Chemical techniques for control of stem canker and black scurf (Rhizctonia solani) disease of potatoes

Thiabendazole, iprodione and benodanil were tested for control of stem canker and black scurf disease of potatoes using seed tubers with or without black scurf planted in soil infested or not with Rhizoctonia solani . Dormant seed tubers were treated with fungicide dusts, dips or sprays and before planting dusts were applied to soil or to sprouts on seed tubers.
Plants grown from seed tubers with black scurf had more stem canker, stolon infection and Thanatephorus cucumeris and progeny tubers had more black scurf than from seed without black scurf. Infesting soil with R. solani increased black scurf but not stem canker or stolon infection.
Fungicide treatment of seed tubers controlled all phases of the disease and sprout and soil treatments also had significant effects. Numbers of tubers in July were usually increased by treatment although by harvest many small tubers (>3 cm) had been resorbed. Fungicide treatment substantially increased yield only when shoot tips were pruned by R. solani .
Regression analyses showed that stolon pruning, Thanatephorus and black scurf were significantly related to stem canker, and numbers of tubers in July but not in September were inversely related to stolon pruning.
The significance of sources of inoculum and the effects of controlling disease on tuber production are discussed in relation to methods of fungicide use.     

Effects of black scurf (Rhizoctonia solani) on potatoes

King Edward and Majestic seed tubers, selected as ‘clean’ (macroscopically symptomless), moderate and severe according to the extent of black scurf, were planted in field experiments at Rothamsted between 1964 and 1968. Seed infection sometimes delayed plants emerging but did not affect final plant populations. Crops from severely diseased seed yielded, on average, 7% less than ‘clean’ tubers (King Edward 6–8% less and Majestic 0–20% less). Seed infection affected tuber size distribution; compared with ‘clean’ seed, severely infected King Edward seed yielded slightly more chats (< 1 ½ in, 3.8 cm) and 1.5 ton/acre (3.8 t/ha) less large tubers (2 ¼–3 ¼ in, 5.7–8.3 cm). The effects were similar with Majestic although differences were smaller. However, total yields from diseased stocks (unselected) seldom differed significantly from the ‘clean’ tubers selected from them. Crops from moderately and severely diseased seed had more Corticium on stems and black scurf on tubers and usually less Oospora pustulans than from ‘clean’ seed.     

Control of silver scurf (Helminthosporium solani) disease of potato with benomyl and thiabendazole

Benomyl and thiabendazole, applied as dusts to seed potatoes before chitting (sprouting), reduced the incidence of silver scurf disease on the progeny at lifting and during subsequent storage. Treatment of seed tubers 4 months prior to planting almost completely suppressed sporulation during storage, even under conditions very favourable for the growth of the fungus. The fungicides appeared not to act systemically because developing tubers grown from treated seed were just as susceptible to infection after inoculation as those from untreated. Control was due to effective inhibition of sporulation on the surface of diseased seed tubers after planting. There was no reduction in the amount of disease in subsequent generations of potato crops without further fungicidal treatment. Seed virtually free from silver scurf, produced from seed treated with fungicide in the previous year, yielded progeny with as much disease as progeny from untreated seed stocks.     

Controlling potato tuber blemish diseases on cv. Estima with chemical and non-chemical methods

In 3 years, seed tubers were treated or not with imazalil in March or April, sprouted and planted in field experiments. Tubers were harvested on several dates and cured under different conditions for 2 wk, or not cured, before storage for 6 months. In some years effects of irrigation, seed tuber size and seed stock were tested. Fungicide seed treatment decreased silver scurf, and was most effective in 1989 when the seed had little infection and the season was dry, but the treatment increased black dot. Silver scurf and black dot were decreased by harvesting early and also by drying tubers before storage (dry curing), and these practices also sometimes decreased black scurf and skin spot. The effects of fungicide seed treatment and of dry curing were greater the earlier the tubers were harvested. Irrigation decreased silver scurf and in one year decreased black scurf but greatly increased black dot. Silver scurf, black dot and skin spot were more common on tubers from large than small seed whereas black scurf was most common on tubers from small seed. In 2 years tubers were affected with a brown superficial blemish (golding blotch). This developed on the undersides of tubers in soil and was decreased by irrigation. Its cause is not known.     

Effects of rotation length, fungicide treatment of seed tubers and nematicide on diseases and the quality of potato tubers

In 1982 – 88, potatoes were grown in 2-, 4- and 6-course rotations with spring barley on a field infested with Globodera rostochiensis. Severity of stem canker and black scurf increased with increasing frequency of previous potato crops, and seed tuber treatment with tolclofos-methyl became less effective in controlling diseases. This suggested that previous crops had increased the amounts of soil-borne inoculum of Rhizoctonia solani. Oxamyl soil treatment increased stem canker in one year and decreased black scurf in four years. Seed tuber treatment with imazalil or prochloraz decreased stem base infection by Polyscytalum pustulans and skin spot and silver scurf on tubers. Black dot was prevalent on tubers in all years and was not affected by seed tuber treatment or previous cropping. Oxamyl increased black dot and common scab in five years and decreased % tuber dry matter in six years. Cysts of G. rostochiensis were found attached to Désirée but not to Maris Piper tubers in August. At harvest tubers of both cultivars were affected by superficial pitting and its severity was related to soil populations of G. rostochiensis at planting. This damage was controlled by oxamyl. It is suggested that the pitting developed from holes made in the tuber skin at larval invasion. In 1989, Désirée seed tubers and healthy mini tubers were planted in all plots and severity of stem canker and black scurf increased with increasing proximity of previous potato crops and with the number of previous crops. Black dot on stems and tubers was not affected by previous cropping but was much less severe in a plot that had not grown potatoes during the seven years of the experiment. The severity of common scab generally decreased as the number of preceding potato crops increased.     

Black scurf and stem canker of potato (Corticium Solani Bourd. & Galz.)

Black scurf and stem canker of the potato was investigated in field trials on infected soil at Warburton, Cheshire, to study the effect of planting clean and contaminated seed, and the relation between the dates of planting and lifting and the contamination of the crop tubers.
Black scurf was prevalent on crops grown from clean seed but was more severe on crops raised from contaminated seed. Under conditions favourable for the disease the yields from clean and contaminated seed were satisfactory and were not significantly different. Young shoots of plants from contaminated seed were severely attacked and tuber formation was checked; these results were not obtained on clean seed plots.
More black scurf occurred on late-dug crops; on early-dug plots the disease, although almost absent in 1941, was prevalent in 1942. Late planting failed to reduce appreciably the amount of black scurf.
Variety trials included Arran Banner, Kerr's Pink (two vigorous varieties), King Edward and Majestic (two less vigorous varieties). All were heavily infected and each recovered well from an attack on the young shoots.
Inoculation of the seed at planting time did not affect the results; in all trials, misses and wilted shoots caused by Corticium were rare and there was no relation between the yield and the amount of black scurf on the crop tubers.
The results indicate that the disease causes little, if any, loss under farm conditions.     

A PCR-based method for detection of potato pathogen, Helminthosporium solani, in silver scurf infected tuber tissue and soils

Silver scurf caused by Helminthosporium solani causes significant economic losses in table stock, seed and processing potatoes. Specific polymerase chain reaction (PCR) primers, Hs1F1/Hs2R1, from H. solani were used for the amplification of a 447-bp product from 20 tissue samples and 54 single spore H. solani isolates, from eastern Canada (27 isolates), western Canada (13 isolates) and North Dakota in USA (14 isolates), but not from other potato fungal pathogens. In addition to PCR analysis, all 54 isolates were studied using conventional detection methods, visual disease symptoms and/or colony morphology and microscopic examination of the morphology of conidiophores and conidia. The PCR assay successfully detected H. solani and the PCR results correlated well with assessments based on conventional techniques. The detection of H. solani by PCR (1 day) is rapid and offers an alternative to the time consuming conventional diagnostic techniques (4-5 weeks). Nested PCR assay was necessary for the detection of H. solani in soils and thus can provide a sensitive technique to study the epidemiology of silver scurf in soils.     

Stem canker (Rhizoctonia solani) on five early and seven maincrop potato cultivars I. Infection of shoots, stolons and tubers

In 1983 and 1984, potato seed tubers of five early and seven maincrop cultivars were inoculated with cultures of Rhizoctonia soluni during planting to simulate severe seed infection. Shoot and stolon infection was assessed in June-August and black scurf on tubers recorded after harvest in October. Almost all shoots of all cultivars had stem canker in both years and disease on shoots, stolons and tubers was more severe in 1984 than in 1983. In 1983 similar amounts of disease developed on all early cultivars and between 11% (Ulster Sceptre) and 32% (Maris Peer) shoots were pruned off. Maris Peer had a stem canker score lower than other cultivars in 1984 but more than half the shoots were pruned off. Shoot pruning on Estima, Ulster Prince and Ulster Sceptre was more common on plants from sprouted than non-sprouted seed. Between 30 and 50% of stolons were pruned off. After harvest in 1985, black scurf was least prevalent on Arran Comet and Maris Peer tubers and in 1984 on Arran Comet and Estima tubers from non-sprouted seed. Of the maincrop cultivars, King Edward plants from sprouted seed had many shoots pruned off in both years. Shoot pruning was also prevalent on Maris Piper and Pentland Squire plants from non-sprouted seed. Record had fewest pruned shoots and stolons and the lowest stem canker score. The disease was more severe on Pentland Crown and Maris Piper plants from non-sprouted than sprouted seed. Black scurf was most common on Cara and King Edward tubers in 1983 and on King Edward and Record tubers in 1984. In both years few shoots but many tubers were infected on plants from non-inoculated seed and the significance of this is discussed.     

Control of skin spot and silver scurf on stored cv. King Edward potatoes by chemical and non-chemical methods

In 3 years, seed tubers of cv. King Edward were planted in field experiments and diseases assessed on the daughter tubers after storage for 24–26 wk. In 1991 and 1992, the seed tubers were treated with a mixture of thiabendazole and imazalil at two rates. Tubers were harvested on several dates from late August to early October and dried under different conditions before storage. In 1990, silver scurf after storage was decreased equally by dry curing for 2 wk and windrowing for 2 h whereas skin spot was decreased most by dry curing, and these effects were greater the earlier tubers were harvested. In 1991, dry curing for 2 wk decreased skin spot and silver scurf more than dry curing for 1 wk, and skin spot was slightly decreased by windrowing for 2 h; windrowing improved the control of both diseases when tubers were subsequently dry cured. In 1991 and 1992 fungicide treatment of seed tubers greatly decreased skin spot after storage and was also effective against silver scurf, but increased black dot when tubers were harvested in September or October. Skin spot was controlled equally well by the two rates of fungicide but silver scurf was less well controlled when the dose was decreased by 75%. It is suggested that amounts of fungicide applied to seed tubers could be decreased provided that the efficiency of application is improved and that crops are harvested early and dried before storage.     

Stem canker (Rhizoctonia solani) of maincrop potatoes.

In two years, potato plants were sampled at 1- or 2- weekly intervals from plots planted with seed tubers bearing sclerotia of Rhizoctonia solani (black scurf) and with seed without sclerotia either infested or not with cultures of R. solani at planting. Sprouted King Edward seed was used in 1981 and sprouted and non-sprouted King Edward and Pentland Crown seed in 1982. In both years 60–80% of shoots from seed with sclerotia and 90% of shoots from seed inoculated at planting were affected with stem canker. Most disease developed before shoots emerged although it gradually increased later when new shoots arising both from seed tubers or as branches on shoots with damaged apices (pruned shoots) became infected before they emerged. Sprouting seed tubers bearing sclerotia decreased the disease on both cultivars but with soil-applied inoculum the disease was more severe on plants from sprouted than non-sprouted seed. Some stolons were infected by R. solani soon after they developed and incidence of infection later increased. Thirty to 50% of stolons were infected on plants from infected seed tubers and 60% on plants with soil-applied inoculum. With both cultivars and sources of inoculum about 70% of the infected stolons had their apices killed (pruned).     

The effect of treating seed potato tubers with benzimidazole, imidazole and phenylpyrrole fungicides on the control of rot and skin blemish diseases

Over 6 yr the effectiveness of imazalil, prochloraz and fenpiclonil, applied either alone or in a mixture, in controlling gangrene, dry rot, skin spot and silver scurf on potato tubers in store was compared with that of 2-aminobutane and thiabendazole. An assessment was also made of their efficiency in controlling the development of these diseases on the daughter tubers of seed tubers treated at harvest or before planting. Overall, 2-aminobutane was more effective in controlling gangrene (Phoma foveata) in store than the spray-applied fungicides. Deposits of imazalil, thiabendazole and fenpiclonil were greater when sprays were applied with an electrostatic sprayer than with a hydraulic sprayer. The opposite was found with the mixture of prochloraz Mn and tolclofos-methyl. More effective gangrene control was associated with the highest deposits. Fenpiclonil and the mixture of thiabendazole and imazalil were more effective in controlling dry rot (Fusarium solani var. coeruleum) than imazalil alone. The development of dry rot was, however, increased by 2-aminobutane treatment on eight out of 14 stocks. 2-aminobutane gave the greatest reduction (83%) in the severity of skin spot during storage whereas thiabendazole alone, and the mixture of thiabendazole and imazalil, gave mean reductions of 70% and 65% respectively. This mixture and fenpiclonil gave the greatest reduction in the severity of silver scurf although, in general, reductions in silver scurf with fungicide treatment were less than with skin spot. The type of sprayer used to apply a fungicide did not affect the effectiveness of the fungicides in controlling either skin spot or silver scurf on tubers in store, or on the daughter tubers. The incidence of gangrene and dry rot on daughter tubers was not reduced consistently by fungicide treatment of seed tubers of the six stocks tested. However, the severity of skin spot and silver scurf was reduced by fungicide treatments of all eight stocks but the reduction in disease was greater for skin spot than for silver scurf. All fungicides gave reductions in the severity of skin spot, and fenpiclonil and the mixture of thiabendazole and imazalil were the most effective for silver scurf. The effectiveness of the fungicides in controlling these diseases was similar for seed treated at harvest and that treated before planting.     

The Influence of the Inoculum Source of Rhizoctonia solani on Development of Black Scurf on Potato

Rhizoctonia solani, the causal agent of stem canker and black scurf on potato, survives as sclerotia on tubers, in soil and in plant residues. The objective of the present study was to evaluate the importance of inoculum source on disease development. Disease‐free minitubers and seed tubers contaminated with low levels of R. solani were planted in fumigated or artificially inoculated growth mixture in greenhouse experiments. Black scurf incidence and severity were significantly higher when the inoculum was present in both seed tubers and soil, compared with either of them separately. The severity of disease symptoms on the subterranean parts of the plant also were significantly higher in plots where both seed tubers and soil were contaminated, compared with plots where the inoculum source was either the seed tubers or the soil. Thus, both major sources of inoculum, seed tubers and soil, are important in disease development. However, when both sources are present, black scurf incidence and severity are increased, leading to economical damage to tuber yield and quality. Additional results from field trials support these findings. Disease incidence and severity on daughter tubers were correlated with levels of contamination in seed tubers and soil. When seed tubers and soil were heavily infested, the levels of black scurf incidence and severity on daughter tubers were very high; when seed tuber and soil infestation were very low, black scurf incidence and severity on progeny were also lower. Disease levels were reduced by in‐furrow fungicide treatment, but were less effective when the initial levels of the fungus on the seed tubers and in the soil were high.     

Black scurf and stem canker of potato (Corticium Solani Bourd. & Galz.): Further field studies on the use of clean and contaminated seed potatoes and on the contamination of crop tubers

Black scurf and stem canker of the potato were investigated in field trials in contaminated soil at Warburton, Cheshire, to determine the effect of planting clean and contaminated seed (vars. Arran Banner and Majestic) on crop yield and on the contamination of the crop tubers.
Black-scurf contamination was prevalent on crops grown from clean seed and was not significantly different from that occurring on plots planted with contaminated seed. It was severe on early-dug tubers, but was more severe on late-dug tubers. Produce grown with and without stable manure was heavily contaminated.
Contaminated seed caused a check to tuber formation and an appreciable increase in stem canker and in the number of primary shoots killed. Nevertheless, the yields from the manured, contaminated seed plots were satisfactory and were not lower than those from the clean-seed plots. There was no relation between the yield and the amount of black scurf on the produce.
The results of a trial made in a field which had been in grass for at least 43 years, suggested that the soil contained little, if any, Corticium Solani. Heavy contamination occurred on tubers grown under relatively dry soil conditions.
In all the trials misses and wilted shoots caused by Corticium were rare and there was no premature yellowing or death of the haulms on the clean or contaminated seed plots.
The evidence obtained in the four seasons from 1941 to 1944 indicates that in this country satisfactory yields of early maincrop and maincrop varieties may be obtained despite the prevalence of C. Solani in the soil and on the seed, provided the soil and cultural conditions are reasonably good.     

The effect of irrigation on powdery scab and other tuber diseases of potatoes

In field experiments seed tubers affected with powdery scab cankers were planted and the effect on disease incidence of timing of irrigation and some seed-tuber fungicides was investigated over 3 yr. For 2 yr, irrigation to maintain soil wetter than—20 centibars (—20 kPa) during the first half of the growing season increased disease compared to unirrigated plots. Disease incidence was not affected by irrigation at 2 wk intervals or when applied during the second half of the season. Little disease developed in 1983 even in irrigated plots, probably because of high soil temperatures. None of the fungicides tested gave consistent disease control. Common scab and silver scurf were both decreased by irrigation but in two years, black dot was increased. The relative importance of black dot could increase in irrigated crops where fungicides are used to control silver scurf.     

Treatment of seed and ware potato tubers with thiabendazole for control of storage diseases

In March 1977 and 1978 King Edward seed potatoes from three commercial stocks and one stock derived from stem cuttings (healthier seed) were treated with thiabendazole at 320 g a.i./t and 46% of the material applied was deposited on tubers. Seed was stored on trays to sprout and in April samples were planted in replicated plots on two farms in Lincolnshire. Treatment did not consistently affect numbers of stemslplant or total yields but decreased infection of underground stems by Polyscytalum pustulans and Rhizoctonia solani and of tubers at harvest by P. pustulans, R. solani and Helminthosporium solani. In samples stored for 20 wk at Sutton Bridge Experimental Station seed treatment decreased the incidence of skin spot from 25 to 4%, of black scurf from 36 to 20% but had less effect on silver scurf (untreated 52% tubers, treated 47%) and did not affect the incidence of black dot (Colletotrichum coccodes) on stored tubers. In another series of experiments 1 t samples of seed from six King Edward stocks (1977) and four King Edward and one Maris Piper stocks (1978), collected from different farms in Lincolnshire in March, were treated with thiabendazole at 40 g a.i./t. Tubers retained 48% of the material applied. The treated seed was planted on the respective farms in a single large plot adjacent to untreated seed similarly stored and sprouted. Seed treatment significantly decreased the incidence of skin spot, black scurf, silver scurf and gangrene in tubers stored at Sutton Bridge in 1977–78. After lifting the experiment in 1978 samples from treated and untreated seed were treated with thiabendazole (40 g a.i./t) before storage (ware treatment). Skin spot was decreased more by seed treatment than ware treatment whereas silver scurf was controlled best by ware treatment. Incidence of black dot was not consistently affected by seed or ware treatment.     

Effects of treating seed potatoes from commercial and stem cutting stocks with benomyl, thiabendazole and 2-aminobutane on yield and disease

Potato seed tubers of six cultivars from commercial stocks and from stocks derived from stem cuttings (healthier seed) were fumigated with 2-aminobutane 2 wk after lifting or treated with benomyl or thiabendazole in January. 2-aminobutane prevented skin spot and gangrene developing on treated tubers. Experiments were planted at Rothamsted (clay with flints soil) and at Woburn (sandy loam soil) in 1973–75. Healthier seed produced more stems/plant than commercial stocks and yielded on average 8% more at Rothamsted in 1973 and 1974 and respectively 5 and 10% more at Woburn in 1973 and 1975. Seed treatments did not consistently affect stem numbers or increase yield although all treatments tended to decrease tuber size. Infection of stem bases and tubers by Polyscytalum pustulans and Rhizoctonia solani was usually less from healthier than from commercial seed and was decreased by benomyl and thiabendazole in 1973 and 1974. Infection by Helminthosporium solani of the skin around tuber eyes was greater from healthier than from commercial seed but was decreased by benomyl and thiabendazole. 2-aminobutane sometimes decreased infection of tubers by P. pustulans and R. solani but neither of stem bases nor of tubers by H. solani. Gangrene on tubers uniformly wounded at lifting was not consistently affected by seed source or seed treatment. Treating seed with benomyl or thiabendazole in 1975 decreased skin spot and black scurf in tubers stored until March 1976. These treatments also decreased silver scurf on the produce of commercial seed at Rothamsted but gangrene was not consistently affected by seed treatments.     

Stem canker (Rhizoctoniu solani) on three early and three maincrop potato cultivars: effects of seed tuber size on growth and yield

Large seed tubers (mean 134 g) and small seed tubers (50 g) of three early and three maincrop potato cultivars, spaced respectively 48 and 30 cm apart within rows, were inoculated with Rhizoctonia solani at planting in 1985 and 1986. All seed of early cultivars was sprouted and maincrop seed was either sprouted or not sprouted. In all cultivars, plant emergence was slower from small than large seed and with both was delayed by inoculation. From 11 wk after planting numbers of stems and tubers and weights of foliage and tubers/m² were usually similar from small and large seed when not inoculated, but inoculating delayed plant growth and decreased tuber numbers and yield more from small than large seed. Inoculating decreased mean yields from large and small seed of early cultivars at 11 wk by respectively 24% and 31% (Arran Comet), 12% and 18% (Estima) and by 10% and 28% (Wilja) and losses were greatest with saleable sized tubers (3–4 cm). When grown to maturity inoculating decreased yields by 7% (Arran Comet), 5% (Estima) and 14% (Wilja). With maincrop cultivars, yields in October from large and small seed were decreased by respectively 4% and 10% (DCsirke), 9% and 12% (Maris Piper) and by 14% and 22% (Pentland Squire). In all cultivars yields of tubers < 44 mm and 44–70 mm were decreased and, with Pentland Squire, tubers > 82 mm were increased. The incidence of stem canker and of black scurf on progeny tubers was not affected by seed size but in all cultivars the percentage of greened tubers was slightly increased by inoculation.     

The development of silver scurf (Helminthosporium solani) disease of potato

The main source of inoculum of Helminthosporium solani was the seed tuber; the fungus was not detected in soils in which infected potatoes had been grown the previous year. Lesions spread rapidly on seed tubers after planting, so that within a few weeks the entire surface was covered. As lesions aged they lost the capacity to sporulate, so most inoculum was produced in the first few weeks after planting. Infection of progeny tubers was first detected at the heel (stolon attachment) end soon after their initiation. Once established, lesions spread slowly on the surface of progeny tubers when in the soil; more rapid spread took place during storage. Potatoes which seemed unaffected at lifting became diseased during storage.     

类芽孢杆菌QHZ11对马铃薯黑痣病的生防效果

[背景] 马铃薯黑痣病是由立枯丝核菌（Rhizoctonia solani）引起的一种典型土传病害,目前该病害生物防治的菌种资源比较有限,相应菌株生防机制的研究更是缺乏。[目的] 明确马铃薯黑痣病病原菌立枯丝核菌（R. solani） JT18的拮抗菌QHZ11对马铃薯黑痣病的生防效果,揭示QHZ11对黑痣病的部分防治机理。[方法] 在灭菌土壤中分别接种R. solani JT18（CK）,R. solani JT18和普通有机肥（Organic Fertilized,OF）,R.solaniJT18和氨基酸有机肥（AA+OF）及R. solani JT18和QHZ11生物有机肥（BOF11）,结合实时荧光定量PCR （Real-Time Fluorescence Quantitative PCR,RT-qPCR）等方法,研究马铃薯全生育期不同处理R.solaniJT18在马铃薯根际和植株不同部位的数量变化及拮抗菌QHZ11与R.solaniJT18的数量消长规律,同时比较不同处理黑痣病的病情指数及相应的防效。[结果] RT-qPCR结果表明,随马铃薯生育进程的推进,马铃薯根际、根系和匍匐茎R.solaniJT18的数量在各处理中均呈现先升高至块茎膨大期到达峰值后下降的趋势,而且各部位R.solaniJT18的数量为CK>OF>AA+OF>BOF11且根际>根系>匍匐茎;拮抗菌QHZ11的数量变化趋势与R.solaniJT18相同,但峰值在块茎形成期,并且同时期同一部位QHZ11的定殖数量均显著高于R.solaniJT18,甚至高出2个数量级,说明QHZ11占用了一定的营养资源和生态位点,严重抑制了R.solaniJT18的生长和繁殖。病情结果表明：CK病情指数最高,OF、AA+OF和BOF11处理均显著低于CK,其中BOF11处理发病最轻;生防结果则相反,为BOF11>AA+OF>OF处理,说明普通有机肥、氨基酸有机肥及生物有机肥均可不同程度地防治马铃薯黑痣病,其中以生物有机肥效果最显著。[结论] QHZ11以有机肥为载体施入土壤后,可以通过在马铃薯根际及植株不同部位竞争营养和生态位点,从而有效抑制黑痣病病原菌R.solaniJT18的生存和繁殖,起到显著的生防效果,这对QHZ11生物有机肥的应用和推广具有重要意义,并为进一步研究QHZ11的生防机制奠定了基础。     

播种期和种植密度对冬油菜籽粒产量和含油率的影响

通过田间试验研究了播种期和种植密度对冬油菜籽粒产量和含油率的影响.结果表明： 播种期主要影响分枝花序籽粒产量,而种植密度不仅影响分枝花序籽粒产量,还对主花序籽粒产量产生一定影响;籽粒含油率不受播种期的影响.主花序籽粒产量占单株籽粒产量的比例随种植密度的增加而升高,主花序籽粒含油率比分枝花序高约1%,因此小区籽粒含油率随种植密度的增加显著升高.研究区冬油菜播种期不能晚于10月中旬,10月下旬播种会显著降低籽粒产量;种植密度在每平方米36～48株可以提高冬油菜籽粒产量和含油率.