Dysschema sacrifica Hubner (Lep: Arctiidae)
from Brazil: A Biological Control Candidate for C. odorata (L.) R.M. King & H. Robinson (Asteraceae) in South Africa


by
R.L. Kluge and P.M. Caldwell
Plant Protection Research Institute
Cedara Weeds Laboratory
Private Bag X 9059
Pietermaritzburg 3200
Republic of South Africa

 

Chromolaena odorata is thought to have been introduced into South Africa in the 1940s. Spreading rapidly, the plant now occurs along the Natal and Transkein coastal belts. It is also a serious weed of crops, plantations and pastures in southern Asia and western Africa.
An arctiid moth, Dysschema sacrifica Hubner1 was collected on C. odorata (unconfirmed but closely resembling our local form) about 50 km north of Rio de Janeiro, Brazil, and imported into South Africa for preliminary screening as a biological control candidate of C. odorata in South Africa.
The larvae were reared through to maturity on the local form of C. odorata in a quarantine laboratory maintained at 20-26°C. The adults were kept in fine gauze cages (40 x 40 x 50 cm or 90 x 90 x 90 cm) with C. odorata bouquets.
Oviposition was poor and only five of the 60 females laid eggs. The number of eggs in each batch was 392, 328, 263, 215 and 53 respectively. The flattish, dome-shape eggs were approximately 1 mm in diameter and cream colored. The eggs hatched after nine days.
There are seven larval instars ranging from 2-30 mm in length. The larvae are yellow with maroon lines running the length of the body between the tubercles and the legs. The number and definition of these lines increases with succeeding instars. The body is covered with long dark brown to black setae. The head is dark brown to black and the anal plate is yellow with a central dark spot.
The overall color of the adults is dark grey to black with pale yellow markings on the abdominal segments. A broad white to pinkish band runs across the length and the width of the forewings. The hindwinds of the female and male are grey and white, respectively, with red, black and cream markings along the fringe which are bolder in the female.
A total of 11 test plants were screened against newly hatched D. sacrifica first instar larvae. These included C. odorata and three near relatives, i.e. Ageratina adenophora, Ageratina riparium and Ageratum houstonianum; four composite weeds, i.e. Bidens pilosa, Tagates minuta, Galinsoga parviflora and Wedelia glauca, and another common weed, Lantana camara all from South America; and two commercially important species, Chrysanthemum sp. and Dahlia rosea.
Bouquets of succulent apical growth tips of the test plants were offered to the larvae in 90 x 25 mm glass tubes with absorbent cotton-wool stoppers. Wet cotton wool was wrapped around the cut end of the bouquets. Bouquets were changed about twice a week or replaced as required. Ten newly hatched first instar larvae were transferred to each test plant. Feeding and survival of the larvae was recorded daily.
Based on the survival of the larvae, the test plants can be divided into three groups. All the larvae died in the first instar on plants in the first group: A. adenophorum, A. riparium, G. parviflora and Chrysanthemum sp. A few feeding lesions and faecal pellets were recorded on A. adenophorum, A. riparium, G. parviflora and W. glauca.
In the second group, larvae developed through to the second instar on A. houstonianum and T. minuta making numerous feeding lesions on the leaves.
In the third group some larvae completed their development on C. odorata, D. rosea, L. camara and B. pilosa. B. pilosa was the best and most consistently acceptable host yielding 15 pupae (50%). The performance of the larvae on the other three plants was variable; a few pupated (in total four) but in some replicates all the larvae died in the early instars.
These results would suggest that this arctiid is oligophagous and not host specific to C. odorata. D. sacrifica is, therefore, not suitably host specific to be considered further as a biocontrol candidate for C. odorata.

1 Identified by M. R. Honey of the British Museum. Pinned specimens (AcCe 1) are housed at the National Collection of Insects, Private Bag X134, Pretoria 0001, South Africa.