Macadamia Nut Research Articles

Extraction, Characterization, and antineoplastic effect of Macadamia nut extracts against cutaneous melanoma Cells: A Comprehensive study Focused on SK-MEL-28 cells

Extraction, Characterization, and antineoplastic effect of Macadamia nut extracts against cutaneous melanoma Cells: A Comprehensive study Focused on SK-MEL-28 cells

Temperature and Precipitation Synergistically Affect Yield, Harvesting Time and Post-Processing Quality of Tropical Macadamia Nuts

In response to climate change challenges and to ensure stable macadamia nut production, this study analyzed empirical data on macadamia nut yield, climate factors, harvesting time, and post-processing quality from 2020 to 2022. Key findings include: (1) During the flowering to fruit growth stage, 2020 had the highest average temperature, followed by 2021, and then 2022. Conversely, 2022 had the highest precipitation, followed by 2021, and then 2020. (2) Lower temperatures and higher precipitation during the flowering to fruit growth stage contributed to a significant increase in macadamia nut yield, which indirectly extended the harvesting time. In 2022, the average yield of the eight macadamia growers was 8.04 t ha−1, significantly higher than the yields of 6.60 t ha−1 and 6.16 t ha−1 in 2021 and 2020, respectively. Furthermore, the average harvesting time for the eight macadamia growers in 2022 was 8.88 days longer than that in 2021, and 12.50 days longer than that in 2020. (3) Temperature and precipitation had a significant impact on the post-processing quality of macadamia nuts. Lower temperature and higher precipitation during the flowering to fruit growth stage significantly increased the proportion of first-grade fruit, as well as the incidence of mildewed and insect-infested fruits. In conclusion, although a lower temperature and higher precipitation can improve macadamia nut yield, they also lead to delayed harvesting and decreased post-processing quality. Given the observed yield sensitivity to temperature and precipitation, targeted water supplementation strategies during peak heat periods emerge as vital. This approach should be integrated with broader climate resilience planning, including the timing of pest control and disease management, to safeguard macadamia nut production against the multifaceted challenges posed by climate change.

The Potential for Hyperspectral Imaging and Machine Learning to Classify Internal Quality Defects in Macadamia Nuts

Tree nuts are rich in nutrients, and global production and consumption have doubled during the last decade. However, nuts have a range of quality defects that must be detected and removed during post-harvest processing. Tree nuts can develop hidden internal discoloration, and current sorting methods are prone to subjectivity and human error. Therefore, non-destructive, real-time methods to evaluate internal nut quality are needed. This study explored the potential for VNIR (400–1000 nm) hyperspectral imaging to classify brown center disorder in macadamias. This study compared the accuracy of classifiers developed using images of kernels imaged in face-up and face-down orientations. Classification accuracy was excellent using face-up (>97.9%) and face-down (>94%) images using ensemble and linear discriminate models before and after wavelength selection. Combining images to form a pooled dataset also provided high accuracy (>90%) using artificial neural network and support vector machine models. Overall, HSI has great potential for commercial application in nut processing to detect internal brown centers using images of the outside kernel surface in the VNIR range. This technology will allow rapid and non-destructive evaluation of intact nut products that can then be marketed as a high-quality, defect-free product, compared with traditional methods that rely heavily on representative sub-sampling.

Combined cellular phenotyping and high-throughput sequencing analysis reveals the symbiotic relationships between different types of macadamia root systems and arbuscular mycorrhizal fungi

Macadamia nuts, scientifically designated as Macadamia integrifolia, are a highly valuable crop that originated in Australia. This study provides a comprehensive examination of the symbiotic relationships between various macadamia root systems and arbuscular mycorrhizal fungi (AMF). The four principal macadamia-producing regions in Yunnan Province were selected for investigation on the basis of meticulous criteria. To determine the AMF infection rate, the roots were stained. Furthermore, high-throughput sequencing was employed to conduct a comprehensive analysis of the fungal diversity in the rhizosphere soil. The findings were definitive, indicating that both normal and cluster roots are capable of establishing a symbiotic relationship with AMF. Secondary forests exhibited significantly elevated fungal diversity relative to normal roots, while cluster roots demonstrated the lowest diversity and notable regional variation, indicating that the environment exerts a considerable influence on inter-root fungi and AMF. The analysis of the fungal community composition revealed that the predominant groups were Ascomycetes and Basidiomycetes. The FUNGuild function prediction clearly indicated distinct differences in the fungal functions of secondary forests, cluster roots, and normal roots. This study provides a scientific foundation for the sustainable development of macadamia nuts and significantly contributes to a deeper comprehension of the intricate interactions between macadamia and AMF, thereby fostering the long-term stable and healthy growth of the macadamia nut industry.

Determination of nut varieties and their detection in festive cookies by MALDI-TOF mass spectrometry.

Nuts contain a large amount of essential fatty acids, amino acids, and whole range of minerals and vitamins valuable for human health, yet certain risks are associated with their consumption, of which allergic reaction is the most important. Considering the growing number of people suffering from allergies caused by allergens of protein origin, the aim of this work is to find out whether nuts can be distinguished from each other on the basis of contained proteins. A total of eleven raw and subsequently heat-treated nuts (almonds, Brazil nuts, cashews, coconuts, hazelnuts, macadamia nuts, peanuts, pecans, pine nuts, pistachios, and walnuts) were analyzed using MALDI-TOF (matrix-assisted laser desorption/ionization time-of-flight) mass spectrometry with the subsequent finding of characteristic m/z values for each analyzed nut. No previous method for protein extraction was used. The characteristic values were used to verify the composition of seven types of festive cookies - six commercial products and one "unknown" cookie, where it was not known in advance, which nut it was made from. The procedure, together with the found characteristic m/z values, could serve to rapidly identify the plant origin of nut products.

An Improved Sampling and Baiting Method for Phytophthora tropicalis and P. heveae Detection in Macadamia integrifolia.

Macadamia nuts are, economically, the second most important crop in the state of Hawai'i. A recent decline in yield and acreage has been attributed to insect damage and diseases such as Macadamia Quick Decline (MQD) caused by Phytophthora tropicalis and P. heveae. To develop an improved methodology for the diagnosis and treatment of MQD, investigations were undertaken to better understand the pathosystem of the disease. These investigations included sampling from multiple locations from sectioned trees utilizing two methods of tissue collection and isolations using two baiting techniques. The collection of tissue from the cambium and phloem of trees after scraping away the bark and in locations of recent or current sap exudation using a narrow diameter steel awl proved to be an efficient means for the molecular detection of the MQD pathogens from infected trees exhibiting MQD symptoms. In addition, a more efficient and cost-effective baiting method using apple puree was developed.

Macadamia nut residue-derived biochar: An eco-friendly solution for β-naphthol and Reactive Black-5 removal

The generation of liquid waste containing dyes and complex organic compounds is a problem in the textile industries. In this work, we evaluated the use of macadamia nut residue as a precursor of a biochar for the treatment of these effluents through the adsorption process. The macadamia nut endocarp undergoes a sequential treatment involving pyrolysis at 600 °C followed by physical activation with CO2 and H2O vapor at 700 °C. Characterization of the resulting macadamia nut residue-derived biochar (MB) is accomplished through various techniques, including X-ray diffractometry (XRD), thermogravimetric analysis (TGA), scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS), nitrogen physisorption analysis and the pH at the zero charge point (pHZCP). Performance studies reveal that pH exerts minimal influence on the adsorption phenomenon. The Elovich kinetic model effectively describes the adsorption kinetics for both β-naphthol and Reactive Black 5 (RB5), with adjusted coefficients of determination (R2adj) of 0.99 and 0.94, respectively. Further analysis using the intraparticle diffusion model demonstrates that β-naphthol adsorption kinetics involve multiple mechanisms, while RB5 adsorption is predominantly governed by intraparticle diffusion. Equilibrium adsorption data for both adsorbates fit well with the Sips isothermal model, yielding maximum adsorption capacities of qmax β-naphthol = 15.16 mg∙g−1 and qmax RB5 = 3.08 mg∙g−1 at 55 °C. The adsorption process for both compounds is spontaneous and endothermic, based on the enthalpy values, it can be inferred that the β-naphthol adsorption is governed by weak van der Waals forces, indicating physisorption. As for RB5, the enthalpy value suggests that the phenomenon occurs due to electrostatic interactions between the molecule and the surface groups with higher energy involved. This study highlights the potential of macadamia nut residue biomass as a precursor for biochar, demonstrating its favorable attributes for application as an effective adsorbent material in the removal of organic compounds such as β-naphthol and RB5 from wastewater streams within the textile industry.

Detection of Fatty Acids and Some Secondary Metabolites in Macadamia and Hazelnut Fruits and their Shells, with Studding the Physiochemical Properties of its Extracted Oil: A comparative Study

General Background: Nuts are widely recognized for their nutrient density, offering a rich source of beneficial fatty acids and antioxidant phytochemicals. Specific Background: Among these, macadamia and hazelnuts are popular for their unique compositions, yet direct comparisons of their nutritional and bioactive profiles remain limited. Knowledge Gap: Despite their recognized health benefits, comparative analyses of the fatty acid profiles, bioactive compositions, and physicochemical characteristics between these nuts are scarce. Aims: The study compared macadamia and hazelnut oils' fatty acid content, lipid-soluble vitamins, phenolic compounds, and physicochemical properties to enhance their functional applications. Results: The findings revealed that hazelnut oil exhibited a higher polyunsaturated fat content, particularly linoleic acid (22.8% vs. 18.25%), while macadamia oil contained significantly more vitamin E, contributing to superior antioxidant potential. Both oils demonstrated the presence of vitamins A, D, and K1, with notable concentrations of quercetin and rutin among other flavonoids. Novelty: This study is novel in its comprehensive comparative analysis of these two nuts, particularly in identifying the unique phenolic compounds in the nutshells, which are often discarded but show potential as nutraceuticals. Implications: Macadamia and hazelnut oils offer significant nutritional benefits, with compositional variations allowing for personalized bioactivity and culinary applications. Further research is recommended for human health promotion. Highlights: Hazelnut oil has more polyunsaturated fats; macadamia oil is richer in vitamin E. Both nuts contain vitamins A, D, E, K1, and flavonoids. Phenolic compounds in nutshells have potential as nutraceuticals. Keywords: macadamia nuts, hazelnut oil, fatty acids, antioxidant phytochemicals, bioactive compounds

Heterogeneous solid residue from macadamia nut processing as viable feedstock for high-temperature gasification

This study delves into the intriguing prospect of concurrently utilizing macadamia husk and nutshell for biomass gasification, aiming to generate sustainable energy. By scrutinizing their physicochemical properties such as thermal behaviors, char conversion kinetics, and syngas properties we unveiled an intriguing revelation. The fusion of these residues creates an apt feedstock for biomass batch-gasification in industrial settings. This resultant blend inherits distinctive traits from its constituent parts, profoundly influencing gasification reactivity and fostering heightened char conversion efficiency and stability. Spanning 2165 s, this process exhibited commendable control. Furthermore, the residue amalgamation consistently yields an average syngas flow rate of 0.00136 [mol (g minute)−1], predominantly composed of CO at 0.00097 [mol (g minute)−1], constituting over 71 % of the syngas. These findings underscore the potential of merging these residues to optimize the conversion process and bolster resource availability, thus propelling advancements in waste-free energy production and sustainable energy technologies.

Efficient removal of emerging pollutant oxytetracycline by cost‐effective biochar–hydroxyapatite composite

AbstractBiochar (BC) and hydroxyapatite (HAp) are widely used in environmental remediation due to their high adsorption capacity, porous structure, large specific surface area, chemical stability, non‐toxicity, and low solubility. Combining BC and HAp is a green and effective strategy for creating new adsorbents (BCH) that have a synergistic impact on wastewater treatment. In this study, BCH composites derived from apatite ore and macadamia nut shells were synthesized by the wet impregnation method to remove oxytetracycline (OTC) from aqueous solutions. The BC‐HAp composite with a ratio of 10:1 (by weight) was the most effective material for removing OTC. The Redlich–Peterson model achieved the highest correlation coefficient among the four models tested (Freundlich, Langmuir, Temkin, and Redlich–Peterson). The maximum adsorption capacity calculated with the Langmuir isotherm was 49.59 mg g−1. It was found that the adsorption process was significantly affected by the solution pH. The bipolar form of the drug was found to be OTC±, and the adsorption was most effective in solutions with a pH of 6. The OTC adsorption dominant mechanisms on nanocomposites could be electrostatic attraction, hydrogen bonding formation, surface complexation, or ion exchange. Therefore, the BCH composite showed great potential for removing OTC pollutants in a cost‐effective, and environmentally friendly manner.

Macadamia (Macadamia integrifolia) Nut-Based Beverage: Physicochemical Stability and Nutritional and Antioxidant Properties

The present work presents an investigation of the effects of xanthan gum (XG) and soy lecithin (SL) on the physicochemical stability, fatty acid profile (FAP), and antioxidant capacity (AC) of macadamia nut-based beverages with thermal treatment (TT), as well as physicochemical changes during storage and sensorial acceptability. An extreme vertices mixture design was used, varying the macadamia nut, SL, and XG. The results show that adding XG and SL decreased the Sauter (D[3,2]) and Brouckere (D[4,3]) diameters of particles in macadamia beverages and increased the zeta potential (ZP), which represents greater stability. After applying TT in beverages, D[3,2], D[4,3], and ZP increased. After processing and TT, the FAP and fat nutritional indices changed due to reducing SFA and PUFA and increasing MUFA relative to macadamia nut. No significant difference (p ≥ 0.05) was observed in the FAP of beverages with and without TT. The AC determined by DPPH and ABTS decreased in most beverages upon TT application. During storage for two months, the beverage particle size increased, there was a decrease in brightness, and no significant difference (p ≥ 0.05) was observed in ZP. Sensory analysis showed that the most stable beverage was not the most acceptable due to its viscosity.

Comparative Transcriptome Analysis Reveals Key Functions of MiMYB Gene Family in Macadamia Nut Pericarp Formation.

Macadamia nuts are one of the most important economic food items in the world. Pericarp thickness and flavonoid composition are the key quality traits of Macadamia nuts, but the underlying mechanism of pericarp formation is still unknown. In this study, three varieties with significantly different pericarp thicknesses, namely, A38, Guire No.1, and HAES 900, at the same stage of maturity, were used for transcriptome analysis, and the results showed that there were significant differences in their gene expression profile. A total of 3837 new genes were discovered, of which 1532 were functionally annotated. The GO, COG, and KEGG analysis showed that the main categories in which there were significant differences were flavonoid biosynthesis, phenylpropanoid biosynthesis, and the cutin, suberine, and wax biosynthesis pathways. Furthermore, 63 MiMYB transcription factors were identified, and 56 R2R3-MYB transcription factors were clustered into different subgroups compared with those in Arabidopsis R2R3-MYB. Among them, the S4, S6, and S7 subgroups were involved in flavonoid biosynthesis and pericarp formation. A total of 14 MiMYBs' gene expression were verified by RT-qPCR analysis. These results provide fundamental knowledge of the pericarp formation regulatory mechanism in macadamia nuts.

Effects of Substrate Composition on the Growth Traits of Grafted Seedling in Macadamia (Macadamia integrifolia) Nuts.

Macadamia nut plantings in China are expanding year by year. In order to breed and promote superior varieties, this study analyzed the effects of different rootstocks and scions on the survival rate of grafted seedlings, and then selected the best substrate composition for plant growth. The results showed that the survival rate of the HAES788 variety as rootstock and Guire No. 1 as scion was the highest, reaching 96%. The optimal grafting time in December was better than that in March. Furthermore, among 16 substrate formulations, T12, T13, T15, and T16 had advantages of agglomerated soil and more well-developed root systems compared to the CK made of loess. The plant height, stem diameter, leaf length, leaf width, and dry weight of the aboveground and underground parts of the grafted seedlings planted in these substrate formulations were significantly higher than those plants planted in the CK. In addition, the substrate formulations T12, T13, T15, and T16 significantly improved the organic matter, total nitrogen, and total potassium content of the substrate soils, but little improvement was observed for total phosphorus content after 13 months. Overall, macadamia grafting times are best in December, with HAES788 and Guire No. 1 being the best rootstock and scion. The optimal substrate formulations are T12, T13, T15, and T16. This study provides a solid foundation for the production of high-quality macadamia plants.

A comparative analysis of the biochemical constituents and nutritional role of the Wild Sour Plum (Ximeniacaffra) nut with commercial nuts for potential commercialisation

The Sustainable Development Goals (SDGs) promote universal access to safe, nutritious food. Thus, the “Zero Hunger” campaign's sustainable efforts to eliminate hunger, by encouraging the cultivation and use of underutilised crops and their value-added products, can improve food systems and community development. Wild sour plum (Ximeniacaffra subs caffra) nuts, an Oleaceae fruit crop native to the Lowveld of Southern Africa, are an underappreciated value-added commodity. In large or small amounts, nuts provide vital nutrients for human consumption. The biochemical components profile of wild sour plum nuts was compared to different commercial nuts to determine their potential role in human nutrition. Wild sour plum, pecan, and macadamia nuts were sampled, each having 24 samples. These samples were tested for various biochemical constituents including total fat and calcium. The study found that pecan nuts and macadamia nuts were superior compared to other nuts, with regards to total fat and calcium content, pecan nuts containing a total fat content of 11.7 g per 100 g dry weight (g/100 g DW), and macadamia nuts containing a total calcium content of 70.5 mg per hundred gram dry weight (mg/100 g DW). The study found that wild sour plum nuts could potentially provide enough nutrients to fulfill the nutritional recommended daily intake for humans. Thus, wild sour plum nuts may be important in human diets, provided crop production is done properly, which includes irrigation, fertilisation, and temperature management of the crop.

Novel edible coating based on Macadamia Nut oil and chitosan to maintain the antioxidant and physical properties of tomato fruits

Innovative approaches for extending the shelf life of tomatoes are required due to increased postharvest losses of climacteric-fruits. The use of edible coatings is recently considered as a promising approach due to their non-toxicity and affordability properties. The coatings form physical barriers that alter the internal atmosphere of the fruit and slow down a ripening process. The influence of an edible coating comprising of chitosan and macadamia nut oil on the antioxidant and physical properties of tomato fruits is reported. The antioxidant and physical qualities of tomato fruits were investigated using different coating solutions. Various concentrations of macadamia nut oil, ranging from 1 % to 2.5 %, were used as independent coating solutions. Additionally, another set of coating solutions was prepared by mixing macadamia nut oil in the same concentration range (1 % to 2.5 %) with 1 % w/v chitosan. The tomatoes were dipped into the coating solutions and stored under a postharvest shed (23.8–30 °C, 65.8–97.5 % RH) for 20 days to monitor total phenolic content, total flavonoid content, ascorbic acid content, color, percentage weight loss, decay percentage, and shelf life after every 5-days interval. The results showed a significant difference (P < 0.05) between coated and uncoated tomato samples. The coated tomatoes showed the significant retention of total flavonoid content, total phenolic content, hue angle and red-green (a*) compared to uncoated tomatoes. On contrast, the decrease of decay, weight loss, the lightness (L), blue-yellow (b*), chroma, and ascorbic acid content was lower for coated compared to control tomatoes. The findings indicated that 1 % macadamia nut oil exhibited the highest retention of antioxidant and physical properties, and lowest decrease in ascorbic acid content from 0.014 mg/100 g on the 5th day to 0.0096 mg/100 g on the 20th day was observed. Thus, the findings from this study suggest that the macadamia nuts can serve as a cheap and low-cost source of edible oil suitable for prolonging the shelf life of tomatoes and related fruits.

Mild modification of sponge-like carbon: Ammonia post-treatment for enhanced CO2 adsorption and suitability for supercapacitors

During the synthesis of carbon-based CO2 adsorbents and supercapacitors, the introduction of nitrogen atoms into the carbon matrix has been identified as a means to enhance their performance. Nevertheless, the intricate effects of nitrogen doping on material properties pose a significant challenge in developing efficient methodologies. In this investigation, porous carbons resembling sponges were fabricated utilizing macadamia nut shells as a precursor and a dual salt comprising K2C2O4-KCl as an activating agent. Subsequent modification of the materials through ammonia post-treatment facilitated the production of nitrogen-doped porous carbon. The alterations in surface characteristics and pore morphology after ammonia treatment were meticulously examined to unravel the underlying mechanism of this modification process. The samples under scrutiny showcased remarkable CO2 adsorption capacities, peaking at 6.97 mmol/g at 0 °C and 4.65 mmol/g at 25 °C. Employing mathematical models to probe the influence of pore structure and surface properties on CO2 adsorption efficacy proved to be fruitful. A linear correlation was established to depict CO2 adsorption behavior, underscoring the joint impact of ultramicropore volume and nitrogen content on the adsorption process. Notably, the material exhibited a specific capacitance of 290.4F/g at a current density of 0.5 A/g within a three-electrode configuration, demonstrating commendable rate capability and cyclic stability. The pivotal findings from this inquiry emphasize that ammonia post-treatment represents a gentle modification strategy exerting minimal influence on the pore architecture, thereby efficaciously enhancing both CO2 adsorption and electrochemical performance.

Revolutionizing Phenolic Content Determination in Vegetable Oils: A Cutting-Edge Approach Using Smartphone-Based Image Analysis.

This study addressed the need for a more accessible and efficient method of analyzing phenolic content in vegetable oils. The research aimed to develop a method that could be widely adopted by both researchers and industry professionals, ultimately revolutionizing the way phenolic content in vegetable oils is analyzed. This study developed a method of determining the total phenolic content (TPC) in vegetable oils using smartphone image analysis in the RGB color model. The method employed a gallic acid calibration solution and demonstrated exceptional determination coefficients for the RGB colors. The R-red color was selected as the basis for the analyses, and the method was statistically equivalent to standard UV/Vis spectrophotometry. The highest TPC was determined in hemp and olive oils, while the lowest was found in rice bran, grapeseed, and macadamia nut oils. This study concluded that smartphone image analysis, mainly using the R component of the RGB color model, was a superior alternative to traditional spectrophotometric methods for determining the TPC in vegetable oils. This innovative approach could revolutionize phenolic content analysis by providing researchers and industry professionals with a cost-effective, safe, and efficient tool. The estimated limit of detection (LOD) of 1.254 mg L-1 and limit of quantification (LOQ) of 3.801 mg L-1 further confirmed the reliability and comparability of the method. With these findings, it was expected that the method would be widely adopted in the future.

An Analysis of the Main Nutrient Components of the Fruits of Different Macadamia (Macadamia integrifolia) Cultivars in Rocky Desertification Areas and a Comprehensive Evaluation of the Mineral Element Contents

This study aims to understand the main nutrient composition and comprehensively evaluate the differences in the mineral element contents of fruits of different macadamia cultivars, as well as screen good cultivars that are suitable for use in rocky desert mountains. Nine macadamia nut cultivars were selected as test materials in rocky desert mountain orchards. The contents of crude fat, crude protein, and total soluble sugar in kernels and N, P, K, Ca, Mg, Fe, Mn, Cu, Zn, and B in peels and kernels were determined, respectively. Then, the kernels’ mineral element contents were comprehensively evaluated based on principal component analysis. The results showed that the kernels were rich in crude fat, protein, and soluble sugar, with the crude fat content reaching 75% or greater, and the variation among cultivars was small. However, the variation in soluble sugar content was extensive. The content of mineral elements varied in different cultivars and parts of the fruit, with the average macronutrient content being K &gt; N &gt; Ca &gt; P &gt; Mg in the pericarp and N &gt; K &gt; P &gt; Mg &gt; Ca in the kernel, and the content of micronutrients in the pericarp and the kernel being Mn &gt; Fe &gt; Zn &gt; Cu &gt; B. By principal component analysis, the 10 mineral nutrient indexes were calculated as four principal components, with a cumulative contribution rate of 88.051%. Using the affiliation function value method and the calculation of the comprehensive evaluation value, the nine cultivars could be classified into three categories. The cultivar with the highest comprehensive evaluation value of the mineral element content was O.C. The one with the lowest value was H2, which indicated that O.C is a suitable variety for popularization in rocky desert mountainous areas. Stepwise regression analysis concluded that P, K, Fe, Mn, and Cu were the indicators significantly influencing the mineral element content of macadamia nuts and fruits in rocky desert mountains.

Aquatic macroinvertebrate community colonisation and succession in macadamia orchard and communal area reservoirs: a case study of Luvuvhu River valley, South Africa

The demand for macadamia nut production worldwide has led to increased use of pesticides and chemicals for pest and disease control. Reservoirs in these macadamia farming sectors are at . The current study investigated macroinvertebrate colonisation and succession associated with two macadamia orchards and two communal area reservoirs. The potential effects of stressors from these land uses was tested for and compared using stone substrates over a 6-week period. Stone substrates from both reservoir types were abundantly colonised over time and the total macroinvertebrate taxa and abundance showed an increasing trend across the sampled weeks, with macadamia orchards having the highest number of macroinvertebrate taxa. Strong ecological succession was observed across reservoirs, with the initial succession of early colonisers – i.e., Chironominae (, Ostracoda (and Anax sp. (predator) within communal area reservoirs, and Chironominae, Ostracoda Radix natalensis (scrapers) in macadamia orchard reservoirs – followed by predatory colonisers such as Gyrinidae larvae, Trithemis sp. (macadamia orchard reservoirs), and Ranatra sp. (communal area reservoirs). Macroinvertebrate community structure differed significantly across sites and weeks, with no similarity being observed for communities across the different reservoirs. Redundancy analyses further highlighted 11 sediment chemistry variables (i.e., pH, resistivity, P, K, Na, Ca, Mg, Cu, B, Fe and S) which were significantly related to macroinvertebrate community structure. Thus, sediment variables were found to be better predictors of macroinvertebrate community structure in macadamia orchard reservoirs than communal area reservoirs. Consequently, we concluded that differences in colonisation ability among taxa and environmental stressors were important factors driving succession. These results add to the understanding of the macroinvertebrate colonisation processes and environmental stressors within agricultural landscapes, which can aid in the development of conservation management of freshwater ecosystems.

Relative abundance and damage by species in the Lepidoptera borer complex of macadamia nuts in the Barberton area, South Africa

Larvae of the nut borer complex, which include Thaumatotibia leucotreta, T. batrachopa, Cryptophlebia peltastica and Ectomyelois ceratoniae, cause extensive economic damage to macadamias in South Africa. Monitoring the changing species composition in this complex over a growing season provides valuable information for managing populations. In this study, pheromone traps were placed in two orchards planted with two different cultivars and used to monitor moth numbers over a 28-week period, while larval numbers and nut damage were monitored weekly over a 21-week period from the onset of flowering. Larvae were identified using a combination of morphology and DNA sequences of ~658 bp of the cytochrome oxidase I (COI) gene. Both larval and moth numbers were dominated by T. leucotreta, followed by T. batrachopa, with respective trap catches of 69% and 27%. Spearman correlations indicated strong linear relationships between nut diameter and numbers of eggs per nut for both the Beaumont and 816 cultivars. Poor correlations were found between weekly moth numbers and the number of eggs per nut. A two- to three-week lag was observed between weekly T. leucotreta trap catches and egg numbers. In contrast, egg numbers correlated strongly with larval infestation levels and the incidence of damaged nuts. Although the numbers of eggs and larvae were higher in Beaumont than cv. 816 nuts, higher incidences of nuts with husk and kernel damage were recorded for cv. 816. This study highlights the importance of monitoring of moth and larval numbers in macadamia orchards and showed that such data could be used to predict pest incidence during the season. This study questions the norm in South Africa, which is that macadamia nut borer (MNB) is usually the most abundant species in the nut borer complex.