Role of the entomogenous fungus, Neozygites floridana, in population declines of the twospotted spider mite, Tetranychus urticae, on field corn

Abstract

In field plots in which populations of predaceous species were suppressed using carbaryl, populations of the twospotted spider mite, Tetranychus urticae Koch, on field corn declined in association with aerial dispersal of the mites or with epizootics of the entomogenous fungus, Neozygites floridana Weiser & Muma. The relative importance of these two factors varied from year to year depending on environmental conditions. When moist weather conditions induced epizootics of N. floridana before corn plants became heavily infested with mites, the pathogen appeared to be the major factor causing mite population declines. When dry weather conditions allowed mite populations to expand unchecked until corn plants became entirely infested, mite aerial dispersal was the major factor associated with mite population declines. In every field in which there was an epizootic of N. floridana, routine applications of the fungicide maneb delayed epizootics and reduced or delayed the impact of the pathogen on mite populations. The total number of Neozygites-infected mites produced in maneb-treated plots throughout the test period was significantly greater than that in untreated plots when epizootics were initiated during periods of mite population growth. Fewer total infected mites were produced in maneb-treated plots compared to untreated plots when epizootics were initiated during periods of mite population decline.

Challenges in modelling complexity of fungal entomopathogens in semi-natural populations of insects

“…Klubertanz et al 1991;Nielsen and Hajek 2005;Smitley et al 1986) but there are also examples from aquatic systems (Burns 1979;Johnson et al 2006). External infectious stages ensure that the fungi persist during periods of low host population density, when horizontal transmission is insufficient to maintain the prevalence in the host population (Filotas and Hajek 2004;Hajek et al 2004).…”

Overwintering and prevalence of Neozygites floridana (Zygomycetes: Neozygitaceae) in hibernating females of Tetranychus urticae (Acari: Tetranychidae) under cold climatic conditions in strawberries

“…Neozygites spp. are considered by many authors to be a major factor causing decline in populations of T. urticae in different crops when microclimatic conditions are right (Boykin et al 1984;Carner and Canerday 1970;Dick and Buschman 1995;Klubertanz et al 1991;Smitley et al 1986b). Pesticides may limit the survival and efficacy of N. floridana and laboratory studies on the effect of pesticides on N. floridana have been conducted, resulting in suggestions on how to manage pesticide application to reduce negative effects on this beneficial fungus (Klingen and Westrum 2007;Klubertantz et al 1991).…”

Role of entomopathogenic fungi in the control of Tetranychus evansi and Tetranychus urticae (Acari: Tetranychidae), pests of horticultural crops

“…Other fungicides, such as chlorothalonil, mancozeb and maneb also reduced the infection level of N. Xoridana in T. urticae populations infesting corn and peanut Welds (Brandenburg and Kennedy 1982;Boykin et al 1984;Smitley et al 1986). Klingen and Westrum (2007) compared the eVect of diVerent pesticides (fungicides, insecticides, acaricides and molluscicides) used in strawberry plantation on N. Xoridana.…”

“…The report in this section focuses on recently published articles published after the reviews by Chandler et al (2000) and van der Geest et al (2000). Tamai et al (2002a) screened 45 isolates of mitosporic fungi against T. urticae, including 32 isolates of Beauveria bassiana (Balsamo) Vuillemin, 10 isolates of Metarhizium T. urticae Kenneth et al (1971) (cited by van der Geest 1985) Neozygites Xoridana T. urticae Weiser and Muma (1966), Kenneth et al 1972(cited by van der Geest 1985, Smitley et al (1986), Keller (1991), Mietkiewski et al (1993), Shih andShiue (1994), Dick and Buschman (1995) (cited by Chandler et al 2000), Smith and Furr (1975) Irigaray et al (2003) evaluated the eYcacy of Naturalis-L ® (a B. bassiana-based commercial biopesticide) against the two-spotted spider mite and obtained lethal concentration values (LC 50 ) of 3184 viable conidia ml ¡1 for the juvenile stages and 1949 viable conidia ml ¡1 for the adults. Naturalis-L ® caused signiWcant egg mortality compared to the control, with no signiWcant diVerences amongst egg age classes (24-, 48-, 72-, and 96-h-old eggs) at the tested concentrations of 1,400-22,800 viable conidia ml ¡1 .…”