Biological Control Agent: Aphthona cyparissiae (Koch).
Invasive Plant Species Attacked: Leafy spurge
(Euphorbia esula) and cypress spurge (E. cyparissias)
Type of agent: Root feeding flea beetle
Status
Tertiary
Description and Biology
Adult:
Adults are light brown or coppery coloured, oval-shaped and measure 3 - 4 mm long.
Their unique feature, a dark brown gap at the top of the wingcovers distinguishes them from
other Aphthona species. Adults begin to emerge in late June and continue through to August,
often persisting later in lower numbers. As with all Aphthona species, adults congregate
for feeding, mating and egg-laying. Adults will breed almost immediately and begin to
lay eggs within one week. Intensive egg laying lasts for two months before it slows for
another two months. Eggs are deposited slightly underground near spurge roots in clusters
of 20 or 30 every 3 - 5 days. Each female will lay up to 285 eggs during this period. Aphthona
cyparissiae has a longer oviposition period than A. nigriscutis. This species
remains high on plants during warm summer days, often taking short flights. On warm days
it avoids predation by jumping readily, but, as temperatures drop to 10°C or less, they move
less and are susceptible to animal grazing.
Egg:
Eggs measure 0.7 x 0.4 mm. During the three week incubation period, the pale coloured
eggs darken to brown-yellow.
Larva and pupa:
Elongated, slender, white larvae with brown heads often maintain a slight 'comma' shape
through the three instars. Upon emergence, the larvae often feed together in small groups
in a parallel formation on the youngest roots, avoiding the latex producing layers. The
first instar completes in eight days. The second instar lasts 25 to 30 days and it no
longer avoids the latex as it feeds on the outer tissue of older roots and freely moves between
them. This feeding pattern continues for 45 days through the third instar. The damage the larvae
create initiates new growth the next year, causing the plant to send out new shoots from the
attacked locations. This is essential for the insect's survival. These new shoots provide
an abundance of young roots for larvae feeding the next year and may subsequently increase
the adult population. At optimal temperatures, the larvae feeding stage will last 75
to 80 days. When cooler temperatures arrive, the larvae prepare for further development
by returning to the soil. Complete development requires a 4-month period with temperatures
at 10°C or less, (surviving to -13°C). Larvae which fail to complete
the required feeding before the onset of winter will not finish development. Pupation
takes 28 to 57 days, occurring the following year during late spring or early summer.
Overwintering stage:
Mature larvae overwinter in a prepared pupal chamber within the soil.
Location and effectiveness of attack
The larvae stage is the main factor of control as it feeds on the various roots, disabling
the plants ability to absorb and store nutrients and moisture. The feeding will suppress
the plants vigour and its reproductive ability, delay flowering, and weaken or kill plants.
Adult foliage feeding is quite impressive as they can completely consume small and young
leaves, however, the larvae contribute to the majority of the plant control. Each Aphthona species
group feeds in a specific manner; brown coloured flea-beetles, including A. cyparissiae feed
on the leaf margins. Adult feeding on leaf tissues and new shoots can impede photosynthesis,
compounding nutrient starvation. Adults usually remain close to the release showing immediate
effects of attack, but tend to disperse after five years.
Visual impacts seen at well established treatment sites:
- Reduced number of flowering stems;
- A temporary increase of short, non-flowing stems is common, and will disappear after
about four years; and
- Native grasses replace the voids left from dead spurge.
Predicted and native habitat
A. cyparissiae prefers habitats similar to that of A. nigriscutis , but,
in slightly moister areas often located in the bottom third of valley slopes and in depressions.
They prefer spurge sites within a bunchgrass plant community where soils have a sand content
between 40 and 60%. A. cyparissiae will do well in areas where A. nigriscutis populations
have decreased from the result of increased moisture. Of all the Aphthona species
in BC, this species is most tolerant of spurge at low density rates of 50 - 125 stems/m²andwhen
mature plants reach at least 51 cm tall. It will not compete well at locations where
there are high ant populations. A climate with a 4-month period of temperatures of 10°C
or less is required for complete development. A. cyparissiae shows a strong preference
for cypress spurge over leafy spurge.
British Columbia Experiences
Origin:
The A. cyparissiae populations released in BC originated from Eurasian stock reared
in Alberta and Saskatchewan.
History:
The first A. cyparissiae BC release in BC occurred in 1989 in the east Kootenays. In 1994, a population
mixed with A. nigriscutis was released near Kamloops and flourished within three years.
Several thousands of adults have been collected from this location for redistribution and today
the site has significantly less spurge. Since 1989 almost 100 A. cyparissiae releases
have been made in BC. A. cyparissiae and A. nigriscutis
occur in mixed populations, dispersing freely in BC.
Habitat:
A. cyparissiae has been released and found established in the Bunchgrass and Interior
Douglas-fir biogeoclimatic zones. It has also been released into the Sub-boreal spruce
zone, but there is no record of it becoming established before a high risk invasive plant established
on the site and required immediate herbicide treatment.
Field results:
Past monitoring results found mixed A. cyparissiae/A. nigriscutis
populations established and well dispersed at most the release sites. It
is difficult to separate these two species and, therefore, it is acceptable to
consider them as mixed populations in field results. Adult populations drop significantly when the plants
become dried in August. When temperatures rise rapidly over a short period, adults become
harder to locate (adults found abundantly in 1998 disappeared quickly after several consecutive,
intensely hot days).
Sweep for adults through early summer on warm and hot days and aspirate to clean the collection.
During bright, hot days, adults rapidly rise on plants, allowing for repeat sweeping. Sites
are usually harvestable by three years following treatment.
Literature sources indicate, new treatments provide earlier results when large numbers
are released. When treatments are made with small numbers, the resulting populations tend to
persist with small numbers, never showing a significant upward surge in population.
Notes
A. cyparissiae and A. nigriscutis habitats overlap and are visually similar,
making identification between the two difficult.
References
Harris, P. 1994. Biological control of leafy spurge on the prairies. Leafy Spurge News.
Vol. XVI, Issue 3: 2.
Harris, P. 2006. Classical biological control of weeds. Established biological control
agent Aphthona cyparrisiae (Koch). Root beetle. Agriculture and Agri-Food Canada. December
8, 2006. http://res2.agr.ca/lethbridge/weedbio/agents/aaphtcyp_e.htm
Mason, P. G. and J. T. Huber. Biological control programmes in Canada, 1981-2000.
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.
Saskatchewan Agriculture and Food and Saskatchewan Rural Development. No date. Biological
control of leafy spurge. Farm Facts. Gov. of Can. 3 p.
Spencer, N. R. 1997. Niche specificity of insects introduced for leafy spurge control.
Leafy Spurge News. Vol. XIX, Issue 1: 8.
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