Tolerance of Pinus caribaea var. hondurensis seedlings to five post-emergence herbicides

Five herbicides were evaluated for their potential to reduce reliance on directed white (mineral) spirits applications and hand weeding for grass control in P. caribaea var. hondurensis nurseries. Post-emergent applications of haloxyfop-methyl, fluazifop-P, fenoxaprop-ethyl and sethoxydim were identified as being selective to P. caribaea var. hondurensis seedlings whilst providing effective grass control. Ametryn was toxic to P. caribaea var. hondurensis seedlings at 1 kg ha^–1.     

骠马防除麦田杂草的施用技术

在同等条件下,麦田施用骠马防除杂草,效果优于绿麦隆。试验结果表明,骠马在低用量的药效表现温和,高用量时杀草迅速彻底。使用69克/升骠马水状乳油时,最佳用量为每亩40—50毫升,一般较不施药增产20%—30%,较施用绿麦隆增产10%左右。施用骠马,对小麦前期分蘖有抑制作用,对后期分蘖成穗有促进作用。不同类型小麦品种对骠马的反应不敏感。     

芝麻秆还田防治水稻病虫、杂草及提高土壤肥力效应的研究

１９９１～１９９２年的试验结果表明，利用芝麻秆还田，晚稻病虫、杂草危害明显减轻，稻谷产量增加１７．０９％～３０．３４％，稻田土壤肥力亦有所提高。为水稻病虫、杂草的生物防治提供一条新途径。     

Solanum nigrum: an indigenous weed reservoir for a tomato yellow leaf curl geminivirus in southern Spain

A tomato yellow leaf curl geminivirus (TYLCV-AL), was first identified in tomato plants in Almeria, southern Spain in 1992. This virus is transmitted by the tobacco whitefly, Bemisia tabaci (Gennadius), and is presently infecting tomato crops throughout the south eastern region of Spain. Solanum nigrum, collected from a field in south east Spain and exhibiting leaf curl symptoms, was squash blotted onto nylon membrane and gave a positive signal when hybridised to a TYLCV-Is DNA probe. Laboratory tests showed B. tabaci to transmit TYLCV-AL from infected tomato plants to S. nigrum seedlings. The virus could then be acquired by B. tabaci and transmitted back from infected S. nigrum plants to tomato, inducing typical TYLCV symptoms. These results indicate the importance of S. nigrum as a weed host/reservoir for a TYLCV and its possible role in the spread of this virus within Europe.     

中国南方女性的奇风异俗及成因新探

中国南方各民族女性有千奇百怪的奇风异俗,笔者将这些奇风异俗分类为经济、恋爱、婚姻家庭、文化、不落夫家等若干方面。关于成因,笔者不赞成"母系社会残余"的公式化解释,而提出"儒与非儒文化的冲突"、"女性是经济活动的主要角色"等理论加以解释。     

Discrimination of native and exotic forest patterns through shape irregularity indices: An analysis in the landscapes of Galicia,Spain

Landscapes resulting from human activity may be expected to present simpler shapes than more natural landscapes. In the case of forest landscapes, the boundaries of native forest patches may be more irregular than those of exotic forest plantations. There is however a lack of quantitative results to this respect, and it is not clear which shape indices are more adequate for such discrimination. In this study, we analysed the shape of a large number of forest classes in the region of Galicia (Spain) using the Spanish Forest Map at a scale 1:50000 as the spatial information source. We considered a set of fifteen shape irregularity indices including those that have been commonly used in landscape ecology studies. We found systematic differences in the shape of the analysed forest classes, with native forests presenting both more complex and elongated boundaries than exotic forests. We suggest that these differences are due to the combined effects of human action and other topographical and hydrological factors. The only index that perfectly discriminated both types of forest was the mean circumscribing circle index. Other six indices provided also a significantly good discrimination: density of shape characteristic points, area-weighted mean perimeter-area ratio, area-weighted mean contiguity index, mean shape index, perimeter-area fractal dimension and mean largest axis index. Comparisons of pure and mixed forests with the same dominant species indicated that an increase in tree species richness is in general associated with more irregular boundaries in the forest. Discarding indices on the basis of a high statistical correlation may not be an adequate procedure to retain the best-performing indices. Finally, we discussed several limitations of some frequently used indices that may be relevant to prevent an improper characterization of landscape shape.     

超高茬麦套稻田杂草发生特点、成因及化除策略

1998～2001年对江苏省5个不同生态区125个麦套稻田示范点的田间杂草发生情况进行了调查分析,初步掌握了麦套稻田杂草的发生特点,主要表现为种类多、发生早、群体大、危害重。免耕方式、前茬余草和前期田间管理粗放是造成杂草发生严重的原因。通过试验提出了"前封后杀"的化除策略,并研究出多项配套化学除草技术,促进了超高茬麦套稻田技术的大面积推广应用。     

Impact of Prosopis (mesquite) invasion and clearing on vegetation species composition and diversity in semi-arid Nama-Karoo rangeland,South Africa

The Nama-Karoo biome occupies 28% of South Africa’s land area. Alien leguminous trees of the genus Prosopis have invaded large tracts of Nama-Karoo rangeland. We evaluated the impact of Prosopis invasion and clearing on vegetation species composition and diversity (alien and indigenous species richness and cover) in Nama-Karoo rangeland on two sheep farms in the Beaufort West district of the Western Cape province of South Africa. Our results suggest that Prosopis invasion and clearing can significantly change Nama-Karoo rangeland species composition. Invasion and clearing appear to have no effect on alien species richness. Invasion, however, increases alien species cover, while clearing restores it to pre-invasion levels. In contrast, invasion reduces indigenous species richness while clearing restores it to pre-invasion levels. Invasion appears to have no effect on indigenous species cover. This lack of effect appears to be the serendipitous result of a site-specific trade-off between a decline in cover of grasses that are negatively affected by Prosopis invasion and a concomitant increase in the cover of positively affected grasses. Clearing increases indigenous species cover to above pre-invasion levels. The higher than usual indigenous species cover after clearing could be a transient legacy of Prosopis soil nutrient enrichment.     

Longer-Term Evaluation of Revegetation of Medusahead-Invaded Sagebrush Steppe

Medusahead (Taeniatherum caput-medusae [L.] Nevski) and other exotic annual grasses have invaded millions of hectares of sagebrush (Artemisia L.) steppe. Revegetation of medusahead-invaded sagebrush steppe with perennial vegetation is critically needed to restore productivity and decrease the risk of frequent wildfires. However, it is unclear if revegetation efforts provide long-term benefits (fewer exotic annuals and more perennials). The limited literature available on the topic questions whether revegetation efforts reduce medusahead abundance beyond 2 or 3 yr. We evaluated revegetation of medusahead-invaded rangelands for 5 yr after seeding introduced perennial bunchgrasses at five locations. We compared areas that were fall-prescribed burned immediately followed by an imazapic herbicide treatment and then seeded with bunchgrasses 1 yr later (imazapic-seed) with untreated controls (control). The imazapic-seed treatment decreased exotic annual grass cover and density. At the end of the study, exotic annual grass cover and density were 2-fold greater in the control compared with the imazapic-seed treatment. The imazapic-seed treatment had greater large perennial bunchgrass cover and density and less annual forb (predominately exotic annuals) cover and density than the untreated control for the duration of the study. At the end of the study, large perennial bunchgrass density average 10 plant ? m^? 2 in the imazapic-seed treatment, which is comparable with intact sagebrush steppe communities. Plant available soil nitrogen was also greater in the imazapic-seed treatment compared with the untreated control for the duration of the study. The results of this study suggest that revegetation of medusahead-invaded sagebrush steppe can provide lasting benefits, including limiting exotic annual grasses.     

AVIAN CHOLERA IN CANARIES (SERINUS CANARIA): REVIEW OF 2 OUTBREAKS

This report describes the evaluation of 2 avian cholera outbreaks in two canary (Serinus canaria) aviaries located in southern Brazil. The first outbreak had its onset after a thermal inversion, when the canaries exhibited clinical signs that included dyspnea, conjunctivitis, cyanosis, and death. The clinical progression of the disease, on average, lasted 2 days, and lead to a 40% loss of birds within the aviary. In the second outbreak the canaries also went through a thermal inversion, ending up with several cases of sudden death (60% of mortality) in a period of 24 hours. Canaries from both aviaries were submitted for microbiological evaluation, where isolates of Pasteurella multocidamultocida, which were resistant to sulfonamide, oxytetracycline, and enrofloxacin, were identified. After the analyzing the antimicrobial susceptibility profiles, canaries in both aviaries were treated with amoxicillin. Following 3 weeks of treatment, the outbreaks were controlled.