Tomato potato psyllid
Find images of this pest and its symptoms on the Western Australian Department of Agriculture and Food website.
New pest in Australia
Tomato-potato psyllid (Bactericera cockerelli) is an exotic plant pest in its own right. It also can vector a bacterium, Candidatus Liberibacter solanacearum that causes zebra chip disease in potato tubers.
Tomato-potato psyllid is a serious threat to potato, tomato and capsicum crops. It was first found in Australia near Perth, Western Australia in February 2017 and could spread by wind and trade.
Symptoms of feeding by tomato-potato psyllid feeding on plants include yellowing, cupping and narrowing of individual leaves and the development of a purple tinge. These symptoms resemble other disorders.
Tomato-potato psyllids have an extensive host range, but tomato, potato, capsicum, chilli and eggplant (solanaceous plants) are preferred. Infections on sweet potato and kumara (convolvulaceous plants) have been reported overseas.
Adults and nymphs of tomato-potato psyllid cause loss of plant vigour and yield to plants by feeding with piercing mouth parts. During feeding a salivary toxin is injected into the plant which leads to the condition called psyllid yellows. Damage symptoms include stunting, chlorosis and purpling of leaves, distorted leaf growth and stem death.
The tomato-potato psyllid vectors the bacterium “Candidatus Liberibacter solanacearum” which causes the disease zebra chip. Zebra chip symptoms are very similar to psyllid yellows but also include discolouration of cooked potato.
In-crop signs of tomato-potato psyllid include aphid-sized insects jumping from the foliage when disturbed.
What is a psyllid?
Psyllids are sap-sucking insects sometimes called plant-lice.
There are three life stages: egg, wingless juvenile and winged reproductive adult.
Adult psyllids resemble miniature cicadas but grow to only 3 mm long. The body is brownish and has white or yellowish markings on the thorax and a broad white band on the abdomen. Wings are transparent and held vertically over the body.
Nymphs look very different to adults. They are 2 mm long, oval shaped and resemble scales. Young nymphs are yellowish green to orange with a pair of red eyes and three pairs of short legs. Older nymphs are greenish and fringed with hairs and have visible wing buds.
Psyllid eggs are less than 1 mm long and are attached to the plant by a short vertical thread. They are usually laid on the lower surface of leaves or along the leaf edge and stalk. Eggs are white when first laid then turn yellow to orange after a few hours.
If introduced into Tasmania, eggs would likely hatch one week after being laid. Nymphs would pass through five instars over three weeks before becoming adults. Female tomato-potato psyllids mate several days after emerging. They live up to 40 days. Each female can produce up to 500 eggs.
Psyllids thrive at 27 °C, while temperatures below 15 °C adversely affect their development and survival. The lower threshold for development is about 7 °C. This pest overwinters in parts of New Zealand that experience frost and snow.
Low summer heat in maritime parts of Tasmania, such as the north-west coast, would likely retard population growth in summer. Perhaps 3-4 generations per year would occur on outdoor host plants in Tasmania.
In protected cropping facilities between 15 and 32 °C development would progress more rapidly.
The tomato-potato psyllid is probably a native of Central America. It has spread to North America and has established in many states in the USA and Canada.
The psyllid was detected in the Auckland region of New Zealand in 2006, and subsequent surveys have shown that it has spread throughout the North Island and over the northern half of the South Island.
Long distance spread of adult psyllids occurs by trade in host plants and probably by wind.
Symptoms in potatoes
Potato plants may have shortened internodes and aerial tubers may develop in the leaf nodes. Potato tops are likely to be smaller than normal. The foliage turns yellow and may have a burnt or purplish appearance. Stems may die completely but regrowth from the base may occur.
Tubers from affected plants may have small stalked tubers protruding from the main tuber and have internal browning of the vascular ring or brownish streaks along the medullary rays.
Symptoms in tomatoes
Foliage symptoms include leaf curling and yellowing. Plants may either become stunted or abnormally elongated. Fruit development is uneven. Tomatoes may be misshapen with a strawberry-like appearance, or no fruit is produced or there is an over-production of small, non-commercial grade fruit. Symptoms vary in severity between cultivars.
Symptoms in capsicums and chillies
Leaves of plants become misshapen, pale green or yellow with spiky tips. Leaf stalks appear stunted. Flowers may drop prematurely and parts of the plant may die back. Symptoms vary in severity between cultivars.
Actions to minimise psyllid risks
Management of tomato potato psyllid solely by insecticides is very expensive and difficult. Other pest control methods are necessary. Crop hygiene includes removing alternative host plants and solanaceous weeds. Some non-solanaceous plants on which the psyllid does not breed can support adult feeding. Regular crop monitoring for pests and beneficial insects and associated maintenance of records are always part of best practice. On-farm biosecurity to prevent entry, establishment and spread of pests and diseases is also best practice and particularly relevant to glass- and plastic-house cropping.
Tomato potato psyllid has not been detected in Tasmania. Reporting of any suspected tomato-potato psyllid is encouraged. The Entomology Team in Plant Diagnostic Services of DPIPWE will identify suspected tomato-potato psyllid at no fee.
If you suspect you have found tomato potato psyllid on your plants or crops, please call Entomologist, Guy Westmore, on 03 6777 2150 or email a photo (with location) to Guy.Westmore@dpipwe.tas.gov.au.