Vladimir Gouli

Colletotrichum acutatum var. fioriniae (teleomorph: Glomerella acutata var. fioriniae var. nov.) infection of a scale insect.

An epizootic has been reported in Fiorinia externa populations in New York, Connecticut, Pennsylvania and New Jersey. Infected insects have profuse sclerotial masses enclosing their bodies. The most commonly isolated microorganism from infected F. externa was Colletotrichum sp. A morphological and molecular characterization of this fungus indicated that it is closely related to phytopathogenic C. acutatum isolates. Isolates of Colletotrichum sp. from F. externa in areas of the epizootic were similar genetically and were named Colletotrichum acutatum var. fioriniae var. nov. based on our findings. In vitro and in planta mating observed between isolates of C. acutatum var. fioriniae could serve as a possible source of genetic variation and might give rise to new biotypes with a propensity to infect insects. Only one other strain, C. gloeosporioides f. sp. ortheziidae, has been reported to show entomopathogenic activity.

Whey for mass production of Beauveria bassiana and Metarhizium anisopliae

Spore production of Beauveria bassiana and Metarhizium anisopliae was studied in a novel whey-based culture media. Spore yield and viability were determined for two B. bassiana (GHA-726 and CA-603) and two M. anisopliae (CA-1 and IMI 330189) isolates following production in three whey-based systems: solid, liquid, and a diphasic production system. Our study indicated that whey permeate can be used effectively for production of spores of entomopathogenic fungi. However, spore yield and viability were significantly influenced by fungal isolate, whey concentration, and the type of production process used. Under the conditions defined in the present study, spore yields ranging from 1.3x10(9)-10x10(11) spores l(-1) of whey medium could be obtained depending on the strain and production process used. Our study revealed that spores produced by all strains in whey-based solid and liquid media showed between 73-99% viability; germination rates were comparable with those obtained using the standard SDA medium. In the two-stage production process, the viabilities of conidia produced by GHA-726, CA-603, and CA-1 were 35-86, 32-98, and 6-29%, respectively; viability was correlated with whey concentration and isolates. Whey permeate can be used as a growth substrate for mass production of biocontrol fungi. We hypothesize that spore yield and viability could be improved by careful selection of whey content in the medium, incorporation of critical additives and optimization of culture conditions.

Effect of the entomopathogenic fungi on mortality and injury level of western flower thrips, Frankliniella occidentalis.

Abstract The harmfulness of western flower thrips, Frankliniella occidentalis, including insect mortality and plant injury level after the application of three productive and active strains of the entomopathogenic fungi, Metarhizium anisopliae, Lecanicillium lecanii, and Beauveria bassiana, was estimated. LC50 of the M. anisopliae for second instar larvae was twice that of L. lecanii and 1.7 times higher than that of B. bassiana. The average number of damage zones on leaf surfaces after the application of fungi (5×106 spores per ml) constituted 3.0 ± 0.7, 15.9 ± 4.6, and 22.4 ± 4.3 per leaf, respectively (control 67.0 ± 5.7). The total damage area of the leaves was 2.2 ± 0.4, 5.2 ± 0.9, and 4.5 ± 0.6% (control 13.7 ± 3.0%), respectively. Fungi B. bassiana and L. lecanii showed the same level of insect mortality but the number of damage zones and the total damage areas had significant differences. The most effective fungus was found to be M. anisopliae which provided higher plant protection as measured by the decrease in plant injury.

Virulence of select entomopathogenic fungi to the brown marmorated stink bug, Halyomorpha halys (Stål) (Heteroptera: Pentatomidae).

The brown marmorated stink bug. Halyomorpha halys, (BMSB) is an exotic pest causing damage to fruits and vegetables. They also transmit diseases. Integrated pest management strategies are lacking for this invasive. For the first time, information is presented on the virulence of several entomopathogenic fungi against BMSB. Three Beauveria bassiana and two Metarhizium anispoliae isolates were bioassayed against adult BMSB. One B. bassiana isolate was the active ingredient in BotaniGard® which produced 85 and 100% mortality in 9 and 12 days post treatment, respectively. Experimental isolates ERL 1170 and ERL 1540 were also efficacious. Metarhizium anispoliae isolates produced lower mortalities than the B. bassiana isolates. Data presented showed the potential for management of BMSB with entomopathogenic fungi.

Haemocytes of the hemlock woolly adelgid Adelges tsugae Annand (Hom., Adelgidae) and changes after exposure to low temperatures

The main cellular components of the haemolymph of Adelges tsugae Annand were identified from individuals collected in Massachusetts, USA in February and October 1997. The cell types present were formative cells, plasmatocytes, adipohaemocytes, vermiform cells, prohaemocytes and oenocytoids. Vermiform cells were the most abundant. Very few oenocytoids were found. They were significantly more cells of all types in the haemolymph of A. tsugae collected in October than in those collected in February. Adelges tsugae collected in February were exposed in the laboratory to ‐20, ‐25 and ‐30°C for 2, 4 and 8h. No intact cells were found in the haemolymph of A. tsugae exposed to ‐30°C. Haemocytes were damaged by exposure to ‐20 and ‐25°C. The effect of these temperatures on the different cell types is presented.

Fungi associated with a natural epizootic in Fiorinia externa Ferris (Hemiptera: Diaspididae) populations.

Stands of eastern hemlock [(Tsuga canadensis (L.) Carrière] in the northeastern United States are in decline, in part from the attack of elongate hemlock scale, Fiorinia externa Ferris (Hemiptera: Diaspididae). From 2001 to the present, a natural epizootic has been observed in populations of F. externa. Initially discovered at the Mianus River Gorge Preserve in Bedford, New York, the epizootic has also been detected in Pennsylvania, New Jersey and Connecticut. Understanding and assessing the identity of the pathogenic micro‐organisms responsible for this natural mortality is crucial for developing biological controls for this pest. We have isolated and taxonomically and genetically identified entomopathogens, phytopathogens and endophytic fungi associated with F. externa. Isolates of the following were obtained: Colletotrichum sp., Lecanicillium lecanii, Beauveria bassiana, Metarhiziopsis microspora, Myriangium sp., Mycosphaerella sp. anamorph, Nectria sp., Botrytis sp., Phialophora sp. and Fusarium sp.

Fungi associated with the hemlock woolly adelgid, Adelges tsugae, and assessment of entomopathogenic isolates for management

Abstract Fungi associated with the hemlock wooly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae), were collected throughout the eastern USA and southern China. Twenty fungal genera were identified, as were 79 entomopathogenic isolates, including: Lecanicillium lecanii (Zimmermann) (Hypocreales: Insertae sedis), Isaria farinosa (Holm: Fries.) (Cordycipitaceae), Beauveria bassiana (Balasamo) (Hyphomycetes), and Fusarium spp (Nectriaceae). The remaining fungal genera associated with insect cadavers were similar for both the USA and China collections, although the abundance of Acremonium (Hypocreaceae) was greater in China. The entomopathogenic isolates were assayed for efficacy against Myzus persicae (Sulzer) (Homoptera: Aphididae) and yielded mortality ranging from 3 to 92%. Ten isolates demonstrating the highest efficacy were further assessed for efficacy against field-collected A. tsugae under laboratory conditions. Overall, two B. bassiana, one L. lecanii, and a strain of Metarhizium anisopliae (Metchnikoff) (Hypocreales: Clavicipitaceae), demonstrated significantly higher efficacy against A. tsugae than the others. Isolates were further evaluated for conidial production, germination rate and colony growth at four temperatures representative of field conditions. All isolates were determined to be mesophiles with optimal temperature between 25–30° C. In general, conidial production increased with temperature, though two I. farinosa produced significantly more conidia at cooler temperatures. When efficacy values were compared with conidial production and temperature tolerances, Agricultural Research Service Collection of Entomopathogenic Fungi (ARSEF) 1080, 5170, and 5798 had characteristics comparable to the industrial B. bassiana strain GHA.

Virulence of BotaniGard® to Second Instar Brown Marmorated Stink Bug, Halyomorpha halys (Stål) (Heteroptera: Pentatomidae)

The brown marmorated stink bug, Halyomorpha halys (Stål) (BMSB) is an exotic invasive insect originating in East Asia, currently causing significant damage to fruits, vegetables and other crops throughout most of the Mid-Atlantic states of the U.S. It also is a nuisance pest, entering homes in the fall in search of suitable overwintering sites. Two formulations of BotaniGard® with a strain of Beauveria bassiana (GHA) as the active ingredient were tested against second instar BMSB. Both the wettable powder and the emulsifiable suspension formulations were efficacious at 1 × 107 conidia mL−1, causing 67%–80% mortality 9 days post treatment and 95%–100% after 12 days. The wettable powder formulation was slightly more efficacious.

Entomopathogenic Fungi Associated with Exotic Invasive Insect Pests in Northeastern Forests of the USA

Mycopathogens of economically important exotic invasive insects in forests of northeastern USA have been the subject of research at the Entomology Research Laboratory, University of Vermont, for the last 20 years. Elongate hemlock scale, European fruit lecanium, hemlock woolly adelgid and pear thrips were analyzed for the presence of mycopathogens, in order to consider the potential for managing these pests with biological control. Fungal cultures isolated from insects with signs of fungal infection were identified based on morphological characters and DNA profiling. Mycopathogens recovered from infected insects were subdivided into three groups, i.e., specialized entomopathogenic; facultative entomopathogens; ubiquitous opportunistic contaminants. Epizootics were caused by fungi in the specialized group with the exception of M. microspora, P. marquandii and I. farinosa. Inoculation of insects in laboratory and field conditions with B. bassiana, L. muscarium and Myriangium sp. caused insect mortality of 45 to 95%. Although pest populations in the field seemed severely compromised after treatment, the remnant populations re-established themselves after the winter. Although capable of inducing high mortality, a single localized aerial application of a soil-dwelling fungus does not maintain long-time suppression of pests. However, it can halt their range expansion and maintain populations below the economic threshold level without the use of expensive insecticides which have a negative impact on the environment.

Persistence of Beauveria bassiana sensu lato and Metarhizium anisopliae sensu lato in Vermont (USA) forest soil

Persistence of granular formulations of Beauveria bassiana sensu lato, strains GHA726 and ERL1170, and Metarhizium anisopliae sensu lato, strains ERL824 and ERL701, applied to forest soil was documented. One formulation was prepared by producing fungi on millet and at application adding cooked, dried millet to provide additional nutrients for fungal growth. The other was made by producing fungi on corn starch ‘packing peanuts’, a biodegradable packaging material, adding additional packing peanuts as a nutrient base. The trial was conducted in three sites in a forest predominating in sugar maple (Acer saccharum) in Underhill, VT, USA. In each site, 33 dominant sugar maples were randomly selected. A 1-m2 plot located 1 m from the bole of the tree was established. Soil samples were collected before application, and 1 h, 2, 4, 8, 12 and 16 wk post-application. Fungal levels were estimated based on number of colony-forming units (CFUs). A significant increase in CFUs was observed 2 wk post-application in plots treated with isolates GHA726, ERL1170 and ERL824 as a result of fungal reproduction on nutrients in the formulations. Evidence of greater persistence for the B. bassiana than the M. anisopliae isolates was observed, based on CFU levels over time. Isolates formulated with millet proliferated more than those on packing peanuts. Use of entomopathogenic fungi in forest soil has potential for managing soil-dwelling insect pests such as pear thrips, Taeniothrips inconsequens, and the black vine weevil, Otiorhynchus sulcatus, though the type of formulation and the specific isolate used must be selected carefully.