The Robinia ‘Frisia’, a popular species of tree used widely on development sites because of its attractive yellow leaves has been struck with disease. The Robinia Pseudoacacia ‘Frisia’, a tree native of North America, introduced into Europe in 1601 by Jean Robin has long been used as an ornamental tree in gardens and public spaces.
The Robinia ‘Frisia’ disease seems to be concentrated in the south of England, with a decline in young and semi-mature specimens exhibiting symptoms such as failing to come into leaf fully in spring, loss of leaflets but with the leaf rib still remaining, extensive dieback of canopy, premature dropping of foliage, brittle branches and occasional visible brown spots on leaves.
Currently, the green leaf variety of Robinia ‘Frisia’ is currently not reported to have been affected.
Causes of the Robinia ‘Frisia’ disease
While the cause of the problems in the Robinia ‘Frisia’ is still unclear, and several possibilities have been discounted, there remains a number of problems that are likely to have added pressure to the species. These can be put into three categories; climate change, leaf disease, insects & pests.
Climate Change and Robinia ‘Frisia’
The UK has experienced milder, wetter summers and winters in the past few years, unlike the hot dry summers and cold winters from previous years, which may account for premature leaf drop due to the lack of environmental triggers. Additionally, the milder winters may mean that the Robinia ‘Frisia’ are not experiencing the full dormancy period they are used to, which leads to greater energy exposure that would normally have been stored for processes such as bud break.
Leaf Disease in Robinia ‘Frisia’
The leaf drop symptoms observed in the Robinia Frisia species are consistent with a wilt fungus blocking the water-carrying vessels in the trunk. However, no evidence of this potential pathogen have been found so far.
Insect & Pests on the Robinia ‘Frisia
The main likely culprit of pest for the Robinia ‘Frisia’ is the Acacia leaf miner. It is so called because the larvae feed between surfaces of the leaves producing visible tunnels leaving the tree rather aesthetically displeasing. However, although the Acacia leaf miner is a known culprit across the globe, the pest remains rare to the Robinia ‘Frisia’ in the UK.
In all honesty I would be lying if I said that the disease and decline of the Robinia ‘Frisia’ upsets me. Quite frankly, I am not fond of this particular tree. Even before many specimens were struck with this new found illness, the trees could look sickly due to their spindly branches which only too easily broke off.
In addition,the Robinia ‘Frisia’s’ fast growth rate can become very problematic and making for very uneven canopies which again makes them look sickly at best.
Nevertheless, the disease is still a problem and needs getting to the bottom of. If you have, or notice, any ailing Robinia ‘Frisia’ trees, the Arboricultural Advisory and Information Service as well as the Royal Horticultural Society are both encouraging people to send samples over to them for further investigations.