Susceptibilities of Candidatus Liberibacter asiaticus‐infected and noninfected Diaphorina citri to entomopathogenic fungi and their detoxification enzyme activities under different temperatures

Abstract

Some entomopathogenic fungi species, Isaria fumosorosea, and Hirsutella citriformis were found to be efficient against the Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae). However, the susceptibility to these fungi increases when the psyllid infected with Candidatus Liberibacter asiaticus (Las), which is transmitted by D. citri and causes citrus greening disease. In this study, we examined the Las-infected and Las-uninfected D. citri susceptibility to entomopathogenic fungi at different temperature regimes (5-40°C). When D. citri adults exposed to cold temperature (5°C), they showed less susceptibility to entomopathogenic fungi as compared with control (27°C). Irrespective of infection with Las, a significantly positive correlation was observed between temperature and percentage mortality caused by different isolates of I. fumosorosea, 3A Ifr, 5F Ifr, PS Ifr, and H. citriformis isolates, HC3D and 2H. In contrast, a significantly negative correlation was found between temperature and percentage mortality for 3A Ifr for both Las-infected and Las-uninfected psyllids. Detoxification enzymes, Glutathione S-transferase levels in D. citri showed a negative correlation, whereas cytochrome P450 and general esterase levels were not correlated with changes in temperature. These findings revealed that detoxification enzymes and general esterase levels are not correlated with altered susceptibility to entomopathogenic fungi at the different temperature regimes. Conclusively, temperature fluctuations tested appear to be a significant factor impacting the management strategies of D. citri using entomopathogenic fungi.

Friend or foe? Relationship between ‘Candidatus Liberibacter asiaticus’ and Diaphorina citri

“…For example, the reduction of gene expression of general oxidases and esterases in Las-positive D. citri promote the susceptibility to most of the commercial insecticides (Tiwari et al 2011a, b, c). The decrease of these enzymes also causes susceptibility to entomopathogenic fungi (Hussain et al 2018). Moreover, Las-infected plants attract the parasitoid T. radiata, in addition to D. citri (Liu et al 2019).…”

Use of the entomopathogenic fungi Beauveria bassiana (Hyphomycetes: Moniliales) and Isaria fumosorosea (Hypocreales: Cordycipitaceae) to control Diaphorina citri Kuwayama (Hemiptera: Liviidae) under laboratory and semi-field conditions

“…The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Psyllidae), is an economically important insect pest of citrus that disperses throughout the citrus growing regions, including tropical and subtropical Asia, Middle East, Central America, South America, Mexico, and Brazil (Grafton-Cardwell et al 2006;Hall et al 2012). Primarily, it attacks young flushes of citrus and can also attack the stressed citrus trees, if the population is high (Hussain et al 2018). Both nymphs and adult psyllid feed directly on phloem of tissues causing the distorted growth of plants as well as shoot dieback.…”

Infection with ‘Candidatus Liberibacter asiaticus’ improves the fecundity of Diaphorina citri aiding its proliferation: A win‐win strategy

“…Prior studies on C Las infected D. citri have shown up‐regulated immune function, with induction of iron‐related proteins, cathepsins and haemocyanin (Kruse et al., 2018). Moreover, several studies have demonstrated that C Las promotes a reduction of gene expression of general oxidases and esterases in C Las‐positive D.citri , and the decrease of these genes causes susceptibility to most of the commercial insecticides and entomopathogenic fungi (Hussain et al., 2018; Tiwari et al., 2011). As such, while boosted fecundity may lead one to posit that the D. citri ‐ C Las relationship is a mutualism, further study on net fitness effects, accounting for other life‐history attributes, are clearly required.…”