Dichlobenil
Trade Names: Casoron
Registration status: This herbicide is registered for use in tender fruit orchards, except apricots.
When to suspect injury: Injury is not expected from use of dichlobenil in fruit trees. A more common problem is loss of the herbicide when applied to warm or dry soils, resulting in poor weed control. If no weeds are growing under trees by the end of the season, excessive applications may have occurred, so check herbicide records and calibration of application equipment.
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: Benzonitrile
Site of Action/WSSA Group: Inhibits cell wall synthesis, Site A (WSSA Group 20)
General Symptoms in Plants
- Seedlings do not emerge from treated soil, because germination and meristem growth is inhibited
Symptoms in Stone Fruit
- Yellow hallos on leaf margins
- Symptoms increase as rate increases
- More risk of injury when herbicide is incorporated
- More risk of injury on coarse-textured soils, or if organic matter (OM) is low
- Symptoms may appear again the following year
Symptoms in Pears
- Tips of mature leaves become chlorotic and burned
- Chlorosis may spread around the entire leaf margin under high rates
- Interveinal chlorosis and small burned area may also develop
- Symptoms usually appear in early- to mid-summer and become progressively worse through the season.
Uptake and Translocation
- Absorbed by the roots
- Rapidly translocated upward in the plant
Persistence
- Will persist and provide weed control for 2-6 months
- Higher rates, and repeated use year-to-year may result in soil residues persisting for more than 1 year
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.
