马铃薯早疫病菌对咯菌腈的敏感基线及其对不同药剂的交互抗性

采用菌丝生长速率法测定了河北省马铃薯主产区的122株早疫病菌Alternaria alternata对咯菌腈的敏感性,并测定了紫外诱导的15个抗咯菌腈突变菌株及其3个敏感亲本菌株对咯菌腈、异菌脲、腐霉利、苯醚甲环唑、吡唑醚菌酯的敏感性。田间马铃薯早疫病菌群体对咯菌腈保持高度敏感,122株早疫病菌对咯菌腈的EC₅₀值在0.0025~0.0857 μg/mL之间,平均值为0.0404±0.0171 μg/mL,相差34.87倍,呈近似正态分布,可作为早疫病菌对咯菌腈的敏感基线。此外,咯菌腈与吡唑醚菌酯和苯醚甲环唑之间无交互抗性关系,而与异菌脲和腐霉利之间存在正交互抗性关系。在田间药效试验中,50%咯菌腈WP施药量为105、115 g/hm²时,对马铃薯早疫病防效达80%以上,显著高于常规药剂80%代森锰锌WP 1 350 g/hm²和25%丙环唑EC 37.5 g/hm²的防效。表明咯菌腈可作为吡唑醚菌酯和苯醚甲环唑的替代药剂用于马铃薯早疫病的防治。     

10种杀菌剂对板栗疫病菌的抑制作用

为了筛选防治板栗疫病的高效、低毒、低残留杀菌剂,采用菌丝生长速率法测定了10种杀菌剂对栗疫病菌菌丝生长的抑制效果。结果表明,苯醚甲环唑+丙环唑、苯醚甲环唑、咯菌腈、咪鲜胺和多氧霉素对栗疫病菌具有很强的抑制作用,EC₅₀在0.014 8～8.752μg/mL之间,为生产上有效地防治板栗疫病提供了依据。     

河南省小麦赤霉病菌对咯菌腈的敏感性

为明确河南省小麦赤霉病菌Fusarium graminearum对咯菌腈的敏感性,采用菌丝生长速率法测定了咯菌腈对从该省11个地市分离的95株菌株的毒力,通过方差分析法及聚类分析法对测定结果进行了分析,并研究了咯菌腈与多菌灵、戊唑醇对病菌毒力的相关性。结果显示：咯菌腈对小麦赤霉病菌菌丝生长的最低抑制浓度为0.1 μg/mL;咯菌腈对供试95株菌株的EC₅₀范围在0.003~0.088 μg/mL之间,平均EC₅₀为0.011 μg/mL;敏感性频率分布图显示,病菌群体中存在着对咯菌腈敏感性较低的亚群体,但67.4%供试菌株敏感性频率呈正态分布,将此部分菌株的EC₅₀平均值0.007 μg/mL作为小麦赤霉病菌对咯菌腈的敏感性基线。方差分析及聚类结果均显示,同一县市内的菌株对咯菌腈EC₅₀的最大值和最小值之比为1.1~8.3;除周口市沈丘县的菌株外,其余县市的菌株对咯菌腈敏感性差异不明显,咯菌腈EC₅₀平均值变化范围在0.005~0.028 g/mL之间,最大值是最小值的5.6倍;小麦赤霉病菌对咯菌腈的敏感性与其对多菌灵、戊唑醇的敏感性之间无明显相关性。表明河南省小麦赤霉病菌群体中尽管存在着敏感性较低的亚群体,但可通过药剂复配进行防控。     

四种熏蒸剂对辣椒疫霉和南方根结线虫的毒力

为明确不同熏蒸剂对土传病原菌辣椒疫霉Phytophthora capsici和南方根结线虫Meloidogyne incognita的毒力,采用密闭熏蒸法测定了4种土壤熏蒸剂氯化苦、棉隆、威百亩、1,3-二氯丙烯的毒力及1,3-二氯丙烯和氯化苦复配的联合毒力。结果表明:氯化苦、棉隆、威百亩、1,3-二氯丙烯对辣椒疫霉的EC₅₀分别为0.12、2.44、8.30、8.45 mg/L; 对南方根结线虫的EC₅₀ 分别为1.23、0.22、0.30、0.18 mg/L。1,3-二氯丙烯和氯化苦以2:1、1:1、1:2比例复配时对辣椒疫霉的EC₅₀ 分别为1.13、0.24、0.14 mg/L;对南方根结线虫的EC₅₀分别为0.19、0.32、0.61 mg/L。结合经济效益和多种病害兼治的原则,推荐使用1,3-二氯丙烯与氯化苦1:1配比,可兼治辣椒疫病和根结线虫病。     

10种杀菌剂对水稻稻叶褐条斑病菌的室内毒力

为了解化学药剂对水稻稻叶褐条斑病病菌的抑制作用,采用菌丝生长速率法,测定了10种杀菌剂对稻黑孢霉菌［Nigrosporaoryzae Berk.etBr.Petch］的敏感性。结果表明：各药剂对稻黑孢霉菌的毒力差异显著。10%苯醚甲环唑水分散粒剂、25%吡唑醚菌酯乳油、50%咯菌腈可湿性粉剂对稻黑孢霉菌毒力居前列,EC50分别为0.5072、0.6398、0.9959mg/L,其次是50%咪鲜胺锰盐可湿性粉剂、30%苯甲·丙环唑乳油、12. 5%氟环唑悬浮剂、25%氟环·醚菌酯悬浮剂,EC50在1. 3803~2. 1182 mg/L,毒力较弱的是40%稻瘟灵可湿性粉剂和70%甲基硫菌灵可湿性粉剂,EC50分别为16.3178、17.4257mg/L,毒力最小的是75%百菌清可湿性粉剂,EC50达41. 5957 mg/L。综合各供试药剂的斜率和EC50、EC90,稻黑孢霉菌对测定的苯醚甲环唑、咯菌腈、咪鲜胺锰盐以及苯甲·丙环唑等药剂最为敏感,这些药剂可作防治稻叶褐条斑病的候选药剂。     

8种杀菌剂对黄瓜枯萎病菌的室内毒力测定

采用菌落直径法,分别测定了7大类8种常用杀菌剂对黄瓜枯萎病菌的室内毒力。结果表明,8种供试杀菌剂对黄瓜枯萎病菌的作用效果均较好,其中三唑类丙环唑的毒力最高,EC50值为0.023mg/L。咪鲜胺、苯醚甲环唑、咯菌腈、百菌清和嘧菌酯的毒力也较高,EC50均低于1.0mg/L;多菌灵和异菌脲对黄瓜枯萎病的毒力分别为1.105和1.181mg/L,仍有较好的作用效果。     

江苏省葡萄炭疽病菌群体对4种杀菌剂的敏感性

为明确江苏省葡萄炭疽病菌Colletotrichum gloeosporioides群体对苯醚甲环唑、吡唑醚菌酯、咯菌腈和戊唑醇4种杀菌剂的敏感性和抗性水平,本研究采用菌丝生长速率法测定了来自江苏省7个地区的68株葡萄炭疽病菌对上述4种药剂的敏感性,建立敏感基线,并分析菌株抗性水平和抗性频率。结果表明：苯醚甲环唑、吡唑醚菌酯、咯菌腈和戊唑醇对供试68株葡萄炭疽病菌的EC₅₀范围分别为0.03～1.20、0.05～3.48、0.14～1.20 mg/L和0.50～12.30 mg/L;对苯醚甲环唑、吡唑醚菌酯和咯菌腈的敏感基线分别为(0.53±0.032)(1.00±0.15) mg/L和(0.38±0.024) mg/L。68株菌株对戊唑醇的EC₅₀平均值为3.61 mg/L,因敏感性频率分布不符合建立敏感性基线要求,故未建立敏感性基线。供试菌株对苯醚甲环唑均表现为敏感,对吡唑醚菌酯和咯菌腈呈现一定的低抗水平,抗性频率分别为4.41%和3.03%;对戊唑醇呈低抗和中抗水平,抗性频率分别为16.18%和5.88%。该研究为防控江苏省葡萄炭疽病提...     

白术两种主要土传病害的分离、鉴定及杀菌剂的室内活性筛选

立枯病和白绢病是白术生产种植中的两种主要土传病害,在苗期和生长期都有发生,危害严重。本研究从浙江省磐安县采集具有典型病症的白术植株,对病原进行了分离、纯化和致病性测定。综合形态学特征及rDNA-ITS序列分析表明,白术上的病害是由立枯丝核菌Rhizoctonia solani Kühn引起的立枯病和由齐整小核菌Sclerotium rolfsii Sacc.引起的白绢病。室内毒力测定结果表明,10种供试杀菌剂对立枯病菌的毒力从大到小为:噻呋酰胺咯菌腈戊唑醇四氟醚唑吡唑醚菌酯丙硫菌唑嘧菌酯啶酰菌胺苯醚甲环唑咪鲜胺;对白绢病菌的室内毒力从大到小为:吡唑醚菌酯噻呋酰胺嘧菌酯戊唑醇咯菌腈苯醚甲环唑丙硫菌唑啶酰菌胺四氟醚唑咪鲜胺,其中噻呋酰胺对两种病菌都具有很高的活性,EC_(50)分别为0.06和0.03mg/L,可用于两种病害的防治。     

葡萄白腐病菌对抑霉唑的敏感基线及其与不同杀菌剂的交互抗性

为明确山东省胶东地区葡萄白腐病菌Coniella diplodiella对抑霉唑的敏感性及抑霉唑与常规杀菌剂之间的交互抗性,采用菌丝生长速率法测定葡萄白腐病菌对抑霉唑等杀菌剂的敏感性,并通过分析抑霉唑与戊唑醇、吡唑醚菌酯、福美双、多菌灵、代森锰锌毒力的相关性,判断抑霉唑与各药剂之间是否存在交互抗性。结果表明,供试69株葡萄白腐病菌菌株对抑霉唑的EC₅₀在0.13~55.53 μg/mL之间,最高值与最低值相差427.15倍;其频数分布图呈多峰曲线,第一主峰内EC₅₀平均值为6.34 μg/mL,可作为胶东地区葡萄白腐病菌对抑霉唑的敏感基线。与敏感基线相比,田间已出现抑霉唑低抗菌株,占检测总株数的8.70%,未检测到中、高抗菌株。选择3个抗性菌株连续继代培养10代后,其对抑霉唑的敏感性明显提高,说明其抗药性不能稳定遗传。抑霉唑EC₅₀对数值与戊唑醇、吡唑醚菌酯、福美双、多菌灵、代森锰锌的EC₅₀对数值之间的相关系数分别为0.799、-0.143、-0.089、-0.268和0.159,说明抑霉唑与戊唑醇存在一定的交互抗性,但与其他4种药剂之间不存在交互抗性。表明抑霉唑可用于胶东地区田间葡萄白腐病的有效防控。     

黄瓜绵腐病病原菌鉴定及防治药剂的筛选

为有效防控黄瓜绵腐病，本研究对自江西省南昌市南昌县武阳镇和八一乡采集的黄瓜绵腐病病样进行分离，基于致病性测定、形态学特征和分子生物学方法对其进行鉴定，并采用菌丝生长速率法测定甲霜灵、霜霉威、霜脲氰、烯酰吗啉4种常用杀菌剂对该病原菌和辣椒疫霉Phytophthora capsici的抑制效果。结果表明，自武阳镇和八一乡采集的病样经分离、纯化培养后分别获得12株和10株菌株；自武阳镇分离的病原菌的藏卵器柄较直，藏卵器大小为18.1~32.9 μm；自八一乡分离的病原菌的藏卵器柄较弯曲，藏卵器大小为15.1~25.3 μm；结合致病性测定及rDNA-ITS测序结果，将自武阳镇分离的病原菌鉴定为瓜果腐霉Pythium aphanidermatum，将自八一乡分离的病原菌鉴定为德里腐霉Py.deliense。室内毒力测定结果表明，甲霜灵对瓜果腐霉和德里腐霉抑制效果最好，EC₅₀分别为0.71 μg/mL和0.25 μg/mL；霜脲氰次之，EC₅₀分别为3.68 μg/mL和3.36 μg/mL，甲霜灵、霜霉威、霜脲氰3种杀菌剂对瓜果腐霉、德里腐霉和辣椒疫霉的抑制效果差别不大，但烯酰吗啉对瓜果腐霉、德里腐霉和辣椒疫霉抑制效果差异明显，EC₅₀分别为18.06、33.58和0.18 μg/mL，表明防治黄瓜绵腐病优先选择甲霜灵。     

Economic weed control with grass carp

Abstract

Conventional methods of aquatic weed control meet increasing objections on economic and/or environmental grounds. An alternative approach is the use of grass carp (Ctenopharyngodon idella Val.), a herbivorous fish. This biological method has mainly been used in Europe and the USA, but since 1976 an Egyptian‐Dutch project has studied the potential of this approach for the Egyptian irrigation systems. All aspects of the production and use of grass carp have been studied and evaluated, Egyptian personnel have been trained, a large‐scale breeding station has been established and practical use of the technique has begun. The programme has shown that a stocked grass carp population not only provides effective weed control, but it also increases the protein production in Egyptian waterways substantially. If managed well, this production can provide continuous revenues that far outweigh the costs of weed control. The necessary management techniques developed are mainly based on yearly restocking with grass carp and cooperation between irrigation authorities and professional fishermen. The experience described in this paper will be of interest to many other countries.     

Ustilago kamerunensis on Napier grass in Kenya

Napier or elephant grass, Pennisetum purpureum Schum., is the major source of fodder for stall-fed dairy cattle in Kenya. In the early 1990s, a new disease, caused by Utilago kamerunensis P. & H. Sydow was reported on the grass. Since there was a lack of information on the general pest and disease status of Napier grass in Kenya, a survey was carried out. The survey confirmed that U. kamerunensis was the major pest and disease threat to Napier grass production in the country, having spread to four districts and occurring in 27% of farm plots sampled. The existence of disease hotspots suggests that the main means of spread is through transport of infected planting material, and that the severity of the disease in Kenya compared with other countries results from an increase in the cultivation of Napier grass over the past decade.     

Competitiveness against grass weeds in field pea genotypes

Summary Field pea is an important pulse crop in southern Australia, but its competitiveness against weeds is low. Two experiments were conducted in consecutive years to examine the ability of different genotypes to compete against grass weeds. Field pea was grown in the presence or absence of Lolium rigidum or wheat. In each experiment significant genotypic differences in field pea competitiveness occurred and some genotypes had consistently high or low levels of competitiveness in both years. Tall genotypes generally suppressed L. rigidum and wheat more effectively than short genotypes. Leaf type (conventional, semileafless or tare-leaf) only affected competitiveness before flowering and had no effect on yield loss from weed competition. Maturity had little effect on competitive ability. A genotype × environment analysis for competitive ability showed that there was considerable variation in the response to the level of competition (environment) as well as in mean competitiveness among field pea genotypes. Using wheat as a weed identified genotypic differences in field peas more effectively and more consistently than using L. rigidum . Visual assessment of wheat growth with field pea was strongly correlated with a specific genotype's competitiveness, which may form the basis of a simple field-based screening method for competitive ability.     

Anthracnose of centipede grass caused by Colletotrichum caudatum

Anthracnose disease was found on centipede grass [Eremochloa ophiuroides (Munro) Hack.] planted as a ground cover on paddy field levees in Shiga Prefecture in 2004. The symptoms were ear blight, stalk blight, and leaf spots. The causal fungus was morphologically identified as Colletotrichum caudatum (Sacc.) Peck. This is the first report of centipede grass anthracnose caused by C. caudatum.     

Defense mechanisms involving secondary metabolism in the grass family

Plants synthesize and accumulate a wide variety of compounds called secondary metabolites. Secondary metabolites serve as chemical barriers to protect plants from pathogens and herbivores. Antimicrobial secondary metabolites are accumulated to prevent pathogen infection. These metabolites are classified into phytoalexins (induced in response to pathogen attack) and phytoanticipins (present prior to pathogen infection). The antimicrobial compounds in the grass family (Poaceae) were studied from the viewpoint of evolution. The studies were performed at three hierarchies, families, genera, and species and include the following: 1) the distribution of benzoxazinoids (Bxs) in the grass family, 2) evolutionary replacement of phytoanticipins from Bxs to hydroxycinnamic acid amide dimers in the genus Hordeum, and 3) chemodiversity of flavonoid and diterpenoid phytoalexins in rice. These studies demonstrated dynamic changes in secondary metabolism during evolution, indicating the adaptation of plants to their environment by repeating scrap-and-build cycles.     

Field-scale estimates of grass weed populations in arable land

Estimates of numbers of weed grass inflorescences in a single wheat field were made using 0·25 m² quadrat counts. Precise estimates of mean field density could be achieved only at high sampling intensity, at least 18 locations (m²) ha^-1. The standard error expressed as a percentage of the mean was less than 20% for more abundant species and over 30% for rarer species at that sampling intensity. However, the data were highly skewed and followed a negative binomial frequency distribution for each species. This implies it may be usual for arable weeds that plants are clumped, with clumps occurring at random. A computer mapping program that interpolates arithmetically between sample points did not reflect accurately plant distributions and was affected by sampling intensity. The implications for decision making for weed control using densities are discussed. Estimation au champ des populations de mauvaises herbes en terrains cultivés Des estimations du nombre d'inflorescences de mauvaises herbes dans un champ de blé ont été faites en utilisant des comptages au cadre de 0,25 m². Les statistiques ont montré que l'estimation de la densité moyenne du champ peut être précise seulement avec une grande intensité de l'échantillonage au moins 18 situations (m²) ha^-1. L'erreur standard exprimée en pourcentage était inférieure à 20% pour les espèces les plus abondantes et supérieure à 30% pour les plus rares, à cette densité d'échantillonnage. Cependant, les données étaient très biaisées et suivaient une fréquence de distribution binomiale négative pour chaque espèce. Cette distribution, qui implique que les plantes sont en touffe, peut être commune pour les adventices des terres labourées. Une représentation graphique par ordinnateur n'a pas donné un reflet exact de la distribution des plantes et était très affectée par la densité d'échantillonnage. Les possibilités de la prise de décision de la mise en oeuvre d'un désherbage à partir des densités d'adventices sont discutées. Schätzung von Gräserpopulationen auf Äckern In einem Weizenfeld wurde die Dichte der Infloreszenzen von Gräsern mit einem Zählrahmen (0,25 m²) bestimmt. Bei der statistischen Analyse zeigte sich, dass die mittlere Dichte nur bei einer hohen Probendichte von mindestens 18 ha^-1 genau geschätzt werden konnte. Der Standard-fehler, ausgedrückt in Prozent vom Mittelwert, war bei dieser Stichprobendichte geringer als 20% für die häufigeren Arten und über 30% für die selteneren. Die Daten jeder Art folgten einer negativen Binomialverieilung mit ausgeprägter Schiefe. Diese Verteilung spiegelt das aggregierte (geklumpte) Auftreten der Pflanzen wider, wobei die Befallsnester zufällig verteilt sind, was für Ackerunkräuter charakteristisch ist. Ein Computer-Program zur Darstellung der Verbreitung mit arithmetrischer Interpolation zwischen den Stichprobenpunkten gab die reale Verteilung nicht genau wieder und hing von der Stichprobendichte ab. Schlussfolgerungen für die Entscheidung über Unkrautbekämpfungsmassnahmen auf der Grundlage von Unkrautdichten werden diskutiert.     

Effects of choke disease in the grass Brachypodium phoenicoides

Using phenotypic and molecular characters, as well as mating compatibility tests, the fungus causing choke disease in Brachypodium phoenicoides was identified as Epichloë typhina . A three year field experiment conducted with infected and uninfected plants of a single clone of B. phoenicoides showed no significant differences in biomass production during their vegetative growth stage, but the content of calcium, magnesium and manganese was significantly greater, and that of sodium was significantly lower in infected plants compared to uninfected plants. Infected plants produced up to twice as many reproductive tillers as healthy plants, but their reproductive tissue biomass was significantly smaller than that of healthy plants, because tiller development was arrested by choke forming stromata.     

The biology of Johnson grass (Sorghum halepense)

The literature on various aspects of the biology of Johnson grass. Sorghum halepense (L.) Pers. is reviewed. Topics discussed include its distribution, cytology, taxonomy, life cycle, variability and the dormancy and germination of its seeds and rhizomes.