Distribution of late instar Lymantria dispar cadavers killed by Entomophaga maimaiga on trunks of several tree species in southwestern Japan

Attachment of late-instar Lymantria dispar L. (Lepidoptera: Lymantriidae) cadavers killed by Entomophaga maimaiga Humber, Shimazu et Soper (Zygomycetes: Entomophthorales) on trunks of five dominant tree species was determined in a broadleaf forest in southwestern Japan. The highest numbers of cadavers were found attached to the trunk of Pasania glabra (Thunb.) Oerst., while there were moderate numbers of cadavers on the trunks of Quercus glauca Thunb. and Quercus serrata Thunb. and no cadavers were found attached to trunks of Ilex pedunculosa Miq. and Clethra barbinervis Sieb. et Zucc.. All examined cadavers contained E. maimaiga resting spores. The differences in cadaver attachment among tree species may influence density of E. maimaiga resting spores around tree bases, which act as reservoirs for fungal survival during unfavorable periods or over numerous years. Our results provide important information as to where to collect E. maimaiga resting spores for biological control of L. dispar, especially in forests containing many tree species.

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Formation and germination of Entomophaga maimaiga azygospores

Canadian Journal of Botany ◽

10.1139/b97-888 ◽

1997 ◽

Vol 75 (10) ◽

pp. 1739-1747 ◽

Cited By ~ 33

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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Pathogen reservoirs as a biological control resource: Introduction of Entomophaga maimaiga to North American Gypsy Moth, Lymantria dispar, populations

Biological Control ◽

10.1016/1049-9644(91)90098-k ◽

1991 ◽

Vol 1 (1) ◽

pp. 29-34 ◽

Cited By ~ 28

Author(s):

Ann E. Hajek ◽

Donald W. Roberts

Keyword(s):

Biological Control ◽

Gypsy Moth ◽

Lymantria Dispar ◽

North American ◽

Entomophaga Maimaiga ◽

Control Resource

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Quantitative Analysis of a Pathogen-Induced Premature Collapse of a “Leading Edge” Gypsy Moth (Lepidoptera: Lymantriidae) Population in Virginia

Journal of Entomological Science ◽

10.18474/0749-8004-34.1.84 ◽

1999 ◽

Vol 34 (1) ◽

pp. 84-100 ◽

Cited By ~ 11

Author(s):

R. E. Webb ◽

G. B. White ◽

K. W. Thorpe ◽

S. E. Talley

Keyword(s):

Gypsy Moth ◽

Lymantria Dispar ◽

Nuclear Polyhedrosis Virus ◽

Leading Edge ◽

Late Season ◽

Early Appearance ◽

Entomophaga Maimaiga ◽

Resting Spores ◽

Nuclear Polyhedrosis ◽

Second Wave

The population dynamics of a “leading edge” (= at the edge of the expanding gypsy moth invasion) gypsy moth, Lymantria dispar (L.), population was monitored for 3 years (1995–97), with emphasis on the interactions of the gypsy moth nuclear polyhedrosis virus (LdNPV) and the fungus Entomophaga maimaiga Humber, Shimazu, & Soper. Gypsy moth populations in the woodlots varied from very sparse to high (potentially defoliating) levels. LdNPV was strongly density dependent, being confirmed only from the higher populated woodlots. In contrast, the fungus was similarly active in both sparse and highly-populated woodlots. In 1995, the fungal epizootic developed late in the season, with most larvae succumbing during stadia 5–6 and producing mainly resting spores (azygospores). Estimated mortality due to fungus averaged 68% in high-density plots and 85% in low-density plots. LdNPV mortality occurred in a two-wave epizootic, although second-wave LdNPV mortality was undoubtedly reduced because of the reduction of late-season larvae due to fungus activity. Estimated mortality due to LdNPV averaged 14% in highly-populated plots and 1% in low-population plots. In 1996, high levels of fungal-induced mortality occurred earlier in the gypsy moth season than in the previous year. Most gypsy moth larvae in 1996 died in a mid-season wave of fungal-induced mortality, with necropsied cadavers containing only conidia. This resulted in relatively few larvae surviving to late instars. At this time, a second wave of fungus-induced mortality occurred, with over half of the necropsied cadavers containing resting spores. The depletion of the gypsy moth populations by the fungus in 1995 resulted in a greatly reduced first wave of LdNPV in all plots in 1996, and perhaps due to the early appearance of the fungus in 1996, LdNPV was nearly absent from late-season larvae collected from all plots. In 1997, gypsy moth populations were uniformly low, and no dead larvae were found in any of the plots.

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

Canadian Journal of Botany ◽

10.1139/b96-089 ◽

1996 ◽

Vol 74 (5) ◽

pp. 708-715 ◽

Cited By ~ 35

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.

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

Silva Balcanica ◽

10.3897/silvabalcanica.22.e78600 ◽

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.

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