Chapter 30

Cover Cropping in Vineyards

Managing Pests with Cover Crops

Cover crops not only play an important role in slowing erosion, improving soil structure, and providing fertility, but also play an increasingly important role in managing pests—insects, diseases, weeds, and nematodes. Cover crops, if properly selected and managed in an organic farming system, can be used to enhance the environment to control pests. Success depends on properly matching cover crop species with the cash crops and anticipated pest threats.

Cover Crops for Managing Insects

Cover crops can provide food and habitat for beneficial insects. Table 30.1 lists beneficial and pest insects that are attracted to or harbored by common cover crop types. It is important to note that an increase in beneficial insects does not always translate into a general decrease in insect pest species.

Managing Cover Crops to Encourage Beneficial Insects

The success of cover crops in preserving or encouraging beneficial insects depends in large part on how the cover crop is going to be destroyed or suppressed so that crops can be planted. The frequency and intensity of disturbance is important to the stability of populations of pests and their natural enemies.

Cover Crops for Managing Diseases

The impact of cover crops on pathogens—agents in the soil, such as bacteria or viruses that cause disease—can be good, bad, or nonexistent. This impact varies broadly depending on individual circumstances and situations. A cover crop can act as a host for soil-borne pathogens, or it can serve as an effective form of biological control for other plant pathogens.

Cover Crops for Managing Weeds

Cover crops suppress weeds by competing for light and nutrients or, in some cases, releasing compounds that inhibit the germination or growth of weeds through allelopathy. Weed suppression by cover crops varies by species, management (e.g., planting dates, planting densities, tillage, and residue management, etc.), existing weed populations, and weather conditions.

Managing Cover Crops to Help Suppress Weeds

Numerous factors can influence the effectiveness of managing weeds using cover crops. Species selection and management should be planned carefully long before cash crop planting. Decisions should account for other farm-specific management goals, available equipment, production costs, and the dates when cover crops can be planted and terminated. Considerations include:

Cover Crop Residues

Cover crops can also serve as a “living mulch” to manage weeds. When the cover crop is killed, its thick residues remain on the surface and hinder weed growth by physically modifying the amount of natural light, soil temperature, and soil moisture that is necessary for weed seed germination.

Allelopathic Compounds for Controlling Weeds

Some legume, cereal, and brassica cover crops release allelopathic compounds (plant-produced natural herbicides) that can reduce weed populations and/or suppress weed growth.

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