Commonly known as greenfly and blackfly, but also found in other colours, sap sucking small insects 1-5mm long. Predominantly female, at summer temperatures they produce living young which reaches adulthood in one week. Within a short space of time one female aphid can reproduce several generations amounting to several tons of aphids, such is their reproductive capacity. 

They are both sexual and asexual and often mate as winter approaches, laying eggs which over winter and emerge in the spring. Adults can be winged and can fly short distances. They can be carried longer distances on wind currents.  

There are over 500 aphid species in the UK.  Many of which affect chrysanthemums, of which the chrysanthemum aphid is the most common. 

Effects on chrysanthemums
Aphids populations can quickly raise to epidemic proportions and severely weaken and distort chrysanthemum growth.  However the biggest danger to chrysanthemums is the transfer of virus diseases from one cultivar to another and in some cases from other plants.

A secondary problem is the sugary sap known as honey dew, this often gives rise to a fungal coating of the leaves known as sooty mould, this blocks leaf pores and stops light reaching the leaves which reduces photosynthesis.

(Picture shows leaf distortion and deposits after a slight infestation.)

Controls
It is important for chrysanthemum stools to be pest free going into the winter in order to get through the propagation phase pest free.  When plants get bigger and as spring temperatures rise aphid populations will raise on outdoor vegetation.  Aphids can gain access to our greenhouses through open ventilators; this is when a keen eye can spot a problem.  In view of the aphids capacity to multiply at an astonishing rate it is important to treat even a small infestation immediately.

Control can be achieved by contact or systemic insecticide.  For the amateur grower Bifenthrin is available as an active ingredient in many products,  Imidachloprid is another useful ingredient and is available as a systemic insecticide in some products.

There are also a number of non-chemical controls available through retail centres.

For the professional grower Imidachloprid, Bifenthrin and Deltamethrin are commonly used active ingredients.  However a quick search in the UK pesticide guide will reveal other products.  

Imidachloprid is by far the most recommended product for aphid control.  It is systemic and has the advantage of longer lasting control because it poisons the aphids immediately they begin to suck sap, thereby avoiding movement from plant to plant resulting in the transfer of virus diseases.  Plants treated before flowering should remain clear of the pest well into the flowering phase.

Systemic insecticides work effectively on leaves and stems.  Therefore it is important to ensue the plants are free of aphids before the buds appear.  It is very difficult to control aphids on developing blooms.
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