Proactive management practices and good drainage can reduce the impact of this weed on the playing surface.

Toad rush (Juncus bufonius) is a common problem on turf surfaces. It is generally more prevalent on bowling greens and, to a lesser extent, golf courses where it can be very disruptive to play. It is an annual, grass-like weed and is autumn germinating. It is most likely to colonise turf surfaces that are either poorly drained or top-dressed with topsoil.

Toad rush with tufted growth and green winter colour.

Toad rush (red colouration) during summer.

The tufted growth habit of toad rush and the difficulty in mowing the plant (particularly later in the year and on bowling greens) can:

• Adversely affect the trueness/smoothness of ball roll; and
• Compromise the visual appearance of the turf surface.

Identifying Toad Rush

During the autumn – early winter period, toad rush is easily confused with grasses as it has narrow leaves of bright, glossy green. Identification is easier with older plants as, from late winter onwards, toad rush takes on a brown/khaki colour, especially at its base. In late spring, the plant turns a red colour as it starts to die with the onset of higher temperatures and moisture stress.

The distinguishing feature in identifying toad rush plants is that they don’t have any leaf veins. This is unlike grasses with their central vein; some grass species also have additional veins running parallel along their leaves.

The toad rush leaf (left) has no veins. In contrast, these grasses do (centre & right).

Toad rush is a prolific seeder.

Toad rush is a prolific seeder. It is most commonly introduced into turf surfaces as a seed contaminant in top-dressing soil. Once established, the plant quickly creates a seed reserve, enabling it to re-establish each year.

The plant is most competitive where the turf cover is weak/open (as with new sowings, damaged areas or late renovation causing slow recovery) or in areas where the drainage is poor, which limits the vigour or ability of grasses/cotula to compete.

Managing the Problem

The following strategies should be considered when trying to avoid or manage toad rush.

Shade (turf cover)

Like most annual weeds, toad rush requires light to germinate. Consequently, the first priority should be on maintaining a complete cover.

Grow-in/recovery

When ‘opening up’ the surface (as with renovation), ensure the desired plant is actively growing and there is adequate time available for a full and rapid recovery.

For new sowings, make sure you prepare a good, granular seedbed as toad rush is more competitive in shallow, compacted soils.

Furthermore, apply sufficient fertiliser to encourage a rapid establishment and/or recovery of the desired turf species or cotula.

Topsoil testing

Seed contamination is generally more of a problem when top-dressing with topsoil, rather than with sand. Conduct a germination test by placing a representative topsoil sample in a seed tray; keep it moist for at least 10 – 14 days and observe what germinates. Where you have excessively weed-contaminated topsoil, consider:

• Sterilising the topsoil (this is rarely carried out these days), or
• For bowls surfaces (assuming you aren’t sowing seed or bulbils), apply a pre-emergent application of oxadiazon (Foresite, Oracle) immediately following renovation.

Drainage

Toad rush is most competitive in poor draining situations. Improving drainage will increase the competitiveness of the desired turf plant (Cotula or grass) over toad rush. The exact drainage strategy required is site-specific.

Grooming/mowing

Once toad rush plants are present in bowling greens, control is difficult and usually needs to be delayed until part way (at least) into the playing season. This is because:

• Dalapon herbicide requires warm temperatures to be effective and is generally not used before October (but the playing season often starts in late August).
• On greens sown with maniototo (mixtures or alone), spraying with Dalapon needs to be delayed until the maniototo is in its summer leaf (November and sometimes December onwards in the North Island). By then, the toad rush will generally be starting to die.

Summer leaf form of Cotula maniototo with its fern-like shape.

To minimise the negative effect of toad rush during the early part of the bowling season (and in other fine turf situations), the key management strategies are to:

• Mow frequently. Too often, mowing is delayed or isn’t frequent enough during the off and early bowling season. The result is that the toad rush becomes too long (> 5-10mm approx.) and is very difficult to cut with a reel mower, i.e. the mower shreds or rolls the toad rush leaves.
• Check the mower’s reel-to-bedknife adjustment. When the toad rush is still young early in the season, a well-adjusted mower will generally keep the weed adequately cut.
• Ensure the bedknife is not excessively worn and the mower is sharp. This is best done prior to the start of the season.
• Groom by verti-cutting/raking plants that are older and have a distinct crown. To determine whether you have a problem requiring increased grooming:
  • Run a jack down several rinks.
  • If the jack bobbles then additional grooming is required.

When verti-cutting/grooming or raking, set the blades (or rake) so that it is going into the crown of the plant but not into the soil surface.

• Weed by hand (especially on new greens). While not the easiest of tasks, hand weeding can be successful. This is especially so on new bowling greens where chemical applications can’t be used on young Cotula. String out the green and gradually weed it for short periods over a few days. Gradually, the green will be covered and the toad rush issue addressed.

Toad rush established in a new green. Hand-weeded area on the right.

Chemical Control

Herbicides for controlling toad rush within turf are limited in number. The main options are summarised below:

Being Proactive

Toad rush can be a significant problem on turf and very disruptive to the playing season. Adopting a sound management programme and addressing drainage issues can reduce both the severity of this weed and its negative impact on play.

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