Pests: find out more APHIDS

Aphids

The Pest

Aphids are small pear-shaped insects that vary in colour both within and between species.  With their alarming rate of reproduction and increasing resistance to pesticides, they are becoming a much more serious threat to greenhouse crops. 

The main species of aphid attacking protected crops are:-
» Myzus persicae (peach-potato aphid) on mainly chrysanthemums and Solanacae
» Aphis gossypii (melon-cotton aphid) on mainly chrysanthemums and cucumbers
» Macrosiphum euphorbiae (potato aphid) on mainly Solanacae
» Aulacorthum solani (glasshouse potato aphid) on mainly Solanacae

All aphids feed by inserting their stylets into the conducting vessels of the plant and feeding on plant sap.  This can damage plants in four ways:
» reduced plant vigour
» distorted growth
» spread of virus diseases
» excretion of excess sugars (honeydew) encourages the growth of sooty moulds on leaves etc., thereby affecting quality and reducing photosynthesis.

There are now effective aphid predators and parasites, and growers have started to rely on these for control. The biological control agent used can depend on several factors including pest levels and aphid species.

Aulacorthum solani

Myzus

Aphids have a complicated life cycle but on greenhouse crops they multiply continuously throughout the year. Very few males are produced and for most of the time females give birth to live young.  The young feed as soon as they are born and are likely to have further young developing inside them.  After moulting several times they mature and begin to reproduce. 

From birth to reproduction takes less than a week in the summer.  When the population becomes dense winged forms are produced which fly to new feeding sites.  Some aphid species have different plant hosts in the winter.  In the glasshouse, aphids may overwinter on weeds or crops left there.

 
Aphid damage