Manitoba Agriculture, Food and Rural Initiatives
Commercial Potato Production - Disease Management
Note: This information is adapted from the publication titled Guide to Commercial Potato Production on the Canadian Prairies published by the Western Potato Council, 2003.
Disease Management
Written by: Tracy Shinners-Carnelley, Piara Bains, Debbie McLaren, Jill Thomson
Potato plants are susceptible to a wide variety of diseases that can severely reduce yield, quality and storability of tubers. Diseases can occur in the field or in storage and are caused by infectious bacteria, fungi, viruses and other related organisms.
Most infectious potato diseases can be controlled using certified seed, proper sanitary practices, crop rotation, and pesticides. The following are the most serious diseases of potatoes in the Prairies. Consult your provincial Guide to Crop Protection for a list of chemicals registered for control of potato diseases.
Bacterial Diseases
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Bacterial ring rot is a highly infectious disease caused by the bacterium Clavibacter michiganensis, formerly known as Corynebacterium sepedonicum. This disease can cause serious losses and is a designated pest in provincial Plant Disease Acts. The Canadian Food Inspection Agency has a zero tolerance for bacterial ring rot in seed potatoes. Foliar symptoms of the disease vary with the potato variety. Symptoms are not always expressed or may be masked by other stresses on the plant. Ring rot may cause wilting of the lower leaves. Leaves on infected plants yellow and the outer edges may roll up and later become brown and brittle. The lower stem of infected plants will exude a milky ooze when cut and squeezed. |
Tuber symptoms are noticeable as a cheesy cream-coloured liquid that oozes from the vascular ring when tubers are cut at the stem end and squeezed. As the rot progresses, the vascular ring breaks away from the rest of the tuber. Secondary rot organisms may also infect the tubers and make it difficult to distinguish the ring rot symptoms. Severely infected tubers turn dark brown or black and completely rot away inside.
During seed cutting, bacteria from infected tubers are smeared on the cutting knives, consequently healthy seed pieces become infected. Ring rot bacteria can survive for five years in dried potato stems and for two years on dry burlap, plastic or plywood surfaces. The bacteria however, live only a short time in soil and are normally killed between fall and winter if all plant debris is ploughed down. Ring rot bacteria can over-winter in infected tubers that survive the winter in the field or in cull piles.
Control Strategies:
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Plant certified seed
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Thoroughly clean and disinfect equipment, tools, trucks and storages with a quaternary ammonium disinfectant (see Section 3.2.3 Sanitation, Handling and Storage of Seed Lots), or limit movement of machinery and personnel between operations (especially seed)
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Dispose of any crops infected with ring rot
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Dispose of mildly infected crops by processing out-of-field rather than out-of-storage
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Sprout inhibit infected potatoes, so they will not grow
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Plant crops other than sugar beets after potatoes
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Plough under infected potato debris or unharvested potatoes prior to winter
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Allow at least one year before replanting potatoes in an infested field
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Dispose of all used potato sacks or bags
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Destroy cull piles by freezing or burying
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Bacterial soft rot is a common and often serious disease that can affect tubers in storage, in the ground prior to harvest, or seed pieces after planting. The bacterium Erwinia carotovora var. carotovora and certain other species of soil and tuber-borne bacteria cause bacterial soft rot. Infected tuber tissue is cream to tan in colour and has a soft granular texture. Bacterial soft rot commonly invades tubers that have been frozen, those that have moisture on the surface, or have damaged skin due to mechanical damage or infection by other pathogens. Tubers infected with Pythium leak, pink rot, ring rot, Fusarium dry rot, or late blight are prone to soft rot. When cold seed pieces are planted into warm, moist soil, moisture may condense on the surface of the seed piece and favour soft rot development. Bacterial soft rot is also common in tubers harvested from waterlogged soils. |
Soft rot may also cause rapid and severe breakdown of washed and packaged fresh-market potatoes if they are not completely dried prior to packaging. Early season potatoes with immature skin are most susceptible to this type of soft rot.
Control Strategies:
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Prior to planting, warm seed tubers to approximately the same temperature as the soil, to reduce condensation on the tubers, which promotes rot
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Clean and disinfect seed cutters, handling equipment, and trucks
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Minimize mechanical damage during harvesting, handling, and packing operations
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Avoid frost injury and properly dry frozen tubers in storage (See section 3.9.4 Special Storage Problems)
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Use clean water that is changed often or chlorinated during washing operations
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Remove potato cull piles, discarded vegetables and plant refuse from fields and storage
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Control other tuber diseases
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Prevent condensation water from forming on tubers by ensuring that cold tubers are ventilated with cool air
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Blackleg is a common disease of potato caused by the bacterium Erwinia carotovora var. atroseptica. Symptoms of the disease are noticeable as soft, water-soaked dark brown to black lesions on the stem. Under humid conditions, infected stems may be slimy, but appear shrivelled under dry conditions. Tuber soft rot may also develop. Blackleg bacteria over winter in the soil and on tubers. Tuber borne bacteria are spread during seed cutting, handling, and planting. Control Strategies:
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The bacteria Streptomyces scabies cause common scab. The scab organism is widespread, occurring naturally in soil where it lives on plant debris. The pathogen causes scab-like lesions on the tuber, which vary in type: erumpent (slightly raised), russet (superficial), and sunken (pitted). Lesions may be circular, but often coalesce to form large, irregular patches on the tuber surface. Scab does not affect yield directly but reduces quality, and may result in higher grade-out. Common scab is more prevalent under hot, dry conditions and in soils with high organic matter. The organism prefers a pH of 5.5-8. Control Strategies:
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Each season, early blight causes significant yield losses on the Prairies. The pathogen causes dark brown to black concentric lesions on leaves and elongated brown or black lesions on stems and petioles. Leaf lesions become angular if a large vein retards them. The lesions enlarge, join together and may cover the entire leaf, which will eventually die. The pathogen may occasionally cause sunken circular to irregularly shaped lesions with a raised purple to brown border on the tuber, however, these symptoms have never been reported in Western Canada. The fungus can survive over winter in soil or on plant debris and initiate infection in the crop. Lesions on infected potato plants produce spores that spread to healthy plants and cause infection. The pathogen attacks weaker tissues; young tissue with high nitrogen content is somewhat resistant to the disease. Alternating wet and dry conditions and temperature between 64 and 77°F (18 and 25°C) are very favourable for disease development during the growing season. |
Control Strategies:
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Plant disease-free seed
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Maintain good soil fertility and crop vigour
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Harvest when skin is mature to avoid bruising and in turn infection of tubers
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Avoid continuous potato rotations (i.e. planting potatoes in subsequent years in the same filed)
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Apply protectant fungicides to the foliage, and follow a fungicide program throughout the growing season. Consult the provincial Guide to Crop Protection for registered fungicides
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Potatoes can be infected by different Fusarium spp. throughout the season. The various Fusarium pathogens cause seed-piece decay, wilt, and dry rot. The disease may initiate from infected seed or from inoculum present in the soil. Wounding is necessary for the development of dry rot and seed piece decay. Wounds to seed pieces at planting are ports of entry for the pathogen to cause seed rot. Wounding at harvest leads to dry rot development in storage. Vascular wilt develops as a result of soil-borne Fusarium infection of the roots. In the field, the symptoms of Fusarium wilt resemble those of Verticillium wilt, and a lab test is required to distinguish these diseases. Tuber yield and quality may be reduced due to wilt, but this disease is not as common as Fusarium dry rot. |
Control Strategies:
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Avoid wounding tubers at any stage of cropping cycle
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Provide conditions that encourage proper wound healing
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se registered fungicide seed treatments
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Avoid planting in extremes of cold or hot and dry or soggy soil
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Harvest in dry and cool weather
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Promote wound healing after harvest: 50-55°F (10-13°C) relative humidity at 95% with plenty of air for 10-14 days
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Apply post-harvest fungicide (resistance of Fusarium spp. to thiabendazole may reduce effectiveness)
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Late blight is one of the most devastating diseases of potatoes. The pathogen can infect all parts of the plant. Depending upon the environmental conditions and age of the tissue, appearance of the lesions may vary. The disease starts as small necrotic spots, which may or may not be surrounded by a pale green border. Lesions may also start as small water soaked areas at the tips of the leaf and enlarge inward. Older lesions generally have a necrotic centre and a pale green border. Dark green to black water soaked lesions develop on stems and petioles. Stem and petiole infections destroy soft tissue and leave only structural parts of the stem. As a result, stems remain standing in heavily infested, defoliated fields. Under humid conditions, a white fluffy growth appears at the lesion edges on the under side of infected leaves. Tubers near the soil surface can be infected if they are exposed or spores are washed into the soil. An irregular and shallow (1/4-1/2 inch, 4-13 mm) coppery brown dry rot spreads through the outer tissue of the tuber. In storage, infected tubers are susceptible to secondary rots caused by other fungi and bacteria; this can result in extensive damage. The late blight pathogen can survive only in living host tissue. It is known to over-winter in seed tubers, cull piles, and volunteer potatoes that over-winter in the field. High humidity and temperatures of 64-71°F (18-22°C) are ideal for development of this disease. Control Strategies:
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Leak is a tuber disease that has the potential to cause significant storage losses. Diseased tissue of tubers infected with leak is soft, watery, granular and dark grey or black in colour. Severely infected tubers may drip or leak, however, in less advanced stages, infected tissue may only be seen when tubers are cut. There is usually a distinct line between healthy and diseased tissue. Tubers may develop soft rot, and then become slimy and foul smelling. The fungus is present in many soils where it over-winters in plant debris, particularly in wet soils. Tubers become infected through wounds in the periderm. The incidence of leak increases with warm temperatures, as 77-89°F (25-30°C) is ideal for disease development. |
Control Strategies:
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Grow potatoes on well-drained soils.
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Harvest when tubers are mature.
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Harvest below a tuber pulp temperature of 65°F (18°C), especially if the soil is moist.
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Grade infected tubers prior to storage to reduce spread to healthy tubers.
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Store tubers promptly after digging at recommended temperatures and humidity.
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Cool tubers harvested in hot sunny weather to below 50°F (10°C) and market immediately.
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Consult your provincial Guide to Crop Protection for registered fungicides.
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The symptoms of pink rot are typically observed in tubers, but severe infections may develop foliar symptoms such as wilting, yellowing, and aerial tubers. Infected tubers exude a clear, watery liquid. The tissue remains intact, but has a rubbery texture. When infected tubers are cut open, a pink colour develops within 30 minutes, and later turns black. The tuber decay may proceed into the tuber from the stolen end, and a line may be visible between healthy and infected tissue. The pink rot pathogen lives in soil and can infect any below ground part of the plant. The pathogen thrives in wet, poorly drained soils and disease progresses quickly during warm temperatures. The disease can spread to healthy tubers during harvest and storage. |
Control Strategies:
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Plant in well drained soils
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Avoid wounding during harvest and handling
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Grade infected tubers prior to storage to reduce spread to healthy tubers
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If pink rot infected areas of fields are identified or suspected, market directly after harvest. If this is not possible, store separately from healthy tubers
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Use a fungicide registered for pink rot control. Consult your provincial Guide to Crop Protection for recommended products
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Powdery Scab |
This disease has been a serious problem for potato growers in New Zealand and parts of Europe for many years, and has recently been recognized as a problem in North America. Powdery scab is caused by the fungus Spongospora subterranea. It produces a resting spore stage (spore balls) that can survive in soil for at least six years. Initial infection occurs at early tuber set, and is favoured by high soil moisture and soil temperatures of 57-64°F (14°C-18°C). The pathogen causes scabs that are initially rounded and discrete, with torn edges of potato skin surrounding the scabs. Lesions frequently form in a band around the tuber or are clustered at one end. Later lesions may coalesce. By harvest time a dry, powdery mass of spore balls may be present in the scab lesions. The presence of these ovoid spore balls, visible under a dissecting microscope, is necessary for a positive identification of the pathogen. It is possible to confuse powdery scab lesions with those produced by common scab. Powdery scab also infects root tissue, forming galls 1/8-3/8" (1-10 mm) that produce spore balls that remain in the soil at harvest. Powdery scab infections increase grade-out, and the scabs may allow entry of secondary rot organisms. The powdery scab fungus is also the only known vector of potato mop-top virus (Refer to the section on mop-top virus). |
Control Strategies:
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Plant disease-free seed into non-infested soil
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Reduce soil moisture levels at tuber set
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Plant late to increase temperature at tuber set, harvest early
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Increase time between potato crops to at least 6 years
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Plant less susceptible cultivars such as Russet Burbank
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No registered fungicides are available (as of December 2001)
**Differentiation between common and powdery scab is important to allow correct management decisions to be made.
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Rhizoctonia stem canker and black scurf (Rhizoctonia solani)
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The symptoms of the disease include development of rusty brown lesions on underground stems and stolons and black sclerotia (fungal bodies) on progeny tubers. The leaves may turn pale green or purple and become curled and upright. Development of aerial tubers in leaf axils may also be observed. Under humid conditions, a white cottony growth develops on the lower stem. The disease initiates from black fungal bodies present on infected seed or from the pathogen present in the soil on plant debris. Cooler conditions at planting favour the development of Rhizoctonia. Delayed emergence increases the likelihood of infection. Control Strategies:
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Seed-Piece Decay
Several species of soil and seed-borne fungi and bacteria cause seed-piece decay. Seed-pieces may develop dry rot or soft rot depending upon the microorganisms involved. Consult individual diseases for their seed piece decay phase.
Control Strategies:
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Avoid bruising the seed
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Preferably plant whole seed
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If using cut seed, follow proper cutting, fungicide seed treatment and storage procedures (see Section 3.2.5 Seed Cutting)
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Prevent condensation on the surface of the seed by warming the seed near to soil temperature prior to planting, and plant in a warm, moist-but-not-wet soil to promote wound healing and rapid sprout growth. If soil temperature is too cold (below 50°F or 10°C) cut seed will not suberize, if it is too warm (above 64°F or 18°C) it is very favourable for multiplication of pathogens.
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Avoid exposure of cut seed to hot sun or drying winds
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This is a disease of the potato skin. The disease has markedly increased since the early 1990s due to the development of resistance in isolates of the pathogen to thiabendazole (Mertect), the only fungicide that was recommended for control of this disease. The skin spots, which are small and pale brown at harvest, enlarge during storage. Older lesions appear silvery, especially when wet. The disease, though more pronounced on white or red-skinned tubers is also found on russet-skinned cultivars. Although the pathogen can survive on plant debris in soil, the diseased seed tubers are considered the most important source of silver scurf initiation in the field. Under warm and humid conditions, the pathogen multiplies and infects daughter tubers. Delayed harvest, especially after vine kill, increases the disease severity. New tubers can be infected during harvest by intermingling with diseased tubers and during the first 2-3 weeks of storage. The pathogen can survive on structural material. |
Control Strategies:
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Plant certified silver scurf-free seed.
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Treat seed tubers with a fungicide seed treatment registered to control silver scurf.
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Avoid planting potatoes in a field that had silver scurf the previous season.
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Apply post-harvest fungicide treatments to newly harvested tubers (resistance in pathogen populations to thiabendazole may reduce effectiveness of this fungicide.)
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Thoroughly disinfect storages before filling.
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Harvest as soon as possible after vine kill or maturity.
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Reduce the amount of soil and plant debris going into the storage.
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Use air to dry wet tubers.
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Remove field heat from tubers as soon as possible, and avoid conditions that promote condensation in storage.
Verticillium wilt (Verticillium spp.)
Verticillium wilt of potato can be caused by V. dahliae or V. albo atrum. The disease can have a significant impact on the crop by reducing both tuber yield and quality. Plants infected with wilt start to show symptoms in the middle of the growing season. Individual leaves first turn pale green or yellow, leaves on affected stems then wilt, and finally the entire plant dies prematurely. Initial symptoms often develop on one side of the plant. The lower stems of diseased plants and tubers have brown discolouration in the vascular tissue when cut open. Verticillium spp. are soil-borne fungi and once established, can live for long periods in the soil even if a potato crop has not been planted for many years. The pathogen can become established in a field through the use of infected seed or by movement of infested soil.
Control Strategies:
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Maintain fertility at levels optimum for high yield
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Irrigate to reduce moisture stress after flowering and during tuber bulking, but do not over-water
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Disease severity may be reduced by incorporating green manure crops in the season prior to potato production
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Practice at least a three year rotation, and preferably a four year rotation
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Do not contaminate clean fields with soil from diseased fields, diseased tubers or plant refuse
Viral Diseases
Of the more than 27 viruses that have been reported to infect potatoes, potato leafroll virus (PLRV) and potato virus Y (PVY) are distributed worldwide and have often been reported to be the most damaging. These are the two most economically important viruses in the Prairie potato crop.
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PLRV is an aphid-transmitted virus. Primary symptoms appear after the virus is transmitted from an infected aphid to a healthy plant. Primary symptoms include upright, rolled leaves and slight yellowing that appears mainly in the young leaves. In some cultivars, young leaves are pink to reddish beginning at the leaf margins. Leaf rolling may only be evident at the base of the leaflet rather than the whole leaflet, and may eventually spread to the lower leaves. Plants infected early in the season may also be dwarfed. In late season infections, primary symptoms may not appear, as potato plants develop resistance to foliar infection with age, which makes diagnosis difficult. |
Secondary symptoms occur when an infected tuber produces an infected plant. Leaf yellowing, along with leaf rolling are often associated with the lower leaves. Leaves are dry, stiff and leathery, and make a paper-like, crisp sound. Plants are often stunted. Secondary symptoms are not as evident in the top of a plant.
PLRV causes net necrosis in infected tubers, rendering them unmarketable (Plate 27). Internal net necrosis is visible when the tuber is cut and is particularly marked in certain cultivars, the most susceptible being Russet Burbank. Net necrosis causes browning of the vascular system within the tuber and is primarily seen when the virus is spread to healthy plants from aphids. It can be seen in tuber-borne infected plants if the disease pressure is high. Timing of net necrosis development in the tuber is dependent on the time of infection in the field. At harvest, tubers may exhibit net necrosis if the plant was infected with the virus early in the growing season. If infection occurred in August or later, net necrosis will not likely show up at harvest but will develop later in storage.
PLRV infection may result in reduced tuber size and number, and yield loss can be as severe as 60-90%. PLRV can also result in rejection of seed lots for certification, and infected tubers with net necrosis are not acceptable for processing.
PLRV is spread primarily by aphids that colonize potatoes, but it is also tuber-borne and therefore spread by infected seed tubers. The most efficient vector is the green peach aphid (3.6.2 Insect Management). PLRV is the only known persistently transmitted potato virus. Persistent means that once the aphid acquires the virus, it carries it for life. PLRV is concentrated in the phloem (vascular) tissue of the plant and is acquired only by an aphid that chooses to feed on an infected plant. Once the aphid acquires the virus from an infected plant, at least 24 hours or more are needed until the newly infected aphid can transmit the virus. Long distance spread of the virus occurs by wind-borne winged aphids. Short distance spread occurs by non-winged aphids moving from plant to plant. PLRV is not mechanically transmitted and therefore aphids are solely responsible for the in-season spread of the disease. Sources of PLRV include plants grown from infected tubers and diseased volunteer potato plants.
Control Strategies:
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Plant virus-free, certified seed, remove volunteer hosts, and rogue infected plants early to eliminate virus inoculum
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Management of aphids is an integral part of PLRV management. Control aphids to eliminate aphid vectors during seed production, during aphid population outbreaks and when cultivars susceptible to net necrosis are grown
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Scout fields regularly and use established action thresholds to determine when insecticide sprays are recommended
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PVY is a common virus that may infect many crops including potato, tobacco, pepper and tomato. Common strains of the virus PVYO occur worldwide. Primary symptoms of PVYO, depending on the cultivar, are necrosis, yellowing of leaflets, mottling, leaf dropping and sometimes premature death. Necrosis may cause leaves to collapse and remain attached to the stem. Symptoms of secondary PVYO infection include mottling, crinkling of the leaves, and stunting of the plants. Foliar and stem necrosis may occur. Necrosis following primary infection is usually more severe than following secondary infection. The foliar mosaic symptom (intermingled light green and yellow coloration) may be masked at high (77°F or 25°C) and very low (50°F or 10°C) temperatures, but at high temperatures the disease can be identified by the rugosity (crinkling) of the foliage. |
PVY is one of the more damaging potato viruses and can have a significant impact on yield. Infection results in reduced tuber number and size. Complete failure of a potato crop may also occur. PVY can also result in rejection of seed lots for certification.
PVY is an aphid-transmitted virus and spread depends mainly on the presence of winged aphids. PVY is transmitted in a non-persistent manner. The aphid can acquire the virus and infect healthy plants in only a few seconds. After a brief period of feeding on healthy plants, infected aphids rapidly lose their virus charge and must again feed on a PVY infected plant to continue to transmit PVY. To determine suitability of a plant as a host, aphids sap-sample the epidermal tissue of a plant. Many aphid species that don't reproduce on potatoes will sap-sample potato foliage, and during this process can spread PVY.
Control Strategies
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Crop borders planted to non-virus host plants such as soybean or wheat provide a landing site where aphids can "clean" their mouthparts from non-persistent viruses before moving into the potato crop. Spread of PVY in potato from sources outside the field can be reduced by up to 60% by using crop borders
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Plant virus-free, certified seed
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Plant early and rogue out diseased plants
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Apply effective aphidicides
- Vine-kill as early as possible and continue use of an effective aphidicide if needed
until vines are completely dead
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PMTV is considered to be an economically important disease of potato. It occurs throughout parts of Europe, South America, Asia, and has recently been detected in North America. PMTV is present in Canada, but the distribution within the country is not known. Foliar symptoms of the disease include dwarfing of shoots resulting in a "mop-top" appearance; pale green V-shaped markings on young leaves; and bright yellow blotches, mottling, rings, and V-shapes on leaves. Tuber symptoms of PMTV infection may include cracking, internal spots, and necrotic rings or arcs referred to as spraing. Tuber symptoms may be difficult to distinguish from tobacco rattle virus or physiological disorders. PMTV is spread by Spongospora subterranea, the fungus that causes powdery scab. The virus survives in the soil within the spore, and together the spore and virus may remain dormant for many years. Plants become infected with PMTV when virus-carrying powdery scab spores infect potato roots, stolons, or tubers. PMTV is also seed-borne. Symptom expression in foliage and tubers is quite variable and is influenced by the type of infection (soil or seed-borne), cultivar, and environmental conditions. Control Strategies Avoid introducing powdery scab and PMTV into uninfested soils by using disease free seed and sanitation practices. Sanitation should be aimed at preventing the movement of powdery scab infested soil on seed, equipment, and in irrigation water. Follow control recommendations for powdery scab. For further details regarding virus management in seed potatoes, please see selected reference number 4. Selected References
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Potato Spindle Tuber Viroid
PSTVd is a serious disease of seed potatoes caused by the spindle tuber viroid. The Canadian Food Inspection Agency has a zero tolerance for PSTVd in seed potatoes. Plants infected with PSTVd are upright, dwarfed, and much thinner than uninfected plants. The stems are often more branched and the branches form very sharp angles where they join to the stem. Affected tubers are dwarfed and are usually narrow and spindle-shaped. Eyes are numerous and the tubers are often cracked. PSTVd is spread by contact, but chewing and sucking insects such as aphids, grasshoppers, Colorado potato beetles, and flea beetles have been implicated in the field spread of this disease. Seed-cutting knives, planters and infected seed (tubers and true seed) also spread PSTVd.
Control Strategies
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Plant certified disease free seed
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Plant whole seed
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Wash knives and other equipment with detergents, household bleach or quaternary ammonia compounds, especially between seed lots
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Control insects
- Remove diseased plants, ensuring that the entire plant is removed
- Avoid leaf contact by people and equipment during field operations
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Blackheart results from an insufficient oxygen supply to internal tuber tissue. The centre of the tuber turns blue-black. The tuber tissue associated with blackheart remains firm, as opposed to the black, soft watery tissue resulting from leak infection. Blackheart may develop if tubers are held in low oxygen environments. This can occur in less than ideal storage conditions, water logged soils, or if condensation forms on tubers. Blackheart is prevented by proper ventilation, storing at recommended temperatures, and improvement of soil drainage. |
Hollow Heart
Hollow heart, a cavity near the centre of the tuber, results from rapid tuber growth. The disorder is found primarily (but not only) in large potatoes. Walls of the cavities are white to light brown. The disorder is difficult to detect because affected tubers have no external symptoms. They can only be removed with expensive X-ray grading equipment. Hollow heart is promoted by growing conditions that cause rapid tuber enlargement. Poor stand increases the incidence of hollow heart. To reduce hollow heart:
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Plant susceptible varieties at closer spacings. See Section 3.1.4 Variety Descriptions for details on varietal susceptibility
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Maintain uniform soil moisture throughout the entire growing season
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Plant to maximize stand of uniform plants and minimize misses
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Ensure adequate potassium fertility
Figure 3.6-6 Hollow heart (Courtesy of Manitoba Agriculture, Food and Rural Initiatives)
Malformed Tubers
Extreme soil temperatures may cause secondary growth, knobs, and other tuber deformities. Other conditions such as nutrient and water imbalances have also been implicated in irregular tuber development. Growth cracks may arise from rapid tuber growth and are often the result of improper fertilizer placement. To prevent or reduce malformed tubers:
- Maintain uniform soil moisture, particularly during tuber development
- Apply recommended fertilizer rates
- Establish a high stand of uniform plants to control tuber growth rates
- See Section 3.1.4 Variety Descriptions for details on varietal susceptibility
Low Temperature Injury
Low temperature or freezing injury can occur to potatoes that are exposed to a heavy field frost or to tubers that have been excessively chilled in storage. Frozen tissue, upon thawing, discolours and breaks down into a soft watery mass (Plate 33). Chilling injury often results in streaks of discolouration in the vascular tissue of the tuber. Frozen or chilled potatoes should not be used for seed as cut surfaces may not heal and seed piece decay will result. Low temperature injury losses can be reduced or prevented by:
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Storing at temperatures above 37°F (3.0°C)
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Proper ventilation and temperature control. See Section 3.94 Special Storage Problems for more details
- Culling frozen potatoes prior to storage
For further information, contact your GO representative.
