Microbial control of phytophagous invertebrate pests in South Africa: Current status and future prospects

Conidial mass production of entomopathogenic fungi and tolerance of their mass-produced conidia to UV-B radiation and heat

We investigated conidial mass production of eight isolates of six entomopathogenic fungi (EPF), Aphanocladium album (ARSEF 1329), Beauveria bassiana (ARSEF 252 and 3462), Lecanicillium aphanocladii (ARSEF 6433), Metarhizium anisopliae sensu lato (ARSEF 2341), Metarhizium pingshaense (ARSEF 1545), and Simplicillium lanosoniveum (ARSEF 6430 and 6651) on white or brown rice at four moisture conditions (75-100%). The tolerance of mass-produced conidia of the eight fungal isolates to UV-B radiation and heat (45 °C) were also evaluated. For each moisture content compared, a 20-g sample of rice in a polypropylene bag was inoculated with each fungal isolate in three replicates and incubated at 28 ± 1 °C for 14 days. Conidia were then harvested by washing the substrate, and conidial concentrations determined by haemocytometer counts. Conidial suspensions were inoculated on PDAY with 0.002% benomyl in Petri plates and exposed to 978 mW m-2 of Quaite-weighted UV-B for 2 h. Additionally, conidial suspensions were exposed to 45 °C for 3 h, and aliquots inoculated on PDAY with benomyl. The plates were incubated at 28 ± 1 °C, and germination was assessed at 400 × magnification after 48 h. Conidial production was generally higher on white rice than on brown rice for all fungal species, except for L. aphanocladii ARSEF 6433, regardless of moisture combinations. The 100% moisture condition provided higher conidial production for B. bassiana (ARSEF 252 and ARSEF 3462) and M. anisopliae (ARSEF 2341) isolates, while the addition of 10% peanut oil enhanced conidial yield for S. lanosoniveum isolate ARSEF 6430. B. bassiana ARSEF 3462 on white rice with 100% water yielded the highest conidial production (approximately 1.3 × 1010 conidia g-1 of substrate). Conidia produced on white rice with the different moisture conditions did not differ in tolerance to UV-B radiation or heat. However, high tolerance to UV-B radiation and heat was observed for B. bassiana, M. anisopliae, and A. album isolates. Heat-treated conidia of S. lanosoniveum and L. aphanocladii did not germinate.

Naturally Occurring Yeasts Associated with Thaumatotibia leucotreta Can Enhance the Efficacy of the Cryptophlebia Leucotreta Granulovirus

Yeasts associated with lepidopteran pests have been shown to play a role in their survival, development, and oviposition preference. It has been demonstrated that combining these yeasts with existing biological control agents can enhance their efficacy. The tortricid Thaumatotibia leucotreta is a phytosanitary pest in the South African citrus industry, with the baculovirus Cryptophlebia leucotreta granulovirus (CrleGV) being one of the components that can control this pest. Several yeast species were shown to be associated with T. leucotreta larvae, which affected their behaviour and development. A series of detached fruit bioassays were performed to determine whether the combination of yeast with CrleGV enhances its efficacy. These assays included determining the optimal yeast/virus ratio, testing all isolated yeast species in combination with CrleGV, and further improving yeast/virus formulation by adding an adjuvant. The optimal yeast concentration to use alongside CrleGV was determined to be 106 cells·mL-1. Pichia kluyveri, P. kudriavzevii, Kluyveromyces marxianus, and Saccharomyces cerevisiae in combination with CrleGV reduced larval survival compared to CrleGV alone. The addition of molasses and BREAK-THRU® S 240 to P. kudriavzevii and S. cerevisiae in combination with CrleGV did not notably improve their effectiveness; however, there was an observed decrease in larval survival. In future studies, field trials will be conducted with combinations of CrleGV and P. kudriavzevii or S. cerevisiae to investigate whether these laboratory findings can be replicated in orchard conditions.

Transmission Electron Microscopy Observation of Morphological Changes to Cryptophlebia Leucotreta Granulovirus following Ultraviolet Irradiation

Cryptophlebia leucotreta granulovirus (CrleGV), a double-stranded DNA virus (genus Betabaculovirus, family Baculoviridae), is highly infective to the citrus insect pest Thaumatotibia leucotreta. The South African isolate CrleGV-SA is formulated into a commercial biopesticide and registered for use in several countries. In South Africa, it is used as a biopesticide in a multi-faceted integrated pest management approach for citrus crops involving chemical and biological control methods. The virus nucleocapsid is surrounded and protected by an occlusion body (OB) composed of granulin protein in a crystalline matrix. Like all other baculoviruses, CrleGV is susceptible to ultraviolet (UV) radiation from sunlight. This reduces its efficacy as a biopesticide in the field and necessitates frequent respraying. UV damage to baculovirus biopesticides is detected by means of functional bioassays. However, bioassays do not give an indication of whether any structural damage has occurred that may contribute to functional loss. In this study, transmission electron microscopy (TEM) was used to observe damage to the OB and nucleocapsid (NC) of CrleGV-SA, following controlled UV irradiation in the laboratory to mimic field conditions. The resultant images were compared with images of non-irradiated CrleGV-SA virus. TEM images of irradiated CrleGV-SA samples revealed changes to the OB crystalline faceting, a reduction in the size of the OBs, and damage to the NC following UV exposure for 72 h.

The case for integrated pest management in Africa: transition from a pesticide-based approach

Pest management in major cropping systems has long been dominated by chemical pesticides in Africa. Smallholder farmers have perceived pesticides as insurance to protect their crops. Consumers are less aware of pesticide-related food-safety issues, and markets providing economic incentives to producers who adopt alternatives to pesticides have been slow to emerge. Hence, overuse of pesticides has been constantly increasing. Although African countries have a number of pesticide-related policies, they are inadequately implemented. However, significant investment has been made on integrated pest management (IPM) innovations in recent decades. Resistant cultivars, agroecological approaches, biological control, and biopesticides have been developed against key biotic constraints in major cropping systems. They have been adopted at several pilot sites, where significant economic and ecological impacts have been documented. However, concerted efforts are necessary to harmonize policies and regulations across the continent to enhance the availability, accessibility, and affordability of IPM innovations to smallholder farmers.

Efficacy of Biopesticides in the Management of the Cotton Bollworm, Helicoverpa armigera (Noctuidae), under Field Conditions

Simple Summary

Cotton remains the most important cash crop in the world. The key insect pests of cotton include the African bollworm Helicoverpa armigera. This pest causes damage to crops estimated at greater than USD 2 billion per year worldwide. Excessive use of insecticides to control this pest has a negative effect on the environment, and is expensive for the farmers. The aim of this study is to explore the field efficacy of different biopesticides as an alternative to control H. armigera. Four biopesticides—namely, Eco-Bb^® (Beauveria bassiana), Bb endophyte (Beauveria bassiana), Bolldex^® (nucleopolyhedrovirus), and Delfin^® (Bacillus thuringiensis)—were evaluated and compared with the pyrethroid Karate^® (lambda-cyhalothrin) and an untreated control. Plots treated with Karate^® had significantly lower numbers of H. armigera larvae compared to the untreated control, and were comparable to the plots treated with Bolldex^®. On average, plots treated with Bolldex^® had a high seed cotton yield compared to the other treatments. Biopesticides showed a moderate reduction in the numbers of H. armigera larvae, and could thus be used within an integrated pest management programme.

Abstract

Cotton is one of the most valuable materials in the world, popularly used in the clothing industry and other products. However, its production is limited by the high infestation of insect pests. A study was conducted to evaluate the effects of different biopesticides on the control of the African bollworm (Helicoverpa armigera) under cotton field conditions. Four biopesticides—namely, Eco-Bb^® (Beauveria bassiana), Bb endophyte (Beauveria bassiana), Bolldex^® (Nucleopolyhedrovirus), and Delfin^® (Bacillus thuringiensis)—were evaluated and compared with the pyrethroid Karate^® (lambda-cyhalothrin) and an untreated control against H. armigera. Field trials were conducted at the Agriculture Research Council, Rustenburg, in the North West Province of South Africa during the 2017 and 2018 cotton seasons. The results revealed that in plots sprayed with Karate^® and Bolldex^®, the numbers of H. armigera were significantly reduced compared to the untreated controls. Plots treated with Bolldex^® had the lowest number of damaged bolls in 2017, while those treated with Karate^® had the lowest number of damaged bolls in 2018. All treated plots had significantly fewer damaged bolls when compared to the controls. A seed cotton yield of 5987 kg/ha was recorded in the plots that were treated with Bolldex^®—significantly higher than the yields from plots treated with Eco-Bb^®, Delfin^®, and Bb endophyte—in 2017. However, the yield in treatments with Eco-Bb^®, Delfin^®, and Bb endophyte was lower than that from the untreated controls during this season. In 2018, plots treated with Bolldex^® had the highest yield, at 6818 kg/ha, which was not different from the other treatments. The highest average seed cotton yield of 6400 kg/ha was recorded in the plots treated with Bolldex^®, followed by Karate^®. In summary, the efficacy of different biopesticides against H. armigera varied significantly, while the synthetic pesticide (Karate^®) and Bolldex^® resulted in more consistent control of this pest. The results suggest that biopesticides may, however, have the potential for use in the sustainable control of cotton bollworms as part of integrated pest management programmes, although further work is required to support this hypothesis.

A review of toxigenic fungi and mycotoxins in feeds and food commodities in West Africa

Fungal contamination is a threat to food safety in West Africa with implications for food and feed due to their climate, which is characterised by high temperatures and high relative humidity, which are environmental favourable for fast fungal growth and mycotoxin production. This report gives perspective on studies on toxigenic fungi (Aspergillus, Fusarium and Penicillium) and their toxins, mainly aflatoxins, fumonisins and ochratoxins commonly found in some West African countries, including Benin, Burkina Faso, Gambia, Ghana, Ivory Coast, Mali, Nigeria, Senegal, Sierra Leone, and Togo. Only four of these countries have mycotoxins regulations in place for feeds and food products (Ghana, Ivory Coast, Nigeria, and Senegal). Food commodities that are widely consumed and were thoroughly investigated in this region include cereals, peanuts, cassava chips (flakes), cassava flour, chilies, peanuts, locust beans, melon, and yam products. In conclusion, authorities and scientists needed to consider research and approaches to monitor mycotoxins in foods and feeds produced and consumed in West Africa.

The effect of climate variability in the efficacy of the entomopathogenic fungus Metarhizium acridum against the desert locust Schistocerca gregaria

Despite substantial efforts to control locusts they remain periodically a major burden in Africa, causing severe yield loss and hence loss of food and income. Distribution maps indicating the value of the basic reproduction number R₀ was used to identify areas where an insect pest can be controlled by a natural enemy. A dynamic process-based mathematical model integrating essential features of a natural enemy and its interaction with the pest is used to generate R₀ risk maps for insect pest outbreaks, using desert locust and the entomopathogenic fungus Metarhizium acridum (Synn. Metarhizium anisoliae var. acridum) as a case study. This approach provides a tool for evaluating the impact of climatic variables such as temperature and relative humidity and mapping spatial variability on the efficacy of M. acridum as a biocontrol agent against desert locust invasion in Africa. Applications of M. acridum against desert locust in a few selected African countries including Morocco, Kenya, Mali, and Mauritania through monthly spatial projection of R₀ maps for the prevailing climatic condition are illustrated. By combining mathematical modeling with a geographic information system in a spatiotemporal projection as we do in this study, the field implementation of microbial control against locust in an integrated pest management system may be improved. Finally, the practical utility of this model provides insights that may improve the timing of pesticide application in a selected area where efficacy is highly expected.

Mutualism between Gut-Borne Yeasts and Their Host, Thaumatotibia leucotreta, and Potential Usefulness in Pest Management

Thaumatotibia leucotreta is endemic to southern Africa and is highly significant for various fruit industries, including the South African citrus industry, due to its classification as a phytosanitary pest. Mutualistic associations between C. pomonella, closely related to T. leucotreta, and yeasts have previously been described and reported to reduce larval mortality and enhance larval development. Here, we determined which yeast species occur naturally in the gut of T. leucotreta larvae and investigated whether any of the isolated yeast species affect their behaviour and development. Navel oranges infested with T. leucotreta larvae were collected from geographically distinct provinces in South Africa, and the larvae were processed for analysis of naturally occurring associated yeasts. Six yeast species were isolated and identified from the guts of these T. leucotreta larvae via PCR amplification and sequencing of the ITS region of rDNA and D1/D2 domain of large ribosomal subunit. Larval development and attraction assays were conducted, and T. leucotreta larvae that fed on Navel oranges inoculated with yeast had accelerated developmental periods and reduced mortality rates. Neonate T. leucotreta were also attracted to YPD broth cultures inoculated with yeast for feeding. Oviposition preference assays were conducted with adult T. leucotreta females. Navel oranges inoculated with yeast were shown to influence the oviposition preference of adult females. Yeasts harbour the potential for use in biocontrol, especially when combined with other well-established control methods. This study provides a platform for future research into incorporating yeast with current biological control agents as a novel option for controlling T. leucotreta in the field.

In Vitro Effects of Leaf Extracts from Brassica rapa on the Growth of Two Entomopathogenic Fungi

This study aimed to determine the inhibitive or stimulatory effects of leaf extracts from two Brassica rapa subspecies on the hyphal growth of two well-known entomopathogenic fungi, Cordyceps fumosorosea and Beauveria bassiana. Extract concentrations of 50, 25, and 10% w/v based on leaf fresh weight were prepared from turnip (B. rapa subspecies rapa) and bok choy (B. rapa subspecies chinensis) leaves. Each concentration was individually incorporated into potato dextrose agar plates for in vitro bioassays. The center of each plate was inoculated with 20 µL of a fungal suspension that was allowed 24 h to soak into the agar before sealing the plates and incubating them at 25 °C under a 14-h photophase. The fungal colony perimeter was marked 5 days after inoculation on two perpendicular lines drawn on the bottom of each plate. Radial colony growth was measured from 4 marks per plate 5, 10, and 15 days later. Radial growth rates for both fungi were 1.3-2.0 and 0.9-1.4 times faster with bok choy and turnip extracts, respectively, at the 25% and 50% concentrations compared to the no-extract control treatment. Therefore, bok choy and turnip leaf extracts can stimulate entomopathogenic fungus growth within 15 days. Biochemical compounds in the extracts include sesquiterpenes, α-copaene, β-selinene, γ-gurjunene, calamenene, cubenene, and α-calacorene.

Genome assembly and annotation of Photorhabdus heterorhabditis strain ETL reveals genetic features involved in pathogenicity with its associated entomopathogenic nematode and anti-host effectors with biocontrol potential applications

The genome sequences of entomopathogenic nematode (EPN) bacteria and their functional analyses can lead to the genetic engineering of the bacteria for use as biocontrol agents. The bacterial symbiont Photorhabdus heterorhabditis strain ETL isolated from an insect pathogenic nematode, Heterorhabditis zealandica strain ETL, collected in the northernmost region of South Africa was studied to reveal information that can be useful in the design of improvement strategies for both effective and liquid production method of EPN-based pesticides. The strain ETL genome was found closely related to the type strain genome of P. australis DSM 17,609 (~60 to 99.9% CDSs similarity), but closely related to the not yet genome-sequenced type strain, P. heterorhabditis. It has a genome size of 4,866,148 bp and G + C content of 42.4% similar to other Photorhabdus. It contains 4,351 protein coding genes (CDSs) of which, at least 84% are shared with the de facto type strain P. luminescens subsp. laumondii TTO1, and has 318 unknown CDSs and the genome has a higher degree of plasticity allowing it to adapt to different environmental conditions, and to be virulent against various insects; observed through genes acquired through horizontal gene transfer mechanisms, clustered regularly interspaced short palindromic repeats, non-determined polyketide- and non-ribosomal peptide- synthase gene clusters, and many genes associated with uncharacterized proteins; which also justify the strain ETL's genes differences (quantity and quality) compared to P. luminescens subsp. laumondii TTO1. The protein coding sequences contained genes with both bio-engineering and EPNs mass production importance, of which numerous are uncharacterized.

Potential Use of Beneficial Microorganisms for Soil Amelioration, Phytopathogen Biocontrol, and Sustainable Crop Production in Smallholder Agroecosystems

Smallholder agroecosystems play a key role in the world's food security providing more than 50% of the food produced globally. These unique agroecosystems face a myriad of challenges and remain largely unsupported, yet they are thought to be a critical resource for feeding the projected increasing human population in the coming years. The new challenge to increase food production through agricultural intensification in shrinking per capita arable lands, dwindling world economies, and unpredictable climate change, has led to over-dependence on agrochemical inputs that are often costly and hazardous to both human and animal health and the environment. To ensure healthy crop production approaches, the search for alternative ecofriendly strategies that best fit to the smallholder systems have been proposed. The most common and widely accepted solution that has gained a lot of interest among researchers and smallholder farmers is the use of biological agents; mainly plant growth promoting microorganisms (PGPMs) that provide essential agroecosystem services within a holistic vision of enhancing farm productivity and environmental protection. PGPMs play critical roles in agroecological cycles fundamental for soil nutrient amelioration, crop nutrient improvement, plant tolerance to biotic and abiotic stresses, biocontrol of pests and diseases, and water uptake. This review explores different research strategies involving the use of beneficial microorganisms, within the unique context of smallholder agroecosystems, to promote sustainable maintenance of plant and soil health and enhance agroecosystem resilience against unpredictable climatic perturbations.

Biological Control of a Phytosanitary Pest (Thaumatotibia leucotreta): A Case Study

Thaumatotibia leucotreta, known as the false codling moth, is a pest of citrus and other crops in sub-Saharan Africa. As it is endemic to this region and as South Africa exports most of its citrus around the world, T. leucotreta has phytosanitary status for most markets. This means that there is zero tolerance for any infestation with live larvae in the market. Consequently, control measures prior to exporting must be exemplary. Certain markets require a standalone postharvest disinfestation treatment for T. leucotreta. However, the European Union accepts a systems approach, consisting of three measures and numerous components within these measures. Although effective preharvest control measures are important under all circumstances, they are most critical where a standalone postharvest disinfestation treatment is not applied, such as within a systems approach. Conventional wisdom may lead a belief that effective chemical control tools are imperative to achieve this end. However, we demonstrate that it is possible to effectively control T. leucotreta to a level acceptable for a phytosanitary market, using only biological control tools. This includes parasitoids, predators, microbial control, semiochemicals, and sterile insects. Simultaneously, on-farm and environmental safety is improved and compliance with the increasing stringency of chemical residue requirements imposed by markets is achieved.

Combined Toxicity of Cannabidiol Oil with Three Bio-Pesticides against Adults of Sitophilus Zeamais, Rhyzopertha Dominica, Prostephanus Truncatus and Trogoderma Granarium

The present study investigates the interaction between cannabidiol (CBD) oil and three biopesticides: Azatin and two baculovirus formulations (Madex and Helicovex), both separately and in combination, in order to investigate their interaction against adults of four major coleopteran stored-product pests: Sitophilus zeamais (Coleoptera: Curculionidae), Rhyzopertha dominica (Coleoptera: Bostrichidae), Prostephanus truncatus (Coleoptera: Bostrichidae) and Trogoderma granarium (Coleoptera: Dermestidae). CBD, which has been understudied for its insecticidal properties, was applied at three different doses (500, 1500 and 3000 ppm). The biopesticides were administered at 1500 ppm. Interactions in the combined treatments were mathematically estimated as not synergistic and mostly competitive except for the combined treatments of CBD (1500 and 3000 ppm) with Azatin (1500 ppm) which were marked by an additive interaction. In its individual application, CBD oil generated the highest insect mortality while its effect was clearly dose-dependent. The findings reveal a promising effect of CBD oil against these coleopterans which had not been previously tested together.

From Diverse Origins to Specific Targets: Role of Microorganisms in Indirect Pest Biological Control

Integrated pest management (IPM) is today a widely accepted pest management strategy to select and use the most efficient control tactics and at the same time reduce over-dependence on chemical insecticides and their potentially negative environmental effects. One of the main pillars of IPM is biological control. While biological control programs of pest insects commonly rely on natural enemies such as predatory insects, parasitoids and microbial pathogens, there is increasing evidence that plant, soil and insect microbiomes can also be exploited to enhance plant defense against herbivores. In this mini-review, we illustrate how microorganisms from diverse origins can contribute to plant fitness, functional traits and indirect defense responses against pest insects, and therefore be indirectly used to improve biological pest control practices. Microorganisms in the rhizosphere, phyllosphere and endosphere have not only been shown to enhance plant growth and plant strength, but also promote plant defense against herbivores both above- and belowground by providing feeding deterrence or antibiosis. Also, herbivore associated molecular patterns may be induced by microorganisms that come from oral phytophagous insect secretions and elicit plant-specific responses to herbivore attacks. Furthermore, microorganisms that inhabit floral nectar and insect honeydew produce volatile organic compounds that attract beneficial insects like natural enemies, thereby providing indirect pest control. Given the multiple benefits of microorganisms to plants, we argue that future IPMs should consider and exploit the whole range of possibilities that microorganisms offer to enhance plant defense and increase attraction, fecundity and performance of natural enemies.

Temperature tolerance and humidity requirements of select entomopathogenic fungal isolates for future use in citrus IPM programmes

Several isolates of Beauveria bassiana (Balsamo-Crivelli) Vuillemin (Hypocreales: Cordycipitacae) and Metarhizium anisopliae (Metchnikoff) Sorokin (Hypocreales: Clavicipitacae) have been investigated as possible microbial control agents of key citrus pests in South Africa. Although laboratory results have been promising, field trials against foliar pests have shown limited success. These findings highlighted the need to investigate other biological attributes of these fungal isolates besides virulence in order to select candidates that may be better suited for the foliar environment. Thus, this study investigated the influence of temperature on the in vitro growth of seven indigenous local isolates and the humidity requirements necessary to promote successful infection, in comparison with two commercial isolates (B. bassiana PPRI 5339 and M. anisopliae ICIPE 69). All the fungal isolates grew across a range of temperatures (8-34 °C) and optimally between 26 and 28 °C. Similarly, fungal infection of Thaumatotibia leucotreta Meyrick (Lepidoptera: Tortricidae) fifth instars occurred across a range of humidity levels (12%, 43%, 75%, 98%) regardless of fungal concentration, although external sporulation was restricted to treatments exposed to 98% relative humidity. It was concluded that neither temperature nor humidity, when considered alone, is likely to significantly influence the efficacy of any of the isolates in the field, given that they are active within temperature and humidity ranges experienced in South African citrus orchards.

Entomopathogenic Viruses in the Neotropics: Current Status and Recently Discovered Species

The market for biological control of insect pests in the world and in Brazil has grown in recent years due to the unwanted ecological and human health impacts of chemical insecticides. Therefore, research on biological control agents for pest management has also increased. For instance, insect viruses have been used to protect crops and forests around the world for decades. Among insect viruses, the baculoviruses are the most studied and used viral biocontrol agent. More than 700 species of insects have been found to be naturally infected by baculoviruses, with 90% isolated from lepidopteran insects. In this review, some basic aspects of baculovirus infection in vivo and in vitro infection, gene content, viral replication will be discussed. Furthermore, we provide examples of the use of insect viruses for biological pest control and recently characterized baculoviruses in Brazil.

Biopesticide based sustainable pest management for safer production of vegetable legumes and brassicas in Asia and Africa

Vegetables are one of the important crops which could alleviate poverty and malnutrition among the smallholder farmers in tropical Asia and Africa. However, a plethora of pests limit the productivity of these crops, leading to economic losses. Vegetable producers overwhelmingly rely on chemical pesticides in order to reduce pest-caused economic losses. However, over-reliance on chemical pesticides poses serious threats to human and environmental health. Hence, biopesticides offer a viable alternative to chemical pesticides in sustainable pest management programs. Baculoviruses such as nucleopolyhedrovirus (NPV) and granulovirus (GV) have been exploited as successful biological pesticides in agriculture, horticulture and forestry. Maruca vitrata multiple nucleocapsid NPV (MaviMNPV) was found to be a unique baculovirus specifically infecting pod borer on food legumes, and it has been successfully developed as a biopesticide in Asia and Africa. Entomopathogenic fungi also offer sustainable pest management options. Several strains of Metarhizium anisopliae and Beauveria bassiana have been tested and developed as biopesticides in Asia and Africa. This review specifically focuses on the discovery and development of entomopathogenic virus and fungi-based biopesticides against major pests of vegetable legumes and brassicas in Asia and Africa. © 2019 Society of Chemical Industry.

Genome Analysis of A Novel South African Cydia pomonella granulovirus (CpGV-SA) with Resistance-Breaking Potential

The complete genome of an endemic South African Cydia pomonella granulovirus isolate was sequenced and analyzed. Several missing or truncated open reading frames (ORFs) were identified, including a 24 bp deletion in the pe38 gene which is reported to be associated with type I resistance-breaking potential. Comparison of single nucleotide polymorphisms (SNPs) with five other fully sequenced CpGV isolates identified 67 unique events, 47 of which occurred within ORFs, leading to several amino acid changes. Further analysis of single nucleotide variations (SNVs) within CpGV-SA revealed that this isolate consists of mixed genotypes. Phylogenetic analysis using complete genome sequences placed CpGV-SA basal to M, I12 and E2 and distal to S and I07 but with no distinct classification into any of the previously defined CpGV genogroups. These results suggest that CpGV-SA is a novel and genetically distinct isolate with significant potential as a biopesticide for management of codling moth (CM), not only in South Africa, but potentially in other pome fruit producing countries, particularly where CM resistance to CpGV has been reported.

First Screening of Entomopathogenic Nematodes and Fungus as Biocontrol Agents against an Emerging Pest of Sugarcane, Cacosceles newmannii (Coleoptera: Cerambycidae)

Cacosceles newmannii (Coleoptera: Cerambycidae) is an emerging pest of sugarcane in South Africa. The larvae of this cerambycid beetle live within the sugarcane stalk and drill galleries that considerably reduce sugar production. To provide an alternative to chemical control, entomopathogenic nematodes and fungus were investigated as potential biological control agents to be used in an integrated pest management system. The nematodes Steinernema yirgalemense, S. jeffreyense, Heterorhabditis indica, and different concentrations of the fungus Metarhiziumpinghaense were screened for efficacy (i.e., mortality rate) against larvae of C. newmannii. The different biocontrol agents used, revealed a low level of pathogenicity to C. newmannii larvae, when compared to control treatments.

Comparative biocontrol ability of chitinases from bacteria and recombinant chitinases from the thermophilic fungus Thermomyces lanuginosus

Microbial chitinases (EC 3.2.1.14) are known to hydrolyse the chitinous gut epithelium of insects and cell walls of many fungi. In this study, seven chitinases from different bacteria and fungi were produced, characterized and their biocontrol abilities against graminaceous stem borers Eldana saccharina, Chilo partellus and Sesamia calamistis were assessed. All chitinases were stable over broad ranges of pH and temperature, however, recombinant fungal chitinases were more acid-stable than the bacterial counterparts. Chitinases from the thermophilic filamentous fungi Thermomyces lanuginosus SSBP (Chit1) and from Bacillus licheniformis (Chit lic) caused 70% and 80% mortality, respectively, in second instar larvae of E. saccharina. Six of the seven partially-purified microbial chitinases inhibited Aspergillus niger, A. flavus, A. alliaceus, A. ochraceus, Fusarium verticillioides and Mucor sp. Overall, microbial chitinases show promise as biocontrol agents of fungi and stalk-boring lepidopterans.