Expression of Entomophaga maimaiga at Several Gypsy Moth (Lepidoptera: Lymantriidae) Population Densities and the Effect of Supplemental Watering

2004 ◽  
Vol 39 (2) ◽  
pp. 223-234 ◽  
Author(s):  
Ralph E. Webb ◽  
Mary Willeford Bair ◽  
Geoffrey B. White ◽  
Kevin W. Thorpe
Keyword(s):  
Gypsy Moth ◽  
Larval Mortality ◽  
High Density ◽  
Mortality Factor ◽  
Egg Mass ◽  
Low Density ◽  
Mortality Factors ◽  
Natural Rainfall ◽  
Resting Spore ◽  
Entomophaga Maimaiga

Assessment of gypsy moth, Lymantria dispar L. (Lepidoptera: Lymantriidae), populations in western Virginia during the year 2000, showed that larval mortality factors differed as a function of population density. Larval mortality, primarily due to the gypsy moth-specific entomopathogenic fungus Entomophaga maimaiga Humber, Shimazu and Soper, was 28.7% in high-density plots (averaging 476.8 larvae per 5 burlap bands) but only 16.5% in low-density plots (averaging 60.8 larvae per 5 burlap bands). On the contrary, “missing” was the dominant mortality factor in low-density plots (6.5% in high-density plots vs 65.6% in low-density plots). This study was designed to assess the potential for inducing an earlier epizootic by facilitating the early germination of resident resting spores by spraying water around the base of trees. Eight of the high-density plots with measured natural E. maimaiga resting-spore loads were selected for a supplemental watering study conducted in 2001. Four plots received weekly watering to supplement natural rainfall, and four received only natural rainfall (control plots). More E. maimaiga occurred in watered plots than in control plots; however, treatment effects for watering were not significant. For a 01 June collection, fungal levels were 17% (ground) and 12% (canopy) for the watered plots vs 12% (ground) and 10% (canopy) for control plots. For a 15 June collection, fungal levels were 74% (ground) and 29% (canopy) for the watered plots vs 60% (ground) and 14% (canopy) from control plots. Height effects were significant for the second date. Egg mass populations in watered plots declined significantly (78%) compared with control plots (4%) (P = 0.0433), possibly reflecting further mortality occurring after the second collection.

scholarly journals Effectiveness of Diflubenzuron and Bacillus thuringiensis Against Gypsy Moth Populations

1997 ◽  
Vol 14 (3) ◽  
pp. 135-140 ◽  
Author(s):  
Kevin W. Thorpe ◽  
Richard L. Ridgway ◽  
Ralph E. Webb
Keyword(s):  
Bacillus Thuringiensis ◽  
Population Density ◽  
Gypsy Moth ◽  
Mass Density ◽  
Larval Mortality ◽  
Larval Density ◽  
Egg Mass ◽  
Percent Reduction ◽  
Moth Population ◽  
Oak Trees

Abstract Aerial applications of Bacillus thuringiensis Berliner subsp. kurstaki (74.1 billion international units/ha per application; single and double applications), diflubenzuron [69 g (ai)/ha], and no treatment were evaluated. Treatment effects were estimated from frass collections, defoliation, counts of pupae under burlap, and egg-mass counts. Estimates of larval density in the canopy 20 days after treatment ranged from 318.3 to 55.5 larvae per m² in the control- and diflubenzuron-treated plots, respectively. Larval density was reduced in all treatments, and was lowest in the plots treated with diflubenzuron and two applications of B. thuringiensis. Population density rapidly declined in the control plots, and by June 20, when larvae were predominantly in the fifth and sixth instars, no significant differences in larval density were detected among the treatments. Significantly less defoliation occurred to oak trees in the treated plots, but no differences were detected among the spray treatments. Counts of pupae under burlap, postseason egg-mass counts, and percent reduction in egg-mass density did not differ significantly among treatments or versus controls. These results suggest that diflubenzuron and double B. thuringiensis treatments caused higher levels of larval mortality than occurred with a single B. thuringiensis application, but that with a naturally declining gypsy moth population the final levels of damage were the same under all treatments. North. J. Appl. 14(3):135-140.

Augmenting Nucleopolyhedrovirus Load in Gypsy Moth (Lepidoptera: Lymantriidae) Populations with Egg Mass Treatments

2003 ◽  
Vol 38 (2) ◽  
pp. 300-313 ◽  
Author(s):  
R. E. Webb ◽  
G. B. White ◽  
K. W. Thorpe
Keyword(s):  
Gypsy Moth ◽  
Early Treatment ◽  
Adult Emergence ◽  
Field Studies ◽  
Host Population ◽  
Egg Mass ◽  
Moth Population ◽  
Egg Masses ◽  
Entomophaga Maimaiga ◽  
Virus Dose

Previous observations show that gypsy moth, Lymantria dispar L., mortality induced by the fungus Entomophaga maimaiga Humber, Shimazu & Soper is quickly manifested as host population density increases. However, the gypsy moth nucleopolyhedrovirus (LdMNPV) lags behind the rebounding gypsy moth population. In this study, egg masses were contaminated with virus to successfully augment LdMNPV in gypsy moth populations in Virginia. Laboratory bioassays determined the approximate LdMNPV dose to apply to egg masses with and without the addition of the virus enhancer Blankophor BBH to the spray mixture. The highest dose of virus (5.3 × 105 PIBs/mL) tested without Blankophor BBH gave 82.3% mortality. Mortality for this virus dose increased to 91.8% when 1% Blankophor BBH was added. Field studies established that application of virus at an earlier date (04 April) was as efficacious as an application made at a later date (12 April); this study also included a further assessment of the addition of Blankophor BBH to the spray mixture. While application of LdMNPV + Blankophor BBH resulted in faster kill, levels of kill were similar (88.0% for early treatment and 78.8% for later treatment for virus applied alone versus 87.8% for early treatment and 89.1% for later treatment for virus + Blankophor BBH). However, a higher than expected number of cadavers in the LdMNPV + Blankophor BBH treatments had few or no polyhedral inclusion bodies (PIBs). Finally, virus infection resulting from the application of LdMNPV to pupae in June 1998 was compared with infection levels seen after the application of virus to egg masses in April 1999. The April 1999 treatment to egg masses clearly resulted in a higher kill of emerging larvae (=79.3% mortality) compared to the June 1998 treatment to female pupae (with virus incorporated into the egg masses laid by females after adult emergence) (=13.7% mortality). The virus was recovered season-long from larvae collected from populations in the treated plots (but not from control plots), indicating within season spread.

Comparison of Aerially-Applied Gypchek Strains Against Gypsy Moth (Lepidoptera: Lymantriidae) in the Presence of an Entomophaga maimaiga Epizootic

2005 ◽  
Vol 40 (4) ◽  
pp. 446-460 ◽  
Author(s):  
R. E. Webb ◽  
G. B. White ◽  
J. D. Podgwaite ◽  
V. D'Amico ◽  
J. Slavicek ◽  
...  
Keyword(s):  
Gypsy Moth ◽  
Larval Mortality ◽  
Larval Population ◽  
Usda Forest Service ◽  
Entomophaga Maimaiga ◽  
Wave Effects ◽  
Late Instar ◽  
Fungal Entomopathogen ◽  
Occlusion Bodies ◽  
Second Wave

The standard strain (LDP-226) of Gypchek®, a nucleopolyhedrovirus product registered by the USDA Forest Service against the gypsy moth, Lymantria dispar (L.), was compared against a strain, LdMNPV-203NL (NL = nonliquefying), that was developed for production in cell culture. Both strains were applied by air to U.S. government property in Prince Georges Co., MD, in early May 2003 at the rate of 1 × 1012 occlusion bodies per ha. The two goals of the study were (1) to compare the first and second wave effects of the two strains against gypsy moth populations; and (2) to delineate the combined effects of the applied virus and the expected epizootic of the gypsy moth specialist fungal entomopathogen Entomophaga maimaiga Humber, Shimazu, and Soper. Heavy rainfall in May and June preceded a massive epizootic of E. maimaiga, whose effects did not mask the first wave of viral mortality. When the effect of application sequence was considered, it was concluded that the two strains were equivalent in their first-wave impacts. High fungal-induced mid and late-season gypsy moth larval mortality suppressed the second wave of virus at all evaluation sites. There were no obvious differences in the second waves engendered by the two LdNPV strains in the greatly reduced late-instar larval population.

Detecting the titer in forest soils of spores of the gypsy moth (Lepidoptera: Lymantriidae) fungal pathogen, Entomophaga maimaiga (Zygomycetes: Entomophthorales)

2002 ◽  
Vol 134 (2) ◽  
pp. 269-279 ◽  
Author(s):  
Ronald M. Weseloh ◽  
Theodore G. Andreadis
Keyword(s):  
Forest Soils ◽  
Gypsy Moth ◽  
Fungal Pathogen ◽  
Spore Viability ◽  
Resting Spore ◽  
Entomophaga Maimaiga ◽  
Resting Spores ◽  
A Site ◽  
Spore Load

AbstractBioassays and direct counts were used to assess the abundance of resting spores of the gypsy moth, Lymantria dispar (L.), fungal pathogen, Entomophaga maimaiga Humber, Shimazu and Soper in forest soils. Resting spores in soil collected in October, January, and March and held under refrigeration germinated as readily as spores collected in April, but those collected in April germinated faster. Bioassays of resting spores in soils from different sites in Connecticut were directly related to results obtained from physically counting spores in the soil, and weakly correlated with a previously developed forest-based bioassay. The number of resting spores in a site was inversely related to the number of years since the site had last been defoliated by the gypsy moth, resulting in an implied maximum viability of resting spores of about 10 years. This maximum longevity was similar to a direct measure of long-term resting-spore viability. The study implies that resting-spore load in the soil may be an important determinant of the ability of the pathogen to control the gypsy moth.

The natural regulation of giant tortoise populations on Aldabra Atoll: recruitment

1979 ◽  
Vol 286 (1011) ◽  
pp. 177-188 ◽  
Keyword(s):  
High Density ◽  
Annual Rainfall ◽  
Egg Mass ◽  
First Year ◽  
Low Density ◽  
Isolated Populations ◽  
High Density Population ◽  
Density Area ◽  
Low Density Area ◽  
Density Population

The reproductive ecology of the giant tortoise ( Geochelone gigantea Schweigger) in three isolated populations was studied for 2 years on Aldabra Atoll. Density-dependent recruitment was demonstrated. Nest destruction in the low density area was dependent on the density of mature females providing a mechanism for regulating population size. Increases in annual rainfall and the resultant increase in food availability induced an increase in mean egg mass in the low density area (and thereby total hatchling production), whereas in the high density population mean clutch size, mean egg mass, total number of nests and total hatchling production all increased significantly. Large eggs produced large hatchlings which survived better during the first year than hatchlings from small eggs. Hatchling mortality was 94 and 81 % in the first year in the high and low density populations respectively. Recruitment into the 5 year age class (after which predation is considered negligible) had almost ceased in the high density population compared with 0.44 per 100 breeding females per year in the low density population.

Types of spores produced by Entomophaga maimaiga infecting the gypsy moth Lymantria dispar

1996 ◽  
Vol 74 (5) ◽  
pp. 708-715 ◽  
Author(s):  
Ann E. Hajek ◽  
Mitsuaki Shimazu
Keyword(s):  
Gypsy Moth ◽  
Lymantria Dispar ◽  
Fungal Pathogen ◽  
Fungal Spores ◽  
Serial Passage ◽  
Molting Cycle ◽  
Resting Spore ◽  
Entomophaga Maimaiga ◽  
Resting Spores ◽  
Study Support

We investigated the association of environmental factors (temperature, photoperiod, host molting status) and fungal factors (isolate, dose, strain attenuation) with the production of conidia versus resting spores by the entomopathogenic fungus Entomophaga maimaiga infecting the larvae of the gypsy moth Lymantria dispar. Fungal spores produced from individual cadavers of larvae killed by E. maimaiga can include conidia discharged from the cadaver surface, resting spores (azygospores) within the cadaver, or both spore types. The single factor having the greatest impact on the type of spore produced was host age; second instars virtually never contained resting spores, independent of temperature, while fifth instar cadavers contained resting spores more frequently at higher temperatures. However, there was increased conidiation at lower temperatures. Photoperiod was the only factor studied that did not significantly influence the type of spore produced. Resting spore production was negatively associated with the molting cycle; cadavers of those larvae that molted or exhibited premolt characteristics during the period between infection and death contained fewer resting spores. Increased fungal dose yielded more resting spores, as did extensive serial passage, which simultaneously caused a decrease in conidiation. Fungal isolates varied in the types of spores produced, with fewer cadavers of larvae killed by the least virulent isolate discharging conidia. Results from this study support the hypothesis that both the condition of the fungal pathogen as well as the environment surrounding it contribute to the types of spores produced. Keywords: fungal sporulation, resting spores, azygospores, Entomophthorales, Entomophaga maimaiga, biological control.

MORTALITY FACTORS AFFECTING EGGS OF THE FOREST TENT CATERPILLAR, MALACOSOMA DISSTRIA (LEPIDOPTERA: LASIOCAMPIDAE)

1972 ◽  
Vol 104 (5) ◽  
pp. 705-710 ◽  
Author(s):  
J. A. Witter ◽  
H. M. Kulman
Keyword(s):  
Larval Mortality ◽  
Malacosoma Disstria ◽  
Egg Mass ◽  
Forest Tent Caterpillar ◽  
Mortality Factors ◽  
Egg Masses ◽  
Factors Affecting ◽  
Egg Mortality ◽  
Significant Difference ◽  
Tent Caterpillar

AbstractParasitism, infertility, and death of fully developed first-stage larvae in eggs (pharate larvae) were the egg mortality factors encountered during a 1967–69 study on the bionomics of the forest tent caterpillar, Malacosoma disstria Hübner, in northern Minnesota. There was no significant difference in the average yearly per cent parasitization and infertility per egg mass; these ranged from 7 to 10% and 1 to 3%, respectively. There was a year to year difference in pharate larval mortality. It ranged from 39% in 1968 to only 9 and 3% for 1967 and 969. Studies showed that egg masses had a tendency to be either nearly complete y hatched or unhatched only in 1968. The variation in pharate larval mortally in these studies suggests qualitative differences in the population. The pharate larval mortality has the potential of influencing population trends of the forest tent caterpillar.

scholarly journals Biological control of gypsy moth (Lymantria dispar) by the entomopathogenic fungus Entomophaga maimaiga in Bulgaria in 2021

2021 ◽  
Vol 22 (3) ◽  
pp. 17-27
Author(s):  
Georgi Georgiev ◽  
Plamen Mirchev ◽  
Margarita Georgieva ◽  
Mihail Kechev ◽  
Sevdalin Belilov ◽  
...  
Keyword(s):  
Biological Control ◽  
Gypsy Moth ◽  
Lymantria Dispar ◽  
Entomopathogenic Fungus ◽  
Control Programme ◽  
Egg Mass ◽  
Moth Population ◽  
Entomophaga Maimaiga ◽  
Forest Enterprises ◽  
Gipsy Moth

In 2021, biological control programme against gipsy moth (Lymantria dispar) populations was carried out by introduction of the entomopathogenic fungus Entomophaga maimaiga on the territory of four State Forest Enterprises: Municipal Enterprise (ME) ‘Management of Municipal Forests, Agriculture and Forestry’, Nessebar; State Game Enterprises (SGE) Nessebar and Balchik; State Forestry (SF) Vidin. The pathogen was introduced during the period 15-26.03.2021 in 34 localities - five in ME Nessebar, eight in SGE Nessebar, ten in SGE Balchik and eleven in SF Vidin. The average number of gypsy moth population density in the locations of introduction was relatively high, ranging between 0.4-15.9 egg mass/tree in the area of ​​SGE Balchik and 11.9-65.0 egg mass/tree in the area of ​​ME Nessebar. The average mortality of young gypsy moth caterpillars (first-third instar) due to E. maimaiga varied between 2.6% (SGE Balchik) and 13.0% (SF Vidin), and of caterpillars in later fourth-sixth instar - between 20.7% (SF Vidin) and 52.4% (ME Nessebar). The overall mortality of the gipsy moth caterpillars due to E. maimaiga was lowest in the region of SGE Balchik (26.1%), followed by SF Vidin (33.7%), SGE Nessebar (48.5%) and ME Nessebar (55.9%). As a result of the introduction, gipsy moth severe outbreaks in the region of Nessebar was significantly suppressed. The high number of E. maimaiga resting spores persists in the surface layers of the soil in the other two areas (Vidin and Balchik) has the potential to suppress L. dispar attacks in next years.

Formation and germination of Entomophaga maimaiga azygospores

1997 ◽  
Vol 75 (10) ◽  
pp. 1739-1747 ◽  
Author(s):  
Ann E. Hajek ◽  
Richard A. Humber
Keyword(s):  
Gypsy Moth ◽  
Lymantria Dispar ◽  
Early Summer ◽  
Resting Spore ◽  
Body Development ◽  
Entomophaga Maimaiga ◽  
Resting Spores ◽  
Late Instar ◽  
Hyphal Bodies ◽  
Hyphal Body

Azygospores (resting spores) of the gypsy moth fungal pathogen Entomophaga maimaiga are produced in abundance during late spring and early summer in late-instar gypsy moth larvae (Lymantria dispar). Azygospores subsequently form, each from an individual hyphal body. Development of azygospores occurs asynchronously over several days; by 5 days after host death, greater than 60% of fungal cells had matured from hyphal bodies to the final double-walled resting state. Azygospores undergo constitutive dormancy and, under field conditions, will not germinate for approximately 9 months after production. Azygospores do not require nutrients to germinate. Germination of field-collected resting spores under laboratory conditions began more than 2 days after transfer from the field to the laboratory. Higher levels of germination occurred with a 14 h L: 10 h D cycle compared with 13 h L: 11 h D or 12 h L: 12 h D. Azygospores germinate relatively slowly and germination rates were greatest between 4 and 8 days, with a total of 71.8 or 72.5% germination by 16 days at 14 h L: 10 h D and 15 or 20 °C, respectively. During 1994 and 1995, resting spores began causing infections in experimental larvae in early May, about 1 – 2 weeks prior to gypsy moth egg hatch, and ceased causing infections in mid to late June, when late instars were present. This latter timing is a correction of previously reported information. Bioassays investigating resting spore activity determined that during 1994, once resting spores began germinating in the field, levels of infection were positively associated with soil moisture. Key words: azygospores, resting spores, entomopathogenic fungi, Entomophaga maimaiga, Lymantria dispar, biological control.

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