Sprays of emulsifiable Beauveria bassiana formulation are ovicidal towards Tetranychus urticae (Acari: Tetranychidae) at various regimes of temperature and humidity

Abstract

Aerial conidia of Beauveria bassiana in an emulsifiable formulation germinated by >95% after 24 h exposure to the regimes of 20, 25 and 30 degrees C with 51%, 74% and 95% RH. Ovicidal activities of the formulation towards two-spotted spider mite, Tetranychus urticae, were assayed at the concentrations of 0, 18, 160 and 693 conidia mm(-2) sprayed separately onto fava bean leaves including 39 (25-76) eggs per capita. All the sprayed eggs on the leaves were directly exposed to the different regimes for hatch after 24 h maintenance in covered Petri dishes. Generally, hatched proportions increased over post-spray days and decreased with the elevated fungal concentrations; no more eggs hatched from day 9 or 10 onwards. Based on the counts of the hatched/non-hatched eggs in the different regimes, the final egg mortalities were 15.0-40.4%, 48.9-66.6% and 62.9-87.5% at the low, medium and high concentrations, respectively, but only 5.6-11.3% in blank controls. The RH effect on the fungal action was significant at 20 and 25 degrees C but not at 30 degrees C whereas the effect of temperature was significant at 51% and 74% RH but not at 95% RH. Probit analysis of the egg mortalities versus the fungal sprays generated median lethal concentrations (LC(50)) of 65-320 conidia mm(-2) at all the regimes, and of only 65-78 conidia mm(-2) at 25-30 degrees C with 74-95% RH. The results highlight ovicidal activities of the emulsifiable formulation against the mite species at the tested regimes and its potential use in spider mite control.

Effect of fungal infection on reproductive potential and survival time of Tetranychus urticae (Acari: Tetranychidae)

“…The mean (±SD) concentration of conidia deposited onto the leaves was 1.13 (±0.14) 9 10 3 , 1.55 (±.22) 9 10 3 and 0.95 (±0.26) 9 10 3 conidia mm -2 for the three isolates, respectively. These estimates were based on five microscopic counts from each of glass cover slips (20 9 20 mm) that had been placed beside the leaf dish to collect deposited conidia during spraying (Shi et al 2008c). …”

Evaluation of alternativePlutella xylostellacontrol by twoIsaria fumosoroseaconidial formulations - oil-based formulation and wettable powder - combined withBacillus thuringiensis

“…Since the 1960s, more than 150 insect biocontrol products based on fungal entomopathogens, including I. fumosorosea , have been commercially available all over the world . A substantial number of mycoinsecticides have been widely used for biological control of insect pests . However, these fungal products make up a small percentage of the total insecticide market, owing largely to their slower insecticidal activity compared with insecticides.…”

Preliminary Evaluation of Paecilomyces lilacinus HY-4 to Control Tetranychus urticae

“…To evaluate efficacy of SD-tower sprayer, we compared the deposited conidia rates with previously reported results using potter tower sprayer in bioassay (Vicentini et al, 2001;Tian et al, 2006;Shapiro-Ila et al, 2008;Shi et al, 2008;Shan et al, 2010;) (Table 1). The result showed that SD-tower sprayer was superior to other sprayers with 0.58% rate of deposited conidia per cm 2 .…”