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•31 microbial-based bioproducts currently registered in South Africa under Act 36 of 1947.•New guidelines for registration of biopesticides published in 2015.•4 locally manufactured ...mycoinsecticides containing Beauveria bassiana (Hypocreales).•1 locally manufactured product containing Cryptophlebia leucotreta granulovirus.•11 endemic Steinernema spp. and 2 endemic Heterorhabditis spp. described to date.
Invertebrate pests pose a significant threat to food security on the African continent. In response, South Africa has become one of the largest importers of chemical pesticides in sub-Saharan Africa, with several hundred active ingredients registered. To address the over-reliance on such chemicals, the South African Department of Agriculture, Forestry and Fisheries (DAFF) has eliminated or restricted several pesticides since the late 1970s. The recent launch of the South African National Bio-Economy Strategy and establishment of the South African Bioproducts Organisation (SABO), together with new guidelines for registration of biopesticides in 2015, also support this endeavour. Concurrently, entomopathogen-related research and bioproduct development has increased over the past decade. Currently, 31 products (seven manufactured locally) are registered under the Fertilizers, Farm Feeds, Agricultural Remedies and Stock Remedies Act 36 of 1947. Commercially important microbes include Beauveria bassiana (Cordycipitaceae), Metarhizium anisopliae (Clavicipitaceae), Cydia pomonella granulovirus, Cryptophlebia leucotreta granulovirus, Helicoverpa armigera nucleopolyhedrovirus (Baculoviridae) and Bacillus thuringiensis subsp. kurstaki and B. thuringiensis subsp. aizawai (Bacillaceae). Both parasitic and entomopathogenic nematodes (EPNs) show potential for development as bioinsecticides with one commercial EPN product, based on Heterorhabditis bacteriophora (Heterorhabditidae), registered under the Act. Rapid scientific progression, supported by a favourable legislative environment, should facilitate further advances in microbial control of phytophagous invertebrate pests in South Africa.
The use of entomopathogenic nematodes (EPNs) as biological control agents is impaired by their short shelf life. In this study, in vitro liquid-cultured infective juveniles (IJs) of Steinernema ...yirgalemense and S. jeffreyense were formulated at high concentrations using diatomaceous earth (DE) formulation of 900,000 and 700,000 IJs/g, respectively, to investigate storage stability and infectivity at different temperatures for 8 weeks. To prevent contamination during storage, antimicrobial agents Nipagin and Procydin were added to the formulation. The two nematode species differed in their survival and infectivity at different storage temperatures. The mean percentage survival decreased over time with all formulations (including the control without microbial agents), though the survival rate was higher at 14°C than it was at 25°C, with room temperature of 67-71% and 42-56%, respectively, after 8 weeks of storage. For the combined effects of antimicrobial agents and DE, Procydin managed to delay the growth of fungi longer than was achieved with Nipagin. However, Procydin lowered the survival rate and pathogenicity of both nematode species against the larvae of Tenebrio molitor. At a lower concentration, Procydin might have the potential for use in EPN formulations directed toward inhibiting fungal growth, though requiring further investigation.
The genus
of the family Enterobacteriaceae, are mutualistically associated with entomopathogenic nematodes of the genus
Although most of the associations are species-specific, a specific
sp. may ...infect more than one
sp. During the
life cycle, insect larvae are infected and killed, while both mutualists produce bioactive compounds. These compounds act synergistically to ensure reproduction and proliferation of the nematodes and bacteria. A single strain of
may produce a variety of antibacterial and antifungal compounds, some of which are also active against insects, nematodes, protozoa, and cancer cells. Antimicrobial compounds produced by
spp. have not been researched to the same extent as other soil bacteria and they may hold the answer to novel antibacterial and antifungal compounds. This review summarizes the bioactive secondary metabolites produced by
spp. and their application in disease control. Gene regulation and increasing the production of a few of these antimicrobial compounds are discussed. Aspects limiting future development of these novel bioactive compounds are also pointed out.
Entomopathogenic fungi (EPF) are important soil-dwelling entomopathogens, which can be used as biological control agents against pest insects. EPF are capable of causing lethal epizootics in pest ...insect populations in agroecosystems. During a survey of the orchard soil at an organic farm, different EPF species were collected and identified to species level, using both morphological and molecular techniques. The EPF were trapped from soil samples taken from an apricot orchard. The traps, which were baited in the laboratory, used susceptible host insects, including the last-instar larvae of Galleria mellonella (wax moth larvae) and Tenebrio molitor (mealworm larvae). The potential pathogenicity of the local Metarhizium majus isolate was tested and verified using susceptible laboratory-reared last-instar T. molitor larvae. The identification of the M. majus isolated from South African soil was verified using both morphological and molecular techniques. The occurrence of M. majus in the South African soil environment had not previously been reported.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Summary
Steinernema bakwenae n. sp. isolate SF857 has been isolated from a soil sample from the North West province of South Africa. The infective juveniles were isolated using Cobb’s decanting and ...sieving method, hand-picked from the nematode population and inoculated directly onto wax moth larvae. Morphological and molecular characterisation provides evidence for placing the new species in the Khoisanae-clade, adding a fifth member to this all-African clade. The new species is characterised by the following morphological features: third-stage infective juveniles with a body length of 1106 (1013-1233) μm, a distance from the anterior end to the excretory pore of 90 (81-103) μm, and a tail length of 87 (76-103) μm. The first-generation males can be recognised by a spicule length of 80 (66-89) μm and by a gubernaculum length of 51 (44-56) μm. The new species was confirmed by means of crossbreeding and characterised by means of sequences of the internal transcribed spacer (ITS), the partial 28S regions (D2-D3) of the ribosomal DNA and the mitochondrial cytochrome oxidase subunit (COI). Phylogenetic analyses show that S. innovationi and S. tophus are the closest relatives to S. bakwenae n. sp. in the Khoisanae-clade.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Using a sand bioassay,
Steinernema yirgalemense gave 93% control of cocooned pupae and emerging moths at a concentration of 20
IJs/cm
2, 7
days after treatment. Moths infected with nematodes were ...able to emerge normally and to fly away from the sand surface, before being trapped in the surrounding container.
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► Six EPN species found during a survey of citrus orchards. ►
Steinernema yirgalemense reported from South Africa. ► Bioassays with nematodes using the soil stages of the false codling moth
Thaumatotibia leucotreta. ► Infection of emerging moths escaping from sand and aerial transport of nematodes shown.
A survey was conducted to determine the diversity and frequency of endemic entomopathogenic nematodes (EPN) in citrus orchards in the Western Cape, Eastern Cape and Mpumalanga provinces of South Africa. The main aim of the survey was to obtain nematodes as biological control agents against false codling moth (FCM),
Thaumatotibia leucotreta, a key pest of citrus in South Africa. From a total of 202 samples, 35 (17%) tested positive for the presence of EPN. Of these, four isolates (11%) were found to be steinernematids, while 31 (89%) were heterorhabditids. Sequencing and characterisation of the internal transcribed spacer (ITS) region was used to identify all nematode isolates to species level. Morphometrics, morphology and biology of the infective juvenile (IJ) and the first-generation male were used to support molecular identification and characterisation. The
Steinernema spp. identified were
Steinernema khoisanae,
Steinernema yirgalemense and
Steinernema citrae. This is the first report of
S. yirgalemense in South Africa, while for
S. citrae it is the second new steinernematid to be identified from South Africa.
Heterorhabditis species identified include
Heterorhabditis bacteriophora,
Heterorhabditis zealandica and an unknown species of
Heterorhabditis. Laboratory bioassays, using 24-well bioassay disks, have shown isolates of all six species found during the survey, to be highly virulent against the last instar of FCM larvae.
S. yirgalemense, at a concentration of 50
IJs/FCM larva caused 100% mortality and 74% at a concentration of 200
IJs/pupa. Using a sand bioassay,
S. yirgalemense gave 93% control of cocooned pupae and emerging moths at a concentration of 20
IJs/cm
2. This is the first report on the potential use of EPN to control the soil-borne life stages of FCM, which includes larvae, pupae and emerging moths. It was shown that emerging moths were infected with nematodes, which may aid in control and dispersal.
The leaf miner, Liriomyza huidobrensis (Diptera: Agromyzidae) is a polyphagous fly, which infests a wide range of vegetables and ornamental plants. However, scant knowledge exists of the biology and ...ecology of the pest in the Western Cape province of South Africa, both of which are essential components in developing an effective management programme. Several aspects of its biology and ecology were studied in two potato Solanum tuberosum L. (Solanales: Solanaceae) fields in the Sandveld region during both winter and summer months. The population densities of adult L. huidobrensis were monitored using yellow sticky traps, which were retrieved and counted once every two weeks (June 2019 to January 2020). The number of leaf miner adults caught throughout the summer and winter monitoring periods was significantly different. In addition, 50 randomly selected plants were assessed for leaf damage (in the form of punctures and mines) using presence/absence sampling. Leaf miner persistence within the soil was confirmed through one-time soil sampling of the two fields, one month after harvesting. Leaf miner pupae were detected in the soil samples after the potatoes were harvested. However, no adult emergence was recorded among the collected pupae under laboratory conditions. The observed trend was that the traps, in both fields, caught an increasing number of leaf miners as the crops matured. Damage occurred in both the monitored fields as early as week four, after plant emergence. Of the five parasitoid species collected, Diglyphus isaea (Hymenoptera: Eulophidae) was the most abundant.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
False codling moth (FCM), Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae), is a priority pest on citrus, stone fruit, and table grapes. Current control focuses on the adult stage; ...however, each stage of the life cycle of the insect should be targeted. The potential of local biocontrol agents against FCM immature stages was investigated. Several entomopathogenic nematode (EPN) and entomopathogenic fungus (EPF) species were identified from soil samples collected from orchards and vineyards throughout the Western Cape province in South Africa. The eggs were proven to be susceptible (30–65%) to several EPN species, at 200 infective juveniles (IJs) per 50 µl. Xenorhabdus indica, the symbiotic bacterium of Steinernema yirgalemense Nguyen et al., caused significantly more mortality than the control. The EPNs were highly virulent against the FCM larvae, with S. yirgalemense causing 100% mortality in all trials. Metarhizium robertsii (78%), M. anisopliae (50%), and Beauveria bassiana (75%) caused high mortality in FCM larvae. The fully formed pupae were the most resistant of the immature stages, with the EPNs causing low mortality at 100 IJs per insect. As the FCM larvae were highly susceptible to S. yirgalemense and M. robertsii under laboratory conditions, they should be further tested, separately and in combination, in field conditions to illustrate the benefits of including them in a FCM‐IPM programme.
False codling moth (FCM), Thaumatotibia leucotreta (Lepidoptera: Tortricidae), is a priority lepidopteran pest in South Africa. Eggs of FCM proved to be susceptible (30–65%) to the entomopathogenic nematode Steinernema yirgalemense (100% mortality). FCM larvae were susceptible to S. yirgalemense (100% mortality), Metarhizium robertsii (78%), M. anisopliae (50%), and Beauveria bassiana (75%). As the immature FCM stages were susceptible to entomopathogens in the laboratory, field tests are needed to illustrate the benefits of including them in an IPM programme.
Entomopathogenic nematodes (EPNs) of the families
Heterorhabditidae
and
Steinernematidae
are efficient biological control agents against important insect pests. In vitro liquid culture production ...technology is a key factor in the success of implementing EPNs as a biological control agent. One of the first steps of in vitro mass culture is to use shake flasks to obtain nematode inoculum for optimising and upscaling to desktop and industrial fermenters. This study was the first attempt on the in vitro liquid mass culture of a local South African isolate,
Steinernema jeffreyense,
in 250 ml Erlenmeyer flasks, together with their mutualistic bacteria,
Xenorhabdus khoisanae
. After the successful in vitro production of
S. jeffreyense
-inoculum, different parameters for optimizing infective juvenile (IJ) recovery (developmental step when the IJ moult to initiate the life cycle) and yield, were investigated. This includes the effect of the volume of liquid medium in the flasks, two different orbital shakers setups and the initial IJ inoculum density. With 30 ml of liquid medium the mean percentage recovery of IJ after six days was 86%, with a yield of 121,833 IJ ml
−1
after 14 days, in comparison to 75% and 99,875 IJs ml
−1
respectively when 50 ml of liquid medium was used. No significant difference was found between IJ recovery and yield, using different orbital shakers setups. Among the three inoculum concentrations tested (1000, 2000 and 3000 IJ ml
−1
), the lowest concentration gave the highest IJ recovery and yield. Pathogenicity of IJs cultured in vitro was higher than those cultured in vivo.
Phlyctinus callosus and P. xerophilus (Coleoptera: Curculionidae) are two cryptic species of native entimine weevils, previously grouped together under the P. callosus sensu lato concept, that are ...pests of economic importance to the deciduous fruit and vine industry in the Western Cape province of South Africa. Laboratory bioassays were conducted using entomopathogenic fungi (EPF) isolates of Beauveria and entomopathogenic nematodes (EPNs), Heterorhabditis indica and Steinernema yirgalemense, to determine differences in susceptibility of adult P. callosus and P. xerophilus to potential biological control agents. The test arena used was 24‐well bioassay plates with an inoculation rate of 200 infective juveniles (IJs)/insect for EPNs and 5 × 105 conidia/insect for EPF. Insects were inoculated using a 12.7 mm filter paper impregnated with 50 μL of entomopathogen suspension. Infection was determined after 96 h incubation for EPNs through dissection of cadavers. Insects inoculated with EPF were incubated in the wells for 18 days and mortality recorded daily. Cadavers were surface sterilized and observed for overt mycosis. Differential susceptibility between P. callosus and P. xerophilus was observed in EPF but not in EPN bioassays. Differential susceptibility to EPF could be due to methodology. Low adult weevil pathogenicity was found for all entomopathogens, with variable results obtained from different bioassay batches.
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