Flumetsulam/ S-Metolachlor
Trade Name: Broadstrike Dual Magnum, Broadstrike RC
Registration status: This herbicide is not registered for use in tender fruit orchards.
When to suspect injury: Injury from flumetsulam may occur when this herbicide was used on fields before orchards were planted. Residues in soil can remain high when soil pH is above 7.5, and organic matter is less than 2%. Injury may also occur from drift from neighbouring fields under windy conditions. If you notice symptoms of stunting, especially in circular areas, look carefully at neighbouring fields, and at weeds in the treated area. Also check the pH in areas of stunted plants, and ask for a five-year history of herbicide use.
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: triazolopyrimadine sulfonanilide
Site of Action/ Group: Inhibitors of acetolactate synthase (ALS) and also called acetohydroxyacid synthase (AHAS) (WSSA Group 2)
General Symptoms in Plants
Symptoms in Fruit Trees
- As above, most likely stunting, and interveinal chlorosis from root inhibition
- Symptoms generally occur in circles in the field, often when soil pH is above 7.5 and organic matter is less than 2%
Uptake and Translocation
- Flumetsulam and s-metolachlor are absorbed by both roots and shoots
Persistence
- Dissipation of both s-metolachlor and flumetsulam is through microbial degradation
- Some crops require 10-26 months after flumetsalem was applied before planting, especially if pH is above 7.5
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.
