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Chromolaena odorata (L.) R.M. King and H. Robinson (Asteraceae) is a perennial weedy shrub of neotropical origin and a serious biotic threat in its invasive range. The Asian-West Africa (AWA) biotype of C. odorata present in West Africa is both morphologically and genetically different from the southern African (SA) biotype. The AWA biotype was first introduced into Nigeria in the late 1930s and rapidly spread across West Africa. Currently, 12 of the 16 countries in West Africa have been invaded, with significant negative effects on indigenous flora and fauna. However, locals in West Africa have found several uses for the weed. As chemical, physical and other conventional methods were unsustainable, costly and largely ineffective, three biological control agents, Apion brunneonigrum (Coleoptera: Brentidae), Pareuchaetes pseudoinsulata (Lepidoptera: Erebidae) and Cecidochares connexa (Diptera: Tephritidae), have been released in West Africa between the 1970s and the early 2000s. However, only C. connexa and P. pseudoinsulata established, contributing to the control of the weed, in six and four countries in West Africa respectively. Limited research funding, the absence of post-release evaluations of the established agents, and the 'conflict of interest' status of C. odorata (i.e. being beneficial for local use but damaging to ecosystem services and agriculture), are serious factors deterring the overall biological control effort. Here, using historical records and field surveys, we examine the invasion history, spread, impacts, and management of C. odorata in West Africa and make recommendations for the sustainable management of C. odorata in the region. [ABSTRACT FROM AUTHOR]

A 9-month laboratory study was carried out to determine the impact of herbivory by a moth with shoot-boring larvae, Dichrorampha odorata Brown and Zachariades (Lepidoptera: Tortricidae) on growth and reproductive ability of its host plant, Chromolaena odorata (L.) King and Robinson (Asteraceae), a major invasive alien plant species in southern Africa. Newly hatched D. odorata larvae were inoculated onto 0 (control), 50 and 100% of the shoot tips of C. odorata in the laboratory. At all treatment levels, the basal stem diameter of C. odorata was not affected by D. odorata larval feeding. Larval feeding by D. odorata significantly reduced the height of the main shoot and flower production in C. odorata relative to the control treatment but promoted branching by increasing the number of shoot tips. However, the differences in plant height and number of flowers between the 50 and 100% inoculation levels were not statistically significant. Dichrorampha odorata is the first shoot-tip attacking agent that is being released as a biological control agent against C. odorata in South Africa. In general, the impacts of D. odorata on the weed were relatively small even though statistically significant. The findings of this study suggest that high levels of damage by the moth will modestly reduce the height, flower production, and the competitiveness of C. odorata, thereby contributing to the biological control of the weed in South Africa. [ABSTRACT FROM AUTHOR]

Dichrorampha odorata(Lepidoptera: Tortricidae) is a moth from Jamaica whose larvae bore into, and kill, the shoot tips of the invasive alien plant,Chromolaena odorata(L.) King and Robinson (Asteraceae). This study reports aspects of the biology ofD. odorata, and also determined the host specificity (larval and adult no-choice trials) of the moth. Adults were short lived (ranging from 2 to 7 days), with females laying a mean of 15.4 eggs. Eggs took 9 days to hatch, larvae 20–23 days to develop and the pupal stage lasted 11–12 days, giving an overall lifecycle period of 41–45 days. Larval no-choice tests using 34 asteraceous test species indicated that onlyC. odoratacould sustain complete development ofD. odoratato adulthood, although there was slight initial boring 14 test species (plus chromolaena). Results from the adult nochoice trials, in which seven test-plant species were exposed toD. odorata, were consistent with those from larval trials, with larval damage, pupae and adults ofD. odoratarecorded from onlyC. odorata. This confirmed that onlyC. odoratais a suitable host forD. odoratain South Africa. Permission has subsequently been granted for the release ofD. odoratain South Africa, thus making it the first shoot-tip attacking agent to be released againstC. odorata. It is hoped that in the field, high levels of damage by the moth will reduce the height and therefore competitiveness ofC. odorata, thereby contributing to the success of biological control of this plant. [ABSTRACT FROM AUTHOR]

Recent studies have demonstrated, through their contrasting results, that relationships between nitrogen levels in host plants and phytophagous insect performance are not simple. This study examined the effect of varying fertilisation regimes on the invasive alien plant,Chromolaena odorata(L.) (Asteraceae) and the response of a specialist folivore (a biological control agent),Pareuchaetes insulata(Walker) (Lepidoptera: Erebidae).C. odorataplants were treated with 3 different levels of fertilisation and plant characteristics were measured within 2–3 months of fertiliser application. Leaves from each of the three treatments were fed to newly hatched larvae until pupation in order to determine the effect of nitrogen fertilisation on herbivore performance metrics such as survival, development time, fecundity and longevity. High and medium fertilisation significantly increased foliar nitrogen concentrations, basal stem diameter, leaf length, shoot height and above-ground biomass ofC. odorataplants relative to low fertilisation. When individuals ofP. insulatawere fed on leaves from medium- or high-fertilisation treatments, they developed faster, grew to a larger size (by 8%) and achieved higher fecundity (19–22%) than leaves from the low-fertilisation treatment. The results suggest that in mass-rearing, increased production of this biological control agent will occur in high- or medium-fertilised plants. [ABSTRACT FROM AUTHOR]

The leaf-mining flyCalycomyza eupatorivoraSpencer (Diptera: Agromyzidae) has become widely established in the eastern regions of South Africa, following its release for the biological control of the invasive shrubChromolaena odorata(L.) King and Robinson. This study was conducted to gain some insight into the impact ofC. eupatorivorapopulations, by assessing their seasonal activity, habitat preferences, levels of leaf exploitation and extent of larval mortality in the field over a 1-year period. Leaf mining intensity was poorly synchronised with leaf availability, with leaf exploitation peaking at the end of the growing season ofC. odorata. Although significantly more mines were recovered on plants growing in shaded situations, the percentage of available leaves that were exploited for mining was not significantly different between plants growing in shaded versus open situations. Overall, the levels of leaf damage were trivial with mines recovered from <5% of available leaves that were sampled during the study. Besides leaf-quality requirements, these low levels of leaf exploitation may have been influenced by high larval mortality which varied between 60 and 83%, depending on whether lower or higher estimates were used. These evaluations have verified the results of earlier laboratory studies which suggested that the impact ofC. eupatorivoraon mature populations ofC. odoratain South Africa will be negligible. [ABSTRACT FROM AUTHOR]

The leaf-mining flyCalycomyza eupatorivoraSpencer (Diptera: Agromyzidae) was released in the eastern coastal regions of South Africa for the biological control of the invasive shrubChromolaena odorata(L.) King and Robinson. Despite widespread establishment, its ability to inflict sufficient foliar damage has been questioned. This laboratory study was initiated to provide some insight into how increasing fly populations (represented by 1, 5 and 10 mating pairs per plant) are likely to influence leaf-mining intensity and the levels of damage. On average, individual plants exposed to five mating pairs displayed significantly more larval mines (248) than those exposed to single pairs (69), while plants exposed to 10 mating pairs were intermediate (125). Similarly, at densities of five mating pairs per plant, the percentages of available leaves that were exploited peaked at 36%, while the percentages of available leaf area that were removed by larval leaf mining peaked at 22%. The non-linear relationship between leaf mining and fly density and the high percentages of unexploited leaves suggest that leaf mining may be influenced by leaf quality, the nature of which is currently unconfirmed. These results also suggest that the levels of leaf exploitation byC. eupatorivorawill be too low to have any meaningful impact in the field. Field evaluations, to be reported in a later contribution, have indeed confirmed that the impact ofC. eupatorivoraon mature populations ofC. odoratais negligible. [ABSTRACT FROM PUBLISHER]