engleski

Insect pests on ornamental trees in Croatia and some results of their control

Ornamental trees in urban areas have been attacked by an increasing number of pests that endanger the existence of those plants and are decreasing its positive influence on human beings. Many of those pests were imported in the second half of the 20th century from other continents. We will present some of the most important pests on ornamental trees in Croatia, especially in Zagreb. First mines of the horse chestnut leaf miner (Cameraria ohridella Deschke et Dimic) were found on one tree in Zagreb in 1989. Strong infestation started in 1995 on all of more than 2000 horse chestnuts trees in Zagreb. In most years C. ohridella totally destroy all leaf greens, as early as in August. In some towns in Croatia, also in Zagreb, the control of this insect pest is organised. The treatments are conducted by foliar spraying diflubenzuron with knapsack mistblowers. In our three years trials the insect growth regulators diflubenzuron and hexaflumuron have shown satisfactory efficacy. The efficacy of the naturalit spinosad and the microbiological insecticide based on Bacillus thuringiensis var. kurstaki was not satisfactory. Both used pheromones showed a very high attractiveness to male of C. ohridella. In co-operation with companies &#8216 ; Intus&#8217 ; and &#8216 ; Arbosan&#8217 ; from Italy we started trials by using different devices and insecticides for the endotherapeutical control of the horse chestnut miner. The sycamore lace bug Corythuca ciliata (Say) was discovered in Zagreb in 1970. This bug can totally destroy the chlorophyll of the leaves of plane trees. The damages were stronger in the 1980&#8217 ; s but in the last years the intensity of infestation of C. ciliata decreased, probably due to natural enemies. Plane trees are also attacked by the leaf miner Phyllonorycter platani St. Infestation with Ph. platani is very high this year. On locust trees we have found two leaf miners: in 1983 Parectopa robiniella Clem. and in 2001 Phyllonorycter robiniella Clem.

urban horticulture; plant health; Cameraria; Corythuca

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