mass-production-entomopathogenic-fungi-metarhizium-robertsii

Mass Production of Entomopathogenic Fungi, <em>Metarhizium robertsii</em> and <em>Metarhizium pinghaense</em>, for Commercial Application Against Insect Pests

Entomopathogenic fungi of the Metarhizium anisopliae species complex have gained importance as the biological control agents of agricultural insect pests. ...

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The potential of entomopathogenic nematodes, Heterorhabditis bacteriophora, Heterorhabditis zealandica and Steinernema khoisanae, to infect pupariating larvae, pupae and adults of Ceratitis capitata and Ceratitis rosa was investigated in laboratory bioassays. Pupariating larvae and adult flies were susceptible to nematode infection, with no infection recorded for the pupae. Pupariating larvae of C. capitata were generally more susceptible to infection than those of C. rosa. Significantly more larvae of C. capitata were infected by H. bacteriophora. For C. rosa, highest infectivity of larvae was obtained with H. zealandica. In contrast, adults of both species were highly infected by S. khoisanae.

Susceptibility of the Mediterranean fruit fly (Ceratitis capitata) and the Natal fruit fly (Ceratitis rosa) to entomopathogenic nematodes.

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 50IJs/FCM larva caused 100% mortality and 74% at a concentration of 200IJs/pupa. Using a sand bioassay, S. yirgalemense gave 93% control of cocooned pupae and emerging moths at a concentration of 20IJs/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.

Isolation and identification of entomopathogenic nematodes from citrus orchards in South Africa and their biocontrol potential against false codling moth.

 (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 , , , and different concentrations of the fungus   were screened for efficacy (i.e., mortality rate) against larvae of . The different biocontrol agents used, revealed a low level of pathogenicity to  larvae, when compared to control treatments.

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

Baitchain is a novel molluscicide system that consists of metaldehyde pellets arranged on a cord and is designed to be tied around the base of tree trunks and act as a physical and chemical control method for molluscs. In this study, Baitchain is tested in a South African apple orchard and compared with traditional metaldehyde pellets (Sluggit) applied to the soil surface to determine the efficacy of the products against the brown garden snail,  (Helicidae). The products were applied at two different concentrations, including 15 g/kg (Baitchain 15 and Sluggit 15) and 40 g/kg (Baitchain 40 and Sluggit 40) metaldehyde, and the products were either applied on their own, or in combination. Both treatments at 40 g/kg metaldehyde caused significant snail mortality when applied either on their own or in combination. However, significant mortality was also achieved by Baitchain 15 when applied on its own as well as in combination with Sluggit 15. The increased efficacy achieved by using Baitchain, even at the lower concentration, indicates that this novel method offers a viable physical and chemical control option for molluscs and could be incorporated as part of an integrated pest management strategy in South Africa, as well as other parts of the world.

Efficacy of a Novel Metaldehyde Application Method to Control the Brown Garden Snail,  (Helicidae), in South Africa.

Bacterial symbionts associated with entomopathogenic nematodes (EPNs) play an important role in terms of the insecticidal properties of nematodes in pest control. Galleria mellonella larvae, shortly after being infected with three different strains of Heterorhabditis zealandica, which were isolated from South African soil, changed from pale white to steel grey-blue (blue), bright red, and yellow with a green tint (green), respectively. The genetic relatedness of the bacterial symbionts that were isolated from the three strains of H. zealandica was determined by means of comparing the 16S rRNA, recA, gyrB, dnaN, gltX and infB gene sequences. Subsequently, comparing the concatenated sequences revealed the presence of three distinct Photorhabdus species. The H. zealandica strain SF41, associated with Photorhabdus heterorhabditis, produced 'blue' G. mellonella larvae. The H. zealandica strain MJ2C, associated with Photorhabdus thracensis, yielded 'green' G. mellonella larvae, while the H. zealandica strain LLM associated with Photorhabdus laumondii subsp. laumondii yielded red larvae. The colour changes in G. mellonella larvae were found to have been instigated by a particular Photorhabdus species associated with H. zealandica. The red and 'green' phenotypes of G. mellonella larvae were found to represent new combinations of Heterorhabditis and Photorhabdus. In future studies, the colour of infected G. mellonella larvae needs to be reported as a phenotypic character, as it indicates the different bacterial species associated with the same nematode host, as shown in the case of H. zealandica.

Colour of heterorhabditis zealandica-infected-Galleria mellonella dependent on the Photorhabdus symbiont, with two new nematode-symbiotic associations reported.

Article	Year
Susceptibility of the Mediterranean fruit fly (Ceratitis capitata) and the Natal fruit fly (Ceratitis rosa) to entomopathogenic nematodes. Journal of invertebrate pathology\| PubMed ID: 18845153	2009
Isolation and identification of entomopathogenic nematodes from citrus orchards in South Africa and their biocontrol potential against false codling moth. Journal of invertebrate pathology\| PubMed ID: 21839086	2011
First Screening of Entomopathogenic Nematodes and Fungus as Biocontrol Agents against an Emerging Pest of Sugarcane, (Coleoptera: Cerambycidae). Insects\| PubMed ID: 31027196	2019
Efficacy of a Novel Metaldehyde Application Method to Control the Brown Garden Snail, (Helicidae), in South Africa. Insects\| PubMed ID: 32668565	2020
Colour of heterorhabditis zealandica-infected-Galleria mellonella dependent on the Photorhabdus symbiont, with two new nematode-symbiotic associations reported. Journal of invertebrate pathology\| PubMed ID: 35124069	2022

Antoinette Paula Malan

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