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Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) or western flower thrips (WFT), has become a global pest of economic importance. WFT is extremely polyphagous, attacking a wide range of host plants in both field and greenhouse production systems. Chemical control is the most frequently used method for the control of WFT, but their cryptic nature, which protects them from contact with insecticides, and their resistance to many insecticides, have become critical limiting factors in terms of control. This has led to heightened emphasis on biological control in integrated pest management (IPM) programmes for WFT. Most commonly used predators are relatively large and unable to enter the cryptic spaces inhabited by WFT, thus limiting their ability to reduce WFT populations. Entomopathogenic nematodes (EPNs) and fungi offer alternative biocontrol options that suit IPM programmes well. This review focuses on WFT and its management, with an emphasis on crops being grown under cover, and on the use of EPNs for biocontrol, from a South African perspective.
The banded fruit weevil (BFW), Phlyctinus callosus (Schönherr) (Coleoptera: Curculionidae), is a polyphagous pest, feeding on a number of plant groups, like grasses, weeds, herbs, and woody plants. Phlyctinus callosus is indigenous to South Africa and has a limited distribution throughout the world. The weevil was only reported in the Western Cape, South Africa, New Zealand and Australia. Where the BFW occurs, it is a major insect pest of grapes and deciduous fruit, causing damage by feeding on the leaves and fruit, including the fruit stalks and shoots. The BFW adults, especially, cause fruit damage by means of feeding on the skin and the underlying flesh, which results in the formation of shallow lesions with phytosanitary implications. Other damage includes foliage damage, berry scarring and ringbarked stems, due to feeding activity. Control has mainly been achieved through the use of trunk barriers, which are effective in preventing the weevil from reaching the fruits, although such use is labour-intensive. Biocontrol agents, like entomopathogenic nematodes (EPNs) and entomopathogenic fungi (EPF), are preferred alternatives, because they have no negative effect on the environment, and because they leave no residues in the fruit intended for export. Using biological control agents in combination to control insect pests emphasises the importance of knowing the biology of the target insect pest, as well as that of the biocontrol agents, such as EPNs and EPF.
Progress since 2007 with the commercial implementation of the sterile insect technique (SIT) for Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae) in citrus orchards in South Africa is discussed. To enable expansion of the SIT programme, rearing equipment was developed and adapted where necessary. Production monitoring systems for traceability, cold chain management and quality management of reared insects were developed and constantly improved. The initial 3300-ha SIT-treated area in the Citrusdal region was increased to 4800 ha by incorporating parts of the Olifants River Valley and sterile insect releases were also introduced into 6500 and 2200 ha of the Sundays River and Gamtoos River Valleys (Eastern Cape Province), respectively. There was a progressive, seasonal improvement in wild T. leucotreta suppression following routine releases of sterile moths in all areas treated, resulting in reduced crop losses and fewer rejections for T. leucotreta in export fruit. The SIT for T. leucotreta was also expanded to the Hex River Valley (Western Cape Province) and the Lower Orange River area (Northern Cape Province) in 2016.
The tomato leafminer, Tuta absoluta (Meyrick), (Lepidoptera: Gelechiidae), is a devastating pest of tomato that has recently become a major threat to tomato production in many countries in the Mediterranean Basin, Africa and Asia. Mariner-like elements (MLEs) are class-II transposons with short inverted terminal repeats (ITR) flanking a single open reading frame (ORF) coding for a transposase. In the present study, we have isolated eight full-length MLEs from the tomato leaf miner by PCR amplification, using a single primer designed from the ITR of Hyalophora cecropia L. Mariner signature sequence D,D(34)D, as well as the conserved amino acid motifs, WVPHEL and YSPDLAP(T)D, were identified. However, sequences analysis revealed defective elements with the presence of several kinds of mutations generating stop codons, frameshifts, and non-functional transposase. Based on predicted transposase sequences, T. absoluta MLEs (Tamar1) belongs to the cecropia subfamily and clustered closely with MLEs from other Lepidoptera members suggesting vertical genetic transmission from a common ancestor. The identification of mariner-like elements in this invasive species will be useful to understand the genome dynamics in Lepidoptera.
Sweet potato (Ipomoea batatas (L.) Lam. is an important food crop adaptable to a broad range of agro-ecological conditions. The knowledge of the performance of the available varieties under a specific ecological condition is important to improve the production. A field experiment was carried out at the University of Ghana farm during the major and minor rainy seasons of 2015 to determine the yield performance of seven improved Ghanaian sweet potato varieties (CRI-Apomuden, CRI-Ligri, Faara, CRI-Bohye, CRI-Dadanyuie, Okumkom, Sauti) and their susceptibility to the sweet potato weevil, Cylas spp. (Coleoptera: Brentidae). Significant difference was found in the storage root yield among the varieties, with CRI-Ligri having the highest in both major (23.11 t/ha) and minor (22.49 t/ha) rainy seasons. CRI-Apomuden and CRI-Ligri scored the highest levels of infestation by sweet potato weevil in the major and minor seasons (1.94 and 2.00, 1.84 and 1.96, respectively) and yield loss (44.44 % and 42.80 %, 23.84 % and 23.87 %, respectively). While the lowest infestation levels in the major rainy season were recorded on Faara and Okumkom (1.18 and 1.31, respectively) with yield losses of 10.32 % and 9.09 %, respectively. However, in the minor rainy season, there was no significant difference among Faraa, Okumkom, CRI-Bohye and CRI-Dadanyuie in terms of infestation level and yield losses. Significant difference was found in all measured root characteristics including the shortest weevil distance, root neck length, root length, root girth and root size index. The storage root infestation had a strong negative correlation with the shortest weevil distance, a strong positive correlation with the root size index and a weak negative correlation with root neck length. In this study, Okumkom appeared to be less susceptible to sweet potato weevil infestation with relatively acceptable yield performance and therefore can be recommended for use by farmers to improve sweet potato production.
Western flower thrips (WFT), Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), is an important field and greenhouse pest of many crops worldwide. To control F. occidentalis is extremely challenging, because of its cryptic behaviour, short life cycle, and resistance to many insecticides. The life history and success rate of WFT on chrysanthemum (Dendranthema grandiflora) leaflets and green bean pods (Phaseolus vulgaris) showed that more first instar larvae hatched, and developed faster, with a higher survival rate, on the former than on the latter, making chrysanthemum a more attractive and suitable host than were the green beans. A total of 11 local South African entomopathogenic nematode species and the exotic Steinernema feltiae, were tested, under laboratory conditions, for pathogenicity against WFT. Generally, Heterorhabditis spp. were more virulent than were the Steinernema spp. The study showed that locally isolated Steinernema yirgalemense (66 %), Heterorhabditis baujardi (67 %), and Heterorhabditis bacteriophora (60 %) had potential for the control of F. occidentalis, in terms of targeting its soil-dwelling stages. Results from the temporal development study showed that both S. yirgalemense and H. baujardi were able to complete their life cycles in the host, and to produce a new cohort of infective juveniles.
The effect of some abiotic and biotic factors on the population sex ratio of the date palm mite (DPM), Oligonychus afrasiaticus, were evaluated on four date palm cultivars in two regions (Riyadh and Qateef) of Saudi Arabia. The week of infestation, fruit stage, and their interactions, as well as the cultivar, significantly affected the DPM sex ratio. The DPM infestation, in the first week, started with a high female proportion (from 0.78 to 1) in both regions of the ‘kimri' fruit stage, and remained female-biased till the fifth week of infestation (from 1.5:1 to 4:1) with a growing DPM population density in both regions. The DPM sex ratio declined to equality (1:1) during the sixth week of infestation, the onset of the ‘khilal’ fruit stage, and further declined to a male-biased sex ratio (4:1) on the Selj, Hamra and Shaishie cultivars, with a declining DPM population density in the last week of infestation. The date fruit stage affected the sex ratio of DPMs negatively in Riyadh and positively in Qateef. The interaction between the week and fruit stage had a significant positive effect on the DPM sex ratio in Riyadh, and a negative effect in Qateef. This study of the DPM sex ratio could be a step in establishing a female-based sampling programme during the early weeks of infestation.
The biological activity of essential oils extracted from four plants of the Lamiaceae family (Lavandula angustifolia Lawrence, 1989 (= L. officinalis Linnaeus), Mentha piperita Linnaeus, 1753, Ocimum basilicum Linnaeus, 1753 and Origanum compactum Bentham) was evaluated on adults of Rhyzopertha dominica Fabricius 1792 (Coleoptera: Bostrychidae) and Sitophilus oryzae Linnaeus, 1763 (Coleoptera: Curculionidae) using fumigation and repellency tests carried out at four doses and different exposure times, under laboratory conditions. The results obtained show that the four essential oils are often more toxic to R. dominica than to S. oryzae. LC50 varied between 15.14 and 18.49 µl/l of air for R. dominica, and between 33.51 and 50.27 µl/l of air for S. oryzae. The LT50 values ranged from 8 to 27 h for R. dominica and between 161 and 601 h for S. oryzae at a concentration of 20 µl/l of air. The oil of O. basilicum caused, after 96 h of fumigation at a concentration of 20 µl/l air/20 g of durum wheat, Triticum durum, 100 % mortality rates for R. dominica and 41 ± 13.87 % for S. oryzae. Oils of O. compactum and O. basilicum were the most active against R. dominica and S. oryzae, with repellency rates of 82 % and 60.5 %, respectively.
Use of the sterile insect technique (SIT) targeting the malaria vector Anopheles arabiensis has been proposed and is currently under investigation. The SIT requires production of large numbers of sterile males and therefore mass-rearing of the target species is required. One critical factor during mass-rearing for sterile releases is the need to synchronise developmental life stages to assist in pupae and adult harvesting during production. However, by nature An. arabiensis egg hatching, and subsequent development is staggered as a survival strategy resulting in unsynchronised production. This causes a loss in efficiency during mass-rearing. This study aimed to investigate the effect of egg storage on egg hatch synchronisation, survival rate of aquatic life stages and the subsequent effect on production lead-time of a laboratory-reared An. arabiensis strain. Eggs from colonised An. arabiensis were collected, drained onto a filter paper to remove excess water, and stored for an increasing number of days, up to four days. After the storage time, proportion hatching and pupating as well as the time to hatch and pupation were measured and analysed using a one-way ANOVA and a Kaplan-Meier Survival analysis, respectively. No significant difference was observed in the proportion hatching or pupating between the different storage durations. However, there was a significant reduction in time to hatch and pupate. In conclusion, egg storage is a viable method to synchronise hatching, which could, in combination with other factors, assist in synchronous production of pupae for this strain without having adverse effects on survival.
The aim of the study was to determine insecticidal potential of three plant extracts (Calatropis procera, Eucalyptus globulus and Mentha arvensis) and crude venom of an orb-web spider, Neoscona theisi, in the laboratory using Musca domestica and Aedes aegypti as model insects. Laboratory bioassays were conducted against three doses of plants extracts (0.2 mg/ml, 0.4 mg/ml and 0.6 mg/ml) and spider venom (10 µg/ml, 20 µg/ml and 30 µg/ml). Ellman et al.'s (1961) method was followed to estimate the activity of acetylcholinesterase of insects. Calatropis procera was found to be more effective in killing the insects. The mortality rate was increased with an increase in plant extract or venom dose. Calatropis procera inhibited acetylcholinesterase more proficiently as compared to the M. arvensis and E. globulus extracts. Crude spider venom also significantly inhibited the estimated activity of acetylcholinesterase in M. domestica and Ae. aegypti. It is concluded from the study that both plant extracts and spider venom inhibited the activity of acetylcholinesterase in M. domestica and Ae. aegypti but C. procera is more efficient in killing the insects.
Saprophagous fly larvae are sustainable protein sources that can improve animal feed and contribute to human food security worldwide. The objective of this study was to understand poultry farmers' perception of the production and use of fly larvae as poultry feed in Burkina Faso. A survey was conducted among 360 households in 12 villages located in nine provinces of two regions of Western Burkina Faso. The survey showed that the majority of the poultry farmers have a good knowledge of the potential utility of maggots in poultry nutrition. Over 15.6 % of the farmers have already produced fly larvae to feed their poultry and 7 % are presently doing it at least occasionally. Other farmers occasionally collect fly larvae in decomposing wastes. However, various constraints limit the production and the use of maggots in the villages, the main ones being lack of knowledge of production techniques, difficulty of access to suitable substrates, socio-cultural constraints and ignorance of the potential of using maggots as poultry feed. The study highlights the need for raising awareness and for the development of sustainable and efficient production systems.
The use of bio-pesticides is the potential alternate of synthetic residual insecticides to cope with the problem of resistance among different insect pests while posing no threats to the environment and biological control agents. Laboratory trials were conducted in the Microbial Control Laboratory, Department of Entomology, University of Agriculture, Faisalabad (UAF), Pakistan, during 2017–18 to investigate the effect of Beauveria bassiana (Balsamo) Vuillemin (1.8 × 107 and 1.8 × 108 conidia/ml) and Bacillus thuringiensis (Berliner) at a dose rate of (0.5 and 1 µg/g) alone and in combination against fifth and sixth larval instars of Rhynchophorus ferrugineus Olivier (Curculionidae: Coleoptera). The insects were exposed to fungal and bacterial treatments by larval immersion and diet incorporation method, respectively. Results revealed that the combined application of B. bassiana at the rate of 1.8 × 108 conidia/ml and B. thuringiensis at 0.5 and 1 µg/g exhibited synergistic effects, while combination of lower fungal concentration with both dose rates of B. thuringiensis showed additive effect against target instars of R. ferrugineus. Moreover, the mortality data showed that fifth instar larvae were more susceptible to microbial treatments than sixth instar. Maximum mycosis and sporulation was recorded in the cadavers of R. ferrugineus where B. bassiana was applied individually at dose rate of 1.8 × 107 conidia/ml. The present work suggests that B. bassiana in combination with B. thuringiensis could be a cost–benefit strategy against R. ferrugineus on date palms.
The control of major insect crop pests of cowpea in Africa often involves synthetic pesticides to protect these crucial agricultural products. However, consequent harms to the environment, humans, animals and beneficial insects by these synthetic pesticides have driven a search for more sustainable integrated insect pest management (IPM) approaches, including the use of biological controls and neem (Azadirachta indica A. Juss) oil as alternatives to synthetic pesticides for the control of the pod-sucking bug Clavigralla tomentosicollis Stål on African cowpea crops. To date, however, no study to the authors' knowledge has investigated the compatibility and effectiveness of biological controls and neem approaches used together. In this study, we assessed the effects of two available preparations of neem oil (cold-pressed and hot-pressed) on the eggs of C. tomentosicollis and its parasitoid Gryon fulviventre Crawford. The main results of the study support the hypothesis that both cold-pressed and hot-pressed neem oil sprays are compatible with biological/IPM control efforts using G. fulviventre. While hot-pressed neem showed stronger effects on levels of egg hatchability and mortality for C. tomentosicollis compared to cold-pressed neem, no differences in outcomes across tested neem concentrations were observed. Future research, including field trials, will have the potential to elucidate any underlying mechanisms of these results and/or to more exactly identify appropriate concentrations needed to successfully integrate biological and non-synthetic controls for major cowpea pests in Africa.
Globally Helicoverpa armigera, a polyphagous pest of many economic crops, has developed resistance to almost all groups of insecticides presently in used for its control. In cotton, its larvae cause severe damage and feeds on all plant parts including young leaves, square, flowers and bolls which in turn cause economic damage. Recent reports on development of its resistance to transgenic cotton which has Cry1Ac and Cry2Ab (Bt cotton) has given an indication of future threat to cotton growers. Therefore, use of semiochemicals as management strategy for these insects would be a great alternative as ethological pest management within insect pest management (IPM) to control this menace. These semiochemicals/volatile organic compounds can be present in insect (egg, larva, female) as well as in the host plant. In the present study, a total of seven volatiles have been identified from methanol extract of eggs and faecal pellets, out of which two volatiles; methyl ester of octadecanoic acid (methyl stearate) and methyl ester of hexadecanoic acid (methyl palmatate), were detected in egg samples. From faecal pellets five volatiles were identified namely octadecanoic acid (stearic acid) and its methyl ester, hexadecanoic acid (palmitic acid) and its methyl ester, tetradecanoic acid (myristic acid), caryophyllene and its oxide, phytol. Interestingly, methyl ester of octadecanoic acid and methyl ester of hexadecanoic acid were detected in both the samples. Volatiles observed in common may be used as effective semiochemicals in ethological pest management of Helicoverpa armigera. However, further study is needed to validate the competency of these fatty acids under field conditions.
A study was conducted for two consecutive years (2016–17 and 2017–18) to understand the relative role of weather parameters and humid thermal ratio (HTR) on population dynamics of thrips, T. tabaci, in bulb onion. Counts were made at five randomly selected spots, consisting of five plants in each spot. Results revealed that the highest peak of 65 thrips per plant was observed during fourth standard meteorological week (SMW). Further, irrespective of the years, higher numbers of thrips were observed during third to sixth SMW. Correlation analysis showed a significant positive correlation (r = 0.587*) with HTR and a significant negative correlation with maximum temperature (r = –0.628*) and minimum temperature (r = –0.566*). The linear and logarithmic regression analysis between HTR and thrips population had explained 50 % of variation. Thus, the present study suggests that apart from temperature, prevailing humid thermal ratio during the growth period could have an impact on occurrence of thrips in bulb onion.
A coleopteran insect, Trachyderma hispida, was collected from the proximity of ceramic factories in Khorshed district, Alexandria, Egypt, to elucidate the testicular damage elicited by heavy metal pollution. Bioaccumulation of heavy metals was estimated by using X-ray microanalysis. Histological and ultrastructure examination revealed various changes in germ cells in insects collected from the polluted region. The inducible histological alterations included: occlusion and collapsed follicles, disrupted cyst wall and necrotic spermatogenic elements. Ultrastructure changes implied abnormal chromatin condensation, ill-defined nuclear membrane, vacuolated cytoplasm, disintegrated nebenkern, deterioration of mitochondrial derivatives and degeneration of axonemes. In addition, agglutinated spermatids, and sperms with a double tail were noticed. The most noteworthy feature in spermatogonia and spermatocyte was the intra-tubular inclusion bodies. Histological and electron micrographs pointed out the structure of the parietal cell which functioned as a Sertoli cell. Adverse damage to these cells by ceramic pollution was reported. In conclusion, by using insects as bioindicators, ceramic production may impair reproduction.
Essential oils extracted from plants provide an efficient and eco-friendly alternate to manage the challenge of mosquito-borne diseases. The use of these oils as larvicidal agents, however, poses the problem of their improper dispersion in larval aquatic habitats. To overcome this, the methodology for the synthesis of Eucalyptus globulus oil nanoemulsions in water was standardised by mixing the oil in water with Tween®-20 in three different ratios (1:1, 1:2 and 1:3) by sonication. On the basis of thermodynamic stability tests, oil emulsions having E. globulus oil and Tween®-20 in 1:2 ratio was found to be the most stable which was characterised using transmission electron microscopy (TEM). The droplets of prepared nanoemulsions were found to have an average size of 40 nm and were spherical in shape. The larvicidal activity of stable aqua nanoemulsions of eucalyptus oil was tested against Aedes aegyptiusing five different concentrations at 100, 90, 80, 70, 60 and 50 ppm (in triplicate). LC50 and LC90 values were found to be 60.30 and 92.20 ppm. Observations revealed that 70 ppm was the most effective concentration, causing 100 % mortality within 24 h.
The present study aimed to evaluate the inherited deleterious effects and protein response of Musca domestica to LD50 of gamma irradiation through three generations at different cross combinations (irradiated female (IF) × irradiated male (IM), unirradiated female (UIF) × irradiated male, and irradiated female × unirradiated male (UIM)). Gamma radiation induced a significant effect on the reproductive potential of M. domestica through the first three generations, where the sterility index was higher than those of the untreated control, especially in F1 and F2 generations. The great inherited deleterious effects occurred when IM × IF and when IM × UIF indicating that the male of M. domestica is more radiosensitive than the female. The electrophoretic separation of protein bands in the third larval instar of M. domestica resulted from different matings (irradiated and unirradiated males and females) vs control was investigated in the present study. The control larvae recorded the highest number of protein bands (27), while the larvae resulted from crossing of UIF × IM (LD50 = 5 Gy) contained the lowest number of protein bands (14). However, the number of protein bands in larvae resulted from crossing of IF × UIM (LD50 = 7 Gy) was 24 bands also the number of bands resulted from crossing IF × IM (LD50 = 4 Gy) was 21 bands. In addition, the results showed that the type of mating affects the distribution of protein bands, where some protein bands appeared and others disappeared in third larval instar resulted from the different irradiated and unirradiated males and females. These results may indicate that males of M. domestica are more radio sensitive than females where the lowest number of bands was separated in larvae resulted from IM × UIF. Consequently, these radiation doses are recommended for the establishment of Male Sterile Insect Technique (SIT) programmes against M. domestica.
The family Aphalaridae in Egypt is revised. Eight species in five genera and two subfamilies are treated, namely Blastopsylla occidentalisTaylor, 1985 (Spondyliaspidinae), Brachystetha nitrariaeLoginova, 1964, Caillardia dilatataLoginova, 1978, Colposcenia aliena (Löw, 1881), Colposcenia elegans (De Bergevin, 1932), Colposcenia tamaricis (Puton, 1871), Crastina heslopharisonii (Samy, 1972), and Crastina linnavuoriiLoginova, 1974 (Aphalarinae). The genus BrachystethaLoginova, 1964 is recorded here for the first time in Egypt with a single species Brachystetha nitrariaeLoginova, 1964, recently collected from Hurghada (Red Sea Governorate). An illustrated key to the Egyptian genera, and diagnoses for the recorded taxa are also given.
The larvae of Tuta absoluta are harmful leafminers that attacks different solanaceous plants such as tomato, potato, colour pepper, eggplant and many others. The life tables of a population are important to control pests because they give the most comprehensive description of the growth, survival and fecundity. Life tables of T. absoluta reared on tomato, potato and eggplant in the laboratory were determined and analysed using the age-stage, two-sex life tables. Developmental periods of eggs, larvae, pupae and adults, and pre-oviposition and oviposition periods of T. absoluta fed as larvae on tomato, potato or eggplant were estimated. Fecundity of a female fed on the same three hosts was 198.3, 172.2 and 133.7 eggs/female, respectively. Life table parameters such as the net reproductive rates (R0) (92.25, 76.25 and 67.82 days), the mean generation time (T0) (31.96, 36.06 and 36.94 days), the intrinsic rate of increase (rm) (0.142, 0.117 and 0.113/day) and the finite population increase (λ) (1.15, 1.12 and 1.12/day) were obtained for T. absoluta fed on tomato, potato and eggplant, respectively. The shortest doubling time (DT) was obtained with tomato leaves (4.9 ± 0.06 days), while the longest DT was obtained with eggplant leaves (6.30 ± 0.08 days). Based on the results herein, it appears that the development and reproductive potentiality of T. absoluta depends on its host plant; this pest can therefore be more dangerous to its suitable host (tomato) than other hosts.
Citrus brown mite, Eutetranychus orientalis (Klein), is one of the most serious pests on fruit, vegetable and ornamental plants in the world. The present study aimed to evaluate the toxicity, and the repellency/attractancy effects of five essential oils (clove, castor, cinnamon, black cumin and anise) on E. orientalis under laboratory conditions. Also, field experiments were performed to investigate the efficacy of two essential oils (castor oil and black cumin 10 %), compared with other acaricides and predacious mites. Two acaricides (abamectin 5 % EC [Biomectin™] and fenpyroximate 5 % SC [Ortus ]), in addition to the predacious mites Phytoseiulus persimilis and Euseius scutalis, applied at two levels of release (200 and 300 individuals/tree). The results showed that after 1 h of the treatment, essential oils of black cumin and anise recorded the highest percentage of repellency (80–100 %) followed by castor oil (30–90 %), and clove oil (50 and 70 %), while cinnamon was the lowest. In addition, castor oil showed good repellency effect after 6 h, while black cumin has the same effect after 1 h of application. Field experiments revealed that castor oil gave the best efficacy in suppressing E. orientalis population compared with control, followed by black cumin oil. While applying the acaricides fenpyroximate and abamectin recorded good reduction of E. orientalis with mortality of 88.85 and 87.92 %, respectively. The numbers of E. orientalis were affected by releasing the biological control agent P. persimilis at 200 and 300 individuals/tree, where the numbers of E. orientalis decreased on trees to 1.5, 1.0 indiv./10 leaves after 15 days of release compared with pre-treatment account 3.0, 2.5 indiv./10 leaves, respectively.
The genus Rhynchophorus (Herbst 1795) (Coleoptera: Curculionidae) is a key pest of palms worldwide, but information on Rhynchophorus spp. attacking the oil palm, Elaeis guineensis Jaquin in Uganda is outdated. This study was carried out to establish the diversity, distribution and incidence of Rhynchophorus spp. on E. guineensis at three production set-ups namely large-scale plantations, adaptive trials and small-scale farms in three (Lake Victoria Crescent, Lake Albert Crescent and Western Highlands) agro-ecological zones in Uganda; and to establish the effect of vicinity to natural vegetation on incidence of the pest. Two surveys were conducted in 2018 during the dry and wet seasons. Oil palm trees in each study site were scored as infested (1) or not infested (0) with Rhynchophorus spp. Heavily infested oil palms were sampled to collect weevils for morphological identification and were found to be of only one species, Rhynchophorus phoenicis(Fabricius, 1801). Incidence of R. phoenicis was compared across sampling sites, season and proximity to natural vegetation; and subjected to a multiple linear regression with temperature, relative humidity and rainfall. Incidence of R. phoenicis was highest in Masaka district in the western side of River Nile in Lake Victoria Crescent agro-ecological zone; and absent in Mayuge and Bugiri district at the eastern side of River Nile in Lake Victoria Crescent agro-ecological zone. The pest incidence was higher in the wet than the dry season; and in fields far away from natural vegetation than those that were nearer. Mean incidence of R. phoenicis did not correlate with temperature, relative humidity and rainfall. These findings offer clues of factors to consider in designing strategies for managing R. phoenicis in Uganda.
The peach fruit fly (PFF), Bactrocera zonata (Saunders), is a serious, multivoltine and polyphagous insect pest that infests fruits directly, causing a serious damage. Increasing incidence of insecticide resistance has led to a renewed interest in developing insecticides with alternative modes of action, lower environmental impact and greater compatibility with integrated pest management (IPM) programmes. Accordingly, a selection of crude extracts (CEs) and essential oils (EOs) of eucalyptus, jojoba, lavender, neem was screened against the PFF and their effects on some biological aspects were studied. Incubation periods of EOs at the used concentrations were lower than that of CEs. The egg hatchability in case of CEs was significantly affected compared to EOs. The average numbers of pupae collected differed significantly according to both CEs and EOs of the tested four plants. In respect of the CEs, the formed pupae of treated individuals were significantly lower than that of the untreated ones. EOs of lavender inhibit pupal formation of B. zonata more strongly than the EOs from the other tested botanicals. The average number of emerged adults of CEs- or EOs-treated larval artificial diets were highly significantly lower than that of the control. The differences between averages of emerged adults of CEs of the four tested botanicals were significant. Neem crude extract was the most potent, showing the lowest average of emerged adults of B. zonata. The differences between averages of malformed adults resulted in both CEs- and EOs-treated larval diets were statistically non-significant. Based on these results, EOs were more effective than CEs of the used plants against the PFF.
Checklists of species of organisms from defined localities have aided scientists who seek to establish new taxon records therein. This work was carried out to update information on the Checklists of Nigerian Termites published about four decades ago and to reconcile information on richness and diversity of Nigerian termites. Taxonomy-related articles published on Nigerian termites were collated, reviewed and compared with the information contained in the world's most comprehensive termite reference by Krishna et al. (2013) to bring this update forth. Currently, Nigerian termites have increased from the previously reported 120 species in 1980 to 147 species in 66 genera from three taxonomic families – Kalotermitidae, Rhinotermitidae and Termitidae.
The cotton leaf worm, Spodoptera littoralis, is one of the most injurious agricultural pests in Egypt. In the present study, the interaction between spinosad and Bacillus thuringiensis, using different pairings, in third and fifth instar larvae was determined. Activities of α- and β-non-specific esterases and acetylcholinesterase (AChE) were also determined. Additionally, AChE transcript abundance using the real-time polymerase chain reaction (PCR) was detected. The cumulative percentage mortality of S. littoralis, third and fifth instar larvae, to spinosad and B. thuringiensis were increased gradually by increasing the concentrations. Spinosad was more potent than B. thuringiensis. Sequential application of these bio-insecticides, on the LC25 level on third and fifth instar larvae, when spinosad was first applied, showed synergistic interaction and additive effect, respectively. On the other hand, when B. thuringiensis was first applied, using the same timing of application, additive interaction was observed for both third and fifth instars. Individual, simultaneous and sequential applications of these bio-insecticides induced variable changes in α- and β-esterases and AChE activities. Real-time PCR (qRT-PCR) revealed an increase in transcript abundance up to 2.0-fold in third instar larvae in case of sequential and simultaneous applications. Based on the results herein, integrated pest management programme using spinosad and B. thuringiensis can be successfully developed for the control of S. littoralis.
Integrated pest management of herbivorous pests relies on combining bio-insecticides and chemical insecticides for a satisfactory population control. The present study focused on evaluating the comparative toxicity of five insecticides, with different modes of action, against third and fifth instar larvae of Spodoptera littoralis and their influence on extent of oxidative stress in insect via detecting vitamin C content as well as measuring the activity of phenol oxidase (PO), catalase (CAT), peroxidase (POX), glutathione-S-transferase (GST) antioxidant enzymes compared to control. The results revealed that emamectin benzoate and indoxacarb were the most potent insecticides among the selected insecticides, based on their respective LC50 values. Thiacloprid, indoxacarb and emamectin benzoate significantly reduced Vitamin C content. Almost all treatments significantly increased PO activity. Only emamectin benzoate and Bacillus thuringiensis significantly induced POX activity. Indoxacarb and emamectin benzoate increased CAT activity in both instar larvae, whereas thiacloprid and indoxacarb decreased GST activity. In conclusion, emamectin benzoate and indoxacarb were the most potent insecticides. Activity of oxidative stress biomarkers upon insecticidal pressure has showed variable response.
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