Tj. Poprawski et al., CONTACT TOXICITY OF THE MYCOTOXIN DESTRUXIN-E TO EMPOASCA-VITIS (GOTHE) (HOM, CICADELLIDAE), Journal of applied entomology, 117(2), 1994, pp. 135-143
The toxicity oi destruxin E for nymphs of Empoasca vitis (Gothe) was a
ssessed in the laboratory using various administrative routes: 10 ml o
f a given concentration of the toxin (30, 100, 300 and 1000 ppm) were
sprayed either on potato leaves or directly onto the insects, and 1 mu
l of a 100 ppm concentration of toxin was applied onto the nora of th
e insects. Checks were made daily for 4 days and mortality in E. vitis
was recorded. Natural mortality was less than 5%. Nymphs of E. vitis
were susceptible to the insecticidal activity of destruxin E in all th
ree treatments. Mortality was concentration-dependent in nymphs expose
d to treated leaves and in nymphs sprayed directly. The potency of des
truxin E was reflected in the low LC(50) values obtained: 46.4 ppm for
insects exposed to treated leaves and 38.2 ppm for insects sprayed di
rectly. The LT(50) values were 3.2 days (at 30 ppm) and 0.2 days (1000
ppm) for nymphs sprayed directly, and slightly higher for nymphs expo
sed to treated leaves. Analysis of data (100 ppm) showed that there wa
s no significant difference in mortality due to either of the three bi
oassay procedures. Mortality rates were 87.5% in nymphs sprayed direct
ly, 93.8% in nymphs exposed to treated leaves, and 78.1% in nymphs in
the topical application test. The LT(50) value in the latter test (at
100 ppm) was 1.3 days. Contact insecticidal activity of destruxin E is
demonstrated here for the first time.