Hirsutella thompsoniU a fungal pathogen of mites. II. Host‐pathogen interactions

Abstract

SUMMARYThe moniliaceous fungus, Hirsutella thompsoniU grown on potato‐dextrose agar (PDA) or on sterile wheat bran, was highly pathogenic to the carmine spider mite, Tetranychus cinnabarinus, and, grown on PDA, to the oriental spider mite, Eutetranychus orientalis. The fungus penetrated the mites' integument mainly through the legs and formed hyphal bodies in chains in the haemolymph. Hyphae, on which the spores were produced, began to emerge through the genital and anal apertures and then all over the body. Various mycophagous mites, a predaceous species and the tick Argas persicus were immune. H. thompsonii grew well on cadavers of diverse insects and mites.The fungus killed most mites and quickest, usually by the 2nd day, at 25o, 27o and 30 oC; least at 13o and 35 oC. It sporulated best on mites at 24o, 27o and 30 oC (full sporulation at 27 oC took place within 12 h after death); it was good, but slower, at 13o and 35 oC. The fungus germinated, penetrated mites and sporulated there very poorly below 100% r.h. When the daily number of hours at 100% r.h. was reduced from 24 to 18 or 6 h, fungus‐associated mortality dropped greatly.In the field, use of the fungus for mite control would be suitable particularly in tropical and humid subtropical areas, and its success in Israel would not be assured. In glasshouses, H. thompsonii could induce epizootics in Israel and elsewhere only if humidities were raised to saturation and the daytime temperature kept below 37 oC.

A tale of three acaropathogenic fungi in Israel: Hirsutella, Meira and Acaromyces

“…A second batch (b) was held for 6 h at ca 50% r.h., and then for 18 h at saturation, and the third (c) was maintained throughout at 100% r.h. Mortality in the latter treatment came to 98%, but in experiment (a) it reached only 65%, and in (b) to 74%. In another experiment, intended to simulate summer greenhouse conditions, conducted like (a) but this time the mites were transferred from 25°C for 18 h at 50% r.h. to 33°C at saturation, their mortality reached Table 1 Infection rates of mites representing pests, natural enemies, scavengers and a tick in several families and orders by Hirsutella thompsonii (HT; data from Gerson et al 1979), Hirsutella kirchneri (HK; data from Sztejnberg et al 1997;Gafni 1997) . A further discouraging opinion, for similar reasons, about mite control with H. thompsonii under protected cultivation was expressed by Rombach and Gillespie (1988).…”

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“…However, very little attention has been devoted to the use of these organisms for control of bulb mites. Fungi of the genus Hirsutella are of particular importance due to their ability to infest a large diversity of mites (Gerson et al, 1979). Recently however, Sztejnberg et al (1997) reported a failure of Hirsutella thompsonii to infest R. robini obtained from laboratory cultures.…”

Epizootic of Acalitus vaccinii (Acari: Eriophyidea) Caused by Hirsutella thompsonii on Southern Highbush Blueberry in North-Central Florida

“…The fungus requires an optimal temperature of 25 to 30°C and a RH of 98% for growth and sporulation (Boucias et al 2007;Gerson et al 1979;Kenneth et al 1979;McCoy 1996). As a parasite it has been reported to cause epizootics of several eriophyoid mites including Calacarus heveae on rubber trees (Tanzini et al 2000), Phyllocoptruta oleivora, citrus rust mite (Fisher et al 1949), and Aceria guerreronis on coconut (Gopal & Gupta 2001).…”