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Solanum tuberosum L.

Solanaceae
Potato

Source: James A. Duke. 1983. Handbook of Energy Crops. unpublished.

  1. Uses
  2. Folk Medicine
  3. Chemistry
  4. Toxicity
  5. Description
  6. Germplasm
  7. Distribution
  8. Ecology
  9. Cultivation
  10. Harvesting
  11. Yields and Economics
  12. Energy
  13. Biotic Factors
  14. References

Uses

Tubers are one of the temperate staples, eaten boiled, baked, fried, stewed, etc. Surplus potatoes are used for fodder and alcohol, and chemurgic applications. The flour can be used for baking. Potato starch is used to determine the diastatic value of starch. Boiled with weak sulphuric acid, potato starch is changed into glucose, fermented into alcohol, to yield "British Brandy." Ripe potato juice is excellent for cleaning cottons, silks, and woolens. Root and leaf diffusates of growing potato plants possess cardiotonic activity. Dried ethanol extracts of above-ground parts show marked hypotensive and myotropic action and a spasmolytic and soothing effect on intestinal musculature. Ethanol extracts of leaves have antifungal properties, active against Phytophthora infestans. Leaves, seeds, and tuber extracts show antimicrobial activity against Gram-positive and Gram-negative bacteria. US per capita consumption of processed products increased from ca 1 kg in 1940 to ca 10 kg in 1956. Potato chips accounted for 42% of processed products produced in America during 1964; frozen products, 36%; followed by dehydrated potatoes, 16%; canned potatoes, 2%; and miscellaneous other products, 4%. About 30% of the total potato crop was utilized by the American processing industry during 1964 (C.S.I.R., 1948–1976).

Folk Medicine

Reported to be alterative, aperient, bactericide, calmative, diuretic, emetic, lactagogue, potato is a folk remedy for burns, corns, cough, cystitis, fistula, prostatitis, scurvy, spasms, tumors, and warts (Duke and Wain, 1981; Hartwell, 1967–1971). The mealy flour of baked potato is oiled and applied to frostbite (Grieve, 1931). The tea, made from the peels of the tuber, is said to be a folk remedy for tumors. The boiled tuber is said to alleviate corns. The powdered tuber, with copper sulfate, is said to help callused fistulas. Europeans tie raw potatoes behind the ears for delirium (Duke, 1984b).

Chemistry

Per 100 g, the tubers contain 76–82 calories, 77.7–79.8 g H2O, 1.7–2.8 g protein, 0.1–0.2 g fat, 17.1–18.9 g total carbohydrate, 0.4–0.6 g fiber, 0.9–1.6 g ash, 7–13 mg Ca, 50–53 mg P, 0.6–1.1 mg Fe, 3–7 mg Na, 396–407 mg K, traces to 25 mg b-carotene equivalent, 0.7–0.11 mg thiamine, 0.03–0.04 mg riboflavin, 1.3–1.6 mg niacin, and 18–21 mg ascorbic acid (Duke and Atchley, 1984). Mineral elements present are (mg/100 g): Mg, 20; Na, 11.0; K, 247; Cu, 0.21; S, 37.0; and Cl, 16.0; small quantities of iodine (11 ug/kg) Mn and Zn are also present. Potato is among the richest foods in potassium, poorest in sodium. The more important sugars are sucrose, glucose, and fructose; some galactose, melibiose, raffinose, stachyose, planteose, myoinositol, maltotriose, manninotriose, galactinol, trigalactosyl glycerol, digalactosyl glycerol, glucosyl myoinositol, ribosyl-glucose, xylosyl-glucose, arabinosyl-glucose. Non-starch polysaccharides include hemicellulose, cellulose, and pectic substances. The pectin content varies from 1.8 to 3.3 percent. The pectic substance consists of anhydrogalacturonic acid (51%) and polysaccharides (49%), composed of rhamnose (6%), fucose (0.6%), arabinose (5.6%), xylose (1.8%), and galactose (86%). The amino acid composition follows: arginine, 6.0; histidine 2.2; lysine, 7.7; tryptophan, 1.6; phenylalanine, 6.6; cystine, 2.1; methionine, 2.3; threonine, 5.9; and valine, 6.1%. The protein is somewhat deficient in sulphur amino acids and probably also histidine. It is rich in lysine. Potato contains also g-aminobutyric acid, a-aminobutryic acid, b-alanine, and methionine sulphoxide. Other nitrogen compounds include: glutathione, choline, acetyl choline, trigonelline, cadaverine, adenine, hypoxanthine, and allantoin. Potato contains a phenolase, also called phenol oxidase, polyphenol oxidase, catecholase, and tyrosinase, which oxidizes phenols. The vitamins present in potato are per 100 g edible material; vitamin A, 40 IU; thiamine, 0.1 mg; riboflavin, 0.01 mg; nicotinic acid, 1.2 mg; vitamin C, 17 mg; and choline, 100 mg. A small quantity of folic acid (total, 7.4 mg/100 g; free acid, 3.0 mg/100 g) is also present. Linoleic acid is the predominant (41.3% of the total) acid in potato fat; other acids present are: palmitic, 24.9; linolenic, 19.4; oleic, 6.4; stearic, 5.4; and myristic, 0.6%; two unidentified acids, and a few hydroxylated fatty acids are also reported to be present. Cholesterol, sigmasterol, and b-sitosterol are present in the unsaponifiable fraction. Organic acids present in the tuber (excluding ascorbic acid, amino acids, and fatty acids) are: tactic, succinic, oxalic, malic, tartaric, hydroxymalonic, citric, isocitric, aconitic, a-ketoglutaric, phytic, caffeic, quinic, and chlorogenic acids. Citric acid is present also in the stems and leaves. Tannins are localized in the suberized tissue of potato and are also present in leaves (c. 3.2%). Potato seeds contain 2 flavonol glycosides, kaempferol-3-diglucoside-7-rhamnoside and the kaempferol-3-triglucoside-7-rhamnoside. The flavonols, myricetin and quercitin are also present. Volatiles from cooked potatoes include: hydrogen sulphide, acetaldehyde, methanethiol, acrolein, acetone, ethanethiol, dimethylsulphide, iso- and n-butyraldehyde, isovaleraldehyde, methylisopropylketone, etc. Fresh potato tops are said to serve as feed for cattle and sheep. Analysis gave (dry-matter basis): total N, 1.82–2.30; EE, 3.06–4.65; CF, 15.36–23.67; NFE, 40.46–50.51; and ash, 15.97–22.28 (C.S.I.R., 1948–1976).

Toxicity

Although the foliage is considered poisonous, some African tribes used the tip as a potherb, while others, like Mauritians extract the.green parts as a narcotic. Solanine is one toxic ingredient in the green tuber and sprouts. The "green fruit has caused fatalities"..."potato with a green discoloration as a result of exposure to the sun, contains solanine and has been known to cause fatal poisonings." (Watt and Breyer-Brandwijk, 1962). There are records of severe solanine poisoning in 60 persons in Cyprus, with one death, from eating green potato shoots collected about the time of flowering and boiled ca 1/2 hour before eating. The shoots contained ca 27–49 mg solanine per 100 g. Animals fed large residues of raw or cooked potato or "distiller's slop" develop a disorder known as potato eruption. Symptoms in mild intoxications include a slight rise in temperature, anorexy, constipation, stiff gait, salivation, lacrymation, all preceding a vesicular inflammation on the lower part of the limbs (Watt and Bryer-Brandwijk, 1962). Persons harvesting, handling, or peeling potatoes may develop allergy or urticaria (Mitchell and Rook, 1979). Sir Walter Raleigh is said to be the first to plant the potato, near Cork, UK, but knowing little about it, he ate the berries. Discovering their narcotic nature, he ordered his plants uprooted (Grieve, 1931).

Description

Erect or clambering succulent herb to more than 1 m tall, the stems sometimes quadrangular or even winged, with tuberiferous stalens just at or below the soil surface. Leaves alternate, imparipinnate, short-stalked, 10–30 cm long, 5–15 cm wide, the leaflets opposite or alternate, very unequal in size and shape, the larger often petiolulate, ovate to ovate-oblong, enequilateral, apically acuminate to acute, basally subcordate, 2–10 cm long, 1–6 cm wide, the smaller more blunt apically, more cordate basally, broadly ovate to orbicular, 2–15 mm in diameter, thinly to densely pubescent. Flowers white or blue, pedunculate in lateral, many flowered cymes, the hairy peduncle 5–15 cm long, the jointed hairy pedicels 3–35 mm long. Calyx campanulate, 5-lobate, 1.5–2 cm in diameter, the lobes acute or acuminate. Corolla twice as long as calyx, 3.5–4 cm in diameter. Anthers free, erect, poricidal, yellow. Fruit a globose 2-celled berry, many-seeded, yellowish green (Ochse, 1931; Vilmorin-Andrieux, 1885).

Germplasm

Reported from the South American, and secondarily, the Middle American and Eurosiberian Centers of Diversity, potato, or cvs thereof, is reported to tolerate aluminum, bacteria, fungi, hydrogen fluoride, high pH, laterites, low pH, nematodes, photoperiod, slope, SO2, ultraviolet, viruses, and weeds, potato sometimes becoming a weed itself in potato fields. Vilmorin-Andrieux (1885) depicts 28 cvs in a rather extensive discussion of some of the older "varieties", some of them long gone. Smith (1981) states that more than 100 varieties are grown in the US, with the leading ones, in acreage, being Russet Burbank, Norchip, Kennebec, Katahdin, and Superior. In Peru clones are being tested to derive from their wide genetic diversity the ability to adapt to extreme temperature conditions. Crossing genetically diverse parents, previously selected for adaptation, might yield heterozygosity to maximize the performance of the hybrids. Mendoza (1977) reports a screening of 6000 clones for germplasm adapted to high temperatures and humidity. Hybrids of tuberosum x neotuberosum and tuberosum x phureja showed promise given the short growing season and the stress imposed not only by the weather but also by weeds, insects, and diseases. Many Andean peasants plant small insurance crops of wild-type potatoes, of poor quality, but good frost resistance. Potato breeders are charged to combine frost resistance with quality and yield potential of Solanum tuberosum. Solanum demissum Lindl. and S. commersonii Dunal ex Poir. are among the frost-resistant species. Richardson and Weiser (1972) list S. acaule Bitter, S. chromatophilum, S. commersonii Dunal ex Poir., S. X juzepczukii Bukas., and S. multidissectum Hawkes as highly resistant; S. ajanhuiri Fozepczuk and Bukasov, S. X curtilobum Juz. and Buk., S. demissum Lindl., S. megistacrolobum Bitter, S. microdontum Bitter, and S. vernei Bitter and Wittm. as very resistant. S. acaule has been reported to tolerate -3 to -9°C. S. brevicaule Bitt. x S. phureja Juz. and Buk. hybrids have survived -4 to -9°C. Frost resistance, like heat resistance, of potatoes can be improved. Solanum megistacrolobum Bitter is an effective donor of frost tolerance. Among tolerances reported are 'Dakota Chief', 'Fillmore', 'Rili', and 'Viking' tolerant to drought; 'Belchip', to fluctuating temperatures; 'Sebago', to frost; 'Alpha', 'Arka', and 'Up-to-Date', to hail; 'Superior' and 'Virgil', to heat; 'Kasota' and 'Yampa', to heavy soil; 'Cherokee' and 'Osage', to muck; 'York', to organic soils; 'Mesaba' and 'Waseca', to peat; 'Atlantic', 'Red Lasoda', and 'Red Pontiac', to photoperiod; 'Yampa', to sand; and 'Osseo', to short season. Cultivars differ in Al tolerance (Duke, 1982a). The potato, a tetraploid species, arose in the Andes. Various species have been postulated as the diploid progenitor, e.g. one source has proposed S. stenotomum introgressed with S. sparsipilum, while another source has proposed S. vernei as one parent. S. stenotomum and S. vernei are similar to S. tuberosum spp. andigena in their cytoplasmic factors and either could have given rise to it with minor (if any) cytoplasmic changes. Results of a study of variation in Fraction 1 protein were consistent with an origin of spp. andigena from chromosome doubling of S. stenotomum and did not support an involvement of S. sparsipilum; S. vernei was not included in the study. Solanum tuberosum spp. andigena was introduced to Europe in the 16th Century and persisted there until late blight struck in the middle of the 19th Century. It is suggested that catostrophic selection among the survivors of the blight gave rise to Solanum tuberosum ssp. tuberosum. Experimental evidence shows that ssp. tuberosum-like plants can be produced through selection from ssp. andigena. Heiser (1979) notes Grun proposed that, at the time of the late blight, ssp. tuberosum was imported to Europe from islands off the coast of Chile. Heiser also notes in their study of cytoplasmic factors, Grun et al found that plants of ssp. tuberosum from the northern hemisphere and coastal Chile shared all or nearly all of the same plasmon sensitivities, whereas they differed from ssp. andigena in eight of the nine plasmon sensitivities tested. Thus ssp. tuberosum, now cultivated in the northern hemisphere, may be derived directly from Chile rather than through the transformation of ssp. andigena (Heiser, 1979). (2n = 24, 36, 48)

Distribution

Originally from Latin America, probably Andean, the potato is now grown in probably all temperate countries and in tropical uplands. Germplasm improvement is gradually pushing the potato into the lowland tropics, but it can scarcely compete with the tropical root crops.

Ecology

Ranging from Boreal Moist to Wet through Tropical Very Dry to Wet Forest Life Zones, potato is reported to tolerate annual precipitation of 0.9 to 41.0 dm (mean of 145 cases = 9.3), annual temperature of 3.6 to 27.8°C (mean of 145 cases 12.9), and pH of 4.2 to 8.2 (mean of 122 cases = 6.2) (Duke, 1978; Smith, 1981). Potatoes are a cool weather crop, the optimal temperature for growth being 15–20°C for most cvs. Growth of tubers is best at soil temperature of 17–20°C, with usually no tubers formed above 32°C. They perform well on a wide variety of soils, sandy loams, silt loams, loams, and peats. Soil moisture tensions between 40 and 60 centibars seem to produce the best yields.

Cultivation

In the temperate zone, potatoes are usually planted in early spring, the "seed" tubers being spaced 40–120 cm apart. Entire tubers or large slices thereof are planted "eyes" up, and covered with 10–20 cm of well pulverized soil. Since the potato is highly heterozygous, seedlings, exhibiting wide variability, rarely come true. Hence, potatoes are vegetatively propagated by so-called seed potatoes, ca 4–5 cm in diameter. These are cut up so that each portion contains 1 or 2 eyes. Sprouting buds, especially if sprouted in sunlight, may be planted. Freshly harvested potatoes, on the other hand, being dormant, cannot be planted immediately. Dormancy can be broken by gassing with carbon bisulphide, or soaking in 1.5–3% ethylene chlorohydrin. Xanthine and gibberellic acid are also reported to break dormancy. Cut pieces of non-dormant seed tubers may yield as well as whole tubers where they are not subject to rot. Disinfecting the cutting knife and treatment of the cut seed with Dithane M-45 (1 kg in 450 liters water) is advised in India (C.S.I.R., 1948–1976). Timing, to avoid excess cold or drought during sprouting periods, the "seeds" may be sown in furrows 7–10 cm deep and then covered, level or ridged. Or ridge can be made and tubers inserted. Seed rates may be as high as 2–3.5 MT/ha. Rows are spaced at 40–50 cm, or 60 cm in mechanized fields. Sprouts usually emerge in 2–3 weeks, with emergence complete or nearly so after a month, depending on the maturity of the eye, the cv, and the weather. According to the Wealth of India, where barnyard and green manures are prevalent "Organic manures are no substitute for chemical fertilizers supplying nitrogen, phosphorus, and potassium." An N-deficiency is suggested by stunted plants with short internodes and pale green foliage. Phosphate deficiency reduces plant growth and internodal length, resulting in dull green leaves. A K-deficiency does not reduce growth and vigor in early stages, but the leaves may be bluish green with marginal scorching, eventually bronzing or yellowing. Smith (1981), in the US, suggests N-fertilization at ca 160–260 kg/ha, P2O5 at 110–410, and K2O at 110–325 kg/ha. When stems are 15–20 cm, potatoes may be simultaneously weeded and earth up, making small hills, which at once tends to keep the tubers from greening up (tubers that form near the surface and receive sunlight may green, an undesirable condition) and fosters their growth closer to the main axis. Some organic gardeners in the US plant potato seed on top of composted leaves, then covering the seed potatoes with more compost. This may completely eliminate the weed problem. Potatoes, frequently considered exhausting to the soil, are often planted in rotation with such things as barley, corn, peas, or wheat, or intercropped, with the intercrop in the bottom or edge of the furrows, the potatoes in the ridge. In India, intercrops of castor, sugarcane, and wheat may individually have their yields lowered though the aggregate yield may be favorably improved. Where the golden nematode prevails, long rotations are recommended, with potatoes only every 3 or 4 years. Early potatoes take 80–100 days to mature, medium 100–120, and late more than 120.

Harvesting

Potatoes are usually dug shortly after maturing, when the haulms have yellowed and died back naturally. In home gardens, potatoes are carefully dug by hand, while the large mechanized farms in the US usually defoliate chemically. After lifting, potatoes should be stored to dry and cure in a cool shady place. Seed potatoes and table stock potatoes keep best near 40°C, while potatoes for processing are stored at 7–13°C.

Yields and Economics

The 1979 world low production yield figure for potatoes was 2,000 kg/ha in Swaziland, the international production yield figure was 15,503 kg/ha, and the world high production yield figure was 37,772 kg/ha in the Netherlands (FAO, 1980a). In India, yields average between 7,500 kg to 9,000 kg, with some states averaging closer to 3,000, others closer to 20,000 kg/ha, with maximum at 35,000 (C.S.I.R., 1948–1976). The Wealth of India compares yields for 5 years in 25 countries, West Germany being highest in 1968 with 29 MT/ha, Bolivia and Peru, near, if not, the centers of origin, being lowest with 5.5 and 6.3 MT respectively, cf 24 MT for the US. These are production figures, India coming out with 8.4 MT/ha. Indian yields are doubled with appropriate fertilization from 9 to 16 MT/ha in the Rabi, and from 17 to 36 in the Kharif (Krishnappa et al, 1980). On Cuban ferralitic soils, tuber yields of 17 cvs from Europe ranged from 13–37 MT/ha (Estevez, 1981). Dibb (1983) compares US yields of 26,600 kg/ha with 9,100 kg/ha in the developing countries, and a reported world record of 94,200. Potatoes are grown commercially in every continent, with 70% of the world's production grown in Eastern Europe and Russia. Although the US produces only ca 4% of world production, it is nonetheless an important crop in the US, ranking as the eighth most important crop; 80% of production occurs in nine states, Idaho, Washington, Maine, Oregon, North Dakota, California, Wisconsin, Minnesota, and New York. The total marketed value of potatoes in the US varies between $1.2 to 1.5 billion annually. Prices received by the farmer averaged between $3.01 and $4.89 per quintal between 1972 and 1977 (Smith, 1981).

Energy

According to the phytomass files (Duke, 1981b), annual productivity is 4 MT/ha in Bavaria. According to one source, the residue potential is calculated by multiplying tuber production by 0.2. Processing wastes at factories or at home, where peels are removed, are calculated by multiplying production by 0.1 to 0.2. Rotten potatoes and the 33 1/3% waste in the potato chip industry can be converted to butanol with a greater energy content than ethanol. Twenty percent butanol can be added to regular gas and up to 40% to diesel as extenders without engine modification (Duke, 1984a). Potato wastes are taken to be 3/17ths of tuber weight, while the moisture content of the haulms (not normally gathered) is figured at 77.5% (Palz and Chartier, 1980). Near Twin Falls, Henry Schutte is tooling up to convert 80,000 tons of cull potatoes a year into alcohol. Schutte's Western Resource Recovery is building a $20 million plant with a theoretical capacity of 5 million gallons of alcohol per year and hopes to convert cull potatoes to alcohol at $1.20 per gallon. The corporation plans to feed its stillage (the material remaining after distillation) to cattle and use the cattle manure to generate methane to power its alcohol stills. At the University of Idaho, Gary Kleinschmidt is checking out potato cvs that may produce more than twice as much as most cvs. These high yielders have distorted tubers or hollow hearts, but that should not matter for alcohol production (McGill, 1981). Germans developed the energetic "Fuselol" from potato alcohol (Watt and Breyer-Brandwijk, 1962). Energy output/input ratios vary from 0.83 in Idaho with yields of 26.7 MT/ha to 1.64 in California with yields of 36.7 MT/ha. Discounting 62 hours labor, the energy inputs are roughly in decreasing importance; diesel 3,700,000 kcals, nitrogen 3,000,000, seeds 1,700,000, herbicides 1,200,000, transportation 800,000, gasoline 770,000, phosphorus 640,000, electricity 610,000, insecticides 365,000, L.P. gas 325,000, machinery 250,000, potassium 165,000, and irrigation 135,000, totalling nearly 14 million kcals per ha for the yield of 36,736 kg/ha (622 kg protein) with an energetic equivalent of ca 22,500,000 kcals. In Australia, Stewart et al (1979) estimated that potatoes would give 104 liters ethanol per ton of production at a raw material cost of $1.06 per liter compared to 117 liters at $1.11 per liter for grapes, 67 liters at $2.86 per liter for apples, 57 liters at $1.93 per liter for pears, 55 liters at $3.46 per liter for peaches, 40 liters at $7.53 per liter for apricots, 59 laters at $4.15 per liter for plums, 69 liters at $10.65 per liter for cherries, 96 liters at $3.04 per liter for bananas, and 71 liters at $1.76 per liter for pineapple (when cereal grains for alcohol were worth only $0.20 to $0.23 per liter, and gasoline was retailing for $0.15 to $0.19 per liter). Comparing crops and conifers, Jarvis (1981) concludes, "the actual annual rate of production of the tree crops and the majority of the agricultural crops are very similar." Citing other scientists conclusions that potential production of C3 crops would be 54 MT/ha/yr for a year round crop (of whatever) and would be 36 for 6 months in the Netherlands, Jarvis tabulates the average yields of DM production and the maximal rates for temperate climates as shown below:

British
average DM
yield (MT) 		Maximum
reported DM
(MT) 		Harvest
index
Abies sachaliensis -- 29 0.65
Avena sativa 3.0 -- --
Beta vulgaris 8.0 42 0.45
Brassica oleracea 'calabrese' -- 12 0.17
Brassica rapa 4.6 -- --
Cryptomeria japonica -- 53 0.65
Glycine max -- 10 0.30
Hordeum vulgare 4.7 18 0.39
Larix kaempferi 3.1 8* --
Lolium perenne -- 26 0.85
Picea abies 3.4 22 0.61
Picea sitchensis 3.5 9* --
Pinus contorta 2.4 6* --
Pinus nigra 3.9 25 0.46
Pinus radiata -- 46 0.66
Pinus sylvestris 2.4 7* --
Pseudotsuga menziesii -- 28 0.71
Solanum tuberosum 5.3 22 0.82
Thuja plicata -- 20 0.68
Tsuga heterophylla -- 43 0.65
Triticum aestivum 4.7 30 0.40
Vicia faba -- 20 0.31
*UK only

High rates of 35–45 MT aboveground DM have been reported for some conifers outside Britain, but Jarvis apparently accepts Ovington's (1962) conclusion that the maximum net rate of current annual production of coniferous forest in western Europe might be 22 MT/ha (17 MT stems alone) with a maximum mean net of 15 MT/ha/yr (12 MT stems alone) over the life of the crop. With an assumption that one MT DM is energetically equivalent to 2.5 barrels oil, one can speculate on the relative importance of these conifers and crops in an energy crisis.

Biotic Factors

Smith (1981) estimates loss from potato pathogens at 19%, or 2.7 million metric tons, annually in the US. Virus diseases include leaf roll, rugose mosaic, mild mosaic, and latent mosaic. Late blight, early blight, common scab, Verticillium wilt, and Rhizoctonia are prevalent fungus diseases. Bacterial diseases such as blackleg, ring rot, and bacterial soft rot are also common. Disease control measures include (1) use of resistant cvs; (2) use of certified seed; (3) roguing of diseased plants; (4) crop rotation; and (5) use of pesticides. Fungi and bacteria include Alternaria solani, Armillaria mellea, Ascochyta lycopersici, Aspergillus niger, Bacillus megatherium, B. mesentericus, Bacterium polymorphum, Botrytis cinerea, Cercospora concors, C. solani, Clonostachys araucariae var. rosea, Colletotrichum atramentarium, Corynebacterium sepedonicum, Cuscuta arvensis, Cylindrocarpon magnusianum, C. radicicola, Erwinia aroideae, E. phytophthora, Erysiphe cichoracearum, Fusarium spp., Gliocladium sp., Gloeosporium sp., Hypomyces ipomoeae, Macrophomina phaseoli, Mycosphaerella solani, Nectria brassicae, Neocosmospora vasinfecta, Oidium sp., Oospora pustulans, Papulaspora coprophila, Pellicularia filamentosa, Penicillium sp., Phoma dulcamarina, P. eupyrena, P. solanicola, P. tuberosa, Phomopsis tuberivora, Phymatotrichum omnivorum, Phytophthora drechsleri, P. erythroseptica, P. infestans, P. parasitica, Pseudomonas solanacearum, Pythium aphanidermatum, P. arrhenomanes, P. debaryanum, P. rostratum, P. ultimum, Ramularia solani, Rhizoctonia crocorum, R. solani, Rhizopus stolonifer, Scierotinia sp., S. minor, S. sclerotiorum, Sclerotium rolfsii, Septomyxa affinis, Spondylocladium atrovirens, Spongospora subterranea, Streptomyces scabies, Stysanus stemonitis, Synchytrium endobioticum, Trichothecium roseum, Verticillium albo-atrum, V. cinnabarium, Xylaria apiculata (Ag. Handbook No. 165, 1960). The many nematodes that attack potatoes include: Ditylenchus destructor, Globodera pallida, G. rostochiensis, Meloidogyne spp., Pratylenchus penetrans, and P. pratensis. In the US, potatoes are injured by more than 100 species of insects, especially the Colorado potato beetle. It and the flea beetle reduce yields by feeding on the foliage. The potato aphid attacks the foliage and also spreads several viral diseases. Potato leaf hoppers cause a destructive disease-like condition known as hopperburn by sucking juices from the plants. The tubers are attacked by wireworms, often rendering the potatoes unsuitable for sale. General pest control is afforded by applications of insecticides to the foliage or soil (Smith, 1981). Chemicals are important in weed control and harvesting. Weeds and annual grasses are controlled by cultivation and by preemergence and/or post-emergence soil application of weedicides such as premerge, linuron, maloran, eptam, dalapon, paraquat, and metribuzin. Various dusts and sprays, including dinoseb, endothall, ametryn, and paraquat, are used to kill the potato vines before harvest. The vines are killed to hasten setting of the potato skin in order to reduce harvesting damage and to facilitate the use of harvesting machinery (Smith, 1981).

References

Complete list of references for Duke, Handbook of Energy Crops
Last update Friday, January 9, 1998 by aw