Biological Control Agent: Calophasia lunula (Hufn.)
Invasive Plant Species Attacked: Dalmatian toadflax (Linaria dalmatica), yellow toadflax (L. vulgaris) and narrow-leaved Dalmatian toadflax (L. genistifolia spp. dalmatica)
Type of Agent: Foliar feeding moth
Description and Biology
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 27oC 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 21oC the egg to adult the cycle takes 58 days to complete.
Eggs are strongly-ribbed, 0.8 mm and conical shaped. During incubation the eggs change to reddish-brown. At 21oC, they hatch in seven days.
Larva and pupa:
There are five instars and when temperatures are 21oC 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 5.0 mm and again at 8.0 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.
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.
British Columbia Experiences
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. C. lunula has since 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. Since 2000, larvae sightings have become common between June 6th and September 7th, 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.
Collection for redistribution
Not available for general distribution at this time.
At the early treatments near Kamloops, cattle consumed young larvae and 90% of the pupae were parasitized by Dibrachys cavus, compounding slow establishment.
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.