Explain why, if u examined Australian gum tree leaves in USA, there would be little evidence of pathogens?

Question

little evidence of pathogens or insect attack

Answer 1

This is because pathogens are usually native to the country of origin of the plant and when the plant (in this case a eucalypt) is grown in an overseas country (USA) the pathogens are usually not present, particularly if the plants are grown from seed.

However, this is not 100% true. Sometimes the insects manage to reach the overseas country and cause problems: thi sis why quarantine inspections are important. Occasionally, a pathogen that affects a related plant in the foreign country can also damage the introduced plant.