David Doll0 commentsApril 13, 2010Weeds

Glyphosate Damage on Almond

A number of calls have came in in regards to glyphosate drift damage. Drift injury from fall applications of the herbicide glyphosate (Trade names Roundup, Rodeo, Touchdown, Ranger, etc.)often appear the following spring upon the first flush of growth. The growth response from glyphosate application is very unique, with the overall tree appearing yellow (Figure 1 and 2) with deformed leaves having a “boot-lace” appearance (Figure 2), bud and limb death (Figure 3), and in severe cases, tree death. Figures 1 and 2: Almond trees showing symptoms of exposure to glyphosate. Most likely, the herbicide drifted onto the tree in the fall, with symptoms appearing the following spring. Many growers ask how a fall application of herbicide can still cause damage the following spring. Glyphosate, being a systemic herbicide, is designed to be stable once inside the plant. When glyphosate is applied to the leaves of a weed, the chemical is able to move through the leaf cuticle and enter into the phloem of the plant. From this point, it is translocated to the root, or other tissues, exits the phloem and inhibits the formation of amino acids that are critical for plant growth, killing the plant. If, however, glyphosate is applied to a woody plant (i.e. tree) entering dormancy, the chemical may not be systemically translocated, but “stuck” in the phloem tissue within the area of application. Once the plant breaks dormancy, the flow of carbohydrates from root to shoot move the herbicide into the newly formed tissues, causing deformed growth and possibly bud and shoot death. Figure 3: “Boot Lace” appearance of almond leaves is often indicative of glyphosate exposure. Figure 4: Dieback of the apical bud of a young almond shoot caused by the accidental application of glyphosate. Glyphosate damage is often confused with zinc deficiency. If

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David Doll0 commentsMarch 22, 2010Weeds

Drift Management to Avoid Herbicide Damage

Written by Kurt Hembree (UCCE Fresno County) Reducing spray drift is necessary to prevent crop injury, both within the field being treated and off-site. Environmental conditions (air temperature inversions, wind velocity, etc.), applicator awareness, type of spray equipment, nozzle selection, spray boom operating pressure, water volume discharge, and other factors affect the degree of drift that may occur during any application. While spray shields do not guarantee drift will not occur, they can greatly minimize the risk of drift, especially in open fields or where young vineyard and orchard plantings are being treated. The following steps should be taken to minimize the risk of drift from ground sprayer equipment: 1. Don’t spray when it’s windy: Do not spray in winds above 6 – 10 mph. 2. Be cautious on calm days: Do not spray under dead calm conditions in early morning, evening, or the night. Calm conditions are often associated with temperature inversions which can result in long-distance spray drift (1 mile or more). Burning brush on calm days can give an indication on the presence of temperature inversions (refer to local regulations on restrictions for obtaining a burning permit). 3. Check the buffer zones: Refer to the product label to determine adequate buffer zones outside of the field treated. Do not spray if the wind is blowing towards a nearby sensitive crop, garden, waterway, or other sensitive area. 4. Use a shield: Consider equipping your sprayer with a protective shield. A number of designs are available that can reduce drift between 35 and 75%. Avoid spraying trunk-to-trunk with unshielded spray booms. 5. Use a spray drift retardant: Spray drift retardants are available that can be added to many products to help reduce off-target drift. 6. Check the formulation: Use amine formulations of 2,4-D when possible. Use special care when

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