import pandas as pd
def assess_pest_risk(field_id):
obs = pd.read_sql("SELECT * FROM pest_observations WHERE field_id = ?", field_id)
severity = 0
for _, row in obs.iterrows():
if row['pest_type'] in ['Aphid','Locust']: severity += 3
elif row['pest_type'] in ['Caterpillar','Thrip']: severity += 2
if row['population'] > 100: severity += 2
return 'Critical' if severity > 8 else 'High' if severity > 5 else 'Moderate' if severity > 2 else 'Low'