Biological Control Agent: Eteobalea serratella Treitschke
Type of agent: Root feeding moth
Status
Primary
Description and Biology
Adult:
The moths have sender bodies measuring 8 - 9 mm long. Adults are black with yellow
heads. Their black wings are covered with golden metallic flecks. Their normal
wingspan of 16 - 18 mm decreases in crowded larval development conditions. Adults begin
to emerge in early summer and live for about two weeks in the field (survival in the lab is
up to four weeks). During this lifespan, they do not feed. Adults are weak fliers.
Females emerge with up to 60 developed eggs and begin oviposition immediately. They will
lay up to 180 eggs close to the stem base. The moths possess a good host finding ability,
seeking new sites within short flights.
Egg:
The white, 0.3 x 0.5 mm eggs change to yellow as they mature. Eteobalea serratella eggs
have parallel lines (striate), differing from E. intermediella eggs which have a network
of irregular meshing lines (reticulate). Eggs hatch in 9 - 10 days at 25°C,
most frequently during the night or early mornings. Just prior to hatching, red eye spots
can be seen inside the egg. E. serratella eggs show less susceptibility to fungal
attack than E. intermediella.
Larva and pupa:
The newly hatched larvae bore into the plant at leaf axils or other soft tissue points
where entry is easiest. The larvae move downward to the root, feeding into the root crown
and on small roots. They can mine all parts of the roots. The tunnels are lined
with a silken substance. Multiple larvae can develop on a single plant, but, the number
depends on the plant and root size. Complete larval development takes 11 months and when
mature they will be a maximum of 12 mm long. There is no rest period required for E.
serratella as the larvae will continue to feed throughout the winter if temperatures and
humidity are optimal. The larvae pupate within the silk tube. Excess soil moisture
has a negative impact during larval development.
Overwintering stage:
E. serratella overwinters in the larval stage and will continue to feed and develop
as long as ideal conditions are present.
Location and effectiveness of attack
The larval stages, notably the later instars, cause destructive control. Overall
plant production is reduced when plants have been attacked by E. serratella. Seed
weight is most significantly reduced and the flowering and seed producing periods are shortened.
Continued attack reduces the plants' ability to develop normally and, therefore, decreases
new seedlings. In dry conditions yellow toadflax can be killed.
Predicted and native habitat
Potential suitable areas are grasslands, pastures, cropland and road or utility right-of-ways. E.
serratella shows a preference for yellow toadflax over narrow-leaved Dalmatian toadflax.
In its native habitat, E. serratella's locations are restricted to dry terrestrial
sites, favouring the northern Eurasiatic areas that coincide with their host plant distribution.
British Columbia Experiences
Origin:
E. serratella populations released in BC originate from Serbia and
Italy. The population from Serbia was reared on Dalmatian toadflax.
History:
Two unsuccessful attempts to propagate E. serratella moths in rearing
tents on Dalmatian toadflax and yellow toadflax were
made in 1992 and 1995.
Habitat:
E. serratella were released in the Bunchgrass biogeoclimatic and
Interior Douglas-fir zones. Insufficient populations developed to allow
for field releases and further study, therefore, their preferred habitat is not
known at this time.
Propagation results:
A small population persisted through the 1997
season, but nothing was found the following year. In 2004, yellow toadflax
plants with larvae infested roots were transplanted into a rearing tent and is
currently under observation.
Not available for general distribution at this time.
Notes
E. serratella can exist with seed feeders Brachypterolus pulicarius and Rhinusa antirrhini (there
is an adventive variety found on yellow toadflax). Yellow toadflax sites in south central
BC should be treated with E. serratella from Rome, Italy.
References
Hansen, Rich. 2006. Biological control: a guide to natural enemies in North America. Eteobalea
serratella Treitschke (Lepidoptera: Cosmopterygidae). November 28, 2006. http://www.nyaes.cornell.edu/ent/biocontrol/weedfeeders/eteobalea_serratella.html
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.
Saner, M. 1990. Impact of the root miner, Eteobalea serratella Tr. (Lep., Cosmopterigidae),
on reproduction of the weed, Linaria vulgari s (Scrophulariaceae). In Proc. Symnp. Biol.
Hung. 39:531-532
Saner, M., K. Groppe and P. Harris. 1990. Eteobalea intermediella Riedl and E. serratella Treitschke
(Lep., Cosmopterigidae), two suitable agents for the biological control of yellow and Dalmatian
toadflax in North America. Internat. Institute of Biolog. Cont. European Station, Delemont,
Switzerland. Final Report. 41 p.
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