Target-oriented dissemination of the entomopathogenic fungus Fusarium subglutinans 12A by the Western Flower Thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae)

Abstract

Target-oriented dissemination of entomopathogenic fungi may have benefits for spore dispersal to pest populations. In this laboratory study, target-oriented dissemination of Fusarium subglutinans 12A was investigated using female Frankliniella occidentalis Pergande for the control of thrips. The aim was to determine changes on mortality with infected / un-infected thrips number ranging from one to five or while the moulded cadavers were in the environment and lastly, with spore concentration applied to the food or habitat. Investigations were conducted using Petri dishes and single-cell cage bioassays and spore concentration (1 × 106 spore/ml) of fungus was applied using the dipping method. When the infected thrips were released to uncontaminated individuals mean mortality rate reached 48.2% and an increase in the number of inoculated individuals had no significant effect on mortality rates. On the contrary, an increase in the number of uncontaminated individuals had a significant effect on mortality rates, in which four uncontaminated thrips were released with infected thrips and the mortality rate reached 60.4%. Results revealed that the presence of 1 × 106 spore/ml of fungus in the habitat raised the mortality rate to 90.9 ± 2.4% on the 7th day. In the experiment where cadavers were present in the environment, the mortality rate reached 45.7 ± 3.7% on the 8th day. Overall, the results suggest that F. subglutinans 12A can be effectively disseminated to uninfected individuals by releasing conspecifics of F. occidentalis inoculated with 1 × 106 spore/ml and the most effective factor was found habitat applications to the determining dissemination of fungus.