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Extension > Garden > Yard and Garden > Fruit > Integrated pest management for home raspberry growers > Herbicide injury

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Herbicide injury

Herbicide injury is most serious with systemic, post-emergence herbicides. Systemic herbicides are taken up into the raspberry plant, and the plant redistributes the herbicide to the roots and new leaves, and the new leaves show symptoms. Common systemic herbicides that hurt raspberries include glyphosate (Roundup), 2,4-D, and clopyralid (used in many broadleaf herbicides for lawns). Pre-emergence herbicides that are used to prevent crabgrass and other weeds from sprouting rarely injure established raspberry plants. Pre-emergence herbicides are most likely to stunt raspberry plants if the soil was sprayed prior to planting or within two months after planting. Contact herbicides (Sythe, vinegar) can temporarily injure raspberries, but new growth will be healthy.

herbicide-injury

Glyphosate injury on red raspberry canes. The old canes were sprayed the previous fall.

Thaddeus McCamant, Central Lakes College

Herbicide injury usually shows up on the leaves of primocanes, the canes that sprout in the spring. Plants with glyphosate injury have narrow leaves that are often white or yellow. Leaves with 2,4-D injury are distorted and cupped with large veins. Plants with clopyralid injury have small, cupped leaves.

Herbicide injury can be caused by spray drift, from raspberries being directly sprayed or from herbicide sprayed on the soil. Glyphosate is rarely absorbed through the soil, and glyphosate injury usually is caused by drift or by the canes being directly sprayed. Raspberry canes can absorb glyphosate through their bark, and canes can absorb glyphosate even during dormancy. 2,4-D and clopyralid can be absorbed by the roots if the herbicide is sprayed on bare soil, but most injury is caused by spray drift when nearby lawns are sprayed. While herbicide injury can occur at anytime of the year, some of the most severe cases occur from fall herbicide applications. In fall, raspberries easily take up and store systemic herbicides in their roots and bark. Plants that were exposed to herbicides in the fall often show few symptoms in the weeks after being sprayed, but the injury will show up the following spring.

If the herbicide injury is minor, the plants will outgrow the injury. Plants sprayed in the spring and summer are more likely to grow out of herbicide injury than plants sprayed in late fall. If the injury is severe, either due to high rates of herbicide or fall applications, the plants will either die or become permanently stunted.


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