Oak processionary moth (OPM)

Since 2019, we have adopted a risk-based approach to managing OPM on our land, in line with other Surrey local authorities. When measuring the risk, we look at:

• presence of OPM in individual trees or groups
• amount of footfall in the area
• risk of exposure to the caterpillar
• vulnerability of individuals: infants, elderly and people with existing health conditions

We assign a risk level of high, medium or low to all our sites:

• high risk – high public usage, known infestations and treatments work carried out previously
• medium risk – moderate public usage and OPM present
• low risk – no OPM or no oak trees

When risk assessing each site we consider each nest's location and the risk to residents. We pay particular attention to densely populated areas and the proximity to vulnerable individuals, for example, children, infants and the elderly. 

How we respond to risks

In high-risk areas:

• insecticide spraying – only in hotspot high risk areas, where OPM is causing a significant problem
• carefully-timed nest removal - all nest removals are carried out by professional tree surgeons with the appropriate training and equipment

In low-risk areas:

• on-site information/education

We also issue regular communications, including via resident newsletters, our website and social media.

Insecticide spraying in hotspot high risk areas

We use a biological insecticide spray specifically formulated for caterpillars. This treatment only takes place in the worst-affected areas. We always take careful consideration of the potential detrimental effect on the biodiversity of an area. 

The insecticide we use does not cause any health risk to humans and pets. However, as a precaution and to guarantee yours and your pet's safety, we ask you to keep away from areas being sprayed. Spraying zones will be clearly signposted.

Why we need to spray caterpillars

Spraying is a necessary preventative measure to limit the spread of OPM in the worst affected areas. To be effective, the treatment must be applied at the beginning of the season, shortly after the caterpillars have emerged and repeated 10 days to 2 weeks after.

The insecticide might not completely stop the OPM spread. Spraying is intended to help control an increasing population in hotspot areas and will not be used for large areas.

Manual nest removal

Although more environmentally friendly, nest removal is a lengthy and costly process that cannot be carried out in large, infected areas. It has to be carried out by qualified contractors with the right qualifications and equipment.