Biological Control Agent: Chirida guttata (Oliver)

Invasive Plant Species Attacked: Field bindweed (Convolvulus arvensis) and Hedge bindweed (Calystegia sepium)

Type of agent: Beetle

Status

Description and Biology

Adult:

Chirida guttata bodies are oval or circular with a wide forewing. Their thorax partially covers their head and hides their legs. Their outer cuticle is clear. At sexual maturity they become golden coloured and vary from bright gold to burnished copper, with mottled black markings. They retain the golden colour until their death. They can alter their colouring by voluntarily pumping fluids between their outer cuticle and body. Adults emerge from their overwintering locations in May and mating begins soon after. Females lay eggs onto lower leaf surfaces and secure them into place with a glue-like substance. The duration from egg to adult takes 26 - 32 days (10 to 15 days quicker than Metriona bicolor). The second generation adults appear in September and feed until hibernation.

Egg:

The eggs are 1.5 x 0.56 mm and are protected with a translucent membrane. The incubation period lasts 6 - 9 days.

Larva and pupa:

The larvae are elongated, oval shaped with thorn-like or spiny protrusions covering their body. Immediately after hatching, the new larvae burrow under the leaf membrane and begin feeding on the underside of leaves. Older larvae continue to feed on leaves and create circular holes inside the leaf margins and between the veins. As the larvae enlarge and moult, they attach their cast off skins onto a forked appendage located at the rear of its abdomen. Excrement is added to the moults and this accumulation is carried over their bodies as they increase/grow. The larvae stage lasts 10 - 13 days. Pupation occurs in the soil and lasts 6 - 8 days.

Overwintering stage:

Adults overwinter in debris near host plants.

Location and effectiveness of attack

Adult and larvae feed on foliage creating irregular or semi-circular holes in leaves, inside the margins and between veins. Their feeding impact has not been measured.

Predicted and native habitat

C. guttata is native to North and Central Americas and is common in Ontario, but, not in western Canada. It has similar habitat requirements as M. bicolor , inhabiting meadows, grassy areas and gardens, but, tolerates cooler temperatures and dryer conditions. Plants that grow with support appear to be favoured over those that are prostrate. British Columbia may not be within its geographic range.

British Columbia Experiences

Origin:

C. guttata came to BC from native populations established in Ontario.

History:

The first C. guttata introduction to BC was in 1969 and again in 1970 when a small number of beetles were brought to the University of British Columbia for lab studies. In 1971, a field release was made on the lower mainland on hedge bindweed. It is not known if the site had established and dispersed before the area was further developed.

Habitat:

The field release and the possible dispersal sightings occur within the Coastal western hemlock biogeoclimatic zone.

Field results:

In 2007, an unconfirmed dispersal sighting was found in the Fraser Valley. Potentially it may be either M. bicolor or C. guttata and is being investigated at this time. In 2008 additional adults and larvae were found and their identification is pending.

Collection for redistribution

Not available for general distribution at this time.

Notes

It may also be referred to as Deloyala guttata and is commonly known as the mottled-tortoise beetle.

C. guttata and M. bicolor (Charidotella bicolor) share the same habitat, feeding on the same Convolvulus plant species, but, the larvae appear at different times.

C. guttata will feed on morning glory, sweet potato and field and hedge bindweeds.

References

Colorado State University. 2000. The "golden lady beetle" - not! Pest Alert, Vol. 17: No. 16: 10.

Hull-Sanders, Helen, Arther G. Appel and Micky D. Eubanks. 2003. Comparative water relations of adult and juvenile tortoise beetles: differences among sympatic species. Elsevier. Comparative Biochemistry and Physiology Part A: 135. Pp. 625-634.

Kellerher, J. S. and M. A. Hulme. 1984. Biological control programmes against insects and weeds in Canada 1969-1980. Commonwealth Agricultural Bureaux, England.

Laliberte, Andrea S. 1994. Field bindweed (Convolvulus arvensis L.) and its control, with an emphasis on biological control. The University College of the Cariboo Department of Natural Resource Science. Work Term Report.