News 105N General News Cacti, Composites and ture, they found evidence that at least 15 fruit-eating birds. Consequently, seedlings Creepers shipments of different strains of cochineal germinate mostly under trees and along insect, collectively identified as D. fences where they may remain unnoticed This issue begins with weed biocontrol opuntiae, had been introduced into Aus- for many years in tall grass and dense bush news, focusing on classical biocontrol initi- tralia. These had originated from a variety because of their trailing growth habit. Dis- atives against some invasive weeds in of Opuntia species in North America, most carded segments root readily, so new South Africa, Australia, New Zealand and of which were low-growing shrub pears infestations are also found on rubbish Indonesia, where significant progress is similar to O. stricta. The cochineal respon- dumps. being made against a number of trouble- sible for the spectacular control seen in Two insects indigenous to South America some species. Australia originated from one or more of and specific to the cactus have been these shipments. However, the material released in recent years. One of them, Hyp- shipped onwards to South Africa for O. ogeococcus festerianus, has, since its first ficus-indica control was almost certainly of Prickly Pair introduction in 1983, been distributed central Mexican origin, and had been col- around the country by PPRI researchers as One of classical biological control's lected from a different and tree-like species, well as resource conservation inspectors Opuntia streptacantha. That strain was enduring images is of stands of prickly pear from the National Department of Agricul- cactus (Opuntia ficus-indica)inSouth selected for South Africa because of its ture (NDA). The mealybugs, which were ability to develop on O. ficus-indica speci- Africa reduced to brown and withered key to controlling the cactus in Australia, mens that had been sent to Australia for stumps by cochineal insects (Dactylopius attack mainly the young growing tissues of testing purposes. Although morphologi- opuntiae). There are now signs that two the cactus, and a toxic substance they inject cally identical, it now appears that the two more cactus species are being brought causes the growing tips to become con- under control there by introduced insects. populations represent different host- torted, fruit production to be reduced, and adapted strains or biotypes. The cochineal insect and the cactus moth gradual die-back of the stems. Results sug- (Cactoblastis cactorum)wereimported A second introduction was made from Aus- gest that all releases of the mealybug in from Australia, where they had been used tralia in 1996, but this time D. opuntiae was South Africa, at some seven locations, have in a successful campaign against Opuntia collected from O. stricta. This new colony resulted in establishment. Adult mealybugs stricta (Australian pest pear or sour prickly (the stricta biotype) was compared to the are sessile, and the young crawlers move pear), in the early twentieth century. The established colony in South Africa (the onlyslowlyandrelyonthewindfordis- moth proved far less effective in South ficus biotype), and survival and develop- persal. It has always been assumed that Africa, and this was attributed to predation ment of each on both O. stricta and O. manual redistribution of infested material of the early stages, mainly by ants and ficus-indica were monitored. Results sug- would be necessary. However, the dispersal baboons. Cochineal insect was an out- gested that each biotype survived and rate of the mealybug during 1998-99 has standing success in controlling O. ficus- developed best on its ‘own’ host, con- called this into question. Infestations have indica but, bafflingly, it barely survived on firming the existence of distinct host races spread between patches of cactus separated O. stricta in South Africa, and certainly had in D. opuntiae. Next, each of the O. ficus- by several hundreds of metres of dense veg- no impact on its control. indica cultivars grown in South Africa was etation, and this cannot be ascribed to wind exposed to the stricta biotype, and the alone. Unwitting help from birds or rodents Opuntia stricta is native to the southeastern results indicated that none of them sup- feeding on the cactus fruits is suspected. USA, and was probably brought into South ported its development. Africa by collectors of succulents. A highly In the past, the NDA have relied heavily on adaptable species, it has invaded thousands In May 1997, the stricta biotype was chemical control (MSMA) to combat the of hectares, and is particularly invasive in released as infested leafpads onto O. stricta cactus. Although active in distributing the KwaZulu-Natal, the Northern and Eastern near Pretoria and in the Kruger National mealybug, they apparently did not have Cape and the Kruger National Park. It is a Park. The results have been spectacular: enough faith in biocontrol to discontinue problem elsewhere in the region, including dense stands of cactus have collapsed, and spraying. Now, instead of insisting that Yemen and Eritrea, and is present in Ethi- surrounding plants are heavily infested. landowners treat infestations with MSMA, opia and Somalia. However, biological Despite their limited mobility, the insects they are supplying them with starter colo- control of O. stricta in these countries have spread more than 100 m in the two nies of the mealybug and showing them presents additional difficulties, because O. years since release. All indications are that how to disperse the insect manually. Chem- ficus-indica is a valued crop (albeit with the newly introduced strain will control O. ical control is still used on small isolated unfortunate invasive tendencies) and thus stricta as effectively in South Africa as in infestations, and biocontrol on large and D. opuntiae is not an appropriate candidate Australia. dense stands. for introduction. Another import by admirers of succulents, Sources: Plant Protection News Nos. 53 & The Weeds Research Division of the Plant harrisia cactus (Harrisia martinii)from 54 (Summer & Autumn 1999). Protection Institute of South Africa (PPRI) South America is succumbing to an intro- The newsletter of the Plant Protection looked at why an insect that could be so duced mealybug. Harrisia is invasive in Research Institute, a member body of the successful against O. stricta in Australia South African pastures, especially in the Agricultural Research Council, South should be a total failure in South Africa. warmer parts of the country. It propagates Africa. Looking back through records in the litera- mainly by seeds, which are dispersed by Further information: Hoffmann, J.H.; Are we on your mailing list? BiocontrolNews and Information is always pleased to receive news of research, conferences, new products or patents, changes in personnel, collaborative agreements or any other information of interest to other readers. If your organization sends out press releases or newsletters, please let us have a copy. In addition, the editors welcome proposals for review topics. 106N BiocontrolNews and Information 1999 Vol. 20 No. 4 Moran, V.C.; Zimmermann, H.G. (1999) young plants and regrowth throughout the and forestry. Three new candidates have Integrated management of Opuntia stricta rest of the year. As a result of this, there has been, or are being, assessed for their host- (Haworth) Haworth (Cactaceae) in South been a significant and noticeable reduction specificity. Actinote ?thalia pyrrha from Africa: an enhanced role for two, in the abundance of the weed in the lowland Brazil is very damaging to C. odorata,but renowned, insect agents. In:Olckers,T.; areas near P. Siantar. This remarkable shows little preference for C. odorata over Hill, M.P. (eds) Biological control of weeds achievement marks the most rapid progress two indigenous Mikania species. It will in South Africa (1990-1999). African against this weed anywhere in the world in thus not be considered for release at Entomology, Memoir No. 1, pp. 15-20. terms of area controlled. present, although the situation following Klein, H. (1999) Biological control of three the release of a congeneric species in Indo- The gall fly is also established and cactaceous weeds, Pereskia aculeata nesia will be followed to see whether it has spreading in lowland areas of Aceh, and is Miller, Harrisia martinii (Labouret) an impact on mikania weed there. A second now present throughout an area of at least Britton and Cereus jamacaru De Candolle Brazilian species is more promising: ovipo- 60 km in all directions from the closely in South Africa. In: Olckers, T.; Hill, M.P. placed original release sites in this province sition and larval development results for (eds) Biological control of weeds in South of northern Sumatra. Around the research no-choice tests on the curculionid stem Africa (1990-1999). African Entomology, station at P. Siantar, the gall fly is present borer Lixus aemulus suggest that the host MemoirNo.1,pp.3-14. for at least 100 km in all directions, except range of this species does not include indig- enous or economically important species in Contact: [stricta] H. G. Zimmermann at higher altitudes. Above 500 m it has South Africa, although adult testing is not [email: [email protected]] spread much more slowly, and above 1000 yet complete. Finally, results of multiple [harrisia] Hildegard Klein m survives only in warm and sunny sites. choice tests for a leaf-mining agromyzid,