Organic gardeners avoid the use of synthetically produced fertilizers, pesticides, and livestock feed additives. However, the term organic gardening has different meanings among different individuals, so a synthetically manufactured fertilizer or pesticide may be objectionable to one organic gardener but acceptable to another. IPM programs rely on monitoring pests and pest damage. Exclusion Devices Examples of exclusion devices include row covers, nets to keep birds away from ripening fruit, paper collars placed around stems of plants to prevent cutworm damage, and proper fencing or barriers to halt the spread of bermudagrass or to prevent pets and wild animals from damaging the garden. Row covers are flexible, transparent or semi-transparent woven or plastic materials used to enclose single or multiple rows of plants.
Row covers as physical barriers have advantages such as being non-toxic with no residues.
Woven and porous or perforated plastic covers allow water and air to pass through, while all row covers allow sunlight to pass through. However, row covers can be labor intensive, especially in windy areas. Also, physical barriers may prevent pollination of fruits and vegetables by insects. To provide for pollination, gardeners must raise the barriers at flowering time. Also, physical barriers may be ineffective against pests that can emerge from the soil under row covers to attack plants.