Description and Life History

Potato psyllids have 3 life stages: eggs, nymphs and adults.

The eggs are very small, football-shaped, yellow to orange in colour and borne singly on very fine stalks, usually along leaf margins. A 10X hand-lens is necessary to see the eggs.

Nymphs are flattened and somewhat scale-like, with a fringe of short spines around the edge. Younger nymphs are pale brown, turning green with each successive molt. Nymphs are usually found on lower leaves and on lower leaf surfaces. When disturbed, they move quite readily. They secrete a white substance that looks like granulated sugar or salt, which collects on leaves beneath the feeding nymphs.

Adults, sometimes referred to as "jumping plant lice," look like small cicadas. They are about 2 mm long and may be greenish to black in colour, with a distinctive white band around the abdomen. Their clear wings are held in a roof-like position over their body. As the name suggests, they jump and fly readily when disturbed. Recently emerged adults are pale yellow to light green and later turn grey or black.

A mature female can lay more than 500 eggs over a typical period of 21 days. On average, the eggs take 15-30 days to develop into adults. Pysllids thrive at a temperature of 27°C, while temperatures below 15°C or above 32°C adversely affect their development and survival.

Damage

Like aphids and leafhoppers, potato psyllids suck plant sap through needlelike mouthparts. They feed in a manner similar to aphids, but instead of producing a shiny film of honeydew on the leaves, they produce a sugary exudate that resembles white powder. The nymphs are the damaging stage. While they feed they inject a toxin that causes a physiological condition known as "psyllid yellows." Feeding by this pest not only causes yellowing of the plant but can also result in loss of vigour and yield due to a combination of reduced fruit set and fruit size. Damage symptoms include stunting, chlorosis and purpling of leaves, distorted leaf growth and small, poor-quality fruit. Infestations of pepper crops by psyllids are reported to be less damaging because no yellowing occurs. However, the powdery deposits on the fruit must be washed off before they can be marketed.

Control Strategies

Monitoring

Carry out weekly inspection of plants to check for the powdery exudate and nymphs that can occur either on the upper or lower leaf surfaces. Yellow sticky cards hung close to the top of the plant canopy will also catch the winged black adults, which, to the naked eye, resemble winged aphids.

Physical Control

This entails removing infested leaves and provides a rapid means for reducing the population.

Biological Control

Some evidence indicates that the predatory bugs Dicyphus hesperus and Orius insidiosus and the parasitic wasp Tamarixia triozae may contribute to the suppression of psyllids. However, use of Orius may not be as useful on tomatoes because young Orius nymphs tend to get caught on the sticky hairs present on tomato plant surfaces.

Chemical Control

There are no pesticides in Ontario that are specifically recommended for psyllids.