The predatory mite Typhlodromips swirskii (Athias-Henriot) is commonly used to suppress pest populations of thrips and whitefly in commercial greenhouses. Many generalist phytoseiid mites can be reared on astigmatid factitious prey. This study investigated the life table parameters of T. swirskii to the astigmatid mite Suidasia medanensis (Oudemans) and the capture success ratio of T. swirskii to different life stages of the prey. Juvenile development time and survival was 5.01 ± 0.10 days and 93 %, respectively. The intrinsic (r m ) and finite (λ) rates of increase were 0.222 and 1.249, respectively, with average oviposition rate of 1.71 ± 0.07 eggs/female/day. The capture success ratio of T. swirskii to S. medanensis was: eggs > freeze killed adults > nymphs > live adults. Typhlodromips swirskii was concluded to exhibit good population growth rates with S. medanensis as prey and, a prey population with predominance of eggs and nymphs to be advantageous to the predator due to an unidentified defence mechanism of adult prey.
The two biocontrol agents Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) and Beauveria bassiana (Balsamo) Vuillemin (Hypocreales: Cordycipitaceae) have the potential to complement one another as part of an integrated pest management programme. While both can suppress whitefly and thrips infestations in protected crops, A. swirskii is primarily used preventatively whereas B. bassiana can be used as a curative treatment at higher pest levels. With this concomitant use in mind, the research presented here aimed to identify potential negative effects of the commercial B. bassiana strain GHA on A. swirskii in a laboratory study. Adult A. swirskii were found to be susceptible to B. bassiana infection with slight to moderate virulence (20.74 ± 3.89 to 48.33 % ± 3.07) depending on the type of exposure and with a reduction in fecundity over time. There was however no negative effect on juvenile survival neither on dry residue nor on the offspring of infected mites. Thus, these two biocontrol agents do have the potential to be complementary. Further trials in the field are still required before a final conclusion can be reached.
Metarhizium brunneum is a highly effective entomopathogenic fungus that also functions as a plant biostimulant. It can act as both an endophyte and rhizosphere colonizer; however, the mechanisms driving biostimulation are multifactorial. In this work, oilseed rape (Brassica napus) seeds were grown in composts treated with different concentrations of M. brunneum strains ARSEF 4556 or V275, or the M. brunneum-derived volatile organic compounds 1-octen-3-ol and 3-octanone. Biostimulation efficacy was found to be strongly dose dependent. Concentrations of 1 × 106 conidia g−1 compost were found to be most effective for the M. brunneum, whereas dosages of 1 µL 100 g−1 compost were found to be efficacious for the volatiles. These optimized doses were assessed individually and in combined formulations with a hydrogel against oilseed rape (Brassica napus), sitka spruce (Picea sitchensis), maize (Zea mays) and strawberry (Fragaria annanassa). Both volatile compounds were highly effective biostimulants and were found to increase in biostimulatory efficiency when combined with M. brunneum conidia. Hydrogels were not found to interact with the growth process and may offer avenues for novel formulation technologies. This study demonstrates that Metarhizium-derived volatile organic compounds are actively involved in plant growth promotion and have potential for use in novel formulations to increase the growth of a wide range of commercially relevant crops.
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