The following pests are a high priority for the Australian potato industry as identified through the development of the Industry Biosecurity Plan for the Potato Industry.
Implementing biosecurity measures to control endemic pests will go a long way towards preventing exotic pests from entering and becoming established on your farm.
To improve biosecurity measures on your farm, include exotic pests when undertaking routine pest surveillance activities. Ensure that all surveillance activities, for both endemic and exotic pests, are recorded. Visit Records for templates to record surveillance results.
Potato pests not currently in Australia (exotic)
Close-up of Colorado potato beetle.
Colorado potato beetle
Colorado potato beetle affects Solanaceae including potato, tomato and eggplant.
Adult beetles are about 10mm in length. They have five dark lines on each wing cover, with a yellow to red underlying colour.
Larvae are also brightly coloured and grow to 15mm in length. Initially they are bright red with a black head and legs, but this changes to a pale orange before pupation.
Which part of the plant will be damaged?
Damages above-ground plant parts.
Leaf defoliation caused by beetle feeding is the most obvious sign of the pest’s presence. Shake potato plants and observe the ground around them for beetles. Larvae and adults can be seen easily on young plants. Also check nearby Solanaceous weeds.
Adults can fly short distances within a host crop but have been known to travel up to 160km when assisted by strong winds. The larvae and adults can be transported as ‘hitch-hikers’ on plant material, produce, machinery and packaging.
The small adult fly is predominantly black with some yellow markings. Image: Central Science Laboratory, Harpenden Archive, British Crown, Bugwood.org
Serpentine leaf miner
Serpentine leaf miner affects 15 plant families but is a key pest of potato.
The black flies are just visible (<3mm in length) and have yellow spots on their head and chest.
Damages leaves.
Adult flies and larvae are not likely to be seen due to their small size. Mines in leaf tissue, caused by larval feeding, are the most obvious sign of infestation. Mining produces white, black and brown dried areas. They are often irregular in shape and increase in size as the larvae mature.
Within the crop the insects spread by flying. Long distance transport is likely to occur through the movement of infested plants, plant tops, soil or packaging.
Adult vegetable leaf miner. Image: Pest and Diseases Image Library, Bugwood.org
Vegetable leaf miner
Vegetable leaf miner damages a wide range of vegetable and flower crops including potatoes, onions, eggplant, beans, celery, peas and tomatoes.
The body is <2mm long and wingspan is <2mm. The head is bright yellow. The abdomen is mostly black with yellow sides. Vegetable leaf miners don’t often fly, but they may be seen walking over the leaves and making short jerky flights to adjacent leaves.
Damages leaves and flowers.
Mines are usually white with moist black and dried brown areas. They are typically snake-like, and tightly coiled. In larger leaves, the mines often form an irregular ‘U’ shape. The excrement of the miners is deposited in black strips on either side of the mine.
Spreads by infested planting material, and some flight within a crop.
American serpentine leaf miner. Image: Central Science Laboratory, Harpenden Archive, British Crown, Bugwood.org
American serpentine leaf miner
American serpentine leaf miner affects a wide host range of over 400 species of plants in 28 families. The main host families and species include Solanaceae (for example potato, tomato, eggplant), Asteraceae, Alliaceae, Cucurbitaceae and Fabaceae.
Adult flies are small, yellow and black. Female adults are larger and more robust than males, but their small size still limits identification in the field.
The larvae are not usually seen as they remain inside the leaf tissue. The mines can be seen and are evidence of larvae presence.
Damages leaves.
Look for small dots or holes in the leaves (as upper leaf cells are destroyed), white or greenish-white mines (lines) and blotches on leaves. Fungal infection may also occur, as the damage makes plants more susceptible to secondary infections.
Within a crop the insects are spread by flying. Long distance transport is likely to occur through the movement of infested plants, plant tops, soil or packaging.
Black bean aphid infestation. Image: Ansel Oommen, Bugwood.org
Black bean aphid
Black bean aphid is a major pest of bean crops, but it has a very broad host range affecting over 80 plant types including potato, cabbage, cauliflower, radish, celery, capsicum, eggplant, cucumber, beets, cucurbits, chilli, and grain.
Feeding causes direct damage to plants, and aphids can transmit plant viruses, making its potential arrival in Australia a problem for many plant industries, including potatoes.
Black bean aphid is <4mm long, is completely black (or very dark green) in appearance and is usually found clustered together in large numbers.
The whole plant may be damaged. Feeding causes damage and the secretion of honeydew causes sooty mould. The main problem for potato growers is that it transmits viruses, including potato virus Y (PVY), potato leaf roll virus (PLRV) and potato virus A (PVA).
Black bean aphids are usually noticed on plants because of their contrasting colour and the presence of ants. Aphids feed by sucking plant sap, so infested growth is often yellowed and curled.
Within a crop the pest spreads by flying. Long distance transport is likely to occur through the movement of infested plants, plant tops, soil or packaging. The aphid overwinters on European spindle plants (commonly found in Australia) and winged aphids spread to host plants in the warmer months.
There are a range of exotic aphids which are not yet present in Australia. If you find an aphid which causes more damage than normal or does not respond to the usual management strategies, including chemical controls or use of beneficial insects, you should call the Exotic Plant Pest Hotline on 1800 084 881.
Potato leaves showing stunting, yellowing and a zig-zag of the upper growth. Image: Whitney Cranshaw, Colorado State University, Bugwood.org
Zebra chip
There are five types of Candidatus Liberibacter solanacearum that cause zebra chip. Types A and B affect Solanaceae (for example potato, tomato, tobacco, capsicum). Types C, D and E affect Apiaceae (carrots and celery).
The whole plant can be damaged.
Foliage symptoms in potato plants include the presence of stunting, yellowing, swollen nodes causing a zig-zag appearance of the upper growth, proliferation of auxiliary buds, aerial tubers and leaf scorching that leads to early dieback.
Underground symptoms include enlarged lenticels and shortened or collapsed stolons. Tubers tend to be smaller and misshapen but more numerous and have rough skin.
When tubers are cut in cross-section, necrotic flecking and brown discolouration in a ring can be seen.
Tuber dormancy is affected, resulting in premature sprouting, internal sprouting and tuber chaining. Affected tubers are unacceptable as planting material.
Infected tubers are not hazardous to human health but are visually unappealing. The disease becomes most distinctive when potatoes are processed – a striped pattern of discolouration appears in fried cross-sections of potato tubers giving rise to the name zebra chip. Potato crisps made with infected potatoes have a burnt appearance and taste and are unmarketable.
Zebra chip is spread by tomato potato psyllids. The disease is not present in Australia and at the time of writing (June 2018) the psyllid was only in Western Australia.
It is not known if other psyllids that are present in Australia could spread the disease.
Leaves of a late blight affected plant. Image: Nancy Gregory, University of Delaware, Bugwood.org
Late blight
Late blight affects Solanaceous species including potato, tomato, eggplant and tobacco.
The whole plant may be damaged.
Symptoms of the A2 mating type of late blight are similar to those of the A1 mating type already present in Australia, but are more severe and may show resistance to Metalaxyl. Symptoms include small brown-black spots on the leaves often surrounded by a pale halo, while the underside of the leaves may take on a white, downy appearance in wet weather.
Blight can spread quickly, causing the complete collapse of foliage within a few days. In severe cases the tubers can become infected, giving rise to sunken patches and a brown rot. This usually leads to secondary infection by other bacteria and fungi resulting in an unpleasant smell as potatoes turn into a mushy mess.
Outbreaks of late blight occur when night temperatures are cool, followed by warm days with mists and rains. Under those conditions the disease spreads rapidly and fields of potatoes can be destroyed in less than two weeks.
Spread of late blight over short to moderate distances between plants and fields occurs by wind or wind-driven rain and can travel as far as 15–20km. Spread over longer distances, across countries and continents, occurs in seed potatoes. The A2 mating type of late blight could arrive in Australia through spores blown in the wind or transported on clothing, through soil on equipment or on illegally smuggled crops. If they arrive in Australia, new strains of late blight could rapidly spread through airborne means and then establish in volunteer crops or overwinter in plant debris or soil for years.
Cysts on the outside of a heavily infected potato. Image: Florida Division of Plant Industry Archive, Florida Department of Agriculture and Consumer Service, Bugwood.org
Pale potato cyst nematode
Pale potato cyst nematode affects potato, tomato and eggplant.
Roots and tubers are damaged. Plant parts above the ground also show signs of disease due to root damage.
Nematodes are microscopic and worm-like. They feed on the roots of potato, tomato, eggplant crops and other plants from the Solanaceae family including night shade.
The symptoms of attack are not specific. They may appear similar to water or nutrient deficiencies or wilt diseases, because infested potato plants have a reduced root system. The root system also becomes abnormally branched and brownish in colour.
Growth is stunted, leaves yellow early or turn a dull colour, flowering is delayed, and plants may wilt and die.
During or after flowering, very tiny white, yellow or brown cysts about the size of a pin head (0.5mm) might be seen on the outside of roots.
Potato cyst nematode can spread on anything contaminated with infested soil including seed potatoes, potted nursery stock and packaging, soil, flower bulbs, any other unwashed root crops for consumption or processing, footwear, livestock, farming equipment and waste from potato grading operations. Potato cyst nematode can survive as cysts in the soil for up to 20 years in the absence of host species.
Knot in a root hair caused by root knot nematode. Image: Onions Australia
Root knot nematode
Root knot nematode has many hosts including potato, tomato, eggplant and solanaceous weeds, onions, lucerne, tobacco, cabbages, wheat and corn, although the preferred host is potato.
Roots and tubers are damaged.
Infested plants are stunted and may wilt: leaves may yellow or display a dull colour. Affected plants have a reduced root system which is abnormally branched and brownish in colour.
At flowering or later, minute white, yellow or brown spheres or cysts, about the size of a pin head (0.5mm) may be seen on the outside of roots.
Damage to the crop varies from small patches of poor growing plants to complete crop failure. Infected plants first occur in isolated patches and these become larger with each new crop if potatoes are continually grown on the infested site.
In light infestations, potato plants may show no above ground symptoms, but yield can be reduced. Light infestations can reduce tuber size, whereas heavy infestations reduce both number and size of tubers. Affected plants can occur in patches bordered by relatively healthy plants.
As a soil-borne pest it is spread by transport of infested soil. For example, cysts can be carried in soil adhering to seed potatoes, farm machinery, implements, boots, bins and plants. Cysts can also be transported by wind and flood water.
Potato pests currently in Australia
Dorsal/back view of adult African black beetle. Image: Hanna Royals, Bugwood.org
African black beetle
African black beetle affects potato, pineapple, eucalypts, sugarcane, grapevine and maize.
Larvae are a white to creamy-white soft bodied curl grub up to 25mm long. Adults are a shiny jet-black scarab beetle with serrated front legs up to 15mm long.
Which part of the plant will be damaged?
Damage is done to stems, caused by adults feeding on the underground stems of young plants, often killing growing points so that the central shoots wither and the plants become dead-hearted.
Older plants usually survive but remain weak and are liable to lodging.
Beetles are often found near the base of damaged plants. Damaged young plants usually produce suckers. Soil sampling will indicate the presence of beetles.
Beetles crawl on the soil or pasture surface at night. Large scale flights are sporadic and may be localised within a district, making them difficult to predict. Although the triggers for flight are not known, weather conditions associated with summer thunderstorms seem to promote swarming flights of beetles and most flight activity occurs in late summer to autumn, which coincides with the emergence of the new generation of adults.
It is present in all states and territories of Australia except Northern Territory and Tasmania.
There are no specific movement controls but spread of this pest onto your property can be limited by using biosecurity measures.
Adult and nymph green peach aphids. Image: David Cappaert, Michigan State University, Bugwood.org
Green peach aphid
Green peach aphid affects a very broad range of plants including potato, tomato, eggplant, cabbage, cauliflower, capsicum, cut flowers, citrus, cucurbits, carrot, cotton, lettuce, apples, avocado, beans, peas, and stone fruit.
They often cause less direct feeding damage than other aphid species, but can spread plant viruses by probing and feeding as they move between plants within or between paddocks.
Green peach aphids grow up to 3mm long and can vary in colour from shiny pale yellow-green, green, orange to pink. Adults are oval-shaped and may or may not have wings. Winged adults have a dark patch on the abdomen, while wingless adults are usually quite uniform in colour.
Juveniles are similar to wingless adults but are smaller in size.
Above ground parts of plants will be damaged.
Aphids will generally move into paddocks from host weeds or volunteer plants located on roadsides, paddock edges or neighbouring paddocks. Damage often appears initially on crop edges, which should be monitored. Inspect the underside of plant leaves.
Aphid distribution may be patchy, so inspect at least 20 plants at each of five representative sampling points across the paddock. Symptoms of virus infections are highly variable.
Winged aphids migrate from weeds in autumn. Populations peak in late winter and early spring: development is favoured when the daily maximum temperatures reach 20–25oC.
Present in all states and territories of Australia except Northern Territory. Note: Resistant biotypes of green peach aphid are present in some parts of Australia.
No specific movement controls exist but spread of this pest onto your property can be limited through implementation of biosecurity measures.
There is a range of exotic aphids that are not yet present in Australia. If you find an aphid which causes more damage than normal or does not respond to the usual management strategies, including chemical controls or use of beneficial insects, you should call the Exotic Plant Pest Hotline on 1800 084 881.
Tomato potato psyllid affects Solanaceae plants including potato, tomato, capsicum, eggplant and Convolvulaceae species including sweetpotato.
The psyllid is a tiny sap-sucking insect that goes through three stages of development – egg, nymph and adult.
Adult psyllids resemble small winged cicadas and are about 3mm long. The body is brownish and has white or yellowish markings on the chest and a broad white band on the abdomen. Wings are transparent and held vertically over the body.
Eggs are <1mm long and are white when first laid, then turn yellow to orange after a few hours. Nymphs are up to 2mm long, oval shaped, flattened and scale-like in appearance.
Which part of the plant will be damaged?
Damage to plants starts above ground but then the whole plant.
Symptoms of psyllid feeding include the appearance of ‘psyllid sugar’, yellowing or purpling of the midribs and leaf margins. The leaves are often cupped, narrow and point upright giving the plant a feathery appearance.
Psyllid yellows, a syndrome that can develop during psyllid infestation, can be easily confused with the symptoms of the exotic disease zebra chip.
Any signs of yellowing, stunting, leaf narrowing, curling or cupping, leaf purpling, fruit distortion and shortened internodes in your potato crop should be investigated closely due to the risk of infection by the disease zebra chip (which is not currently in Australia).
The psyllid can spread through the movement of plants and plant materials including fruit, vegetables and nursery stock, on horticultural machinery and equipment, and also by wind and flight.
Adult psyllids can fly and move short distances. Wind can carry adult psyllids long distances, as can machinery and vehicles.
Juvenile psyllids do not fly and can be transported via infested plant material. Zebra chip requires the tomato potato psyllid as a vector for movement from plant to plant.
Present in Western Australia (since February 2017).
Movement controls exist for various plant products leaving Western Australia destined for South Australia, New South Wales, Victoria, Queensland and Tasmania. Movement controls also exist in Western Australia to prevent further spread within the state.
Cluster caterpillars affect a wide host range of plants including potato, tomato, eggplant, onion, cauliflower, cabbage, citrus, chilli, coffee, soybean, cut flowers, apple, lucerne, tobacco, peppers, cocoa, grapevine and maize.
Eggs are laid in a furry cream mass on the underside of leaves.
Young larvae ‘cluster’ together and are translucent green with a darker chest. Medium-sized larvae are variable in colour, smooth-skinned with a pattern of red, yellow and green lines, a dark patch on the hump behind the head and dark spots along each side.
Large larvae are initially brown with three thin pale lines down their back. They have a row of black dots along each side, and a row of dark half-moons along the back. In the final larval stage caterpillars are dark and can exceed 50mm in length.
Adult moths have brown forewings with criss-cross cream streaks and translucent white hindwings edged with brown. They have a wingspan of 30–45mm.
Eggs hatch in two to seven days and the caterpillar stage lasts two to six weeks depending on temperatures. The life cycle from egg to adult takes about 30 days in warm weather and up to eight weeks in cooler conditions.
Damage is to leaves.
Moths lay clusters of eggs on the underside of the leaf. Young larvae feed in close groups and destroy one side of the leaf leaving the opposite side intact. Damaged areas appear clear at first but quickly turn brown.
When larger and more solitary, larvae feed on the rolled up ‘cigar leaf’ and a ‘shot hole’ effect becomes apparent when this leaf expands. Defoliation of crops can occur quickly in hot weather.
The moths are strong fliers and can invade crops any time from emergence through to harvest.
Found in the Australian Capital Territory and limited distribution in New South Wales, Queensland and Western Australia.
No specific movement controls exist but spread of this pest onto your property can be limited by using biosecurity measures.
Adult of potato tuber moth, showing narrow, markedly fringed wings. Image: Central Science Laboratory, Harpenden, Bugwood.org
Potato tuber moth
Potato tuber moth affects potato, tomato, eggplant, capsicum and tobacco.
It’s a small moth, measuring about 10mm in length, coloured pale brown with darker marbling. Wing span 15–17mm. The head and chest are pale brown. The front wings are pale brown with small blotches of mid-brown, and hind wings are pale grey.
Damages leaves, roots and stems.
On growing plants, leaf mines show the presence of larvae, and the stem is weakened or broken.
On tubers, detection is more difficult without them being cut open when larvae will be apparent within the potatoes.
Adults disperse in short ‘hopping’ flights near the ground, in the direction of the wind. The moths can move up to 250m to infest plants or tubers, although it has been observed that they do not move from potato fields unless the field is harvested.
Dispersal over long distances is on potato tubers, which has spread the moth around the globe.
It is found in parts of Western Australia: present in all other states and territories.
No specific movement controls exist but spread of this pest onto your property can be limited by using biosecurity measures.
Symptoms of bacterial wilt on a potato plant. Image: National Plant Protection Organization, The Netherlands, Bugwood.org
Bacterial wilt
Bacterial wilt attacks more than 200 plant species. These include potato, tobacco, tomato, eggplant, pepper, banana, peanut and beans. Thorn apple and nightshade are two common weed hosts that can harbour the disease.
Roots and tubers are damaged, but it can lead to wilting of the whole plant.
Typical symptoms are wilting, yellowing and some stunting of the plants, which eventually die back. Wilting is first seen as a drooping of the tip of some of the lower leaves, similar to that caused by a temporary shortage of water. Affected leaves later become permanently wilted and roll upwards and inwards from the margins. The wilting then extends to leaves further up the stem, followed by yellowing.
Brownish-grey areas can be seen on the outside of tubers, especially near the point of attachment of the stolon. Cut tubers may show pockets of white to brown pus or browning of the vascular tissue which, if left standing, may exude dirty white globules of bacteria.
As the disease progresses bubbly globules of bacteria may exude through the eyes: soil will often adhere to the exuded bacteria, hence the name ‘sore eyes’ or ‘jammy eyes’.
It’s mostly spread, both locally and over longer distances, by infected seed potatoes. Lightly infected tubers, which show no visible symptoms, pose a serious threat by spreading the disease to new areas.
Heavily infected tubers are not normally the problem since these generally rot away, only contaminating the land in which they were grown. If a paddock is infected with bacterial wilt the disease may remain in it for five or six years after the initial outbreak.
Bacteria can also be spread to clean tubers from an infected seed-cutter or knife.
There is also a danger of infection if second hand bags are used, or if bins have held infected potatoes and not been cleaned properly. Growers should be aware of these risks and take precautionary measures.
Spread between areas usually by vegetative propagation material that is contaminated with the pathogen.
Found in all states and territories except Tasmania.
No specific movement controls exist but spread of this pest onto your property can be limited by using biosecurity measures.
There are bacterial wilts of potatoes which are not yet present in Australia. If you observe bacterial wilt symptoms which cause more damage than normal or do not respond to the usual management strategies you should call the Exotic Plant Pest Hotline on 1800 084 881.
Potato plant on right infected with the potato cyst nematode compared to healthy plant on left. Image: Christopher Hogger, Bugwood.org
Golden potato cyst nematode
Golden potato cyst nematode (RO1 strain) affects potato, tomato and eggplant.
It damages roots.
Nematodes are small worm-shaped organisms, <1mm in length, that live in soil and attack plant roots.
The cysts of golden potato cyst nematode are white, yellow or golden in colour when they first form on roots and become tan brown in colour when they mature.
Look for leaf wilting and discoloration, root cysts and reduced root system, yield reduction and smaller potatoes, dwarfing of plants and early senescence.
At flowering or later, minute white, yellow or brown spheres or cysts about the size of a pin head (0.5mm) can be seen on the outside of roots.
Damage to the crop varies from small patches of poor growing plants to complete crop failure. Potato cyst nematode is not greatly influenced by soil type and temperature because the nematode thrives wherever potatoes are grown.
Potato cyst nematode is a soil-borne pest and is spread by transport of infested soil. For example, cysts can be carried in soil adhering to seed potatoes, farm machinery, implements, boots, crates and plant material, particularly bulbs. Cysts can also be transported by wind and flood water.
Locally, potato cyst nematode is usually dispersed by farming activities including sharing farm equipment contaminated with infested soil.
It’s found in Victoria (only the RO1 strain has been recorded).
No potatoes are permitted to enter the Gin Gin and south-west potato growing areas in Western Australia (except from Tasmania).
There are strains of golden potato cyst nematodes which are not yet present in Australia. If you observe nematode symptoms which cause more damage than normal or do not respond to the usual management strategies you should call the Exotic Plant Pest Hotline on 1800 084 881.
Typical leaf symptoms of potato spindle tuber viroid on potato cultivar Kennebec (right), healthy plant (left). Image: RP Singh, Bugwood.org
Potato spindle tuber viroid
The primary natural host of potato spindle tuber viroid (PSTVd) is potato, but the viroid also affects tomato and other Solanaceae plants.
It damages the whole plant.
There are both mild and severe strains. Symptoms may be confused with those of nutrient imbalance, spray damage, insect damage or other plant diseases such as true viruses. Symptoms become more pronounced in warm conditions and under high light intensity.
Foliage symptoms are often difficult to recognise and are rarely distinguishable before maturity. Stems remain upright and internodes are longer and more slender than normal. Leaflets are slightly smaller in size with fluted margins. Leaves near ground level are held in an upright position, in contrast to healthy plant leaves that often rest on the ground.
Infected tubers have pointed ends, giving them a spindle shape with a round cross-section. Infected tubers are also often smaller than healthy ones. Eyes are deep, more prominent and surface cracking occurs.
Tubers of some cultivars develop knobs and swellings and are severely misshapen. With some strains, foliage and tuber symptoms are mild versions of the above, or may not be visible. The foliage and tuber symptoms become progressively more severe with each generation.
PSTVd is a highly contagious disease, transmitted between plants by touch. The use of cutting or pruning tools, contaminated machinery or any form of physical contact between plants can result in disease transmission.
PSTVd is also reported to have been transmitted by green peach aphid from plants that are co-infected with potato leafroll virus.
In potatoes the most important means of PSTVd spread from one generation to the next is via infected seed potatoes. It is transmitted through seed potatoes at varying rates depending on the host cultivar and the strain of PSTVd present. PSTVd can also survive in dried potato sap for more than eight weeks and in infected leaf debris for over six months.
It’s found in Queensland and Western Australia.
Movement of potatoes, or machinery or soil that when moving has come into contact with potatoes, is restricted into various potato plant protection districts in Victoria and specific parts of south-east, central west and northern New South Wales. Potatoes must be washed or brushed free of soil and in new packaging before being allowed onto Kangaroo Island (South Australia).
There are strains of PSTVd which are not yet present in Australia. If you observe PSTVd symptoms which cause more damage than normal or do not respond to the usual management strategies you should call the Exotic Plant Pest Hotline on 1800 084 881.
