| Popis: |
Over the past about a dozen years in Croatia there has been a considerable increase of damage caused to ornamental plants in urban surroundings. The appearance of Cameraria ohridella Deschka et Dimić in 1989 have pointed to the need of a more considerable plant protection in urban surroundings as well. Since horse chestnut is very common in most Croatian cities, damage caused by chestnut miner has provoked the attention of a wide public. This was the reason why other pests attacking the urban vegetation also came into focus. C. ohridella is in Croatia prevented mostly with knapsack mistblowers. The lacks of this method are the risk of polluting human environment by pesticides and treatment up to only 6-10 m. Still, according to our four-year experience, if applied timely, this constitutes a good protection of horse chestnut against C. ohridella. The basic precondition is the monitoring of pest population through pheromone use and visual inspection of plants. In the course of 2003, we have also started the research of endotherapeutic methods in horse chestnut protection against pests. The only agent today permitted for use in C. ohridella prevention in Croatia is the insect growth regulator diflubenzuron, applied through foliar treatment. The research includes only one other insect growth regulator hexaflumuron. During trials, horse chestnut trees 8-15 m high were treated twice a year within terms set according to the monitoring of the pest population dynamics. Dimilin SC 48 (diflubenzuron) was prepared in concentration of 0.05%, and Sonet 100 EC (hexaflumuron) in that of 0.2%. During application, the liquid application rate per tree was 1.5-3 l. The graph shows that there are no statistically significant differences between the efficacy of diflubenzuron and that of hexaflumuron. The application of both insect growth regulators resulted in very good protection against the chestnut leaf miner. Somewhat poorer chestnut protection was achieved in 2002 because the application was too late. |
