单轴等效线法评价精喹禾灵与灭草松相互作用的研究

为正确评价单子叶杂草防除剂与双子叶杂草防除剂的相互作用,以精喹禾灵与灭草松混用为实例对等效线法进行了改进,提出单轴等效线法及其增效倍数的计算方法。该研究结果表明,两种药剂混用对马唐Digitaria sanguinalis和反枝苋Amaranthus retroflexs均有增效作用,其平均增效倍数分别为0.42和0.34。采用单轴等效线法可以正确评价单子叶杂草防除剂与双子叶杂草防除剂的相互作用。     

Physiological and molecular basis for ALS inhibitor resistance in Bromus tectorum biotypes

Primisulfuron‐resistant (AR and MR) and ‐susceptible (AS and MS) Bromus tectorum biotypes were collected from a Poa pratensis field at Athena, Oregon, and in research plots at Madras, Oregon. Studies were conducted to characterize the resistance of the B. tectorum biotypes. Whole plant bioassay and acetolactate synthase (ALS) enzyme assay revealed that the AR biotype was highly resistant to the sulfonylurea (SU) herbicides, primisulfuron and sulfosulfuron and to a sulfonylaminocarbonyltriazolinone (SCT) herbicide, propoxycarbazone‐sodium. However, the AR biotype was not resistant to imazamox, an imidazolinone (IMI) herbicide. Results of the whole plant bioassay studies showed that the MR biotype was moderately resistant to all ALS inhibitors tested. However, there were no differences in ALS sensitivities between the MR and MS biotypes. The nucleotide and amino acid sequence analysis of the als gene demonstrated a single‐point mutation from C to T, conferring the exchange of the amino acid proline to serine at position 197 in the AR biotype. However, this mutation was not found in the MR biotype. Results of this research indicate that: the resistance of the AR biotype to SU and SCT herbicides is based on an altered target site due to a single‐point mutation; resistance in the MR biotype is not due to a target site mutation.     

Role of underground parts of barnyardgrass (Echinochloa crus-galli (L.) Beauv. var. formosensis Ohwi) in its sensitivity to thenylchlor in soil

In the present study, the phytotoxic activity of top-soil applied with thenylchlor [2-chloro- N -(3-methoxy-2-thieny)-2',6'-dimethylacetanilide] on the growth of rice ( Oryza sativa L.) was dependent on the emergence depth in soil but its activity on barnyardgrass ( Echinochloa crus-galli (L.) Beauv. var. formosensis Ohwi) was only slightly affected by the emergence depth. However, the phytotoxic activity on barnyardgrass and rice was similar irrespective of the different emergence depths in its treatment to all soil layers. Thenylchlor treatment to the mesocotyl of barnyardgrass induced significant inhibition of shoot elongation, whereas the treatment to the coronal root only inhibited the coronal elongation without inhibiting shoot elongation. Absorption and translocation of ¹⁴C-thenylchlor in barnyardgrass were determined in water culture. The different amounts of radioactivity per plant among the treatments to the underground parts were due to the plant part that came in contact with ¹⁴C-thenylchlor. The radioactivity per dry weight was found to be higher in the basal part of the shoot than in its upper part in all treatments to the underground parts. It was suggested that the phytotoxic activity of thenylchlor on the growth of barnyardgrass in soil is induced by its accumulation in the basal part of the shoot through translocation. This primarily occurs after the absorption substantially by the mesocotyl from the herbicide-treated layer and additionally by other underground parts.     

Current status of biological control of paddy weeds in Vietnam

Rice is a staple food in Vietnam and accounts for > 7.7 × 10⁶ cultivated ha, which provide 35.5 × 10⁶ t of rice, of which 4.2 × 10⁶ t were exported in 2004. The enlargement of the cropping area and the enhancement of rice yield have rapidly increased the amount of agrochemicals, including herbicides, in crop production in Vietnam. From 1990–2003, the percentage of herbicides in total pesticides has increased ≈ 10-fold to 30.2%. In addition, the improper use of herbicides caused environmental hazards, unsafe agricultural products, and human health problems. Biological management integrated with traditional weed control techniques might help to reduce the dependence on synthetic herbicides and build eco-friendly, sustainable agricultural production in Vietnam. This paper reviews the efforts in establishing a strategy for biological management of weeds that was conducted in recent years by Vietnamese weed scientists. This has included cropping system management, water and soil management, integrated pest management, and utilization of plant allelopathy as major components of the strategy. Many plants with strong allelopathic potential can be a source for biological weed suppression and soil fertility improvement. The utilization of allelopathic properties in rice might also help to provide new rice cultivars with weed-suppressing characteristics.     

Reduced herbicide doses in field crops: A review

Farmers are becoming increasingly interested in more comprehensive weed management programs that reduce weed populations over time and in the use of reduced herbicide doses that lower their production costs. Research indicates that there is good potential to reduce the number of herbicide applications and utilize lower herbicide doses within competitive cropping systems. Diverse crop rotations, competitive cultivars, higher crop seed rates, reduced row spacing, specific fertilizer placement, and cover crops have been identified as integral components of competitive cropping systems. This review paper explores the potential for successful use of reduced herbicide doses within competitive cropping systems that have a multiyear approach to weed management. The utilization of decision support systems or new methods of assessing active weed growth are discussed in light of further enhancing the successful use of reduced herbicide doses and advising farmers on when (and when not) they might be a viable option.     

Modelling interactions between herbicide dose and multiple weed species interference in crop–weed competition

The effects of a range of herbicide doses on crop–multiple weed competition were investigated. Competitivity of Galium aparine was approximately six times greater than that of Matricaria perforata with no herbicide treatment. Competitivities of both weeds decreased with increasing herbicide dose, being well described by the standard dose–response curve with the competitivity of M. perforata being more sensitive than that of G. aparine to a herbicide mixture, metsulfuron‐methyl and fluroxypyr. A combined model was then developed by incorporating the standard dose–response curve into the multivariate rectangular hyperbola competition model to describe the effects of multiple infestation of G. aparine and M. perforata and the herbicide mixture on crop yield. The model developed in this study was used to predict crop yield and to estimate the herbicide dose required to restrict crop yield loss caused by weeds to an acceptable level. At the acceptable yield loss of 5% and the weed combination of 120 M. perforata plants m^?2 and 20 G. aparine plants m^?2, the model recommends a mixture of 1.2 g a.i. ha^?1 of metsulfuron‐methyl and 120 g a.i. ha^?1 of fluroxypyr.     

油菜田新型除草剂丙酯草醚的应用技术

丙酯草醚（ZJ0273）是具有我国自主知识产权的新型除草剂，为明确其应用前景，采用室外盆栽法和温室盆栽法，以油菜田发生的主要杂草为试材，对新型除草剂10％丙酯草醚EC杀草谱、施药适期和作用速度等特性进行了研究，并对作物的安全性和除草效果进行了总结和分析。结果发现，该药剂在60g ai／hm^2剂量下，对看麦娘、日本看麦娘、牛繁缕、小藜、茼草、硬草、早熟禾、棒头草、刺果毛茛和荠菜等10种杂草的防效在80％以上；该药剂属于缓效型除草剂，杂草1～3叶期为施药适期；丙酯草醚对甘蓝型双低油菜品种的安全剂量是推荐用量的2倍；不同地区田间使用丙酯草醚防除油菜田杂草应在杂草1～3叶期施药，推荐剂量为45～60g ai／hm^2，总体除草效果为72.3％～97.6％．     

烟嘧磺隆在土壤中的吸附及与土壤性质的相关性研究

采用平衡振荡法研究了烟嘧磺隆在8种不同类型土壤中的吸附,结果表明,其吸附过程均符合经典的Freundlich模型,最大吸附常数为6.891,最小吸附常数为0.798。根据土壤有机吸附常数和吸附自由能的大小对该除草剂的移动性能进行了评价,认为其在8种土壤中均以物理吸附为主,且具有中等或较高的移动性能。通过对吸附常数Kf与土壤有机质含量、粘土含量和pH值的关系进行分析,发现土壤有机质含量、粘土含量和pH值在吸附过程中均属支配因素,Kf与土壤有机质含量、粘土含量呈正相关,而与土壤pH值呈负相关。     

4种混配除草剂防除大蒜田杂草效果研究

本文对4种混配除草剂防除大蒜田杂草的试验情况进行了总结,并介绍了试验田杂草发生的基本情况,以期对大蒜田化学除草剂的推广和应用有所帮助。     

二化螟田间为害株率与为害丛率间的关系

通过不同调查者调查相同稻田内二化螟为害的枯鞘、枯心和白穗等受害稻株,分析平均受害株率和平均受害丛率的关系。结果表明,“平均受害丛率”在不同调查者之间的误差小于“平均受害株率”。受害株率和受害丛率之间呈正相关的关系,当受害丛率小于60%时,受害株率与受害丛率的相关系数超过0.91,用受害丛率可以较准确地估计受害株率。