Which control method involves using physical materials to prevent pest access?

The control method that involves using physical materials to prevent pest access is the use of row covers. Row covers are typically made from lightweight fabric that acts as a barrier, shielding plants from pests while still allowing light, air, and moisture to penetrate. By physically obstructing pests, row covers provide a protective environment for plants, which can reduce the need for chemical pesticides and promote healthier growth.

In contrast, chemical sprays refer to the application of insecticides or fungicides, which actively kill or repel pests rather than preventing access. Soil treatments often involve the application of chemicals or biological agents to the soil to control pests residing there, without the physical barrier aspect. Nematicides are specific types of pesticides targeting nematodes in the soil and do not provide physical protection against pests.