1500 species in North America alone, mostly preferring one or two hosts only can all make a gardener very unhappy.

Dead aphids on leaf underside which also has damage from a leaf cutter bee. Live aphids sucking on young rose stem

This year in the south east corner of British Columbia, the conditions have been ideal for aphids to thrive. They like cool dampish weather and then a rise in warmth sends them into overdrive. These conditions make the tender young new growth on plants easy to get into and favor aphid reproduction. Aphids reproduce asexually. The mostly, female aphids can quickly produce many eggs which in turn produce young female aphids or nymphs already pregnant with more eggs to be delivered asexually. At the end of summer some aphids will produce wings, flit off, find a male and lay fertilized eggs to overwinter in the bark of trees and other nooks and crannies.

Aphids, greenfly or blackfly appear every year, some years producing more than others. They can do considerable damage by sucking on the sap of the particular plant for which they have an affinity.  Their purpose in the web of life it would seem is to provide other insects with the sweet honeydew which they excrete as waste from over indulgence on plant sap.  This shiny sticky substance is one of the first things to be noticed when aphids have moved in. Aphids frequently feed on the underside of leaves and so are not always noticed immediately but the honeydew will drip on to other leaves and surfaces leaving a sticky shiny residue. Ants love the honeydew as do many other insects, which have a symbiotic relationship with aphids.

As mentioned there are many species of aphids. Gardeners commonly encounter rose aphids which are green, black aphids which can appear on Prunus varieties, black wooly aphids on Lupins and cabbage aphids on brassicas. Evergreens too have their own species of aphids. There are aphids of all colours it would seem. All aphids have similar attributes; small, soft egg shaped bodies about 1-5mm long with long legs and antenna. A characteristic feature is a pair of tube like structures on their abdomens which secrete protective pheromones. Honeydew is secreted as waste from their digestive system not through the cornicles.

So how should gardeners deal with these little beasts that shrivel our roses and look quite repulsive in large numbers? There are plenty of concoctions on the market to spray on them but the downside is that those sprays will also kill beneficial insects some of which are eating the aphids. They do have natural enemies – predatory midges, parasitoid wasps, lacewing larvae, rove beetles, hoverfly larvae and ladybugs, which can actually be ordered by mail. The difficulty with this form of natural control is these insects cannot be forced to stay in your garden. The best way to encourage them is to maintain a healthy diverse ecosystem in the garden. However no matter how hard you try, other forces at play may well mean a heavy infestation some years.

I have found the two simplest ways to get rid of them are to squish the affected leaves or stems between your fingers. It is not pleasant but works if the numbers are small. If the numbers are larger a blast of water repeated every day until they are gone works. If the infestation does not disappear or is so widespread that is not possible, there are commercial soapy formulae that can be sprayed on then but care needs to be taken when other beneficial insects are around. These formulae will leave residue whereas water will just evaporate away. The key is to get to these pests early. Our cherry tree last year was badly affected but I found blasting water from the hose on to the top branches worked well when done every day for a week. The tree recovered. It is also possible to make your own soapy spray and there are many formula in the internet. This one:

• 1 x tablespoon Liquid soap
• 1 x tablespoon white vinegar
• Mix in 4Lt of water

Vinegar helps to repel further infestations but is optional. A good tip is to take a sponge with the spray bottle and wipe the leaves of the affected plants rather than spraying indiscriminately, which will kill beneficial insects. There are recipes which include Neem oil if available and crushed garlic. I personally prefer to use just water as much as possible.