Spreading decline of citrus is caused by…

✅Explanation:
Radopholus similis, commonly known as the burrowing nematode, is the primary cause of spreading decline in citrus. This microscopic worm infects the feeder roots of citrus trees, causing them to decay and die. As a result, the tree's ability to absorb water and nutrients is compromised, leading to a decline in overall health and productivity.

📌Other Options Explanations:
(b) Aphelenchoides sp.: These nematodes are known as foliar nematodes and primarily infect the leaves and stems of plants.
(c) Ditylenchus sp.: This genus includes stem and bulb nematodes, which affect various crops.