In spite of the winter's extended harsh conditions, Chafer grubs are expected to have weathered well. As a result, activity is now increasing. Bayer recommends an annual preventative approach as the only way to gain real control.
"Chafer grubs have the potential to cause serious damage to turf playing surfaces and present a tough repair challenge," says Dorin Pop, Bayer's Technical Manager.
"The adult insects burrow into the turf and lay their eggs close to the soil surface before the grubs hatch and start feeding," he explains. "They essentially cut the roots off and kill the turf. In worst cases, the turf surface will actually come away from the ground and peel off like a carpet being lifted."
Fine sports turf is most at risk, especially golf greens and tees where a smooth, even playing surface is essential, particularly at this time of year as green keepers and turf managers prepare for the busy season ahead. Dorin says that being able to understand the different pest species and their associated lifecycles is essential in order to gain total control.
"There are four common species in the UK," notes Dorin. "The Cockchafer can take up to four years to go through one lifecycle whilst the Garden Chafer completes its lifecycle in one year, the Summer Chafer in two to three years and the Welsh Chafer in two years."
Dorin explains grubs at multiple stages of their lifecycle present a key challenge. "Typically, some eggs will have been laid during the spring of the previous year but will be present alongside larger grubs laid two years before.
These larger grubs will have passed the 1st and 2nd instar development stage and so insecticide treatments won't control them. . In fact, by the time the grubs have passed the 2nd instar stage, the damage will have been done. This is why understanding the grub's lifecycle is an advantage."
The difficulty comes when trying to identify the species. "It is very difficult to tell the Welsh and Garden Chafer apart, says Dorin. He advises that the most effective method of gaining complete control is to apply an insecticide treatment like Bayer's Merit® Turf, when the beetles are laying their eggs. This tends to be in late spring and can be anytime between the end of April through to July.
However he explains that due to the extended winter, activity is three or four weeks behind this year. Merit® Turf's systemic mode of action means that when the larvae eat the roots, they ingest the insecticide and subsequently stop feeding before dying.
The newly hatched larvae are also controlled through coming into contact with the product in the soil.
"A turf professional will need to apply an insecticide at this time of year, every year as not all grubs will die with just one application," says Dorin.
Whilst frequency of treatment is a key issue, Dorin adds that application technique is also important. "Merit® Turf needs to be applied evenly across the whole turf area before being thoroughly irrigated. Watering-in is critical for successful control and to move the active ingredient through the thatch and into the root zone of the turf."
More information about the product can be found on the Bayer website at: www.escience.bayercropscience.co.uk