Gd. Inglis et al., INFLUENCE OF ULTRAVIOLET-LIGHT PROTECTANTS ON PERSISTENCE OF THE ENTOMOPATHOGENIC FUNGUS, BEAUVERIA-BASSIANA, Biological control, 5(4), 1995, pp. 581-590
The effect of ultraviolet light (uv) protectants on persistence of con
idia of the entomopathogenic fungus Beauveria bassiana was investigate
d in laboratory and field environments. The survival of conidia applie
d in water onto glass coverslips or crested wheatgrass (Agropyron cris
tatum) leaves was reduced by greater than 95% after 15 min exposure to
uv-B radiation in a controlled environment. Substitution of oil for w
ater increased the survival of conidia on both substrates. However, co
nidial survival in oil was more pronounced on glass (74% mortality aft
er 60 min) than on leaves (97% mortality after 60 min). The decreased
protection provided by oil on leaves was attributed to spreading and/o
r absorption of the oil by the leaf tissues. None of 21 potential suns
creen formulations were toxic to nongerminated conidia in vitro. On wh
eatgrass leaves, 5 of the 12 water-compatible and two of the nine oil
compatible formulations enhanced survival of conidia after 3 h exposur
e to uv-B radiation in a controlled environment. Four water-compatible
and three oil-compatible sunscreen adjuvants were subsequently tested
in a repeated held experiment. The water-compatible fluorescent brigh
tener, Tinopal LPW (conidial survival slopes of -2.1 and -1.7 in trial
s one and two, respectively), and a clay emulsion (slopes of -2.5 and
-2.0) significantly increased survival of conidia compared to the wate
r control (slopes of -3.3 and -2.7), whereas Congo Red (slopes of -3.1
and -2.8) and the optical brightener, Blankophor BSU (slopes of -4.2
and -3.7), were ineffective. Conidial survival in the field was not en
hanced by the three oil-compatible adjuvants tested (oxybenzone, octyl
-salicylate, and ethyl-cinnamate). The use of uv-B protectants in form
ulations can increase conidial survival and may enhance the efficacy o
f B. bassiana for controlling insect pests in epigeal habitats.