It is hard to start off a new year with a warning of doom and gloom. However, the recent upswing in temperatures towards double digits is enough for me to share information on a new virus, commonly called Black Death.
While scientists in both England and the United States still do not know a whole lot about this disease, what they do know is rather scary. There is no cure.
To back up a bit, Black Death has been identified as a viral disease which is species specific to hellebores. (“Species specific” means it only attacks plants in the Helleborus genus.)
So far, no one has been able to determine how this virus developed but it has been spreading further afield in the UK over the last 20 years. And probably longer, as it would have taken a while for someone to pick up on the fact this disease was something new.
Now in North America
More recently, Black Death has begun to show up in North America, thanks to global trade traffic. While reported incidents on this side of the pond are relatively few, to date, lovers and collectors of hellebores must be on the alert.
Black Death – or to give it its new botanical name, Hellebore net necrosis virus (HeNNV for short) – usually begins as distortions on the new foliage which stunts the plant’s growth. Black streaks will start to appear on the leaves…generally following along the veins.
But do not be fooled! Black Death has been known to develop a pattern of rings, rather than streaks, which can confuse a gardener into thinking their plant is afflicted with the much less deadly disease, black spot. (Regardless of which disease is causing the black or dark brown spots, promptly remove infected leaves and destroy them.)
If your plant is indeed smitten with Black Death, the damage will become progressively worse as spring advances. Black streaks will start to develop on the stems and extend onto the flower petals.
Still studying
Research on HeNNV is ongoing, with scientists focussing on how it is transmitted. Early suspicions place the fault on everyone’s pest scourge: the aphid. And they are pointing fingers at the species specific aphid, Macrosiphum hellebore, although any aphid is quite capable of carrying the virus from one plant to the next.
Recommended control of Black Death is to dig up all infected plants and destroy them. It would also be wise to guard against aphid infestations by ensuring your plants are well nourished and cared for. Healthy specimens are far less likely to come under attack by pests. And so far, scientists believe this is exactly how this lethal virus is being transmitted.
Book update
On a brighter note, I have recently heard from Dr. Linda Gilkeson on the progress of her upcoming book release with updates on local pest and disease infestations.
Remember back to the fall when I canvassed readers for information on this topic? Well, I heard from quite a number of gardeners who supplied some useful information which was all passed on to Dr. Gilkeson.
Good news is: the book should be released sometime this month. Resilient Gardens 2016: Climate Change, Stress Disorders, Pest Update is magazine-sized and will be available in hard copy and downloadable ebook formats. Linda will be adding it to her website (lindagilkeson.ca) where you will be able to purchase it.
This companion update to her earlier book, Natural Insect, Weed, & Pest Control, will be a useful reference for local gardeners. Help in identifying new pests and diseases, coupled with shared insights on growing challenges in our changing climatic conditions…this is one resource for everyone’s library.