Chapter 24

Pesticides for Grapevines

Herbicides

Herbicides are chemicals that inhibit or interrupt normal plant growth and development. They are used widely in vineyards for weed management and are cost-effective in controlling weeds with a minimum of labor. Appendix J, Herbicides Registered for Use in Vineyards, list common names (active ingredient) along with trade names of currently registered herbicides in the United States for use on grapes.

Methods of Application

Soil-applied Herbicides

These herbicide groups have little or no foliar activity and are applied mostly for preemergence control of seedling grasses and some annual broadleaves.

Foliar-applied Herbicides

Herbicides used on established weeds are called foliar-applied herbicides. They are separated into two groups, contact and systemic.

Time of Application

Pre-emergence

Preemergence herbicides are active in the soil against germinating weed seedlings and will not control weeds after they emerge. These herbicides are applied to bare soil and are leached into the soil with rain or irrigation where they kill germinating weed seeds.

Post-emergence

Post-emergence herbicides are applied directly on the weeds growing in vineyards. They have either contact or systemic activity and require uniform wetting of the weeds to be effective. Post-emergence herbicides can be combined with preemergence herbicides to control weeds that emerge later or applied as spot treatments during the growing season. Most post-emergence herbicide applied in vineyards are nonselective, or herbicides that control annual or perennial grasses, but not broadleaf weeds.

Mode of Action

Herbicides can be grouped according to their mode of action (MoA). The mode of action is the way in which the herbicide kills weeds. It usually describes the biological process in the plant that the herbicide interrupts, affecting normal plant growth and development.

Mobility

Contact Herbicides

Contact herbicides destroy only the plant tissue in contact with the chemical. Generally, these are the fastest acting herbicides.

Systemic Herbicides

Systemic herbicides are translocated through the plant, either from foliar application down to the roots, or from soil application up through the roots to the leaves.

Target Site

Selective Herbicides

Selective herbicides can be used to control certain plant species without injuring others. This characteristic can be used to control weeds while avoiding harm to desirable plants.

Non-selective Herbicides

Some herbicides are non-selective and must be used with extreme caution. They are used primarily in situations where complete removal of vegetation is desired, such as on transportation rights-of-ways.

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