Glyphosate
Trade Names: Glyfos, Roundup, Touchdown, Vantage
Registration status: This herbicide is registered for use in tender fruit orchards as a directed spray, avoiding trunks, root suckers, leaves and fruit.
When to suspect injury: Injury from glyphosate could result anytime the spray contacts the bark, leaves or fruit. Injury from in-season applications takes several weeks to appear, whether from drift from a neighbouring field, or from under-tree applications. If glyphosate contacts your tree after terminal growth has stopped, symptoms will not appear until the following spring. Suspect drift injury when symptoms appear near field edges, and when neighbouring fields show herbicide burn-down symptoms (general necrosis). Suspect injury from mis-application under trees when lower limbs show symptoms of narrow, strappy leaves. Once glyphosate is in the tree, symptoms may appear annually for several years unless the product is diluted in the tissue.
Herbicide Information: Knowing how the herbicide works will help to determine the likelihood of injury from either direct application or drift. Consider how the herbicide works in plants, behaves in soils and what symptoms are common in other plants.
Chemical Family: Amino acid
Site of Action/WSSA Group: Inhibitors of 5-enolpyruvaylshikimimate-3-phosphate synthase (EPSP)/ Group 9
General Symptoms in Plants
- Inhibited growth
- General foliar chlorosis and necrosis within 4- 20 days depending on temperature at time of application
- Immature leaves and growing points are often the first to undergo chlorosis
Symptoms in Tree Fruits
- Symptoms appear in leaves emerging after application: Leaves emerged at time of application will not show symptoms
- Symptoms appear in the growing tips and newly emerging leaves
- Leaves are puckered, narrow, and strappy, almost needle-like
- All leaves emerging after application will show similar symptoms
- Injured tissue may allow invasion by disease eg. Fire blight
- In stone fruits, especially peach, bark on the trunk may crack and become sunken
- Late summer and fall applications will not show symptoms until the following spring
- Symptoms may appear for several years after mis-applications
General Symptoms in Plants
- Inhibited growth
- General foliar chlorosis and necrosis within 4- 20 days depending on temperature at time of application
- Immature leaves and growing points are often the first to undergo chlorosis
Uptake and Translocation
- Absorbed through foliage
- Translocated throughout the plant
Persistence
- None - crops can be planted or seeded directly into treated areas following application
- Half life in field: 47 days
If you suspect herbicide injury, laboratory analyses of herbicide levels in plant tissue are necessary to confirm the presence of herbicides, although symptoms may be helpful in diagnosing which herbicides caused the problem.
Both damaged and healthy plant tissues should be analyzed, because comparison levels are not readily available for many herbicides. Contact your lab for instructions on which plant parts should be sampled, how to handle and ship the sample, and what costs are involved to ensure an accurate and timely diagnosis.
