Fernando Mc Kay
Marina Oleiro

Cooperator: Arne Witt, Agricultural Research Council, Plant Protection Research Institute, Pretoria, South Africa.

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The weeds

Cardiospermum grandiflorum, commonly known as Balloon vine, is a perennial slightly woody climber of the Soapberry family (Sapindaceae). Original from Tropical and Sub Tropical America (Panamá to Argentina), this tendril-bearing vine also occurs in Australia and Africa (Ferrucci 1991). Balloon vine, the plant’s common name, responds to the conspicuous spherical to ellipsoidal fruit the plant has. Cultivated as an ornamental garden creeper, it is now a declared weed in South Africa (Henderson 2001). First recorded in Kwa-Zulu Natal at Eshowe in 1937, it has now become a serious invader in many parts of the country (http://www.graemark.co.za). It forms dense but localized infestations, competing with and smothering indigenous plants in forest margins, watercourses and urban open spaces in subtropical regions. Categorized as transformer, this environmental weed can completely smother even a 10 meter high tree, forming a canopy which starves underlying foliage of light and harbors pests and diseases which destroy ecosystems (http://www.geocities.com/wessaaliens/species/balloon.htm). Although plant re-grows from root fragments, it reproduces mainly by seeds, which are dispersed inside the floating capsules by the wind and along waterways (http://www.graemark.co.za). So far, no agents have been released to control this plant in South Africa.

Campuloclinium macrocephalum (Less.) DC. Asteraceae). This ornamental perennial herb of the Asteraceae family, native to South and Central America and Mexico (Cabrera 1974), is considered a serious invasive weed in South Africa (Henderson 2001). First recorded in wild areas around Durban (1970´s) and Pretoria (1980´s), it has become a prominent weed in Gauteng, and is expanding its distribution into other Provinces of South Africa (Limpopo, Mpumalanga, NW Province, KwaZulu-Natal, Eastern Cape and the Free State), where it constitutes a serious threat to grassland areas, rapidly displacing native species and reducing the biological diversity (http://www.arc.agric.za/v-arcroot/institutes/ppri/main/divisions/weedsdiv/electronicpompom.htm). Pompom weed has showy pink flower heads at the end of green to purplish aerial stems (up to 1.3m high). The plant has a short woody rootstock that ends in thick tuber-like perennial roots, that enables the plant to survive fires, frost and drought conditions. The ability to produce new stems from rootstock, a prolific seed production, plus, the efficient wind dispersal of the seed, combined with enormous reproductive potential, are characteristics that constitutes the “weedy” nature of pompom weed. (http://www.arc.agric.za/v-arcroot/institutes/ppri/main/divisions/weedsdiv/electronicpompom.htm). Mechanical control is not an option as it causes too much disturbance and vegetative regrowth, and given the rate at which pompom weed is expanding, chemical control will become impractical and unaffordable. Therefore, Pompom weed is an “urgent candidate” for biological control in South Africa (L. Henderson - http://www.arc.agric.za/institutes/ppri/main/news/number63/number12.htm). Field surveys conducted on C. macrocephalum in Argentina revealed the presence of natural enemies attacking different parts of the plant.

Pereskia aculeata (Cactaceae). Commonly known as Barbados gooseberry, this leaf cactus is a perennial, shrubby to clambering vine native to the West Indies and South America (Argentina and Brazil) (Henderson 2001). The plant has become a weed from garden and cultivation escape in Central America, Florida, Australia and South Africa (http://www.weeds.crc.org.au/documents/wmg_leaf_cactus.pdf). Early records indicate that P. aculeata was imported into South Africa in the late 1800’s for its fruit (made into desserts, preserves and jams) and to be used as security hedging, which may have been the origin of many of the current infestations (http://www.ru.ac.za/academic/departments/zooento/Lin/lin.html). First reported in 1972 in plantations and natural forest of KwaZulu-Natal, at present the plant is declared a noxious weed and a transformer in several provinces in South Africa, where it poses a threat to indigenous and commercial forest by clambering over the canopy of neighboring plants, smothering underlying vegetation and causing trees to fall (http://www.ru.ac.za/academic/departments/zooento/Lin/lin.html). Pereskia reproduces from branch cuttings, leaves and seeds. Birds and monkeys, by eating the fleshy, gooseberry-like fruit, constitute the main cause of the spreading of the plant. Due to its spiny nature and ability to grow in inaccessible places, Pereskia is difficult to control chemically or mechanically, which makes it an ideal candidate for biological control (http://www.ru.ac.za/academic/departments/zooento/Lin/lin.html). Implementation of biological control program by PPRI researchers against Barbados gooseberry, led in 1991 to the release of the leaf-feeding flea beetle Phenrica guerini (Coleoptera: Chrysomelidae). Insects are inflicting considerable damage to pereskia plants at Port Alfred (Eastern Cape Province), but although the beetle was also released widely in KwaZulu-Natal Province, it has apparently not become established there (http://www.arc.agric.za/institutes/ppri/main/divisions/weedsdiv/pereskia.htm). The need of additional biocontrol agents against this weed, have led PPRI researchers to initiate a cooperative research project with the SABCL, to discover and study natural enemies of this weed in Argentina.

Four exploratory trips were made between January and June 2005, to the northern provinces of Argentina (Chaco, Corrientes and Misiones). Initial surveys revealed the presence of promising natural enemies.

Balloon vine (Cardiospermum grandiflorum)

Cissoanthonomus tuberculipennis Hustache (Coleoptera: Curculionidae). This weevil was found developing inside fruits of Cardiospermum grandiflorum. Adults are about 6 millimeters in length, have a brown to grey coloration and prominent tubercles on the elytra. Good numbers of this weevil were obtained from balloon vine pods in all the collecting sites throughout Misiones Province (northeast Argentina). Adults probably insert the eggs inside young green pods, since young larvae were found feeding on green seeds inside developing fruits. In most cases, only one seed was destroyed by a larva to reach maturity. Green bluish pupae are found attached to the inner face of the fruit walls, and then adults emerge from the ripening, well-developed pods. No specificity tests have been conducted yet but, based on field observations we consider this seed-feeding weevil a promising candidate to control this weed.

The “hairstreak moth” Chlorostrymon simaethis sarita (Skinner) (Lepidoptera: Lycaenidae), was found utilizing both Cardiospermum grandiflorum and Cardiospermum halicacabum as host plants in northeast Argentina. Adults of this “silver-banded hairstreak moth”, have a distinctive and characteristic wing pattern coloration. The underside of both wings in males and females is green with a silver-white post median band, while the upper side of the males’ wings is brown with purple iridescence and the upper side of the females’ is dull grey. Round green bluish eggs are laid singly on the surface of the young fruit. Larvae bore through the papery fruit walls to reach the green seeds. In most cases, only one mature larva is responsible for destroying all the seeds within a single pod. Its damaging capacity, abundance, and easiness to rear, has encouraged PPRI researchers to culture the insect in quarantine facilities.

Pyralidae: Phycitinae #1 (Lepidoptera). Another moth was found developing inside Cardiospermum grandiflorum. A single white yellowish larva was responsible for destroying all the seeds (3) within a pod.

Leaf-feeding insects

Gargaphia sp. (Hemiptera: Tingitidae). A leaf-sucking lace bug was found feeding on leaves of Cardiospermum grandiflorum. Egg batches are mostly deposited on the leaf under-surface. Nymphs and adults are mostly found feeding gregariously on the undersides of the leaves, although some can occasionally be found on the upper leaf surface. Given its damaging capacity, high density aggregations and feasibility for rearing and testing, PPRI researchers have started to culture Gargaphia n. sp. in quarantine facilities. In a preliminary host specificity test conducted in South Africa under quarantine conditions, Gargaphia n. sp. fed on beans (Phaseolus sp.). These results need to be confirmed since there were possibly more than one species among insects used in the tests. To clarify the situation, specimens collected on balloon vine from different localities of Argentina were sent for identification to Dr. Thomas J. Henry, USDA, Systematic Entomology Laboratory.

Pompom weed (Campuloclinium macrocephalum)

Stem-boring insects

The stem-boring, Zeale (=Adesmus) nigromaculatus (Coleoptera: Cerambycidae), was found feeding on C. macrocephalum. The presence of this borer inside rootstock and stems of living plants of C. macrocephalum constitutes a new host record for this plant in Argentina. Z. nigromaculatus is known to use other Asteraceae as host plants in Argentina such as Ambrosia scabra, Coniza sp., Eupatorium hecatathum, Pluchea sagittalis, Senecio grisebachi, Senecio sp., Solidago chilensis, Xanthium strumarium and X. spinosum (Di Iorio et al. 1998). It has also been reported as a pest in cultures of mint, Mentha arvensis var. piperascens (F: Lamiaceae) (Pastrana 1964, 1965 in Di Iorio et al. 1998). Given the broad host range of this insect, its consideration as a biocontrol agent will depend on the risk this beetle could pose on the South African indigenous Asteraceae species.

Carmenta n. sp. (Lepidoptera: Sesiidae). A clearwing moth was found boring plants of C. macrocephalum. Boring larvae were found attacking medium and large-sized plants. Most sesiid moths have a rather narrow host preference, with certain genera being restricted to a single host plant genus or family (e. g. Zenodoxus in Malvaceae) (Eichlin 1986). At least two clear wing moths have been studied as weed biological control agents: the argentine root-boring moth Carmenta haematica (Ureta), considered a potential biological agent against snakeweeds (Gutierrezia spp.) in the U.S. and Carmenta mimosa Eichlin and Passoa, released in Australia as a biocontrol agent against Mimosa pigra (Leguminosae) (Julien & Griffiths 1998). These antecedents support the idea of considering this new species of Carmenta a potential candidate to control pompom weed in South Africa.

Leaves and shoot feeder

A thrip was found damaging leaves and stem tips of C. macrocephalum. Stems of infested plants suffer a shortening of their internodes, and bear no flowers (Fig. 12). In autumn, when aerial parts of the plant die, thrips remain feeding on the shoots of the perennial rootstock. By bringing infested cuttings from the field and attaching them to stems of healthy potted plants, we managed to obtain a small culture of insects at the laboratory. Adult specimens were sent for identification to Dr. Laurence A. Mound (CSIRO Entomology), who said that this thrip is a slightly unusual member of the worldwide "Liothrips-lineage". According to Mound, the thrip collected on C. macrocephalum is different from the argentine Liothrips species, and would constitute a new species. At the moment, PPRI researchers are maintaining a healthy culture of the thrip at Cedara quarantine facilities, in order to run preliminary host specificity testing in the next growing season.

Flower feeders

Among the insects found damaging flower heads of Campuloclinium macrocephalum, a Gelechiidae and a Pterophoridae moth, resulted the most common and abundant. In most of the collection sites, plants capitula registered infestation by these two moths. Large numbers of a tephritid fly, Trupanea sp. were also obtained from flower head samples of different collection sites. A culture of all these insects is being kept at the PPRI, Pretoria quarantine facilities.       

Barbados gooseberry (Pereskia aculeata)

Initial field surveys along northeastern Argentina (Misiones Province) revealed the presence of a fruit-feeding moth (Lepidoptera: Crambidae: Pyraustinae). Yellowish larvae are found feeding actively on green to ripened pods. This insect has not been recorded in previous exploratory trip along the studied area. Considering the destroying capacity of this moth on the fruits of this plant, after confirming its identity, it would be worth evaluating its potential a as biocontrol agent against pereskia in South Africa.

 

Balloon vine. Photo by D. Gandolfo.	Pompom weed. Photo by D. Gandolfo.	Barbados gooseberry. Photo by D. Gandolfo.
Adult of Cissoanthonomus tuberculipennis feeding on a flower bud of balloon vine. Photo by F. Mc Kay.	Larva of Chlorostrymon simaethis feeding on seeds of ballon vine. Photo by F. Mc Kay.	Chlorostrymon simaethis (male) found on ballon vine. Photo by F. Mc Kay.
Carmenta n. sp. Photo by F. Mc Kay.	Thrip damage on stem tips of pompom weed. Photo by F. Mc Kay.	Infested fruit of Barbados gooseberry with a moth larva (Lepidoptera: Crambidae: Pyraustinae). Photo by F. Mc Kay.
Adult of the Pyraustinae found in Barbados gooseberry. Photo by F. Mc Kay.

 

 

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