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A Third Way for Entomophthoralean Fungi to Survive the Winter: Slow Disease Transmission between Individuals of the Hibernating Host.

Eilenberg J, Thomsen L, Jensen AB - Insects (2013)

Bottom Line: Experimentally we documented that even at the low temperature of 5 °C, the fungus was able to maintain itself in Pollenia cohorts for up to 90 days.From these observations the full winter cycle of this fungus is elucidated.The three types of winter survival are discussed in relation to fungus epidemic development.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK 1871 Frederiksberg C., Denmark. Jei@life.ku.dk.

ABSTRACT
In temperate regions, insect pathogenic fungi face the challenge of surviving through the winter. Winter is a time when hosts are immobile, low in number or are present in a stage which is not susceptible to infection. Fungi from Entomophthoromycota have so far been known to survive the winter in two ways: either as (1) thick-walled resting spores released into environment from dead hosts, or as (2) structures inside the dead host (e.g., hyphal bodies). Here we report, from the Danish environment, a third way to survive the winter, namely a slow progression and transmission of Entomophthora schizophorae in adult dipteran Pollenia hosts that hibernate in clusters in unheated attics, sheltered areas outdoors (under bark etc.). Fungus-killed sporulating flies were observed outside very early and very late in the season. By sampling adults at the time of their emergence from hibernation in late winter/early spring we documented that the fungus was naturally prevalent and killed flies after a period of incubation. Experimentally we documented that even at the low temperature of 5 °C, the fungus was able to maintain itself in Pollenia cohorts for up to 90 days. From these observations the full winter cycle of this fungus is elucidated. The three types of winter survival are discussed in relation to fungus epidemic development.

No MeSH data available.


Related in: MedlinePlus

Mortality of Pollenia caused by Entomophthora schizophorae. Adult flies (284 in total) were sampled October 25, 2001 on a hibernating site (Ørslev, Skælskør, Denmark) and incubated individually at 10 °C or 5 °C.
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insects-04-00392-f002: Mortality of Pollenia caused by Entomophthora schizophorae. Adult flies (284 in total) were sampled October 25, 2001 on a hibernating site (Ørslev, Skælskør, Denmark) and incubated individually at 10 °C or 5 °C.

Mentions: In a few cases we found old and desiccated fungus-infected cadavers indoors around window panes during winter at hibernating sites. We were not able to inspect the sites of the clusters without destroying parts of the construction, but the few dry cadavers proved that infectious flies must have been around the overwintering sites. The earliest sporulating Pollenia from outdoors was recorded on April 1, 1999, from one specimen collected in Jægerspris, Denmark. At this time of the season the Pollenia flies are just about to leave the hibernating sites and the outdoor temperatures (daily average mostly below 5 °C) do not allow an infection cycle to complete itself except after a long period of incubation. Therefore sporulating flies found outdoors very early in the season must have been infected before leaving their place of hibernation. The latest outdoor record of sporulating Pollenia was observed November 7, 2009, in one specimen collected in Copenhagen, Denmark. Sporulating flies found so late in the season strongly indicate that upon gathering for hibernation, some adult Pollenia are carriers of E. schizophorae infection and bring the infection into hibernation places. Thus, sporulating E. schizophorae-killed hosts are present outdoors from the very early start of the season immediately after winter and until the very end of the season immediately before winter. This was also confirmed by the incubation of autumn sampled Pollenia where both individuals and cohorts proved to be infected by E. schizophorae (Figure 2, Figure 3)


A Third Way for Entomophthoralean Fungi to Survive the Winter: Slow Disease Transmission between Individuals of the Hibernating Host.

Eilenberg J, Thomsen L, Jensen AB - Insects (2013)

Mortality of Pollenia caused by Entomophthora schizophorae. Adult flies (284 in total) were sampled October 25, 2001 on a hibernating site (Ørslev, Skælskør, Denmark) and incubated individually at 10 °C or 5 °C.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4553471&req=5

insects-04-00392-f002: Mortality of Pollenia caused by Entomophthora schizophorae. Adult flies (284 in total) were sampled October 25, 2001 on a hibernating site (Ørslev, Skælskør, Denmark) and incubated individually at 10 °C or 5 °C.
Mentions: In a few cases we found old and desiccated fungus-infected cadavers indoors around window panes during winter at hibernating sites. We were not able to inspect the sites of the clusters without destroying parts of the construction, but the few dry cadavers proved that infectious flies must have been around the overwintering sites. The earliest sporulating Pollenia from outdoors was recorded on April 1, 1999, from one specimen collected in Jægerspris, Denmark. At this time of the season the Pollenia flies are just about to leave the hibernating sites and the outdoor temperatures (daily average mostly below 5 °C) do not allow an infection cycle to complete itself except after a long period of incubation. Therefore sporulating flies found outdoors very early in the season must have been infected before leaving their place of hibernation. The latest outdoor record of sporulating Pollenia was observed November 7, 2009, in one specimen collected in Copenhagen, Denmark. Sporulating flies found so late in the season strongly indicate that upon gathering for hibernation, some adult Pollenia are carriers of E. schizophorae infection and bring the infection into hibernation places. Thus, sporulating E. schizophorae-killed hosts are present outdoors from the very early start of the season immediately after winter and until the very end of the season immediately before winter. This was also confirmed by the incubation of autumn sampled Pollenia where both individuals and cohorts proved to be infected by E. schizophorae (Figure 2, Figure 3)

Bottom Line: Experimentally we documented that even at the low temperature of 5 °C, the fungus was able to maintain itself in Pollenia cohorts for up to 90 days.From these observations the full winter cycle of this fungus is elucidated.The three types of winter survival are discussed in relation to fungus epidemic development.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK 1871 Frederiksberg C., Denmark. Jei@life.ku.dk.

ABSTRACT
In temperate regions, insect pathogenic fungi face the challenge of surviving through the winter. Winter is a time when hosts are immobile, low in number or are present in a stage which is not susceptible to infection. Fungi from Entomophthoromycota have so far been known to survive the winter in two ways: either as (1) thick-walled resting spores released into environment from dead hosts, or as (2) structures inside the dead host (e.g., hyphal bodies). Here we report, from the Danish environment, a third way to survive the winter, namely a slow progression and transmission of Entomophthora schizophorae in adult dipteran Pollenia hosts that hibernate in clusters in unheated attics, sheltered areas outdoors (under bark etc.). Fungus-killed sporulating flies were observed outside very early and very late in the season. By sampling adults at the time of their emergence from hibernation in late winter/early spring we documented that the fungus was naturally prevalent and killed flies after a period of incubation. Experimentally we documented that even at the low temperature of 5 °C, the fungus was able to maintain itself in Pollenia cohorts for up to 90 days. From these observations the full winter cycle of this fungus is elucidated. The three types of winter survival are discussed in relation to fungus epidemic development.

No MeSH data available.


Related in: MedlinePlus