Potato pests and diseases

Potatoes can suffer from a range of pests and diseases – ranging from scab, which causes superficial damage, to blight, which can destroy a whole crop. The best strategy is to take the following steps to prevent problems arising. Pest and disease prevention Variety choice: Varieties are available with resistance to blight, blackleg, scab, potato cyst eelworm and other problems. Seed potatoes: Use certified seed potatoes to avoid introducing pests and diseases. Home saved seed from healthy crops can be used for a year or two, but virus levels may build up quickly. Never save seed from a diseased crop. Crop rotation: Grow potatoes on a 3 or 4 year rotation to help avoid build-up of soil-borne pests and diseases, such as potato eelworm and scab. See factsheet GG19, Crop rotation, for more information. Soil improvement: Compost and other rotted organic materials help keep soil borne pests and diseases under control. They also help the soil to retain moisture, encouraging strong growth. Compost fed plants are less attractive to pests than those given artificial fertilisers.   … [Read more…]

Potato blight

Potato late blight is caused by the fungus Phytophthora infestans. It infects potato leaves, stems and tubers and can cause devastating crop losses. Tomato blight is also caused by the same fungus (see factsheet DC20 – Tomato Blight). Typical symptoms Leaves and stems: Dark brown/ blackish round patches, often surrounded by a pale halo. In warm, damp weather the patches quickly spread to rot the whole leaf. Stems can also be infected. The underside of the infected leaf develops a downy white coating of spores in moist conditions, particularly noticeable early in the morning. If weather remains warm and damp, the disease spreads rapidly, reducing the foliage to a rotting mass within a few days. Tubers: Dark, sunken areas on the surface, which may extend to cover the whole potato, giving a dry firm rot. Cutting the potato in half will show patches of chestnut-coloured rot starting just under the skin. Other fungi and bacteria may follow, invading the tuber to produce a wet, foul smelling soft-rot. Seemingly healthy tubers may rot later when in store. Another blight: Potato early blight (Target spot) symptoms may be mistaken for late blight. Early blight, Alternaria solani, however generally occurs earlier in the season (July) and spreads under warmer and drier conditions than late blight. The distinctive smaller dark brown spots, somewhat angular with concentric rings, are bounded by the leaf veins. Early blight rarely causes significant loss of yield and no treatment is necessary. … [Read more…]

Potato blackleg

Potato blackleg, Erwinia carotovora, is a common bacterial disease of potatoes, especially in wet seasons. It can be a particular problem on potatoes grown through a thick straw or hay mulch. It can occur at any stage of plant development. Typical symptoms Symptoms appear early in the season, before the potato haulms meet across the rows. Affected plants will be stunted and scattered throughout the crop. Foliage: Leaves turn pale green or yellowish. Margins of upper leaves roll inwards. Later, leaves turn brown and the haulm dies. Early attacks may result in non-emergence of foliage. Stems: Turn brown or black approximately 10cm above and below soil level. During wet periods, or as the season progresses, this basal rot darkens, and becomes wet and soft. Stems can be easily pulled out. Black streaks may be found higher up the stems; the plants wilt and collapse rapidly. Not all the stems on one plant are necessarily affected. Tubers: A black rot can extend from the heel end or from lenticels (the breathing pores of the tuber skin). In bad attacks the tubers may all decay in the ground. More commonly, the tubers appear sound on lifting, then rot in storage. Infection will spread between tubers in store.   Life cycle The main source of infection is the planting of infected tubers; even certified seed can contain a certain amount of blackleg. Infected tubers can carry the disease without showing any symptoms. Healthy tubers can be infected from diseased ones which have rotted in the soil, or in store. The bacteria can migrate through moist soil and can be found in potato debris, but these are unlikely to be important sources of infection. The disease is unlikely to spread from plant to plant during the life of the crop. Prevention and control There is no way of controlling this disease once a plant is infected. Some approaches can be taken to prevent infection, but this is not easy when the disease can be introduced in purchased seed tubers! Storage: Do not store any tubers which show signs of rot or damage, or that have come into contact with rotting tubers. Check through sacks of stored tubers regularly and remove any that have rotted Cultural control: Never save tubers for replanting from an infected crop. Avoid waterlogged and wet sites. Remove ‘volunteer’ potatoes that have survived from the previous season. Do not cut seed potatoes up prior to planting as this increases the likelihood of tubers becoming infected Resistant varieties: Choose varieties that are less susceptible. These include Osprey, Kestrel, Merlin, Saxon and Stroma. Avoid very susceptible ones such as Estima, Wilja, Epicure and Maris Bard. No varieties show complete resistance to the disease Harvesting: Lift crops during dry weather if possible. If not, allow the tubers to dry out before storing. For more information on storage conditions, see also: GG16 Storing the Harvest The British Potato Council has a useful website: https://potatoes.ahdb.org.uk/ Courtesy of Garden Organic: https://www.gardenorganic.org.uk/   … [Read more…]

Sarvari Research Trust (SRT)

The Sarvari Research Trust (SRT) is the organisation that breeds new, disease resistant varieties of potato that are traded by Sarpo Potatoes Ltd (SPL).  At its core is one of the UK’s leading experts on late blight of potato, Dr David Shaw.  David retired as a lecturer and researcher in Genetics and Plant Pathology at Bangor University in 2002 to begin the work that led to the formation of the Trust. The Trust aims to make potato growing globally less dependent on chemical and energy inputs by producing and promoting low-input varieties. Ideally these should be blight and virus resistant, capable of smothering weeds and have natural dormancy that prevents early sprouting in store.  The Trust would be happy to make some of these varieties available to developing countries where blight and virus are major problems and where subsistence farmers cannot afford expensive chemicals. SRT is based at Henfaes Research Station, the farm owned by Bangor University in North Wales.  Henfaes is wedged between the Carneddau mountains (part of Snowdonia) and the sea, near the village of Abergwngregyn on the beautiful North Wales coast. You can read more at http://sarpo.co.uk/home/ … [Read more…]

The lost garden skill – Potato Breeding

Credit: East Anglia Potato Day – http://www.eapd.btck.co.uk/AmateurPotatoBreeders Amateur Potato Breeders Group The Sarvari Trust and Alan Romans, author of the Guide to Potato Varieties booklets have set up this group. Many of its members met in March and are now in contact via e-mail. Here is Alan’s manifesto from early this year: The lost garden skill – Potato Breeding Could you be a next generation Sarpo breeder? Gardeners leave the production of new potato varieties to the scientific “experts.”  Yet before 1930 all varieties were produced by gardeners or farmers using what facilities they had. To this day nearly all European varieties are produced by “hobby” breeders – farmers or growers with an association with one of the large continental potato companies or co-ops.  The Sarpo varieties Mira and Axona are the most blight resistant varieties we know. They have many garden-friendly characteristics – virus resistance, weed suppressing foliage, high food value, continual tuber growth through the season and long dormancy. They are not commercially successful because:  the tubers can grow very long with a twist, and are prone to having green ends,  they can have extremely high starch levels at the end of the growing season,  when over-mature they are often hollow with blackening,  they have poor skin colour and  they have strong stolons which are often still attached after harvesting.  The weed suppressing foliage is slow to start, ironically leading to early weed problems and  at the end of the season the foliage is unwilling to die back and is difficult to clear for harvest. Sarpo Mira and Axona produce flowers readily and have strong male and female fertility. They make good mums and dads! Time to move on and breed the next generation with top blight resistance. The “experts” are engaged elsewhere and there is room for a group of British hobby breeders to cross the Sarpos with other varieties to seek a generally acceptable tuber with top virus and blight resistance. There is a small amount of technical advice available from the Sarvari Trust in North Wales but it would be down to group members to make use of their own facilities – garden/ allotment space, tools, pots, perhaps a greenhouse or polytunnel. Nimble fingers help.  Members could specialize in crossing to produce seed, raising seedlings and selecting potentially useful varieties from the seedlings, or trialing the potentially useful varieties or go for the lot. A meeting is planned by the Sarvari Trust in North Wales in March to discuss what is involved and what relationship is possible between them and hobby breeders. For the moment we want to gather details of anyone interested. Home Alan Romans East Anglia Potato Day supports this Group. There is room for more members so get in touch if you want to be involved. We will need: Your Name    Your Facilities   Your Skills   Your email address New crosses have already been germinated, grown on, planted out, and are now facing selection by potato blight. Other crosses are … [Read more…]