The glasshouse leafhopper is a small sap-feeding insect, that causes pale mottling on the upper leaf surface of a wide range of plants.
The name suggests they are restricted to the greenhouse but in fact they can also affect house and garden plants.
Adult leafhoppers are 3mm (1/8") long, oval shaped, and are pale yellow with grey markings, and are generally first noticed when they jump off leaves when disturbed.
They lay their eggs in early to mid summer in the leaf veins and hatch into wingless off white nymphs.
The leaf mottling is caused by the feeding activities of the adults and nymphs.
If the infestation is severe, the spots join together, giving the leaves a chlorotic look, meaning the problem is sometimes mistaken as chlorosis.
A sign of nymph activity can be seen when their cast off white skins are found attached to the underside of damaged leaves.
The nymphs shed their outer skin up to fives times as they grow into adulthood.
The affected leaves will remain discoloured and usually drop off the plant, however, new growth will develop normally once the pest has been brought under control.
Several generations can remain active throughout the year on indoor plants.
There are two forms of control; Biological and Chemical.
Biologically they can be controlled with the introduction of a parasitic wasp* (anagrus atomus) who's larvae develop inside the leafhoppers's eggs.
This form of control requires warm temperatures to be effective,meaning that it is best used in confined spaces such as the greenhouse, rather than outdoors.
*anagrus atomus can be purchased by mail order from suppliers of biological controls.
This should be applied when the first signs of spotting appear.
There are a number of branded insecticides available in garden centres to treat this problem e.g.
Products with the active ingredients acetamiprid, pyrethrum or thiacloprid are generally suitable.
Read the instructions on the packaging carefully particularly if treating plants that are producing edible parts.