As soil conditions begin to warm up, the activity of leatherjacket feeding damage will become more evident.
Larvae that have survived the winter are larger and start to feed voraciously, as they build up fat reserves ready for adult flight, warns
Syngenta Technical Manager, Sean Loakes.
Playing surface effects typically result in horribly uneven ball roll where larvae have created pock marks as they nibble around aeration holes each night. While below the surface they feed away on roots – weakening turf and making it significantly more susceptible to stress.
Added to that, predators in the form of birds, particularly crows, pecking at the surfaces, or worse larger badgers rooting for grubs, can cause catastrophic damage.
While greens treated last autumn may have seen leatherjackets well controlled, wider areas, tees or approaches that were outside treatment programme areas could now be subjected to heavier pressure. All efforts over the spring should be focused on symptom management for turf recovery and building plant strength to withstand the larvae feeding activity, including:
- Good nutrition
- Adequate irrigation
- Wetting agent strategy
- PGR programmes
- Cutting height
- Large scale sheeting
- Aeration
Trials have shown little or no beneficial effect from insecticide treatment with Acelepryn in the spring. The larvae are generally too large and mature to be killed by the paralysing effect of the insecticide.
For now, affected areas require ultimate attention and care with nutrition, irrigation, wetting agent programme, PGR and turf management actions to alleviate stress and make turf more resilient to damage.
Nutrition may need to be tailored slightly in the spring, to include nutrients to give plants opportunity to outgrow leatherjackets’ feeding damage, as well as leaf growth that can mask the effects of damage. Furthermore, Primo Maxx II programmes will promote root mass to counter the effects of leatherjacket larvae feeding, as well as using a wetting agent programme strategy designed to maximise root growth during periods where soils may dry down.
The impacts of leatherjacket damage inevitably put turf plants under greater stress, which will then make them more susceptible to other challenges – be that drought, sunlight, disease or effects of heavy play wear and tear.
Any Integrated Turf Management (ITM) practices that can alleviate stress will help develop more resilient plants.
Raising the height of cut can be a challenge where members constantly demand faster speed. However, even a small change can significantly improve the health of the turf. Allowing slightly more leaf area will also support a hugely greater percentage of root mass and make plants more resilient to stress effects. Even if that is only through the worst period of leatherjacket activity, and then cut returned to summer levels.
Trials have also shown that keeping turf in tight Primo Maxx II growth regulation enables the same speed of ball roll cut at 3.2mm, compared to 2.6mm in untreated – that gives the plant 20% more green leaf area. Furthermore, the PGR treated turf continues to putt more consistently right through to the evening.
Issues can be compounded where cutting height has to reduced to try and alleviate leatherjacket feeding damage around aeration holes, which could further exacerbate stress; each situation has to be managed as best a practical solution possible.
Artificial lighting has been used to promote recovery of specific areas. It is only likely justified for a limited number of high-end courses, but could be considered if a localised prime position were under severe pressure, on the 18
th green by the clubhouse bar, for example.
Evidence of feeding activity around the top of aeration holes can worsen any damage. Switching to slit tines that leave no space to the leatherjacket to hide may be a viable strategy.
Some courses have had success with a sheeting strategy on affected greens, to attract leatherjacket larvae up to the surface overnight and then clearing away large numbers. It does generally require repeated actions over three or four nights and will only ever reduce the pest pressure, but in severe cases can certainly help.
Small scale sheeting, pegging down 1m2 sheets overnight, can effectively monitor for presence of leatherjacket populations, to prioritise areas for wider sheeting or other spring actions. As well as a guide for risks and areas for future actions.
Syngenta research continues to evaluate the potential for spring nematode treatments. However, the nematodes require a minimum soil temperature of 8⁰C to work effectively, along with adequate soil moisture to survive and seek out their prey – which could both be limiting factors for early spring applications.
Reports from greenkeepers at BTME repeatedly highlighted that the late summer or early autumn applications of Acelepryn and NemaTrident F nematodes had been highly effective in reducing leatherjacket damage so far over the winter.
Armed with the knowledge of where larvae are active now can better enable application timing to coincide with peak flight and egg laying of the target crane fly species, Tipula padulosa. That will have optimum insecticide concentration in the soil when eggs hatch and larvae are at the smallest and most vulnerable first instar stage.
While many other species of cranefly are likely to be seen flying over the spring and summer, most lay their eggs in woodland or other habitats, so it is essentially T. padulosa that is the primary target to protect golf surfaces.
Focusing now on spring ITM strategies will help to build stronger turf, more resilient to leatherjacket damage and summer stress effects, while preparing for treatment actions at appropriate timing later in the season.
