|Checklist of the Collembola: Entomobrya multifasciata feeding on pollen grains in Sweden|
Department of Biology, University of Antwerp (RUCA), Antwerp, B-2020, Belgium
Nedstam, Barbro, Swedish Board of Agriculture, Plant Protection Centre, P.O.Box 12, S-23053 Alnarp, Sweden.
Hesseldahl, Kersti, von Essens v. 16, S-18494 Akersberga, Sweden.
Note: open any image to observe details in a larger magnification
On 1998.02.04, Kersti Hesseldahl, selling biocontrol products to pot plant producers around Stockholm, Sweden, contacted Barbro Nedstam of the Swedish Board of Agriculture, Plant Protection Centre, Alnarp, Sweden, requesting for help. Being very successful with biocontrol methods, some pot plant producers have now quitted spraying completely, and then the field is free for surprises to show up: such as springtails (Collembola).
|Fig.1. Impatiens hawkeri x hybrida ("New Guinea")|
All around the world it is very rare to find a grower not spraying his Impatiens regularly, so possibly noone else has so far noticed this still relatively small problem.
What to do? The first question : what is causing the damage?
A preliminary description, as observed by the grower with the naked eye: "elongate, cream-coloured with black stripes across the body." This description matches some species of the genus Entomobrya. A preliminary determination: Entomobrya multifasciata.
|Fig.2. Degeeria annulata LUBBOCK, 1873.
Lithograph Hollick, A.T., .
|Fig.3. Degeeria nivalis LUBBOCK, 1873.
Lithograph Hollick, A.T., .
The easiest way to catch those jumping springtails and collect them in a proper condition for identification, is to use a simple exhaustor (Fig.4). You can make one yourself with recycled plastic waste material :
----------+ +-------------- in --------+ | | +------------ out | | | | | | | | |XXX| |XX| |XXX| | | | | | | | ... | | | | | | | +--------------+ Fig.4. Exhaustor.
To use the exhaustor : just put the inlet in the neighbourhood of the springtail and suck the air from the outlet. The springtail will be sucked up by the airstream. The small filter in front of the outlet will prevent that you end up eating the springtails :-)
It becomes more easy to collect them with the exhaustor when you put an infested flower in a small white plastic box (about 5 cm high). Then disturb the springtails by ticking on the box/flower, so the irritated springtails jump from the flower onto the box floor. Then with the exhaustor it becomes very easy to collect them.
To preserve the springtails for taxonomic purposes it is best to put the live springtails into Gisin's fixative 1. If the specimens keep floating on the surface of this mixture, put a few extra drops of ethyl ether on top of the floating specimens, so they sink.
According to von Törne, the 750 ml ethanol + 250 ml
ethyl ether can be replaced by 1000 ml isopropanol.
von Törne adviced this to make the mixture more stable in time.
The ethyl ether evaporates gradualy. So, Gisin's fixative tends to degrade
in time... The isopropanol makes the fixative stable.
After 2-3 days in this mixture, put the specimens in 96% ethanol. This will make sure that body shape and colours are preserved at best.
For transport : put the preserved specimens in a glass vial with screw cap. (use a cap with rubber seal inside). Tape the cap firmly to the vial, to make sure it will not get loose by vibrations, and to prevent loss of ethanol due to heat expose during transport. Pack the vial into some loose paper tissue, and put it together into a properly sized plastic bag (blow some air into the bag, so it functions as a real air bag to protect the vial against shocks). Put the bag into a cardboard tube with metal screw caps (so the customs can check the contents...) Make sure that you put the customs sticker 'of no commercial value' onto the tube and put some description of contents (eg. scientific material : sample of Collembola, place, date, etc...) inside it.
|Ordo Entomobryomorpha BÖRNER, 1913|
|Familia Entomobryidae SCHÖTT, 1891|
|Entomobrya RONDANI, 1861 multifasciata (TULLBERG, 1871) BROOK, 1883|
|SE1||Stockholm||Färentuna||???||1998.02.12||1a25j3||Hesseldahl K||Janssens F||KAVE4 Janssens F|
The sample contains 6 specimens : 1 adult and 5 juveniles. The specimens are rather small, possibly the result of starvation or a highly specialised diet of Impatiens pollen... Entomobrya multifasciata TULLBERG, 1871 (Sweden), is a widely ditributed species, closely related to Entomobrya nivalis. That close related that some taxonomists make multifasciata a colour variant of nivalis. Anyway, Entomobrya nivalis is easely distinguished from multifasciata by the dark U shaped colour pattern on the tergite of the fourth abdominal segment. See the nice reproduction of the lithograph made in 1860 of Degeeria annulata (= Entomobrya nivalis) (Fig.2). The dorsal colour pattern of the specimens from Färentuna matches nicely with the drawing of Entomobrya decemfasciata PACKARD, 1873 (US) (cf. Handschin 1929:81(fig.150)). Schött (Sweden) has synonymised this species with Entomobrya multifasciata in 1891:17. Stach (Poland) in 1963 has made a very detailed drawing of a specimen from Samsun (Turkey) : Pl.VI fig.8, that has exactly thesame colour pattern as these specimens from Sweden. Typical for this population are the dark transverse regular stripes on thorax II to abdomen III, with triangular patches on abdomen II and III. Stach has also described a new colour variant in 1963 : regularis, that lacks the triangular patches. The pale juvenile specimens resemble that variant even more.
|Fig.5. Gut pellet with pollen fragments. 400x.
Photograph Frans Janssens © 1998.
|Fig.6. Pollen of Impatiens. 1000x
Photograph Dr Keith D. Bennet © 1995.
|Fig.7. Mandibula of E. multifasciata
Photograph Frans Janssens © 1998.
As Kersti Hesseldahl never found the eggs in the flowers they should be in the potting substrate (mainly peat). According to Dr Tryggve Persson (in litt.) eggs of Entomobrya sp. are put in the soil and the juveniles also stay in the soil (they are more sensitive to drought than the adults) before entering up on the plants. Gamasid mites will probably eat the juveniles, so the question is to find suitable predators in the soil.
|Fig.8. Hypoaspis miles.
Photograph Koppert Co. © 1998.
According to Kersti Hesseldahl's observations the infestation was reduced some time after high numbers of soil-dwelling predatory mites, such as Hypoaspis miles (Fig.8), had been introduced.
As a preliminary conclusion, Entomobrya multifasciata will not cause a lot of damage to the flowers but the commercial value of the with Collembola excrements contaminated flowers is reduced anyway... It could be that these springtails mainly feed on pollen and that the flowers get a dirty look because of over-crowding, bad table manners, excrementa... They are rather unwanted guests than pests, but for the grower this still means part of his production might not even reach the market. Biological control using polyphagous predatory mites could be a practical solution to the problem.
|95% ethanol||750 ml|
|ethyl ether||250 ml|
|glacial acetic acid||30 ml|
|40% formaldehyde||3 ml|
2 Gisin's clearing medium (1960) :
|lactic acid||100 ml|
|40% formaldehyde||4 ml|