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Biocontrol News and Information 30(2), 17N–48N pestscience.com General News Better-matched Cochineal Biotype Nails Killer An attempt was then made to find a better-matched Cactus cochineal population by introducing a culture of D. tomentosus from C. rosea growing in its natural hab- Eight years ago, Helmuth Zimmermann promised itat in central Mexico, but again the insects and the his wife that he would find a way to curb the inva- target weed seemed to be incompatible. siveness of the cactus weed, Cylindropuntia fulgida var. fulgida (Cff). The occasion was a visit to the town This raised the suspicion that a cholla species other of Douglas, in the Northern Cape Province of South than C. rosea might be involved. During a visit to Africa, where they found dead rabbits and small Mexico, Helmuth Zimmermann became convinced antelopes impaled on the terrible spines of the inva- that the species in question was the chain-fruit sive cactus, and livestock that had become covered in cholla (Cff), although no records existed in South the spines to the point where they were unable to Africa of cactus plants bearing chain-fruits, which walk. It was not easy to fulfill the promise, but at last are one of the characteristics of Cff. A PhD student, the long-desired moment seems to have arrived. Catherine Mathenge (then still known under her maiden name Githure), became involved at this Cff is a branched, jointed cactus with long, dense, stage, and compared the performance and specificity whitish spines. It belongs to the subfamily Opuntioi- of the cochineal insects, confirming their incompati- deae, generally known as ‘chollas’, and occurs bility (see article by Catherine Mathenge and Paul naturally in the Sonora desert of Mexico and the Holford, this issue, below). During a visit to an infes- southern USA, where it is commonly known as the tation of the problem cactus on the Zimbabwean side chain-fruit cholla or the jumping cholla – the latter in of the Limpopo River, where the cactus is not subject reference to the ease with which its cladodes attach to the chemical control regime that was mandatory themselves to animals or humans brushing past the in South Africa, Helmuth Zimmermann, Catherine plant. It was probably imported into South Africa as Mathenge and John Hoffmann indeed found some an ornamental, at least as early as the 1940s, but is man-sized specimens of the cactus to have chain- now encroaching upon natural pastoral land and fruits. This confirmed the identity of the problem conservation areas in the warm, arid parts of the cactus in both South Africa and Zimbabwe as Cff. country. The worst infestations occur near Douglas and Kimberley (Northern Cape Province), and on both sides of the Zimbabwean border at Beit Bridge Now it was clear that the Sonora desert of Mexico near Musina (Limpopo Province). Herbicidal control and Arizona, the natural home of Cff, would have to of the problem cactus, using first picloram and later be surveyed for effective biocontrol agents. A culture MSMA, has been in practice in South Africa since the of the cochineal, D. tomentosus, was collected from late 1970s, but without much success. The costs the target cactus in Arizona, but Helmuth Zimmer- involved in this control method were prohibitive, par- mann then stumbled upon a cochineal on a cactus ticularly for the low-value land on which many of the species, Cylindropuntia cholla, in Baja California infestations occurred. Biological control was Sur, Mexico, which is very similar to C. fulgida var. regarded as the best alternative, based on the large mamillata. He brought both cochineal cultures to number of cactus weeds in various countries that are South Africa for comparison. Catherine Mathenge under effective biological control. Cochineal insects conducted research on the biology, performance and (Hemiptera: Dactylopiidae), which have been used in host specificity of these and other cultures of the various biocontrol projects in South Africa, were cochineal, D. tomentosus, on the South African weedy known to be highly restricted in their host range and C. fulgida as well as a selection of closely related potentially very damaging, which made these sap- cactus species (see article by Mathenge and Holford, sucking insects the first choice for introduction below). Surprisingly, the cochineal from Baja Cali- against chain-fruit cholla. fornia Sur turned out to be the most damaging to chain-fruit cholla. Meanwhile Catherine Mathenge The first hurdle in the way of effective control of Cff relocated to Australia. was its initial misidentification in South Africa as rosea cactus, Cylindropuntia rosea. It was known It was only during 2007, when the Working for Water from the literature that the cochineal insect, Dactylo- (WfW) Programme of the Department of Water pius tomentosus, was a damaging natural enemy of C. Affairs and Forestry agreed to fund the revival of the rosea in its native home, Mexico. This insect species biocontrol project against Cff, that a fresh culture of was already present in South Africa, having been D. tomentosus could be collected from C. cholla in introduced during the 1970s via Australia as an effec- Baja California Sur. Helmuth Zimmermann had tive biocontrol agent of a closely related cactus weed, since retired, but remained involved in the project, Cylindropuntia imbricata. Consequently, the weedy which was now managed by Hildegard Klein. The ‘C. rosea’ in the Northern Cape was inoculated with introduced cochineal culture was cleared of preda- cochineal insects collected from the nearest C. imbri- tors and contaminants under quarantine conditions cata plants. The insects persisted on the inoculated at Rietondale, Pretoria, and mass reared to obtain plants, but were unable to damage them sufficiently. sufficient numbers for release. Are we on your mailing list? Biocontrol News 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. 18N Biocontrol News and Information 30(2) The first release of the new cochineal biotype in select an area with a more evenly distributed infesta- South Africa was made during October 2008, near tion of Cff in the Northern Cape, where the cochineal Douglas in the Northern Cape by Debbie Sharp from is not yet present, and to make new releases that will WfW. A month later, on 18 November 2008, cochi- be monitored earlier. There is also a need to establish neal-infested cactus cladodes were attached to a official relations with the phytosanitary authorities number of large chain-fruit cholla plants growing in in Zimbabwe, to ensure that this successful biocon- the dry bed of the Limpopo River near the border trol agent reaches the large infestations of Cff on the post at Beit Bridge, again with the assistance of Zimbabwean side of the border at Beit Bridge, which WfW. A clearing team of WfW has been active in this have already reached crisis levels, and where the area for several years, combating the cactus chemi- local community is desperate for a solution to this cally as part of a public works programme. cactus problem that is causing stock losses and dev- astating their pastures. On 18 March 2009 (exactly four months after release, during which the insects might have completed two On a cautionary note: the devastation that Cff can generations), Hildegard Klein and Helmuth Zimmer- cause to biodiversity was brought home once more by mann, together with five employees of the WfW the pitiful sight of three dead Woodlands Kingfishers Programme, visited the release site again, hoping to that had become impaled on the spines of cactus find some early signs of insect establishment. To specimens a small distance from the cochineal their utter amazement the cochineal had not only release site. Zimbabweans living near Beit Bridge become established on each of the inoculated plants, report that the cactus is a huge threat to livestock but the inoculated plants were virtually covered from grazing as well as game in the area, and that not top to bottom with clusters of D. tomentosus females. even rats can pass through some of the cactus The branches were hanging, and many of the lower thickets. Cactus collectors are urged to keep the cladodes on these plants were dead and had dropped invasive potential of cacti in mind in countries where off the plants. What is more, the insects had already they have no natural enemies, and to resist the temp- started dispersing, with most of the Cff plants within tation to plant introduced cacti on their property but, a radius of 3 m or more from the inoculated plants above all, not to discard them in such a way that they infested, which is a relatively large distance for the might escape into the wild. crawlers (first instar nymphs) of the sedentary, flightless insects to cover. Many small plants con- By: Hildegard Kleina & Helmuth G. Zimmermannb sisting of only a few cladodes had already died and young plants less than 1 m tall were collapsing. aAgricultural Research Council: Plant Protection Research Institute, South Africa. It is already evident that the WfW clearing team will Email: [email protected] have to make some serious adjustments to their chemical control programme to take full advantage bHelmuth Zimmermann and Associates (HZ & A), of this new cochineal. The team members will prob- formerly Agricultural Research Council: Plant ably in future be harvesting cochineal-infested Protection Research Institute, South Africa. cactus cladodes and redistributing them, instead of Email: [email protected] applying herbicides.