Garden pests and Aphids in particular, seem to just simply appear from nowhere. Most of them have a simply life cycle - or rather, they lead quite a simple life, which allows them to thrive - or at least survive.
The Blackfly Aphid - also known as the Black bean Aphid -is one such garden pest that regularly appears on certain plants at specific times of the year.
Knowing a little about how Blackfly lives its life, is useful in allowing us to be prepared for the invasion that so often happens, or even prevent the invasion of these sap sucking pests happening in the first place.
In studying the Life habit of a Blackfly Aphid, you don't have to know too much about biology. In fact, they lead quite a simple life in a chain of events which allow them to survive. thrive even!
The Blackfly has adapted itself over many years, to life based upon our gardening habits and methods. Whether or not it will change further if we break into its life cycle remains to be seen. Here's some insight about its life!
The first we know about the Blackfly, is when it suddenly appears on various crops to which it is particular - at various times of the year. In fact, it depends for survival on some very specific gardening events happening. Those events, we as gardeners are happy to stage, often oblivious to the fact that most things we do, have an to the macro environment of our garden.
Where does the life cycle of a Blackfly start? A bit like asking about the chicken and the egg! So let's start at the point where it first becomes visible - a pest no less!
If you grow vegetables - and why not? If not! - then Blackfly - female blackfly - will inevitably show up on your broad beans in mid to late Spring. To be more precise, they will be visible having a feast on the new shoots at the top of the bean plants. At this time of year, there is little else they fancy, so they will seek out your beans even if they have had to fly a great distance. The fact that they are winged females at this stage is important - for they are not always winged insects. Their ability to fly enables them to fly from their winter habitat, where they have just hatched and are ready for a meal - on your beans.
This first wave of female Aphids quickly mature into child-bearing maturity, and without any help from a male blackfly aphid, they give birth to live young Aphids. More females - but this time wing-less! The only way they can get to a fresh food supply, is to crawl further down the stems of the Broad Beans. Tops of the plants will have been sucked dry by their mothers, so they now have to make do with the tougher lower parts of the plants - and the pods! This all happens over the course of just a few weeks - at most. Image by kind permission of Alves Gaspar.
Food starts to get short as the sap dries up and the stems start to toughen up, so these wingless Blackfly now also give birth - without any help from the non-existent males at this point! This time the live young are born with wings.
The wings allow them to wander off in search of more succulent growth - such as runner beans, French beans. These of course start into growth later than the winter-grown hardier broad beans. Very soon after this - if not the same time, then Dahlias, Poppies, Nasturtiums will be the feeding ground. More young are born - with wings - without Dads. These can then fly to wherever the food source is, and as any grower of nasturtiums and Dahlias in particular will tell you, Blackfly are a PEST!
Late summer and early Autumn, the food supply comes to an end for these sap suckers! Growth of the plants slows down considerably - as does the flow of life giving sap!
In late Summer - after the food runs out - yet another batch of Blackfly are produced - with wings - without Dads! These Blackfly Aphids - some of which are now males - have one thing left to do after a quick munch at their place of birth. They fly off to their Autumn mating grounds. Viburnum opulus is a favourite, as are the Philadelphus varieties - especially the larger leaved Philadelphus. Euonymus europaeus is another favourite.
The males soon get about their business, and the females obligingly participate with the result that many eggs are laid - normally in the buds, or in protected situations on the stems. The eggs of the Blackfly Aphid are fully hardy - though some end up in the stomachs of birds - and they see it through the winter until first sign of Spring. They then hatch into females - without wings, who feed on the shoots of their winter hosts. A little later - just as the Broad Beans start to produce new succulent shoots - they give birth to a batch of females. Female Blackfly with wings.
Back to the top for the start of the life cycle of the Blackfly Aphid!