From house guests to farm pests: The hidden impact of Daddy Long-Legs on agriculture
Have you ever noticed the delicate, spindly-legged insects known as ‘Daddy Long-Legs’ fluttering around your home?
Scientifically known as Tipula paludosa, or crane flies, these insects might seem harmless indoors, but Science Communication and Engagement Officer at Teagasc, Eimear Ferguson explains how they pose a significant threat to agriculture during their early development (larval stages).
The larvae of crane flies, called leatherjackets, can wreak havoc on grazing pastures and crops by feeding on the roots and stems, leading to substantial agricultural damage.
The damage caused by leatherjackets to grasslands in Northern Ireland, for instance, has been estimated at a staggering £1.5 million annually. This estimate included the costs of insecticide applications and fertiliser use. However, one of the primary insecticides used against leatherjackets, Chlorpyrifos, was effectively withdrawn from agricultural use in 2019 due to its harmful environmental and genotoxic effects. Since then, no updated economic assessments have been conducted, highlighting a critical area for ongoing research and development.
A team from the Crops, Environment, and Land Use Programme at Teagasc Oak Park recently published a paper that offers hope for more effective and sustainable pest management strategies against invasive leatherback populations, helping farmers protect their crops and livelihoods. Dr. Aisling Moffat (pictured below) conducted this research during her Walsh Scholarship postgraduate programme at Teagasc, under the guidance of Research Officer, Dr. Louise McNamara.
Aisling explained: "Our research delves into how farming practices and climate variables influence leatherjacket populations over the long term, particularly focusing on grassland farms in Scotland. Given the similarities in land use and climate between Scotland and Ireland, these findings are very applicable to Irish farms.”
By analysing data from 1980 to 2020, with a specific focus on the years 2009 to 2018, Aisling gathered valuable insights that could help farmers manage these pests more effectively.
The research indicates that leatherjacket populations are heavily influenced by farm management practices and local weather conditions. The study found that intensive farm management practices, such as pesticide use and sheep grazing, generally lead to lower leatherjacket populations.
Conversely, less intensive management practices tend to result in higher populations.
Aisling added: "Interestingly, the size of the fields and the presence of grazing sheep play crucial roles in controlling leatherjacket populations. Larger fields and those grazed by sheep tend to have fewer larvae. Sheep grazing, in particular, helps distribute grazing pressure evenly across the field, disturbing larval habitats and reducing their numbers."
Weather conditions also significantly impact leatherjacket populations. Temperature and precipitation are particularly influential. Warmer temperatures tend to reduce larval populations at the adult and second instar (L2) stages but benefit the third instar (L3) larvae, especially during warmer winters. Rainfall has a more complex effect, generally boosting larval numbers during certain stages, particularly the L2 and L3 stages.
In the below video, Aisling Moffat discusses her research on leatherjackets:
The findings underscore the importance of integrated pest management (IPM) strategies that consider both farming practices and local weather conditions. Incorporating sheep grazing and maintaining larger field sizes can help control leatherjacket populations more sustainably than relying solely on chemical pesticides. By understanding the relationship between weather patterns and pest population dynamics, farmers can improve their forecasting models, allowing for better prediction and management of infestations. This, in turn, can mitigate the impact on crops, leading to improved crop yields and more sustainable farming practices.
Going forward, the research group plans to explore more specific and sustainable farming techniques, such as diverse crop rotations and organic farming. These practices could help control leatherjacket populations while also promoting overall farm biodiversity. By adopting these strategies, farmers can achieve a more balanced and environmentally friendly approach to pest management.
Access the paper published from this work in the Journal of Applied Entomology here.
Featured photo caption: Crane fly pictured by Dr Aisling Moffat