pathogenic fungi insect defoliation soil chemical stress microorganism activity
I gave my students this multiple choice question: Oak tree decline is linked to the effects of pathogenic fungi, insect defoliation, soil chemical stress, and microorganism activity. Which factor is an abiotic condition that is affecting oak tree decline?

Only one answer is correct among these 4 choices:
- pathogenic fungi
- insect defoliation
- soil chemical stress
- microorganism activity

Could you tell me which one is correct?

soil chemical stress