Final answer:
Suppressing Nardonella in weevils leads to a decreased symbiotic relationship, which could adversely affect the weevil's survival and reproduction due to a reduced capacity to obtain essential nutrients.
Step-by-step explanation:
The primary effect of suppressing Nardonella in weevils is c) Decreased symbiotic relationship. Nardonella bacteria are endosymbionts that live within weevils and contribute to their host's nutrition by synthesizing essential amino acids and other nutrients that are scarce in the weevil's diet. Suppressing Nardonella would impair this mutualistic interaction, potentially leading to a reduction in the weevil's ability to thrive on nutrient-poor diets, which could have adverse effects on their survival and reproduction.