Tama Assist Protecting Forage Crops From Rodents: Why the Problem Is Growing
Rodent damage in stored forage is nothing new, but recent changes to UK rodenticide regulations mean the issue is set to become far more challenging for farmers and contractors. Understanding how rodents behave (and what the law now allows), is essential for protecting bales and minimising losses.
Rodents do not chew through twine or net because they want to eat it. Their incisors grow continuously, and they must gnaw to wear them down. Straw bales are particularly attractive because:
- Residual grains provide a food source
- The interior of a bale offers warmth and shelter
- Straw is easier to burrow into than hay
This is why one stack can be heavily infested while another (stored in the same location) remains untouched. The key factor is crop cleanliness, not the type of twine or net used.
Hay bales, which contain fewer grains and are denser, are rarely affected.
Sisal Twine
Historically, sisal twine was treated with repellent products. In practice:
- The treatment is low dose and breaks down quickly outdoors
- Exposure to rain, sunlight, and handling removes most of the effect
- It offers little to no protection once bales are stacked
Sisal has also largely fallen out of use due to cost, durability, and rot issues.
Synthetic Twine
Polypropylene twine is:
- Chemically inert
- Odourless and tasteless
- Not a food source for rodents
But this neutrality does not make it rodent‑proof. If a rat wants to get inside a bale, it will cut through any material in its way, including PP twine.
Repellent additives cannot be incorporated into PP twine in a way that remains effective, because the material cannot absorb or retain liquid repellents.
Netwrap
Netwrap is made from high density polyethylene, another inert plastic. It is no more attractive to rodents than twine, but no more resistant either. If rodents want to nest inside a bale, they will chew through net just as readily.
From 4 July 2024, the UK restricted the use of five key second‑generation anticoagulant rodenticides (SGARs):
- Brodifacoum
- Bromadiolone
- Difenacoum
- Difethiolone
- Flocoumafen
These SGARs can now only be used inside and around permanent buildings, and only by trained, certified users.
They cannot be used:
- In open fields
- On bale stacks stored outdoors
- In temporary or movable structures
- Under open barns or ‘lean tos’
- In yard stacks
- Anywhere not classed as a fixed building
This is critical because most bale stacks on UK farms are not legally considered buildings.
What this means in practice
The only rodenticides that truly work on farms ( SGARs) can no longer be used where most bales are stored. As existing farm stocks run out, rodent pressure will inevitably increase.
Many farmers are currently:
- Using up old SGAR stock
- Using SGARs legally on fixed buildings but unofficially baiting stacks
- Switching to less effective first‑generation rodenticides
- Supplementing with terrier packs (only possible when stacks are dismantled)
But these are short term workarounds. The long term trend is clear; rodent numbers around bale stacks will rise.
No binding material (sisal, polypropylene, polyethylene, treated, coated, or otherwise) can prevent rodents from accessing a bale if they want to.
Rodents chew to:
- Wear down their teeth
- Reach residual grain
- Create nesting space
The material itself is irrelevant. The driver is behaviour, not taste.
This means:
- No twine can be made “rodent‑proof”
- No additive can be incorporated into PP or PE that remains effective outdoors
- No netwrap can prevent rodent entry
- The problem is environmental, not material-based
Protecting bales requires a ‘whole site’ strategy, not a change in twine or net.
Effective measures include:
- Regular monitoring of storage areas
- Reducing food sources (especially spilled grain)
- Keeping stack areas clean and tidy
- Using approved rodent control methods where legally permitted
- Employing terrier packs during stack removal
- Improving storage infrastructure where possible
Only active rodent management can protect bales, not the binding material.
Rodent damage is not caused by twine or net, and cannot be prevented by them. The real issue is rodent behaviour, now amplified by new UK regulations that limit the use of effective rodenticides in the very places bales are stored.
As farms adapt to these changes, the need for innovative, compliant, wildlife friendly rodent management solutions will only increase.