INSTYTUT DENDROLOGII

Reaction of trees on insects grazing and pathogenic fungi infection in the polluted environment and elevated temperature condition

Analysis of simultaneous influence of environmental pollution and elevated temperature on relationships between host plants - insects and host plants - fungus were an aim of my studies. I chose fluorine compounds as an object of my research because fluorides are one of the most important air pollution. They are more toxic than other common pollutants such as SO₂, NO_x and even O₃. According to a report of the Intergovernmental Panel on Climate Changes the average global surface temperature had increased 0.6°C since the late 19th century. IPCC predicts that the average global increase of temperature will amount to 0.9-3.4°C from 2000 to 2100 year.

In my investigation I tested following hypotheses:

1. Environmental pollution and increase of temperature directly affect performances of insects and pathogenic fungi;
2. The pollution and elevated temperature affect changes of the metabolite content;
3. Changes of compounds content affect attractiveness of plants for herbivorous insects and susceptibility to infections by pathogenic fungi.

Three experiments were done during my study.

3-years old seedlings of Scots pine (Pinus sylvestris L.) and English oak (Quercus robur L.) were used in the first experiment. Caterpillars of nun moth (Lymantria monacha L.) and gypsy moth (L. dispar L.) were put on needles or leaves of seedlings. A part of seedlings were polluted by sodium fluoride solution. With the aim of the increase temperature, seedlings were put in cages with walls covered by transparent plastic foil. The increase of the temperature amounted 1°C.

In the second experiment leaves of 3-years old seedlings of English oak were infected by fungus oak mildew (Microsphaera alphtoides Griff. et Maubl.). With the purpose of the increase temperature, seedlings were put in a tent made of transparent plastic foil. The average temperature for that treatment was 1.5°C higher than for control seedlings. A part of seedlings were watered by sodium fluoride solution.

In the third experiment nun moth and gypsy moth larvae were kept in Petri dishes in 15, 20 and 25°C fitotron chambers. Caterpillars were fed on needles/leaves collected in a polluted (by fluorine compounds) and unpolluted sites.

Results of my researches show, that direct influence of environmental pollution and elevated temperature is more significant than indirect influence. Furthermore effects of pollution and elevated temperature depend on species of plant and herbivorous insect or pathogenic fungus.