Effect of temperature, humidity and photoperiod on mortality of Mononychellus tanajoa (Acari: Tetranychidae) infected by Neozygites cf. floridana (Zygomycetes: Entomophthorales)

Abstract

The effect of temperature, humidity and photoperiod on the development of Neozygites cf. floridana (Weiser and Muma) in the cassava green mite, Mononychellus tanajoa (Bondar) was studied in the laboratory. Dead infected mites began to appear 2.5 days after inoculation. At 33 and 28°C peak mortalities were higher and occurred earlier (after 2.5 days), than at 23 and 18 ° C. Mean LTs0 (time for half the infected mites to die) decreased with increasing temperature as follows: 3.9, 3.0, 2.9 and 2.5 days at 18, 23, 28 and 33 ° C, respectively. When placed under conditions of high relative humidity for a period of 24 h, the percentage of dead infected mites from which the fungus sporulated was highest at 28 ° C (51.4%) and lowest at 33 ° C (6.5%). The development of the fungus inside the mite was not significantly affected by ambient humidity or photoperiod. No significant interactions between tested factors were found.

Lessons from interactions within the cassava green mite fungal pathogen Neozygites tanajoae system and prospects for microbial control using Entomophthorales

“…They die within 3-5 days at ca. 28°C (Oduor et al 1995a). Freshly dead infected mites dry out and become mummified (hence called 'mummies') in a few hours, after which they sporulate if conditions are favourable.…”

Modelling Fungal (Neozygites cf. Floridana) Epizootics in Local Populations of Cassava Green Mites (Mononychellus Tanajoa)

“…The results are presented in Table 1 Per capita rate of transition to the halo stage, a : The rate at which infected mites become infectious (a) is estimated as the inverse of the sum of the time spent in the three host infection phases together: (1) incubation (the time from host contact with the capilliconidia to host death), (2) sporulation (the time it takes for the primary conidia to be liberated from the mummies) and (3) germination (the time to formation of the capilliconidia from the liberated primary conidia). Each of the component time periods can be influenced by climatic conditions (Oduor, 1995;Oduor et al, 1995aOduor et al, ,b, 1996a.…”

“…In the case of a strain of Neozygites cf. floridana Fisher, originating from Bahia in Brazil, the effect of these conditions on the time from host infection to the formation of capilliconidia was studied (Oduor, 1995;Oduor et al, 1995aOduor et al, ,b, 1996a. It may now be questioned to what extent the development of the epizootics can be attributed to climatic conditions alone.…”

Failure of the mite-pathogenic fungus Neozygites tanajoae and the predatory mite Neoseiulus idaeus to control a population of the cassava green mite, Mononychellus tanajoa

“…Attempting either to harness this in new areas via the establishment of exotic strains or to improve upon it by the artificial introduction of inoculum or conservation is dependent upon the conditions being adequate for cycling of the fungus, both in terms of the abiotic conditions and the availability of potential hosts (Oduor et al 1997;Elliot et al 2002a). The sensitivity of the pathogen to abiotic conditions, particularly saturation deficits, has been demonstrated in laboratory (Oduor et al 1995a(Oduor et al , b, 1996a(Oduor et al , b, 1997 and field studies (Elliot et al 2002a). In the latter case, we followed a field population of M. tanajoa so as to identify the potential for the introduction of an inoculum in this sort of setting.…”