I am sure many of you are dreading the icy nights which virtually came out of nowhere. I was joking with a client just last week about how I rarely wear long pants to work… I guess I spoke too soon, what a shock to my system. I do love the heat, but what a relief it is for our gardens to finally get some cold weather.
Johannesburg especially has had very mild winters for the last six years; it’s when we get frost and black frost that I know that we have had a chilly winter. One of the side-effects I am sure you have noticed, is the abundance of flies, mosquitos and insect infestations now that we have had a few years of warmer weather.
Since I am outdoors all day it is easy for me to notice how the diseases and bugs are affecting the plants. In fact you might have noticed some trees with leaves that has what looks like mould on them, this is called sooty mould with the european nettle, chinese hackberry and white stinkwood particularly prone to this.
Sooty mould is found in conjunction with woolly aphids. If your trees are covered with this sooty mould, you must treat the tree for the woolly aphids first and then the sooty mould.
Woolly aphids are insects that survive on plant fluids and produce a waxy white covering which looks similar to cotton wool. These aphids secrete honeydew which infects citrus and celtis trees alike.
An infestation of aphids for example can weaken the tree, thus the tree is open to attack by other pests and diseases such as sooty mould and canker.
Sooty mould really does do significant damage; the fungus which covers the plants, leaves and stems is associated with Woolly aphids and the honeydew they secrete. If your tree is infected with either of the insects or funguses the chances of other plants directly beneath the tree being infected are very high. You will also notice discoloration on walls, paving and even a waxy substance on windows and leaves around the tree.
The thing is that due to the high winter temperatures and mild winters we’ve been experiencing, the cold is not exterminating the insect and fungus populations. We are really in need of something other than chemical pesticides to kill off these menaces this is why we’re all hoping this year is a chilly winter.
Now is the time to start putting frost guard on the tender plants within your garden. Frost guard acts as a buffer so that dew forms on the material and not on the leaves which get burnt by frost at sunrise.
If your garden is just too big to cover with frost guard, then I would recommend changing your irrigation system to water your tender plants at sunrise, this will help melt the ice crystals which have formed on the leaves of your plants.
As the weather changes, now is a good time to plant primula’s and poppies, they love the cold. Most garden centres around South Africa will have these two annuals in stock.
Important!: Please let us know if you have seen the woolly aphid and sooty mould in your garden, this will help us in working out the distribution of this infestation.
Got a gardening question? Email email@example.com and we’ll be sure to assist you
Who is Nicholas Spargo?
Nicholas Spargo, owner of Spargo Landscape Consultants, has been in the landscape trade for 12 years as well as being a lecturer at the Lifestyle Garden Design Centre for the past year. He was awarded a Gold for a design at the Lifestyle Garden Design Centre Design Show in 2008, is an Invasive Species Consultant and is affiliated with the South African Green Industries Council.
Landscaping and education are very close to his heart.