It is a pest of huge economic importance, which initially affected potatoes and in recent years has become a problem for other Solanaceae crops such as tomatoes, peppers, aubergines, and tobacco. The potato psyllid was considered a minor pest until it was found to be responsible for serious crop damage, both directly and indirectly, the latter causing the greatest concern and proving difficult to control. In light of this, the export of fruit from susceptible crops to some parts of Europe, and the import into Mexico, is difficult, since Candidatus Liberibacter is considered a quarantine pest.
Lifecycle and appearance of the potato/tomato psyllid
The eggs are egg-shaped with a bright orange-yellow colour. They are attached to a strand which connects them to the surface of leaves and can be found on the underside and leaf edge. Hatching occurs three to seven days after being laid. They pass through five nymphal stages. The key characteristics are their flat, oval-shaped appearance, distinctive red eyes, and waxy strands around their body. The entire development process lasts around 12 to 24 days, during which they visibly change colour over the different instars, starting with orange, then greenish-yellow, and finally green. When they hatch, the adults have a yellowish-green colour and whitish wings, which become transparent over time, and their bodies become a dark brown or black colour with white or yellow lines and a distinctive white stripe on the abdomen. They are small in size, around 2.5 mm, and they live between 20 and 60 days.
The main direct damage, caused by potato psyllid nymphs when feeding, is known as ‘psyllid yellows’, which results in delayed growth, weakness in the new leaves, chlorosis/reddening or purple colouration of the leaf bases and internodes, and poor-quality fruit. The bacterium Candidatus Liberibacter solanacearum which is transmitted by potato psyllid amplifies the feeding damage and causes ‘zebra chip’ in potatoes Indirect damage causes the most harm, since the consequences are wide-ranging and there are no ‘solutions’ or ‘cures’ for the problems caused. Psyllids spread purple-top disease in potatoes and permanent yellowing disease in tomatoes, both of which are very harmful to the affected crops.