefly preference was the least when 20 aphids fed on the leaves for 72 h. Tests of indirect effects revealed that the major factor that affected whitefly preference for a host plant was the interval between the time of aphid removal after infestation and the time of whitefly release. The importance of the four factors that affected the induced plant defense against whiteflies can be arranged in the following order: time intervals between aphid removal and whitefly release > durations of aphid infestation > density of aphids > leaf positions on the plants. In conclusion, the density of aphid infestation and time for which they were feeding influenced the production of induced compounds by tomatoes, the whitefly responses to the plants, and reduced interspecific competition.     

Germination and effect of reduced humidity on expression of pathogenicity in Verticillium lecanii against the glasshouse whitefly Trialeurodes vaporariorum

Fifteen isolates of the entomopathogenic fungus Verticillium lecanii, from various hosts and locations, were bioassayed in the laboratory at 19 ± 1°C and > 95% r.h. against fourth instar scales of Trialeurodes vaporariorum. Highly pathogenic isolates generally originated from whitefly; however, there was no correlation between conidiospore size or germination rate on agar, and pathogenicity. LT₅₀ values ranged from 5.7 to > 9 days and LC₅₀ (7 days) from 1.3 × 10⁵ to 4.2 × 10⁷ spores/ml. The effect of periods in low humidity (70% r.h.) following 16 or 96 h at > 95% r.h. after immersion of whitefly scales on tomato leaf discs in a suspension of 1 × 10⁶ spores/ml, was compared for five isolates. Progressively longer periods at 70% r.h. following 16 h at > 95% r.h., reduced significantly (P < 0.001) the pathogenicity of all isolates. In these conditions isolate A was least affected by low-humidity transfer. The high pathogenicity of isolate A was associated with its more rapid development on the host cuticle during the first 16 h in high humidity. When inoculated whitefly scales were transferred to 70% r.h. after a preliminary 96 h incubation in high humidity, all five isolates achieved a higher level of pathogenicity compared with their transfer to low humidity after 16 h high humidity. Thus the screening of V. lecanii isolates in limiting humidity conditions provided a more critical assessment of their pathogenicity and of their potential success in whitefly control relevant to the glasshouse environment.     

Control of aphids by the fungus, Verticillium lecanii: Effect of spore concentration

In laboratory bioassays, aphid mortality rose while killing time decreased with increasing spore concentrations of Verticillium lecanii. However, in the glasshouse, the ability of the fungus to be spread among aphid populations on chrysanthemums quickly masked the initial effects of spraying different spore concentration. Hundred-fold differences in spore concentrations produced equally good control of the aphid, Myzus persicae, in the glasshouse.

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Controle des pucerons par le champignon: Verticillium lecanii: effet de la concentration en spores

Résumé Dans des essais de laboratoire, la mortalité des pucerons augmente et est plus rapide quand la concentration en spores de Verticillium lecanii s'élève. Cependant, en serre, la possibilité de pulvériser le champignon sur les populations de pucerons sur chrysanthème a masqué rapidement les effets initiaux des différentes concentrations de spores. Ainsi des concentrations de spores différent de cent fois produisent des résultats aussi bons en serre, contre le puceron Myzus persicae.

     

Cost-benefits of reduced aphicide usage on dwarf hops susceptible and partially resistant to damson-hop aphid

Soil‐applied imidacloprid at full (125 g a.i. ha^?1) and half approved doses gave levels of control of damson‐hop aphid, (Phorodon humuli), similar to that provided by foliar spray(s) of tebufenpyrad on the aphid‐susceptible dwarf hop cvs First Gold and Herald. On those cultivars, aphid control was unreliable on plots treated with quarter dose imidacloprid and was generally no better than on untreated plants. Aphids were virtually eliminated from the leaves by the end of July each year in all treatments consistent with the action of natural enemies. Aphid contamination of cones reflected the numbers on foliage at flowering time, but varied widely between years. Yields and percentage α‐acids content of dried hops were unaffected by the numbers of aphids on leaves early in the season and in cones at harvest, but aphid contamination reduced the economic values of crops by as much as 80%. Few P. humuli colonised the partially aphid‐resistant breeding line 23/90/08 before their numbers were regulated and consistent with natural enemy activity. Yields, percentage α‐acids content, and commercial value of harvested cones were similar in all treatments on 23/90/08 whether or not plants were treated with aphicides. The commercial risks posed by P. humuli preclude substantial reductions in aphicide usage on aphid‐susceptible dwarf hop cultivars, but future cultivars expressing a similar level of partial resistance to aphids as 23/90/08 should not need treatment with aphicides.     

The effect of leaf excision on the performance of Myzus persicae and Brevicoryne brassicae in relation to the nutrient treatment of the plants

Two groups of brussels sprout plants of one variety given different fertilizer treatments proved ‘resistant’ and ‘susceptible’ to both Myzus persicae and Breicoryrie brassicae, as measured by aphid mean relative growth rate. The hypothesis that leaf disc would fail to reflect differences in ‘nutritionallybased’ plant resistance was confirmed with B.brussicue but not M.persicae. Both aphids grew more slowly on discs than leaves of ‘susceptible’ plants; the reverse tendency showed on ‘resistant’ material. Total:(, amino nitrogen proved poorly correlated with aphid performance. Previously published (van Emden & Bashford, 1971) equations relating individual amino acids to aphid performance gave a better fit to the results, but still failed to account for the reduced performance of the aphids on ‘susceptible’ discs.     

Evaluation of Lecanicillium longisporum, Vertalec for simultaneous suppression of cotton aphid, Aphis gossypii, and cucumber powdery mildew, Sphaerotheca fuliginea, on potted cucumbers

The commercial preparation of Lecanicillium longisporum, Vertalec^® was evaluated for simultaneous suppression of cotton aphid and cucumber powdery mildew on potted cucumber plants. Vertalec was applied onto cucumber plants that had been infested with either cotton aphid, spores of Sphaerotheca fuliginea or both. Irradiation-inactivated Vertalec (II Vertalec) was also applied to an identical series of cucumber plants as a control. The Vertalec was highly pathogenic against adult aphids with an LT₅₀ of 6.9 days. II Vertalec did not affect aphid survival. Application of either active or II Vertalec significantly suppressed spore production of S. fuliginea compared to the water control. For dual control assays, Vertalec applications were made one day after infestation of both aphid and S. fuliginea onto potted cucumbers. Fifteen days after the Vertalec treatments, the numbers of surviving aphids and the production of powdery mildew spores were significantly reduced compared with the water control. The presence of aphids also suppressed S. fuliginea spore production. Our results suggest the potential of a dual role for Vertalec as a microbial control agent of aphids and powdery mildew in cucumber.     

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

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

Does the presence of grassy strips and landscape grain affect the spatial distribution of aphids and their carabid predators?

• 1 We investigated, over the course of 2 years, the spatial distribution and abundance of two species of aphid, Metopolophium dirhodum and Sitobion avenae, and predatory species of carabid. This was undertaken in 24 wheat fields in ‘coarse‐grain’ and ‘fine‐grain’ landscapes in western France. A greater percentage of the latter landscape was covered by hedgerows and grassland and the total area covered by fields and the average size of the fields were smaller.
• 2 The effects on aphid abundance of the distance from field margins, the presence of grassy strips and carabid abundance were determined in both landscapes.
• 3 Both aphid species were more abundant in the ‘fine‐grain’ landscape, which may have been a result of the higher density of semi‐natural elements. In both types of landscape, the total numbers of aphids were negatively correlated with the distance from the field margin. This may have been because aphids were dispersing from overwintering sites in field margins. The abundance of M. dirhodum was strongly negatively correlated with the presence of grassy strips in the ‘coarse‐grain’ landscape, although there were no such significant correlations for either of the aphid species in the ‘fine‐grain’ landscape.
• 4 Aphid and carabid abundances were negatively correlated in the ‘fine‐grain’ and positively in ‘coarse‐grain’ landscape.
• 5 The results obtained in the present study emphasize the importance of semi‐natural areas in agricultural landscapes in shaping the spatial distribution of aphids and carabid beetles, their natural enemies, at different spatial scales.

     

Horizontally transferred genes as RNA interference targets for aphid and whitefly control

RNA interference (RNAi)-based technologies are starting to be commercialized as a new approach for agricultural pest control. Horizontally transferred genes (HTGs), which have been transferred into insect genomes from viruses, bacteria, fungi or plants, are attractive targets for RNAi-mediated pest control. HTGs are often unique to a specific insect family or even genus, making it unlikely that RNAi constructs targeting such genes will have negative effects on ladybugs, lacewings and other beneficial predatory insect species. In this study, we sequenced the genome of a red, tobacco-adapted isolate of Myzus persicae (green peach aphid) and bioinformatically identified 30 HTGs. We then used plant-mediated virus-induced gene silencing (VIGS) to show that several HTGs of bacterial and plant origin are important for aphid growth and/or survival. Silencing the expression of fungal-origin HTGs did not affect aphid survivorship but decreased aphid reproduction. Importantly, although there was uptake of plant-expressed RNA by Coccinella septempunctata (seven-spotted ladybugs) via the aphids that they consumed, we did not observe negative effects on ladybugs from aphid-targeted VIGS constructs. To demonstrate that this approach is more broadly applicable, we also targeted five Bemisia tabaci (whitefly) HTGs using VIGS and demonstrated that knockdown of some of these genes affected whitefly survival. As functional HTGs have been identified in the genomes of numerous pest species, we propose that these HTGs should be explored further as efficient and safe targets for control of insect pests using plant-mediated RNA interference.     

Influence of <Emphasis Type="Italic">Lecanicillium attenuatum</Emphasis> on the development and reproduction of the cotton aphid, <Emphasis Type="Italic">Aphis gossypii</Emphasis>

The activity of entomopathogens on insect pests has been investigated for many species but the influence of entomopathogenic fungi on factors other than mortality relating to population increase has not been frequently studied. The influence of Lecanicillium attenuatum CS625 (=Verticillium lecanii CS625) on development and reproduction of cotton aphid (Aphis gossypii) was investigated. A conidia suspension of the isolate was applied onto first instar nymphs. Increased spore concentration did not significantly affect each nymphal stage, total nymphal period, pre-reproductive period and the age of first larviposition. A significant dose effect on reduction of life span, reproductive period and fecundity was observed in 1st and 3rd instars after spore application. When conidia were applied to 1st instars, life span was significantly reduced to 10.8 and 8.4 days at 1 × 10⁴ and 1 × 10⁸ conidia/ml, respectively from 12.2 days in the control. During the life span, total fecundity was 41 ± 7.3, 26 ± 0.8 and 22 ± 5.7 nymphs per female at 1 × 10⁴, 1 × 10⁶ and 1 × 10⁸ conidia/ml, respectively compared with 51 ± 2.0 nymphs per untreated female. Reproduction period was also significantly shortened with increasing spore concentration. Application of spores to 3rd instars showed a similar trend. However, daily fecundity of individual aphids was not affected by spore dose. It was concluded that the isolate of L. attenuatum is able to affect populations of cotton aphid by reducing life span and total fecundity as well as by killing the aphids directly.     

Hyperparasitism of Puccinia horiana and other Microcyclic Rusts

Verticillium lecanii and Aphanocladium album infected in 5 days 90–95 % of the teliospores of Puccinia horiana, the major pathogen of Chrysanthemum. This suggests the possibility to expand the use of V. lecanii, a commercial biocontrol agent against aphids, in order to control P. horiana, V. lecanii and A. album parasitized other microcyclic rusts but with a lesser frequency: P. dianthi (82 and 88 %), P. malvacearum (72 and 60 %) and P. glomerata (57 and 61 %). Cladosporium sphaerospermum and C. uredinicola were less effective than V. lecanii and A. album against all rust species tested.