portugese millipede

Strathnaver Reserve, Strathmore has a huge population of portugese millipedes, which I think are reducing the natural regeneration levels on site. What are the options for control? If fire is the answer, then at what time of year? They are very active now, with many juveniles present. What are the stories and possible solutions? Strathnaver Res is a grassland with many grassy weed species and insensitive plantings of trees. Is this an urban thing? Jalle