Different pre-emergent herbicides have different application timing and soil cover requirements. I have heard that it would be nice to have charts organizing those herbicides by their requirements. Below I have put together those charts.
The charts below only list one example herbicide for each pre-emergent active ingredient. The active ingredient of an herbicide is the chemical in the herbicide that works to kill the plant. There are usually several different formulations of each active ingredient, made by different manufacturers or by the same manufacturer with different formulations. For example, flumioxazin is an active ingredient that works to kill a plant by blocking chlorophyll biosynthesis. Valent makes three formulations of flumioxazin, Chateau EZ, which is a suspension concentrate, Chateau SW, which is a water dispersible granule (although Chateau SW is being phased out), and BroadStar, which is a granule only for use in non-bearing fruit trees. These may appear like three different herbicide options for you, but since they are the same active ingredient, their activity and application procedures are very similar. Similarly, diuron is an active ingredient the works to kill a plant by inhibiting photosynthesis. Many manufacturers. Such as Adama, Alligare, Loveland, and Drexel Chemical Company all make a diuron product. Again, these different options do have differences in formulation and price, but they essentially work in the same way. Listing one formulation is a way to simplify the charts, and is not a recommendation of one product over another. Hopefully these will help you think about which products are available when, and what preparation needs to happen to use each product. Always read the label before applying any pesticide and apply according to the label.
Table 1. List of pre-emergent apple herbicides that must be applied to bare soil. Remove existing plant debris before applying
Active ingredient (example herbicide)
Activation and incorporation
Application window
DICHLOBENIL (Casoron 4G)
Incorporate with 0.5-1 inch of water. When temperatures are hot, incorporate with shallow cultivation.
To target annuals, apply early spring before germination or after cultivating to remove growing weeds.
INDAZIFLAM (Alion)
Apply to dry soil. Allow soil to remain dry for 48 hours while herbicide binds to soil particles, then activate with water
Apply anytime the soil is not frozen or covered with snow.
ISOXABEN (Trellis)
Herbicide is stable on the soil surface for up to 21 days but must be incorporated into the soil with water or a shallow cultivation (1-2 inches) to activate.
Apply any time prior to germination of weeds or immediately after cultivation.
NORFLURAZON (Solicam)
Incorporate with water within 4 weeks of application.
ORYZALIN (Oryzalin)
Incorporate and activate with 0.5-1 inch of water or a shallow cultivation (1-2 inches).
OXYFLUORFEN (Goaltender)
Activate with at least 0.25 inches of water within 3-4 weeks of application. Do not redistribute treated soil or weed control will be reduced.
Do not apply between bud swell and final harvest.
SIMAZINE (Princep)
Immediately incorporate with 0.5 inches of water. Shallow cultivation can be used if conditions are dry.
HALOSULFURON-METHYL (Sandea)*
Avoid rain or irrigation within 4 hours of application.
*Do not move or activate after application.
Table 2. List of pre-emergent apple herbicides that do not mention plant debris removal in the label but may work better on small weeds or before weeds have emerged.
Active ingredient (example herbicide)
Activation and incorporation
Application window
PENDIMETHALIN (Prowl H2O)
Incorporated with water or a shallow cultivation (1-2 inches). A two-pass cultivation is best.
If applying before transplanting trees, avoid contact of roots with treated soil.
DIURON (Karmex)
Moisture activation required. Best if activated within 2 weeks of application.
Apply between March and May (1 application of 4 lbs/A) or after harvest until prior to bud break (2 applications of 2 lbs/A).
RIMSULFURON (Matrix SG)
Incorporate with 0.5 inches of water within 2 weeks of application.
Soil should be moist at the time of application. Do not apply to frozen or snow-covered soil.
Table 3. List of pre-emergent apple herbicides where the plant debris should not be removed before applying or control may be reduced.
Active ingredient (example herbicide)
Activation and incorporation
Application window
DICHLOBENIL (Casoron 4G)
To target perennials, incorporate immediately after application.
To target perennials, apply between November 15 and February 15.
FLUMIOXAZIN (Chateau EZ)
Activation with at least 0.25 inches of water.
Apply prior to silver tip, when soil is not frozen or snow-covered.
Table 4. List of pre-emergent apple herbicides that can also be applied post-emergent.
Active ingredient (example herbicide)
Activation and incorporation
Application window
DIURON (Karmex)
Apply with a surfactant when weeds are young/succulent, humidity is high, and temperature is above 70F.
Apply between March and May (1 application of 4 lbs/A) or after harvest until prior to bud break (2 applications of 2 lbs/A).
OXYFLUORFEN (Goaltender)
Apply in a high spray volume (minimum 20 gallons of water per acre) to ensure good coverage when weed density is high or there is heavy plant debris.
Do not apply between bud swell and final harvest.
RIMSULFURON (Matrix SG)
Apply when weeds are less than one 1 inch and not be stressed. Cold, dry conditions delay herbicide activity. Avoid rainfall or irrigation within 4 hours of application.
Do not apply to frozen or snow-covered soil.
HALOSULFURON-METHYL (Sandea)*
Apply with a non-ionic surfactant. Avoid rain or irrigation within 4 hours of application. Wait to cultivate for 7-10 days after an application.