Impiego del <i>Bacillus thuringiensis</i> Berl. nella lotta alla <i>Lymantria dispar</i> L. in boschi di<i>Quercus suber</i> L. 3: risultati della sperimentazione condotta nel 1992.

Abstract

The study was carried out in a North Sardinian cork oak forest in 1992. To control the gypsy moth population three commercial preparations of B. thuringiensis subsp. kurstaki were applied by helicopter: Activator THK and Bactospeine at low volume and Foray 48B at ultra low volume, when 80-90% of the gypsy moth larvae were in 1st and 2nd instars. At 14d after treatment, Activator (applied at 5 l/ha) did not cause significant population reductions, while Bactospeine (applied at 32 B.I.U./ha) and Foray 48B (applied at 31.75 B.I.U./ha) caused average mortalities respectively of 40 and 53%. All preparations showed a good compatibility with the activity of the gypsy moth natural enemies. Smaller mortalities, compared with previous tests, seem to be related with the low average temperatures, between 13.9 and 16.8°C, of the post-treatment week which slowed down both feeding and metabolism of the larvae just when there was the largest amount of spores on the foliage