Veteran forester Christopher Rhodes is calling on the industry to cease its use of hazardous substances in forest management. His argument is informed by painful personal experience of the dangers.

IN the mid-1970s I was a forestry worker in the Forestry Commission. One of our tasks was killing off broadleaved woodland by the application of chemicals containing dioxin.

These acts of what would now be considered environmental vandalism were in line with FC policy at the time – at least in the Conservancy where I worked – of replacing broadleaves with conifers. We questioned the health risks of handling a chemical containing dioxin, the chemical constituent used as a defoliant in the Vietnam war. The high number of birth defects, deformities and increased health risks in the Vietnamese population was attributed to dioxin exposure. The FC assured us it was safe. One forester even went as far as to say he would act as a 'spotter' should the FC decide to spray aerially.

I was reminded of those events when diagnosed with bladder cancer in 2015. I had permanently returned to the UK after a 30-year career as a forester/conservationist in Africa and, in order to survive the long winter months, decided to do some tree planting, starting 10 years ago. Most trees were pre-treated with cypermethrin – now replaced by acetamiprid – and further exposure came from follow-up spraying. I was also exposed to glyphosate during vegetation control work.

Research has shown that bladder cancer has only two known causes – smoking and exposure to industrial chemicals. I had stopped smoking more than 35 years previously and thought it unlikely, though of course not impossible, it had caused the cancer. That left industrial chemical exposure. I looked into the research for links between cancer and two of the chemicals I had been using: glyphosate and acetamiprid.


There has been a lot of scientific and medical research into the health hazards associated with glyphosate. Glyphosate is an endocrine-disrupting chemical and was listed 'probably carcinogenic to humans' by the International Agency for Research on Cancer (IARC) in 2015. This category is used when there is limited evidence of carcinogenity in humans and sufficient evidence of carcinogenity in lab animals. The IARC warned the probability of developing cancer depends on factors such as the type and extent of exposure. Forest workers are extensively exposed to this chemical, as are farmers and landscapers.

Exposure is far higher than, for example, a householder occasionally spraying Roundup on garden weeds.

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Glyphosate is now banned or restricted in at least 21 countries. Germany will ban glyphosate by 2023 under a systemic reduction strategy. In 2018, a former groundskeeper from California with terminal cancer won $39.2 million in compensatory damages and $250 million in punitive damages from the manufacturer for failing to warn consumers that exposure to Roundup weed killer causes cancer. The jury found the manufacturer acted with malice, oppression or fraud and should be punished for its conduct.

Researchers have noted the manufacturer's own early studies revealed some trends in animal models that should not have been ignored. More than 40 years of glyphosate exposure has provided a living laboratory where humans are the guinea pigs and the outcomes are alarmingly apparent. There is strong evidence glyphosate is likely contributing to the increased prevalence of multiple types of cancer in humans. Overall, evidence of the carcinogenity of glyphosate is compelling and multifactorial.


Acetamiprid is a contact insecticide for sucking type insects. It is a neonicotinoid insecticide that works by antagonizing the nicotine acetylcholine receptors in the neural pathways. It is used in some UK forests to protect young planted trees from damage caused by pine weevils (Hylobius abietis) and black pine and spruce beetles (Hylastes spp.). Acetamiprid has so far not been labelled carcinogenic, but there is mounting evidence that it can be harmful to humans.

The following table lists some of the research findings for acetamiprid:

The Forestry Stewardship Council (FSC), which certifies all state forests and most private forests in the UK, says this about chemicals: “These pesticides should only be used in FSC-certified forests if there is no viable alternative. Non-chemical methods or less hazardous pesticides shall be preferred."

It is not clear if this advice is aimed at reducing the impact of hazardous chemicals on benign animals and insects or if the FSC has fully understood the human health risks as well. Incidentally, the FSC has not banned glyphosate, yet categorises it as a carcinogen.

The FSC considers acetamiprid 'highly hazardous' to mammals yet, as with glyphosate, the FSC permits its continued use. I have asked the FSC to comment if and how it has assessed the risk to forestry workers, but have not had a satisfactory response.

The potential damage to newly planted young trees from weevils, particularly on upland sites in the UK, can be considerable and in some cases result in 100-per-cent mortality.

This is not disputed. The Forestry Commission has developed a tool for assessing or predicting the risk of damage at individual planting sites. The FC Hylobius Management Support System (2017) is a decision support tool that utilises ‘billet counts' to measure insect presence in combination with a model based on an understanding of Hylobius population dynamics to predict if damage is likely on site and therefore what action or treatment is required. For example, on isolated, small re-stocking sites it should be possible to reduce damage to acceptable levels by good ground preparation such as mounding and delayed planting.

The Forestry Commission has carried out research on non-chemical alternatives to weevil and beetle control which includes fallowing, rapid planting, ground preparation, brash treatments and plant size.

What I have found both confusing and frustrating is the variation in vegetation and insect control strategies in different parts of the country, even in the same area of the country, from year to year. For example, until 2016, one forest management company working in the north of England didn't use glyphosate to control weed growth. Neither did they use mechanical or hand weeding. Planting stock was large and left to compete with weeds.

On the retirement of a forest manager, the new management started to buy smaller trees and use glyphosate to control vegetation.

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It's a similar situation with weevil control. Some Forestry England sites are left fallow for several years before planting and neither pre-treated trees nor follow-up spraying with acetamiprid is required. It seems the FC's Hylobius Management Support System is not always followed by every forest manager, either due to the amount of work involved in implementing the system or because of entrenched or even lazy thinking that says chemical treatments are the easiest solution.

The people who make the decisions as to whether or not to use chemicals are not the ones who have to spray trees and vegetation. They might argue forest workers are required to wear PPE and therefore safety is assured. This fails to take into account site hazards. Almost every re-stocking site I’ve worked on has been highly hazardous. Felling residue – branches, stumps and roots – is left on site. This is hazardous enough immediately after felling, but even more so when sites are covered in a dense blanket of grass and weeds. Most every forest worker will have tripped or fallen down a hole while carrying a knapsack sprayer and nearly every one will have been splashed on exposed skin by chemicals leaking from a sprayer during a fall.

Planting young trees pre-treated with acetamiprid is not risk free, even with PPE. Trees are treated with acetamiprid in the nursery, bagged and delivered to planting sites.

Water can get into bags and roots often become saturated. Even taking the greatest care, planters can rarely avoid being splashed on the neck, face and eyes. The same risk can occur even when water doesn't get into bagged trees – loose soil from the roots can be both breathed in and end up on the skin and in eyes.

All this leads me to believe that not enough is being done to reduce health risks to forest workers. The fact that non-chemical weed and insect control strategies are routinely used in some parts of the country suggests some forest managers recognise the risks and deliberately avoid chemical control methods. The primary aim should be to eliminate risks and this can only be achieved by non-chemical strategies. Yes, not using chemicals can be more costly and involve more planning, but in the UK in 2021 should a trade-off between worker health and cost really be on the table at all? 

Forestry Journal: Hylobius abietis on Scots pine Hylobius abietis on Scots pine

During the past year, my local MP has tabled questions in parliament concerning chemical use in UK forests. The government says it is following a 25-year elimination strategy. The government must be aware of the research highlighting the risks to human health from exposure to chemicals yet expects poorly paid and poorly represented forestry workers to carry all the risk for perhaps a further 25 years. This demonstrates an egregious disregard for the health and safety of UK workers and an immediate change in government strategy and policy is not only necessary, but the right thing to do.

My MP is continuing to ask questions of the Secretary of State. Can forest managers who continue to use chemical control strategies go one better than the government and immediately stop using these highly hazardous substances?