Chapter 7

Crop Rotation on Organic Farms

Management of Insect Pests with Crop Rotation

Managing insect pests in crops without using pesticides is no easy task for organic farmers. Organic farmers rely largely on good management practices, such as crop rotations, to keep pests in check. Crop rotation is most effective against insect pests with a limited host range, long life cycle (one or fewer generations a year), and limited ability to move from one field to another. The primary goal in managing insects through crop rotation is to interfere with the needs of the pest throughout its life cycle. It is therefore important to be familiar with insect life cycles, feeding habits, and crop preferences. Needless to say, crop rotations will not control all insect pests. Most insects have a period during the adult stage when they are very mobile. Often this highly mobile stage comes when insects are emerging from their overwintering stage in the spring, so crop rotation from one year to the next will not affect them. Other insect pests feed on many different host plants and may build up in large numbers on one host, then move to another. An awareness of these possibilities can help a grower avoid potential problems.

Insects Controlled by Crop Rotation

Some key insect pests can be managed through crop rotation. An example is European corn borer, which can be controlled by several years without corn in the rotation. Western corn rootworm and northern corn rootworm can be easily controlled by crop rotation too. The adults have an annual life cycle and a host range restricted to grass species. Eggs are laid in the soil of a corn field during the summer months, then overwinter and hatch the next spring. If corn is rotated the next year with a corn rootworm non-host crop—small grains, soybeans, sorghum, or broadleaf crops, hatching larvae will starve and die.

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