By Lane Tredway, Ph.D., technical services manager for Syngenta

There are many best practices to consider to ensure the best performance from any product application. When targeting soilborne pests and pathogens, post-application irrigation (or “watering-in”) is one of the most important factors. This is especially true for nematodes, fairy ring, summer patch and insects such as white grubs and annual bluegrass weevils (ABW).

Nematodes | Fairy ring | Summer patch | Grubs and ABW

Nematodes​​​​​

To achieve the best results with Trefinti^® nematicide/fungicide or Divanem^® nematicide/miticide the active ingredients must be moved into the soil where nematodes are active. For the best results:

• Divanem should always be tank mixed with a soil surfactant to aid movement through the thatch layer. Soil surfactants also improve the efficacy of Trefinti and can be applied either as a tank-mix or separate application.
• Divanem applications are best made to wet turf, but if dew is not present, use a short irrigation cycle to moisten the turf before application. 
• Trefinti and Divanem should be watered-in immediately after application with at least 0.125 in. Divanem can benefit from an additional 0.125 in. within 24 hours after application. 
• Hollow- or solid-tine aerification before applying Divanem or Trefinti can also help the active ingredients to move deeper into the root zone.

Nematode-damaged roots not only absorb less water and nutrients but are also more susceptible to disease. The dual mode of action of Trefinti as a nematicide and fungicide is particularly beneficial for this reason. Divanem or Trefinti can also be tank-mixed with Heritage^® Action™ fungicide to further improve turf quality, turf density, root growth and root quality, as well as provide enhanced biotic and abiotic stress tolerance. The Divanem + Heritage Action Multipak contains 0.5 gal. of Divanem plus 5 lb. of Heritage Action and provides convenience when applying these products together.

Fairy ring​​​​​

If fairy ring is the primary target of a fungicide application:

• Irrigation should be applied immediately to maximize the amount of active ingredient moving into the thatch and soil
• Adjust the amount of irrigation based on the depth of the fairy ring infestation
  • If fairy ring is limited to the thatch layer, irrigate with 0.1-0.15 in. of water following the fungicide application
  • If fairy ring is 2-3 in. deep, irrigate with 0.25 in. of water following the application
• Tank-mixing with a soil surfactant can facilitate movement of the active ingredient deeper in the soil, especially if fairy ring symptoms are already present
• Hollow- or solid-tine aerification may also be necessary if hydrophobic conditions have developed in the soil
• Repeat applications at regular intervals to maintain consistent suppression in the soil

A 28-day rotation of Velista^® and Briskway^® fungicides, both applied at 0.7 oz./1,000 ft.², is a solid foundation for any fairy ring prevention program. These products are available year-round in a Multipak containing six 22-oz. bottles of Velista and one 1-gal. bottle of Briskway. Other excellent options for fairy ring prevention in the Syngenta portfolio include Trefinti, Posterity^® XT, Headway^® and Heritage Action fungicides.

For more information about fairy ring control, view our Fairy Ring Guarantee Program.

Summer patch

Summer patch is a root-infecting pathogen that affects annual bluegrass, Kentucky bluegrass and fine fescues. Creeping bentgrass putting greens are also commonly affected in transition zone environments. Since the pathogen is soil-borne, it is often recommended to water-in all fungicide applications. While this is effective in many situations, some caution needs to be taken with annual bluegrass on greens. Watering-in fungicides like Heritage Action and Headway is recommended in the spring, when Poa roots are actively growing and will be deeper in the soil. Applying 0.1-0.15 in. of water is often adequate to move the fungicide into the soil. The active ingredient in both products, azoxystrobin, is taken up by the roots for protection.

However, during the heat of summer it is common for annual bluegrass roots to die back. Once this occurs, Heritage Action or Headway should be applied in four gallons of water per 1,000 ft.² to place the fungicide closer to the soil surface where the active roots reside.

• If this volume of water is not achievable, water-in with 0.05 in. of water, or no more than a light syringe
• If too much post-application water is applied, it may move the active ingredient below the active roots, lessening the fungicide’s protection

For more information, view this article about application timing, products and rates for protecting turf against summer patch.

Grubs and ABW​​

Watering-in can also have a positive effect on insecticide performance. Although Atexzo^® insecticide/miticide, Acelepryn^®, Meridian^® 25WG and Acelepryn Xtra insecticides are more forgiving than most if they are not watered in within 24 hours, in most cases it’s still recommended that they be watered in. The key is to target the upper 1-2 in. of soil where the insects hatch and develop.

Watering-in requirements for the control of ABW can be more complex and recommendations will vary with the target life cycle and insecticide.

• For control of ABW adults, it is not necessary to water-in the insecticide
  • Pyrethroid insecticides, like Scimitar^® GC insecticide, should be allowed to remain in the canopy of the turfgrass.
  • If watered-in, there is the likelihood that the active ingredient will be moved into the soil and reduce adult control.
• For optimal control of ABW larvae, it is generally a good practice to wash the insecticide off the upper leaf tissue to the crown of the plant
  • Watering-in applications of Atexzo, Acelepryn and Ference^® insecticide with 0.05 to 0.1 in. of water can improve ABW control.
  • Research has shown that Ference does not require watering-in; however, if allowed to stay on the surface, much of the product can be removed by mowing and ABW control may be reduced, especially if the application was made to control large larvae.

Provaunt^® WDG insecticide is an excellent product for curative control of crown-feeding ABW larvae or third to fifth instar. Once applied to the turf, it will move into the cuticle and translaminar across the leaf. Therefore, it is important to water-in immediately with 0.1-0.15 in. of water to move Provaunt WDG to the crown of the plant where the ABW larvae are feeding.

For application timing and tips, visit WeevilTrakPlus.com and be sure to subscribe to access the blog.

© 2026 Syngenta. Important: Always read and follow label instructions. Some products may not be registered for sale or use in all states or counties and/or may have state-specific use requirements. Please check with your local extension service to ensure registration and proper use. Divanem and Scimitar GC are Restricted Use Pesticides. The trademarks or service marks displayed or otherwise used herein are the property of a Syngenta Group Company.