Mass Production of Entomopathogenic Fungi, Metarhizium robertsii and Metarhizium pinghaense, 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. The increase in pest resistance to chemical insecticides, the growing concerns regarding the negative effects of insecticides on human health, and the environmental pollution from pesticides have led to a global drive to find novel sustainable strategies for crop protection and pest control. Previously, attempts to mass culture such entomopathogenic fungi (EPF) species as Beauveria bassiana have been conducted. However, only limited attempts have been conducted to mass culture Metarhizium robertsii and M. pinghaense for use against insect pests. This study aimed to mass-produce a sufficient number of resilient infective propagules of South African isolates of M. robertsii and M. pinghaense for commercial application. Three agricultural grain products, flaked oats, flaked barley, and rice, were used as the EPF solid fermentation substrates. Two inoculation methods, conidial suspensions and the liquid fungal culture of blastospores were used to inoculate the solid substrates. Inoculation using conidial suspensions was observed to be relatively less effective, as increased levels of contamination were observed on the solid substrates relative to when using the blastospore inoculation method. Flaked oats were found not to be a suitable growth substrate for both M. robertsii and M. pinghaense, as no dry conidia were harvested from the substrate. Flaked barley was found to favor the production of M. robertsii conidia over that of M. pinghaense, and an average of 1.83 g ± 1.47 g of dry M. robertsii conidia and zero grams of M. pinghaense conidia was harvested from the substrate. Rice grains were found to favor the conidial mass production of both M. pinghaense and M. robertsii isolates, with an average of 8.2 g ± 4.38 g and 6 g ± 2 g harvested from the substrate, respectively.

Potential of in vivo- and in vitro-cultured entomopathogenic nematodes to infect Lobesia vanillana (Lepidoptera: Tortricidae) under laboratory conditions.

Entomopathogenic nematodes (EPNs) have been successfully applied as biological control agents against above ground and soil stages of insect pests. However, for commercial application, it is crucial to mass culture these nematodes using in vitro liquid culture technology, as it is not attainable when using susceptible insects as hosts. Lobesia vanillana (Lepidoptera: Tortricidae) is regarded a sporadic pest of wine grapes in South Africa. The in vivo- and in vitro-cultured South African EPNs, Steinernema yirgalemense and Steinernema jeffreyense (Rhabditida: Steinernematidae), were evaluated against larvae and pupae of L. vanillana in laboratory bioassays. For larvae, high mortality was observed for all treatments: In vitro-cultured S. yirgalemense (98%) performed better than S. jeffreyense (73%), while within in vivo cultures, there was no difference between nematode species (both 83%). No significant difference was detected between in vivo- and in vitro cultures of the same nematode species. The LD50 of the in vitro-cultured S. yirgalemense, was 7.33 nematodes per larva. Mortality by infection was established by dissecting L. vanillana cadavers and confirming the presence of nematodes, which was > 90% for all treatments. Within in vitro cultures, both S. yirgalemense and S. jeffreyense were able to produce a new cohort of infective juveniles from L. vanillana larvae. Pupae, however, were found to be considerably less susceptible to EPN infection. This is the first study on the use of EPNs to control L. vanillana. The relative success of in vitro-cultured EPN species in laboratory assays, without any loss in pathogenicity, is encouraging for further research and development of this technology.

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

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, Cornu aspersum (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.