Biological Control Agent: Aphthona flava Guill.
Invasive Plant Species Attacked: Leafy spurge
(Euphorbia esula) and cypress spurge (E. cyparissias)
Type of agent: Root feeding flea beetle
Status
Primary
Description and Biology
Adult:
Adults are orange-coppery coloured and 2 - 4 mm long. Of all the biocontrol Aphthona species
released in BC, Aphthona flava is the largest, with females slightly larger than males.
The flea beetles emerge from mid June through mid August, and persist into the fall if temperatures
are warm. One week after emerging, females begin to oviposit the eggs in clusters of
20 to 30 underground near spurge stems. Egg laying is done every 3 - 4 days, with females
averaging 224 each over the 3.5 month period. Oviposition is intense for the first two
months, tapering off thereafter. Adults are uniquely sensitive to air movement and shadows,
which enables them to better cope within grazed pastures where they readily jump to avoid being
consumed by livestock. Adults will move into light or filtered shaded areas.
Egg:
The pale yellow, 0.7 x 0.4 mm eggs hatch in 20 days.
Larva and pupa:
Larvae are white and slender with brown heads and often in a comma-like position.
The youngest larvae feed on latex-free fibrous roots. The later instars feed on larger
young roots. The larvae stage requires 168 days over 11°C. Once mature,
they are hardy to -6°C. Active feeding lasts about 105 days before they construct
and move into a soil particle chamber. Larvae that have not completed the required feeding
before winter or fail to experience at least 4-months of 10°C or less will not mature.
Mature larvae pupate the following spring within the chamber. Pupation begins after 28
- 57 days of warm spring temperatures. It will spend 20 - 25 days in pupae form before
emerging.
Overwintering stage:
Larvae overwinter within the soil in soil particle chambers.
Location and effectiveness of attack
Larvae feed on root hairs, young roots and parts of the main root, reducing the plant's
ability to absorb moisture and accumulate nutrients.
Adult foliar feeding is quite impressive as they consume small leaves and buds. Each Aphthona species
group feeds in a specific manner; brown coloured flea-beetles, including A. flava feed
on the leaf margins. Foliar feeding can impede the plants' photosynthesis and can cause
nutrient starvation.
Predicted and native habitat
A. flava require warm sunny locations where soils are sandy or coarse gravel.
They prefer sites with a high water table, therefore, gullies and river valley bottoms are
suitable. The flea beetles are often found on sites where widely spaced spurge grows
near cottonwood trees. Of all the Aphthona species, they require more heat units
for development. Short surrounding vegetation (grazed areas) can increase the heat at
what would otherwise be non-suitable locations. A climate with a 4-month period of temperatures
of 10°C or less is required for complete development. Like all Aphthona species,
they too compete poorly where ant populations are present.
British Columbia Experiences
Origin:
A. flava released in BC originate from Hungary and Greece. The
flea beetles were released in 1982 and 1983 near Cardston, Alberta and reared to
collectable levels before they were shipped to BC.
History:
The first A. flava release was made north west of Clinton in 1990. No recovery has
been found at this particular location. Subsequent treatments from the
Alberta population were made between 1992 and 1995 in the southern interior and have
successfully
established. In 1999 the first field collection was made from a small
site near Kamloops and continues to provide populations for redistribution.
Habitat:
A. flava has established in the Bunchgrass, Interior Douglas-fir and Ponderosa pine biogeoclimatic
zones. A release made into the Montane spruce zone has not established
and is believed to be outside of A. flava's desired habitat. All
the successfully established sites are hot locations with cottonwoods and/or water sources
nearby and have an almost equal ratio of open canopy
and lightly filtered canopy. One consistent feature at all successful
locations is where the host plants are surrounded by a mix of other plants of
similar height to the spurge. At one non-established Bunchgrass site, it
is believed that the plant density is too high and, therefore, not desirable.
The flea-beetles appear to favour widely spaced plants mixed with other
vegetation.
Field results:
A. flava sites easily established at many of the sites revisited.
Further work has been limited because many of the release sites have become
developed and are not longer accessable. In the past adults were located
the first week of August, in recent years they have been observed earlier, with
collections starting in mid July. In 1998 a site near Kamloops had no plants
remaining and by 2005 the plants had re-established and so had the A. flava
population. Since then, the site has remained intact and is used as
a collection source for further redistribution. Dispersal sampling done in 2008
indicates that A. flava may not disperse as freely as other
Aphthona species.
Not available for general distribution.
Notes
A. flava's ability to drop and leap away when threatened enables the adult to survive in a grazed
environment.
References
Harris, P. 2003. Classical biological control of weeds established biocontrol agent Aphthona
flava Guill. Root beetle. Agriculture and Agri-Food Canada. October 6, 2003. http://res2.agr.ca/lethbridge/weedbio/agents/aaphtflv_e.htm
Manitoba Agriculture, Crop Management Section. 1993. Biofacts. Provincial Government of
Manitoba.
Mason, P. G. and J. T. Huber, (editors). 2002. Biological control
programmes in Canada, 1981 - 2000. CAB International.
MFR staff observations and comments.
Powell, G. W., A. Sturko, B. Wikeem and P. Harris. 1994. Field guide to the biological
control of weeds in British Columbia. B.C. Min. For. Res. Prog.
Rees, N. E., Quimbly, Jr., P. C., G. L. Piper, E. M. Coombs, C. E. Turner, N. R. Spencer,
L. V. Knutson (editors). 1996. Biological control of weeds in the west.
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