Aspects of the biology, thermal physiology and nutritional ecology of Pareuchaetes insulata (Walker) (Lepidoptera: Erebidae: Arctiinae), a specialist herbivore introduced into South Africa for the biological control of Chromolaena odorata (L.) King and Robinson (Asteraceae)

Chromolaena odorata (L.) King and Robinson (Asteraceae) is an invasive weedy shrub native to the Americas that has proven to be a significant economic and ecological burden to many tropical and sub-tropical regions of the world where it impacts negatively on agriculture, biodiversity and livelihoods. A distinct biotype of C. odorata was first recognised as naturalized in KwaZulu-Natal (KZN) province, South Africa, in the 1940s and has since spread to other climatically suitable provinces. Pareuchaetes insulata (Walker) (Lepidoptera: Erebidae: Arctiinae) was released in KZN, South Africa, as a biological control agent against the weed between 2001 and 2009. Although the moth did establish at one out of some 30 release sites, its population level is generally low in the field. This thesis attempts to unravel the reasons for the poor performance of P. insulata in South Africa.Studies of life history traits of P. insulata in the laboratory indicated that the moth possess good biological attributes such as low mortality, high fecundity, egg hatchability and high female mating success. Overall, adult female moths eclosed before their male counterparts suggesting the presence of protogyny. Beyond the contribution of this study to our understanding of the life history traits of erebid moths, it hypothesized that the absence of protandry might have contributed to the low population levels of the moth in the field. To determine if a degree of agent-host plant incompatibility is culpable for the poor performance of P. insulata, insect performance metrics were compared on two distinct C. odorata plants (one from Florida and another from South Africa) in laboratory experiments. Pareuchaetes insulata performance metrics were similar on both plant forms; there were no significant differences in total leaf area consumed, egg and larval development, immature survival rates, feeding index (FI), host suitability index (HSI), growth index (GI), and fecundity between the Floridian and southern African C. odorata plants. In sum, there was no evidence to demonstrate that differences in plant forms in C. odorata are culpable for the poor performance of P. insulata in South Africa.The effects of temperature on the developmental and reproductive life history traits, locomotion performance and thermal tolerance range of P. insulata were studied in order to elucidate the possible role of temperature on the poor performance of the moth. The results showed that at temperatures below 25 °C, mortality increased and development time was prolonged. Fecundity and egg hatchability were negatively affected at a constant temperature of 15 °C. Results futher showed that third instar larvae were unable to initiate movement at 6 °C and locomotor abilities were significantly reduced at 11 °C. In sum, it is hypothesized that both direct and indirect negative impacts of low temperature may partly explain the poor performance of P. insulata in South Africa. Theeffects of seasonal and spatial variations in the leaf characteristics of C. odorata on the performance of P. insulata were investigated. Foliar nitrogen and magnesium concentrations were higher in shaded plants during winter due to low temperatures. Leaves of C. odorata plants growing in the shaded habitat (relative to full sun) and leaves of plants during autumn (relative to winter) were more nutritionally balanced and suitable for herbivore performance. Consequently, P. insulata developed faster, had heavier pupal mass and increased fecundity when reared on shaded leaves (relative to full sun) or when reared on autumn leaves compared to leaves growing in winter. This study demonstrates that low winter temperatures can indirectly affect insect herbivore performance by changing the phytochemistry of host plant and hypothesized that excess nitrogen and possibly magnesium may have detrimental effects on the insect herbivore performance.A cross-feeding experiment was conducted to determine P. insulata response to a change in the diet of offspring due to a shift in plant quality in shaded versus full sun habitats. The results showed that a ‘negative switch’ in herbivore diet (i.e. when progeny from parents reared on shaded leaves were fed on full sun leaves) resulted in high (40%) mortality, prolonged development time and reduced fecundity. Thus full sun foliage is an inferior diet for P. insulata offspring. In laboratory experiments, foliar nitrogen was positively correlated with the performance of P. insulata. From this study, it is demonstrably evident that the poor performance of P. insulata on C. odorata in South Africa is caused by multiple factors such as low temperatures as well as spatio-temporal variations in the leaf characteristic of C. odorata leaves. This study shows the complexity of determining the causes of low populations and apparent low impact of biological control agents and herbivorous insects generally, in the field. The implications of this research to the biological control programme against C. odorata and the direction of future research for the control of C. odorata are discussed

Evaluation of the repellent and insecticidal activities of the leaf, stem and root powders of siam weed (Chromolaena odorata) against the Cowpea Beetle, Callosobruchus maculatus

This study investigated the repellency and toxicological activity of C. odorata root, stem and leaf powders against adults of the cowpea beetle, Callosobruchus maculatus (Fab.) (Coleoptera: Chrysomelidae). Adults of C. maculatus were exposed to grains treated separately with the root, stem and leaf powders of C. odorata at different exposure periods of 12, 24, 36, and 48 hours. All the three plant parts significantly repelled C. maculatus with the root powder showing the highest percentage repellency, although this was a function of exposure time. The order of repellency after 48 hours exposure was 88, 83 and 76% for the root, leaf and stem powders, respectively. Powders from the three plant parts exhibited insecticidal activity by causing varying levels of mortality to C. maculatus with mortality increasing with increase in exposure time. The root powder accounted for the highest adult mortality (74%) while the leaf powder accounted for the least mortality (51%) after 48 hours exposure time. The high repellent and insecticidal activities demonstrated by the root powder compared to the leaf and stem powders suggest that the root powder should be prioritized for the control and management of C. maculatus.Keywords: Chromolaena odorata, plant powder, toxicity, mortality, repellency, Callosobruchus maculatu

The Impact of Pareuchaetes pseudoinsulata (Lepidoptera: Arctiidae), on the Growth Rate of Chromolaena odorata (L.) in Southern Ghana

The abundance and effectiveness of Pareuchaetes pseudoinsulata Rego Barros (Lepidoptera: Arctiidae) in controlling the Siam weed, Chromolaena odorata (L.) King and Robinson in southern Ghana was assessed in C. odorata infested fields through monthly sampling and monitoring surveys carried out between October 2007 and March 2008. Insect data was collected using line transects of 100 metres long and 100 metres apart and the removal, sweep net and direct count methods were used and data on the impact of feeding damage on the weed was collected by measuring several plant characteristics. The populations of P. pseudoinsulata were generally low in all sites investigated, throughout the study period. However, higher numbers of the bio-agent were recorded at site #1 (Akotokyire, Central Region) compared to the other sites and this was significantly (P<0.05) different. Populations of P. pseudoinsulata reached their highest densities between October and December. The damage caused to C. odorata in the field by P. pseudoinsulata was too minimal and insignificant to impact negatively on the weed, thus the damage levels recorded are insufficient to meaningfully affect the growth rate of C. odorata. @ JASE

The Physicochemical Characteristics of Ibiekuma River Ekpoma, Nigeria

The Ibiekuma River is an important source of livelihood to its catchment. It contributes enormously to research success and living standard of students and staffs of the Ambrose Alli University Ekpoma, Nigeria. The aim of the study was to determine the impact of anthropogenic activities on the physicochemical properties of Ibiekuma River. Twenty seven water samples were collected at four stations during the study period and analyzed accordingly. The results obtained shows that the physicochemical parameters of the river were in conformity with the World Health Organization (WHO), National Agency for Food, Drug Administration and Control (NAFDAC) and Nigerian Industrial Standard (NIS) safe limits, except for pH values which ranged from 4.69 to 4.81. The heavy metal concentrations were found to be within the limit of the guidelines prescribed by WHO and NAFDAC. Also, there was no significant difference (P > 0.05) in the concentrations of the physicochemical parameters across the four stations sampled along the Ibiekuma River. Water obtained from Ibiekuma River will be fit for domestic use, only if purified

The life history traits of the arctiine moth Pareuchaetes insulata, a biological control agent of Chromolaena odorata in South Africa

Pareuchaetes insulata (Walker) (Lepidoptera: Erebidae: Arctiinae) was released in KwaZulu-Natal, South Africa, as a biological control agent against Chromolaena odorata (L.) King and Robinson (Asteraceae) between 2001 and 2009. Although the moth did establish at one out of some 30 release sites, its population level is generally low in the field. Two closely related biological control agents, P. pseudoinsulata Rego Barros and P. aurata aurata (Butler) had previously failed to establish despite several years of releases. Studies of life history traits of P. insulata (males and females) were conducted to determine whether several aspects of its developmental and reproductive biology can explain its poor performance, and to compare the development and reproductive biology of P. insulata with the two other closely related species. At 25 °C, overall mortality of immature stages was generally low (below 12 %). Although the duration of the larval life stage was statistically longer for females, overall they eclosed as adults before the males (i.e. protogyny). Pupal mass, growth rate and total leaf area consumed were higher in females. Mated females laid 74% of their eggs on the first four nights following eclosion and lived an average of 5.92 ± 0.19 days. The moth also showed good biological attributes such as high fecundity (number of eggs), egg hatchability and female mating success (the number of matings that resulted in fertile eggs). Significant positive correlations were detected between insect performance metrics and leaf consumption and between fecundity and pupal mass. A 23 % greater lifetime reproductive output (387.62 ± 19.50 eggs per female) for P. insulata compared with P. aurata aurata was recorded. We hypothesize that the absence of protandry in P. insulata might have contributed to the low population levels of the moth in the field. The results of this study contribute to our understanding of the life history traits of erebid moths in the subfamily Arctiinae deployed for the biological control of C. odorata

Nitrogen fertilisation improves growth of Chromolaena odorata (Asteraceae) and the performance of the biological control agent, Pareuchaetes insulata (Erebidae)

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. odorata plants 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 of C. odorata plants relative to low fertilisation. When individuals of P. insulata were 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

Flavonoids isolated from the South African weed Chromolaena odorata (Asteraceae) have pharmacological activity against uropathogens

BACKGROUND: Urinary tract infections (UTIs) caused by opportunistic pathogens are among the leading health challenges globally. Most available treatment options are failing as a result of antibiotic resistance and adverse effects. Natural sources such as plants may serve as promising alternatives. METHODS: Compounds were isolated from the South African weed Chromolaena odorata through column chromatography. Purified compounds were tested for antimicrobial activity using the p-iodonitrotetrazolium chloride (INT) colorimetric method, against uropathogenic Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, Aspergillus fumigatus and Cryptococcus neoformans. Anti-biofilm, anti-adhesion and metabolic inhibition activities were investigated against selected strains. Safety of the compounds was determined against Vero monkey kidney, C3A human liver and colon (Caco2) cells. RESULTS: Four compounds identified as pectolinaringenin (1), (±)-4′,5,7-trimethoxy flavanone (2), 5-hydroxy-3,7,4′- trimethoxyflavone (3) and 3,5,7-trihydroxy-4′-methoxyflavone) (4) were isolated. Minimum inhibitory concentration (MIC) varied between 0.016 and 0.25 mg/mL. Compounds 2 and 3 showed promising antimicrobial activity against E. coli, S. aureus, K. pneumoniae, A. fumigatus and C. neoformans with MIC between 0.016 and 0.125 mg/mL, comparable to gentamicin, ciprofloxacin and amphotericin B used as positive controls. Compounds 2 and 3 showed good anti-biofilm and metabolic inhibition activities against E. coli and S. aureus but weak anti-adhesion activity against the organisms. Low toxicity with selectivity indexes between 1 and 12.625 were recorded with the compounds, indicating that the compounds were rather toxic to the microbial strains and not to the human and animal cells. CONCLUSION: Pharmacological activities displayed by compounds 2 and 3 isolated from C. odorata and low toxicity recorded credits it as a potential lead for the development of useful prophylactic treatments and anti-infective drugs against UTIs. Although known compounds, this is the first time these compounds have been isolated from the South African weed C. odorata and tested for antimicrobial, anti-biofilm, metabolic inhibition and anti-adhesion activities.The National Research Foundation, South Africahttps://bmccomplementmedtherapies.biomedcentral.compm2020Paraclinical Science

The Impact of Pareuchaetes pseudoinsulata (Lepidoptera: Arctiidae), on the Growth Rate of Chromolaena odorata (L.) in Southern Ghana

The abundance and effectiveness of Pareuchaetes pseudoinsulata Rego Barros (Lepidoptera: Arctiidae) in controlling the Siam weed, Chromolaena odorata (L.) King and Robinson in southern Ghana was assessed in C. odorata infested fields through monthly sampling and monitoring surveys carried out between October 2007 and March 2008. Insect data was collected using line transects of 100 metres long and 100 metres apart and the removal, sweep net and direct count methods were used and data on the impact of feeding damage on the weed was collected by measuring several plant characteristics. The populations of P. pseudoinsulata were generally low in all sites investigated, throughout the study period. However, higher numbers of the bio-agent were recorded at site #1 (Akotokyire, Central Region) compared to the other sites and this was significantly (P<0.05) different. Populations of P. pseudoinsulata reached their highest densities between October and December. The damage caused to C. odorata in the field by P. pseudoinsulata was too minimal and insignificant to impact negatively on the weed, thus the damage levels recorded are insufficient to meaningfully affect the growth rate of C. odorata. @ JASE

Larvicidal activity of the cold and hot water leaf extracts of Azadirachta Indica a. Juss (meliaceae) against the larvae of Culex guinquefasciatus say (diptera: culicidae)

This study investigated the potency of the cold and hot water leaf extracts of Azadirachta indica A. Juss (Meliaceae) against the third instar larvae of Culex quinquefasciatus (Say) (Diptera: Culicidae), the vector of lymphatic filariasis. Ten actively swimming third instar larvae of Cx. quinquefasciatus were exposed to different concentrations of 0.0, 1.0, 2.0 and 3.0 % (w/v) of cold and hot water leaf extracts of A. indica, after which percentage larval mortality was monitored for 24 and 48 hours. Results from this study revealed that both extract types (cold and hot water) of A. indica demonstrated excellent larvicidal activities against the larvae of Cx. quinquefasciatus at all tested concentrations (excluding the control – 0.0 % w/v). Percentage larval mortality was slightly a function of both concentration and exposure duration. Following a 48 hour exposure period of Cx. quinquefasciatus larvae to different concentrations of A. indica cold and hot water leaf xtracts, the highest concentration (3.0 % w/v) of both extract types was observed to demonstrate a perfect larvicidal activity (100 %) against the test insect. In conclusion, this study recommends the application of A. indica cold and hot water leaf extracts in the control of Cx. quinquefasciatus specifically at their potential breeding sites and also in areas where lymphatic filariasis is endemic.Keywords: Azadirachta indica, Leaf extracts, Larvicidal activity, Culex quinquefasciatu

Repellence and toxicological activity of the root powder of an invasive alien plant, Chromolaena odorata (L.) (Asteraceae) against Callosobruchus maculatus (Fab.) (Coleoptera: Chrysomelidae)

Although several studies have demonstrated the repellent and insecticidal activities ofthe leaf extracts or powder of the invasive alien plant, Chromolaena odorata againststored product pests, studies focusing on the activities of the roots are scarce. Thepresent study investigated the repellent and insecticidal activity of C. odorata rootpowder against the cowpea weevil, Callosobruchus maculatus. Beetle infested cowpeagrains were exposed to two concentrations (2.43 and 3.98 g) of C. odorata root powderfor 12, 24, 36, 48 and 72 hours after which percentage repellence and mortality werecalculated. The root powder of C. odorata significantly repelled C. maculatus, and therepellent activity was a function of both concentration and exposure time. Following a48-hour exposure period, 3.98 g of C. odorata root powder exhibited the highest (91%)repellent activity against C. maculatus. Mortality of C. maculatus caused by the rootpowder of C. odorata plants was high and also observed to be concentration andexposure time dependent. At a low concentration of 2.43 g, C. odorata root powderaccounted for 100 % mortality of C. maculatus after a 72-hour exposure period. Thisstudy demonstrates the potential of C. odorata root powder in the control of C. maculatusin Nigeria, and portends an avenue for the utilization of an invasive alien weed in Nigeria.Keywords: Cowpea, Chromolaena odorata, Root powder, Toxicity, Mortality, Repellence,Callosobruchus maculatu