Acquisition of lethal doses of Beauveria bassiana conidia by western flower thrips, Frankliniella occidentalis, exposed to foliar spray residues of formulated and unformulated conidia

A tritrophic effect of host plant on susceptibility of western flower thrips to the entomopathogenic fungus Beauveria bassiana

“…Ugine et al (2005b) reported that probit slopes for LC regressions were lower than the slopes for LD regressions in tests of B. bassiana against western flower thrips (i.e. exposure of thrips to B. bassiana-treated bean leaf disks) and suggested that this occurred because the rate of conidial acquisition, defined as the number of conidia per insect with respect to the number of conidia per mm 2 of leaf surface, decreased as the number of conidia per mm 2 increased.…”

“…We know that the acquisition rate is highest at those values that have the lowest number of conidia per mm 2 (see Ugine et al, 2005b and Table 6). Thus, we identified the lowest dosage (conidia/mm 2 ) within each LC assay that yielded significant mortality; and inserted into the equation of a line (Y = a + bx) the slope from the LD probit regression line, the log of the selected low dose, the probit value for the percent mortality associated with the selected dose, and solved for the intercept.…”

Compatibility of Amblyseius swirskii with Beauveria bassiana: two potentially complimentary biocontrol agents

“…Immature stages are often less susceptible to fungal infection due to germinating conidia being shed during ecdysis (Vey and Fargues 1977;Ugine et al 2005). Short immature life stages, and therefore frequent ecdysis, combined with relatively low persistence of B. bassiana conidia on leaf surfaces can explain the low susceptibility of juvenile A. swirskii to this pathogen.…”

Fungal conidia distribution on chrysanthemum: varying spray parameters

“…The most important requirement is to maximise the contact of the active ingredient to the target pest. The LD 50 of the GHA strain of Beauveria bassiana on the second instar of western flower thrips, Frankliniella occidentalis, for example, is 33-66 conidia per immature (Ugine et al 2005b) and for adults it is 19 conidia per mm 2 (Ugine et al 2007). The factors that contribute to deposition density are: the type and size of the spray nozzle, the angle and pressure at which the formulation is sprayed onto the plant, the duration of the contact of the formulation with the plant, and the distance between the plant and nozzle.…”