Leatherjacket Control on UK Greens (Cultural + Biological, post-Acelepryn)

What it is

Leatherjackets — the larvae of the crane fly (Tipulidae) — are the main insect pest affecting UK and Ireland golf greens. They feed beneath the surface on turf roots, compromising the plant's ability to recover and producing patchy spring weakness when greens fail to respond uniformly to spring fertiliser and weather warming [r-and-a:gc2030-itm-parkland].

Where the damage shows up

Two distinct damage modes [r-and-a:gc2030-itm-parkland]:

• Direct root damage — root-system depletion that "can extend well into the summer months, particularly if spring growth and recovery potential is poor." Greens look thin or off-colour, recovery is slow, and there's no obvious cause until cores reveal grub population.
• Secondary bird-pecking damage — birds (crows in particular) forage for leatherjackets and produce surface holes that impair ball roll. The pecking is the symptom turf managers see first; the underlying leatherjacket population is the actual problem.

Chemical control history — Acelepryn is gone

The insecticide Acelepryn (chlorantraniliprole) had Emergency Approval on UK golf greens for four summers — 2018, 2019, 2020, 2021 — covering preventative control of leatherjackets and chafer grubs where damage was "problematic, as advised by a suitably qualified and BASIS registered advisor" [r-and-a:gc2030-itm-parkland]. The R&A note explicitly that "the annual renewal of an Emergency Approval authorisation is not guaranteed," and the 2021 expiry has not been followed by re-approval. The chemistry-loss is the operational backdrop for everything below.

Cultural and biological controls

The R&A name three working approaches that "are gaining traction" post-Acelepryn [r-and-a:gc2030-itm-parkland]:

• Black plastic overnight sheeting — covers damp turf at night; larvae rise to the surface seeking moisture and are collected the next morning. Labour-intensive; targeted to known hotspot greens.
• Starling bird boxes near affected greens — "shown to be effective in reducing grub numbers and minimising turf damage." Starling-pecking produces "smaller and cleaner [holes] than those caused by crows," so bird-led biocontrol shifts the cosmetic footprint of pest predation toward the more recoverable end.
• Biological control with parasitic nematodes — already available; the R&A note adoption will accelerate "once there is a better understanding of how to use these products most effectively."

When to deviate

The supe's own threshold always overrides this entry. Reasons to escalate or modify the cultural-only default:

• Member-event week / championship prep — historical bird-pecking rates on a known-hotspot green warrant pre-treatment with parasitic nematodes 2–4 weeks ahead, even on greens where population pressure hasn't been confirmed by coring
• Population-confirmation coring — visible thinning + ≥10 leatherjackets per 0.1m² is a commonly-cited (though not in this R&A source) action threshold; supes who use it should record the reading on course_inspection and apply via known IPM rotation
• Severe outbreak — if an emergency authorisation is re-issued for Acelepryn or a successor product in a given year, BASIS-advisor consultation precedes any application

Related

• itm-parkland-greens-rA — companion R&A anchor entry covering the broader ITM doctrine + the chemistry-loss
  • 75% insect-biomass-decline context that drove withdrawal of every full-approval insecticide on UK golf courses
• withdrawn-actives-uk-reference — loss-of-actives reference; this entry's Acelepryn-EA-expiry timeline is one specific case under that broader doctrine
• earthworm-casts-management-uk — companion pest-management entry on the other top UK greens-area pest with no chemical option; same chemistry-loss + cultural-first framing
• chafer-grub-control-uk — Acelepryn EA covered chafer grubs too (2018–2020 per ITM Parkland p.16); R&A note chafers "rarely cause problems on golf greens unless from associated damage by foraging mammals" so a dedicated entry is lower priority (future entry; flag in _index/gaps.md if requested)
• nematode-resistance-mgmt-crow-2026 — reciprocal cross-link to the parasitic-nematode research-frontier entry; the same word ("nematodes") covers two distinct populations — beneficial entomopathogenic nematodes (this entry's §"Biological control" cultural lever) and plant-parasitic nematodes (the pest in the Crow-program entry) — the cross-link prevents reader confusion
• aeration-timing-cool-season — aeration is in this entry's linked_tasks because aeration timing affects crane-fly oviposition site availability; July–August scheduling decisions interact with leatherjacket pressure
• climate-adaptation-uk-course-management — the multi-supe doctrine on adapting to combined climate + chemistry-loss pressures; this entry's post-Acelepryn cultural + biological programme is the pest-specific expression of that doctrine on the Tipulidae side

<!-- WRITER NOTE (library-curator-2, 2026-05-19, PR #2 / scout-sweep-v2-pests): PR #2 pest-cluster entry derived from R&A ITM Parkland Greens p.15 (verified during PR #1 verifier pass). Acelepryn EA span for leatherjackets is 2018-2021 (four summers) per p.15 — distinct from the chafer-grub span 2018-2020 (three summers) per p.16; the discrepancy is in the R&A source itself and faithfully reproduced here as in companion `itm-parkland-greens-rA.md`. The "≥10 leatherjackets per 0.1m²" threshold in §"When to deviate" is NOT cited from the R&A source — it's industry-common shorthand (GreenCast / Syngenta-aligned scouting guidance, varies by source). Verifier: this is a deviate-trigger floor, not a published R&A recommendation; the "though not in this R&A source" parenthetical makes the provenance explicit. If verifier insists on R&A-only threshold sourcing, strip the bullet — entry still stands on cultural-control content. -->