Biological Control Agent: Calophasia lunula (Hufn.)
Type of Agent: Foliar feeding moth
Status
Primary
Description and Biology
Adult:
Adult moths are light brown-grey with a wingspan of 27 - 30 mm. The forewings have
a white crescent mark and irregular white flecks while the rear wings are brownish white. Calophasia
lunula is a strong flier. Adults appear between May and August. Mating begins
immediately and egg laying starts 1 - 2 days later. Females lay 100 and 400 eggs each.
Eggs are laid singly on leaf and flower surfaces and are usually laid after midnight.
When temperatures are 27°C most will be laid within four days. Adults can
be found at dusk feeding on toadflax flower nectar. Their life span is linked to temperature,
usually surviving 10 - 25 days. At 21°C the egg to adult the cycle takes 58
days to complete.
Egg:
Eggs are strongly-ribbed, 0.8 mm and conical shaped. During incubation the eggs change
to reddish-brown. At 21°C, they hatch in seven days.
Larva and pupa:
There are five instars and when temperatures are 21°C the larval stage lasts
27 days. Newly hatched larvae are grey-black and about 5 mm long. Mature larvae
are pearly-white to bluish-white with lateral rows of black spots, five yellow stripes and
two broken black lines. The larvae are very distinct and grow to 4 cm long. Moulting
between instars depends on feeding conditions. A specific amount of food is required
to reach a size to initiate the moult. During the entire larval stage, each will consume
38.6 cm of stem foliage. The first two instars each last five days, preferring to feed
in flowers and moulting at 5 mm and again at 8 mm. Feeding becomes more aggressive during
the final three stages and encourages the larvae to disperse. The third instars last
five days and moult at 12 mm. The fourth instars last about seven days and moult at 19 mm.
The final instars require 12 days to complete but do not moult. They prepare for
pupation by moving into the soil where they construct cocoons from chewed leaves, litter, or
soil. Pupae measure 15 mm x 4.5 mm and become golden or reddish-brown. The earliest
to complete pupation will go on and produce a second generation of adults that will appear
in late summer or early fall. In some climates a third generation is possible, but, usually
they will overwinter as second generation pupae.
Overwintering stage:
Pupae overwinter within the soil in cocoons constructed from chewed leaves, plant litter
and soil particles.
Location and effectiveness of attack
Larvae feed on flowers, floral buds and foliage. The young larvae can completely
destroy flowers during the first two instars feedings. Older larvae feed on the new vegetative
shoots, tender leaves, and flowers. When new foliage is not available, mature leaves
will be consumed. In sufficient numbers the defoliation is quite impressive. The
feeding depletes stored nutrients and overall vigour of the plant which impacts the plant during
the next growing season. Flower and bud feeding decrease seed production.
Predicted and native habitat
Areas with warm summer temperatures are required for larvae development. Its preference
for drought stressed plants confirms the need for sites that remain warm during summer.
Yellow toadflax sites near water may be favoured. It is suggested that different strains
of C. lunula prefer either yellow or Dalmatian toadflax.
The native distribution of C. lunula occurs in central Europe and central Asia into the
Amur region of the Pacific. A remote population occurs in Scandinavia. It is absent
from areas with high rainfall and cool summer temperatures. It occurs in areas where
the temperature can be as low as -40o C and as high as +40o C (or greater).
British Columbia Experiences
Origin:
Canadian populations came from European stock. The first C. lunula releases were made in five
provinces, including British Columbia.
History:
The first C. lunula releases began in the 1960's. Several attempts were made to establish
them in and near Kamloops. Larvae were seen later, within the same year as the release, but,
not thereafter. In the 1980's rearing plots were established to
increase populations for redistribution. Collections taken from the
rearing plots were used to create several new sites in the southern interior.
In 1997 the first field collection was made in BC.
Habitat:
C. lunula has been released and found established and dispersed within the Bunchgrass,
Interior cedar hemlock, Interior Douglas-fir, and Ponderosa pine biogeoclassification zones
as well as on the fringes of Montane Spruce. It is too early to
determine the status of the release made in the Coastal western hemlock zone.
Field results:
Since 2000, larvae sightings have become common from late May and early
September, in varying habitats throughout the southern interior. The moth is
establishing and dispersing along road edges, gullies, and occasionally near
water. A common observation at established sites was the absence of
excessive plant litter. Large volumes of plant litter may inhibit larvae
movement between plants. During the hottest parts of the day, larvae are
found in slightly shaded areas out of direct sunlight. After extended
periods of hot weather, the larvae appear to completely avoid dried plants,
preferring adjacent green plants. In 2008, a dispersed population found on a mixed stand of yellow toadflax and Dalmatian toadflax was
collected from the North Thompson and released
onto Dalmatian toadflax on Vancouver Island.
Not available for general distribution at this time.
Notes
At the early treatments near Kamloops, cattle consumed young larvae and 90% of the pupae
were parasitized by Dibrachys cavus , compounding slow establishment.
References
Harris, P. and A. McClay. 2003. Classical biological control of weeds established
biocontrol agent Calophasia lunula (Hufn.) Defoliating moth. May 20, 2003.
http://res2.agr.ca/lethbridge/weedbio/agents/acalophas_e.htm
Karny, M. 1963. The possibilities of Calophasia lunula Hufn., (Lep.: Noctuidae)
in the biological control of toadflax, Linaria vulgaris Mill. Commonwealth Instit.
Biolog. Contr., European Station, Delemont. Switzerland. Tech. Bul. No. 3. 27 p.
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. 1996. Biological control of weeds in the west. Western Soc.
of Weed Sci., USDA Agric. Research Serv., MT Depart. Agricul., Mont. State Univer.
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