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ŠUMARSKI LIST 5-6/2012 str. 26     <-- 26 -->        PDF

The best results were achieved after two applications in one season (with average period between two applications of 43 days) with imidaclopride (91.4–97.2 % efficacy) and insect growth regulators (IGRs) – diflubenzuron (89.5–94.9%), hexaflumuron (84.6–96.3 %), methoxyfenozyde (85.6–94.9 %) and lufenurone (85.8–94.4 %). Single application of imidaclopride (88.9–97.7%) and diflubenzuron (85.9–95.3 %) did not achieved statistically different efficacy in horse chestnut leafminer control than two applications in one season. Efficacy of spinosad (67.4–89.3%) and combination of B. thuringiensis and imidaclopride (52.4–91.6 %) did not satisfy. Even lower efficacy was achieved after two applications of B. thuringiensis in one season (52.2–83.7 %) and after single application in one season (30.3–84.7 %) (Table 8). In this period untreated control trees were infected with average of 22.4 –84.2 larvae/leaf (Tables 3–7), depending on date of examination.

Results of those five-year trials results show that is possible to protect horse chestnuts if foliar insecticides application is provided in period of first generation’s larvae hatching. The most suitable insecticides were insect growth regulators (IGRs), while imidaclopride is not appropriate in urban area due to its high toxicity. B. thuringiensis provides very good initial protection, but it has very poor residual effect so it is advisable to apply B thuringiensis twice or more times in one season (Tables 3–8).

Key words: horse chestnut protection, foliar threatment, insect growth regulators, IGRs, imidaclopride, Bacillus thuringiensis, spinosad, efficacy