Compatibility of Metarhizium sp. (M201-NL strain) in Insecticide and Herbicide Mixtures

Abstract

Field application of Metarhizium to control Oryctes rhinoceros in oil palm plantations may be overlapped with pesticides (insecticide and herbicide) spray. These chemicals may harm the fungus leading to poor virulence. This paper, however, shows that Metarhizium sp. M201-NL strain may react differently against some pesticides tested using poisoning media method. In the first experiment, the growth of mycelium of the Metarhizium sp. was observed in plated media mixed with insecticide. The highest mycelium radial growth was Fipronil 0.15 % (51.9 mm) which was not significantly different compared to the control, without insecticide (52.2 mm). However, suppression of growth of mycelium was observed in other insecticides. The radial growth of mycelium was significantly lower compared to the control if either Ethiprol, Lambdha cyhalothrin or Acephate was applied at 14 DAI. The second separate experiment involved herbicides. It was found that some herbicides did not inhibit the radial growth of mycelium. These include Metsulfuron-methyl 0.098 % (84.0 mm), Metsulfuron-methyl 0.19 % (82.75 mm), Glyphosate 19.6 % (82.5 mm), Glyphosate 9.8 % (81.6 mm) and Metsulfuron-methyl 0.39 % (80.37 mm) which were not significantly different compared to control, without herbicide (86.12 mm) at 21 DAI. In contrast, the growth of mycelium was significantly retarded when Paraquat, Triclopyr, Glyphosate, and 2.4-D was applied separately. Further study was undertaken to observe sporulation and virulence (bioassay) of the treated mycelium. The sporulations of mycelium treated with Fipronil 0.15 % or Metsulfuron-methyl of different concentrations were not statistically different to control. Similar results were also shown from bioassay. The infection rates of O. rhinoceros larva treated with mixtures of Metarhizium sp. spores with either Fipronil or Metsulfuron-methyl were insignificantly different compared to the control.