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1.
Field trials were conducted in 1997 and 1998 wet seasons to determine the effect of seed treatment of different sorghum varieties with brine (NaCl) on the control of Striga hermonthica in sorghum. The varieties of sorghum used were ICSV 1002, ICSV 1007 (improved resistant varieties from ICRISAT, Mali), BES (a local improved variety), and War-warabashi (a local susceptible variety). Different concentrations of brine at 0.5, 1.0, 1.5, and 2.0 M were used. The results show that the varieties, ICSV 1002 and ICSV 1007 had significantly higher establishment count than the BES and War-warabashi varieties, but had shorter plants. Similarly, the ICSV 1002 and ICSV 1007 and War-warabashi varieties had significantly larger LAI values than the BES variety, although the BES significantly out yielded them. The susceptible War-warabashi variety supported the highest number of Striga emergence than the improved varieties. The effect of brine treatments on plant establishment, growth and yield of sorghum under Striga infestation shows that there was a decrease in crop stands with increase in brine concentration, with the least value at 2.0 M brine treatment, which was damaging at this rate. Plant height and, leaf area index (LAI) of sorghum increased with increasing concentration of brine to a maximum at 1.5 M and declined at 2.0 M brine treatment. The 1.5 M brine treatment produced the highest grain yield. Striga shoot emergence significantly declined with increasing brine concentration reaching the lowest values at 1.5 and 2.0 M brine treatments. The interaction between sorghum varieties and brine concentrations shows that War-warabashi with 1.5 M brine treatment had the tallest plants and largest LAI, while BES and 1.5 M brine produced the highest grain yield. In general, the interaction between the varieties and all the brine concentrations significantly reduced Striga emergence. Irrespective of the sorghum varieties the use of brine at 1.5 M was found optimal for controlling Striga emergence resulting in increased crop growth and grain yield. This implies that which ever variety farmers are using either resistant, tolerant or susceptible, they could easily use brine at 1.5 M to effectively control Striga and increase in grain yield. The mechanism by which brine successfully controlled Striga, is, however, not clear and needs to be investigated. 相似文献
2.
High herbicide levels can be localized on or near seed of acetolactate synthase (ALS) resistant maize (Zea mays). The magnesium salt of imazapyr was optimal for seed dressings (drenching, priming, and coating), for preventing field damage from parasitic Striga hermonthica (witchweed) in three seasons. Striga emerged on untreated maize from 6 to 12 weeks after planting. There was almost no Striga emergence for 3 months on imazapyr-dressed homozygous ALS-R 3245IR maize seeds. Occasional Striga that emerged and flowered formed no seed by harvest. Dust or polyvinylpyrrolidone adhesive coatings were safer in maize and as effective in Striga control as priming. Seed dressing coupled with pulling Striga escapes reduces infestation and can be used to deplete the Striga seed bank until genetic crop resistance becomes available. 相似文献
3.
Farmers in Africa have limited resources to invest in Striga control practices and longer term, low-input approaches are needed. Long-term Striga control approaches focus on controlling the production of new Striga seeds and on reducing the number of seeds in the soil. Several seasons of hand weeding are required before the beneficial effect on the cereal crop can be observed. Rotations with trap crops can reduce Striga seed banks but selection of a rotation crop should be based on socio-economic factors such as market value in addition to whether or not it can stimulate Striga seeds to germinate. Striga seed banks can be readily reduced in suppressive soils. Organic matter and fertilizer additions may help induce suppressiveness. Extension of long-term Striga control approaches requires intensive interaction with farmers. 相似文献
4.
Twelve samples of Striga hermonthica seed were collected from four host crops [millet (4), sorghum (4), a sorghum/millet intercrop (3) and maize (1)] from all the main areas of S. hermonthica infestation in Nigeria and were tested on eight genotypes of three test crops [maize (4), sorghum (2) and millet (2)] in two screenhouse trials. Plants of each test genotype were sown in pots and heavily infested with S. hermonthica. Emergence count of the parasite, test crop damage rating (1–9), and test crop plant height were measured at 9 weeks after planting. The effects of genotypes, samples and their interaction for all three traits measured were highly significant (p = 0.001). Of the 12 samples of S. hermonthica, all have high emergence on both maize and sorghum. Seven samples gave low emergence on millet genotypes and two none at all. Three of the four samples from millet sources gave higher parasite emergence on sorghum and maize than on millet. For Striga damage rating, millet had the lowest average scores, followed by maize and sorghum. The responses of maize genotypes to samples from millet and sorghum sources were significantly different. Millet genotypes also had different responses to the samples from millet sources. For plant height differences, samples from sorghum sources interacted significantly with test maize genotypes, and millet samples with sorghum genotypes. The results indicate that both intercrop and intracrop strains of S. hermonthica are present in Nigeria. 相似文献
5.
EPTC was tested in glasshouse and field experiments for its potential as a herbicide to control Bromus species in winter cereals. Bromus hordeaceus, Bromus commutatus, Bromus pectinatus and Bromus sterilis were all selectively controlled in barley by EPTC. Winter wheat was found to be susceptible but winter barley tolerated doses up to 2·0 kg a.i./ha. The barley cultivar Sonja was more resistant than both Athene and Maris Otter. In the first field trial, 1·0 kg a.i./ha EPTC reduced B. sterilis plant numbers by 75% giving a barley yield increase of 2·84 t/ha. In the following year 2·0 kg a.i./ha reduced B. sterilis numbers by 54% and increased yield by 1·75 t/ha. 相似文献
6.
Zusammenfassung Die physiologische Alterung der Pflanzknollen durch Lagerung bei überoptimalen Temperaturen (jahresunterschiedlich 16–29,5°C,
1988–90 vor dem Pflanzen abgekeimt, 1991 vorgekeimt wie Kontrolle) führte im Vergleich zur vorgekeimten Kontrolle im Mittel
von 25 Sorten in allen Versuchsjahren zu einer Verminderung der Bestandesdichte und des Ertrages. Eine Gruppe von Sorten erwies
sich in allen Jahren als relativ tolerant gegen die Alterung, eine andere als signifikant empfindlicher, dazwischen lag ein
breites Mittelfeld mit zum Teil erheblichen Schwankungen in den Jahren. Die Reaktion der Sorten zeigte keine Beziehung zu
ihrer Reifegruppe und ihrer Keimintensit?t, dagegen war die sortentypische Ertragsdepression nicht sehr eng, aber signifikant
mit dem Schwund w?hrend der Lagerung korreliert.
Summary Seed tubers were stored at above optimal temperatures. Mean temperatures varied during test years from 16 to 29.5°C (in 1988–1990 tubers desprouted before planting; in 1991 chitted tubers as in control; Table 1). This procedure of physiological ageing of seed tubers resulted in reduced plant density and lower yield compared to the chitted control in every year of the test period (average of 25 cultivars). The emergence was significantly delayed as compared to the control in all years (Table 2). Assessed for yield, the cultivars Désirée, Sanetta, Astilla and Andra showed a significantly higher degree of tolerance to warm storages (>80%, when compared to the control) than the cultivars Arkula, Dorisa, Karlena and Koretta (<25%; Table 3). Between these two extremes there was a large number of intermediate levels of tolerance, a result of fluctuating reactions of various cultivars to changing conditions in the years of the test period (Fig. 1). No correlation could be found between the cultivars' reactions and their maturity group or their sprouting behaviour. There was, however, for each cultivar a significant negative correlation between loss in weight through transpiration and respiration and plant density and yield (r=−0.55 and −0.54; Table 4). Plant density and yield were closely correlated (Table 4). The regressions between loss of plants and reductions in yields show that after seed tuber storage at higher temperatures a reduced yield must be expected even when plant density is not reduced (loss of plant 0%; Fig. 2). With complete stands, the use of physiologically aged seed tubers that were desprouted before planting (1988–1990) resulted in a reduction of yield of 17–20%; when old seeds were chitted as in control a loss in yield of 15% was calculated.相似文献
7.
水稻潜根线虫的致病性和综合防治技术 总被引：10，自引：1，他引：9
接种试验证实潜根线虫侵染水稻能引起减产,主要是减少有效穗和千粒重;返青期为感病期,这一时期每株稻苗接种300条和470条潜根线虫,分别减产8.8%和13.5%。综合防治措施包括烟 稻轮作、稻草还田、冬翻冬种、利用耐病品种和药剂防治。返青期为防治适期。 相似文献
8.
The long-term approach to parasitic weeds control: manipulation of specific developmental mechanisms of the parasite 总被引：11，自引：0，他引：11
Daniel M. Joel 《Crop Protection》2000,19(8-10):753-758
Parasitic weeds pose a tremendous threat to world agriculture, mainly because they are at present almost uncontrollable. The root parasites Striga (witchweed) and Orobanche (broomrape) are vicious pests in both tropical and sub-tropical areas. A thorough understanding of their biology, including detailed knowledge of the specific mechanisms of parasitism, is needed in order to develop novel control methods. Some main developmental steps are described for the root parasites: seed conditioning and germination, haustorium formation, penetration into host tissues, maturation of the haustorium, and seed production. All these stages can be targeted in order to achieve parasite control. For example, based on our findings regarding gibberellin synthesized during seed conditioning, we were able to prevent parasitism by soil application of an inhibitor of gibberellin synthesis. Other developmental stages, such as germination stimulation, the enzymatic penetration of the haustorium into host tissues, and the source–sink relations between host and parasite are also possible targets for control, and the mechanisms involved may be manipulated for specific control of the parasites. 相似文献
9.
10.
Effect of planting date on severity of frogeye leaf spot and grain yield of soybeans 总被引：1，自引：0，他引：1
The influence of soybean (Glycine max) planting date on seasonal epidemics of frogeye leaf spot caused by Cercospora sojina and on grain yield, was evaluated during the 1991 and 1992 cropping seasons. Two susceptible (Samsoy 1 and TGx 849-313D) and one resistant (TGx 996-26E) soybean cultivars were used in field trials at Zonkwa, in the southern Kaduna state of Nigeria. Four field plantings were made at 14-day intervals from late May to mid0July. For each planting date, half the plots received foliar applications of benomyl at R1 and R3 growth stages, and the other half was untreated. Frogeye disease severity ratings were taken for all plots at R4 to R5 growth stages, and grain yield for each plot was measured at harvest. There was a significant (p < 0.05) increase in disease severity between the first and third plantings on the two susceptible cultivars in 1991, and on TGx 849-313D only in 1992. Corresponding yield reductions for the two susceptible cultivars averaged 13 and 31% for the treated and untreated plots, respectively, with each 2-week delay beyond the first planting date in 1991, and 5 and 6%, respectively, in 1992. There was no significant difference in disease among all treatments on the resistant cultivar, TGx 996-26E. Under Nigerian conditions, an increase in frogeye leaf spot severity can be expected with delayed planting of soybean after 1 June, and this can result in a corresponding loss of crop yield. 相似文献
11.
D. L. Liu K. R. Helyar M. K. Conyers R. Fisher G. J. Poile 《Field Crops Research》2004,90(2-3):287-301
Field experiments were conducted on four acid soils which were typical of the eastern section of the cropping region in southeastern Australia. The response of three cereal varieties to application of limestone or elemental S was measured as a function of soil pH. The cereals were selected to cover the known range of tolerance to acidity: Triticale (×Triticosecale wittmack cv. Currency) (tolerant); wheat (Tritcum aestivum cv. Matong) (moderately tolerant) and barley (Hordeum vulgare cv. Schooner) (sensitive). A two asymptote logistic equation was used to describe the relationship between soil pH and rates of limestone and elemental sulphur. The upper asymptotes for the four sites were well below the pH of lime saturation as the agriculturally practiced rates of lime were lower than the rates that could achieve the maximum pH in the field. The same equation was used to fit higher rates of lime application to a similar soil type to one of the four sites in this study and resulted in an upper asymptote of 7.26. Crop yield responses to lime application were well described by soil pHCa (0.01 M CaCl2). Soil pHCa ranges which gave 95% of maximum yield were pHCa 4.3–5.6 for Matong wheat, 4.4–4.8 for Currency triticale and 4.7–5.8 for Schooner barley. It was found that rainfall played an important role in limiting the yield response of crops to lime application. Lime reaction, lime requirement and grain yield models should include rainfall and soil water content as these influence the rate and extent of dissolution of limestone and subsequent plant response in a semi-arid environment. 相似文献
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14.
Laboratory, greenhouse and field studies were conducted to assess the allelopathic potential of 44 rice cultivars (Oryza sativa L.) on barnyard grass (Echinochloa crus-galli P. Beauv. var. oryzicola Ohwi). Rice cultivars exhibited marked differences in the inhibition of barnyard grass growth and development. In the laboratory, Gin shun rice cultivar extracts exhibited the greatest activity on the weed seedling growth, reducing dry weight by 61%, while Kasarwala mundara cultivar extracts exhibited the greatest activity on seed germination, reducing germination by 23% and germination speed by 46%. In a greenhouse study of a residue mixture, the Philippine 2 cultivar showed the greatest inhibition percentage on seedling emergence (57%), total seedling length (74%) and dry weight (73%). In the field study, the Juma 10 cultivar demonstrated the most inhibitory effect by reducing barnyard grass tiller number (80%), leaf area (49%) and leaf (61%) and stem (74%) dry weight (68%). These results suggest that there are differences among the varieties for allelopathic inhibition of barnyard grass, and that the development of barnyard grass suppressive rice cultivars that have greater allelopathic potential may be possible. 相似文献
15.
Effects of cultivar resistance and single fungicide application on rice sheath blight, yield, and quality 总被引：1，自引：0，他引：1
The increased number of sheath blight (Rhizoctonia solani)-resistant rice (Oryza sativa) cultivars available will allow producers to use less fungicide and avoid significant reductions in grain and milling yields. Among cultivars currently in cultivation in the southern United States, sheath blight resistance levels range from very susceptible to moderately resistant. A study was conducted to determine the response of cultivars, with different levels of susceptibility, to sheath blight inoculations and fungicide application and to determine the impact of sheath blight disease development on rice yield and quality. Sheath blight epidemics in field plots were initiated by inoculation at the panicle differentiation growth stage in 2006 and 2007. Azoxystrobin at 0.17 kg a.i. ha−1 was applied at mid-boot. Inoculation significantly increased sheath blight severity and incidence and caused yield losses of 8% in moderately resistant cv. Jupiter to 40% in very susceptible cv. Trenasse. Milling yields were affected to a lesser extent. Fungicide treatments reduced sheath blight incidence and severity, regardless of cultivar except in Jupiter. Single azoxystrobin applications were effective in minimizing yield loss due to sheath blight in all cultivars. 相似文献
16.
Chang-chi Chu Henry Plate David L. Matthews 《American Journal of Potato Research》1984,61(10):591-597
To investigate fertilizer injury to potatoes under field conditions, a three year study from 1979 to 1981 was undertaken in Central New York. The study was carried out on a well drained Howard gravelly silt loam; pH 6.6–6.8 with high organic matter (6.1–6.4%) and cation exchange capacity (CEC) of 13.4–14.9. When applied at a normal rate equivalent to 1,685 kg/ha of 10-15–15-1.2 the blended fertilizer containing urea N did not significantly reduce the tuber yield compared to ammoniated fertilizer and blended fertilizer containing ammonium nitrate (AN). However, when it was placed in contact with the seedpiece, the urea delayed emergence and early growth of the plant. Fertilizers containing urea-diammonium phosphate (DAP) and ureatriple superphosphate (TSP), applied at higher than normal rates and placed in contact with the seedpiece, significantly delayed emergence and reduced tuber yield. 相似文献
17.
Missing plants in potato crops can be caused by diseases and other factors, and can result from non-emergence or from plants incapacitated at any time during the growing season. Field experiments were conducted to simulate missing plants and to estimate the resulting yield losses by removing different percentages of plants at random from plots at emergence and/or later stages. The recorded yield losses were not proportional to the percentage of missing plants. Two surveys of fields of table stock and seed stock of the cultivar Netted Gem in New Brunswick in 1972 showed that approximately 25% of the plants were missing at emergence, probably causing around8% loss in total tuber yield. Assuming all cultivars have similar levels of misses, the yield loss clue to missing plants at emergence in New Brunswick in 1972 was equivalent to a financial loss of approximately $1 1/2 million. 相似文献
18.
种植抗虫品种和减量使用杀虫剂的白背飞虱可持续治理技术的田间试验 总被引：1，自引：0，他引：1
采用田间虫情和天敌数量调查、水稻产量与千粒重测定和水稻生产实际收益比较的方法,在浙江富阳和重庆秀山两地进行了种植抗虫品种和减量使用杀虫剂的白背飞虱可持续治理技术的田间试验.设使用杀虫剂2次和农户管理(使用杀虫剂4～5次)两个处理,无杀虫剂作为对照.试验结果表明,抗虫品种嘉花1号在各种杀虫剂处理中,白背飞虱成、若虫数量最低(0.9～3.3只/株),是感虫品种中香1号无杀虫剂处理的0.12%.无杀虫剂处理的蜘蛛数量分别是农户管理和杀虫剂2次处理的2.8～5.5倍和1.6～4.1倍.在同样的杀虫剂处理条件下,抗虫和耐虫品种的稻谷损失量和损失率较感虫品种明显地低.水稻生产的实际收益比较显示,无杀虫剂处理,种植嘉花1号可以增收1.13%～15.91%.因此,稻农种植抗虫或耐虫品种,减量使用杀虫剂至2次或不使用杀虫剂,充分利用蜘蛛等天敌的控制作用,完全能够有效地抑制白背飞虱种群的发生和发展,获得与常规杀虫剂用量(4～5次)相仿或更高的收益. 相似文献
19.
Zeyaur R. Khan Charles A.O. Midega Esther M. Njuguna David M. Amudavi Japhether M. Wanyama John A. Pickett 《Crop Protection》2008,27(7):1084-1097
The ‘push–pull’ technology (PPT), developed in Africa, offers effective control of cereal stemborers and Striga weed in maize-based cropping systems. It involves intercropping maize with desmodium, Desmodium uncinatum, with Napier grass, Pennisetum purpureum, planted as border around this intercrop. Desmodium repels the stemborer moths (push) that are subsequently attracted to the Napier grass (pull). Desmodium also suppresses and eliminates Striga. We assessed economic performance of this technology compared to the conventional maize mono- and maize–bean intercropping systems in six districts in western Kenya over 4–7 years. Ten farmers were randomly recruited in each district and each planted three plots representing the three cropping systems. The cost–benefit analyses were carried out, together with the systems’ net returns to land and labour and their discounted net present values (NPV). Maize grain yields and associated gross margins from the PPT system were significantly higher than those in the other two systems. Although the production costs were significantly higher in the PPT than in the two cropping systems in the first cropping year, these reduced to either the same level or significantly lower than in the maize–bean intercrop from the second year onwards in most of the districts. Similarly, the net returns to land and labour with the PPT were significantly higher than with the other two systems. The PPT consistently produced positive NPV when the incremental flows of its benefits compared to those of the two conventional systems were discounted at 10–30%, indicating that PPT is more profitable than the other two systems under realistic production assumptions. PPT is thus a viable option for enhancing productivity and diversification for smallholder farmers who largely depend on limited land resource. Hence, enhancing farmers’ access to less costly planting materials and promoting quality education and training in the use of this knowledge-intensive technology could stimulate its successful adoption. 相似文献
20.
A field study was conducted in 2001 and 2002 at Blackville, SC, to evaluate broadleaved weed control and economics of conventional and glyphosate-containing herbicide programmes in glyphosate-resistant soybean planted in 97-cm-wide rows. Treatments included chlorimuron plus sulfentrazone or chlorimuron plus metribuzin applied pre-emergence followed by post-emergence applications of lactofen or glyphosate 4 wk after soybean emergence (WAE). Other treatments were glyphosate applied 4 WAE, sequential applications of low dose glyphosate applied 2 and 4 WAE, and a non-treated control. Pre-emergence herbicides followed by glyphosate, controlled Ipomoea lacunosa L. 8 WAE. I. hederacea var. integriuscula Gray control with pre-emergence herbicides followed by glyphosate was 100% with similar control from chlorimuron plus sulfentrazone followed by lactofen, whereas control following the single glyphosate application was 84%. Amaranthus palmeri S. Wats. control 9 WAE was 100% following single or sequential glyphosate applications, while control ranged from 76% to 96% with pre-emergence herbicides followed by lactofen. However, early season weed interference when a single application of glyphosate was delayed until 4 WAE reduced soybean yields an average of 389 kg/ha compared to pre-emergence herbicides followed by glyphosate. Based on mean contrasts, pre-emergence herbicides followed by glyphosate had greater gross profit margins than a single glyphosate application alone, but were similar to sequential glyphosate applications. Gross profit margins from pre-emergence herbicides followed by lactofen were not different from glyphosate alone. 相似文献