杨树重要病害生物防治初探

自然界各种微生物生活在一起,成为复杂的群落。它们相互促进、制约,构成生物体的生态平衡。在森林病害防治中,利用益菌控制病菌的生存和活动,达到生物防治的目的。为了寻求这一新途径,在1982—1984年,对4种杨树重要病害进行了生物防治探索,从筛选和防病上作了研究。     

A method for observing and manipulating roots and root associated fungi on plants growing in nonsterile substrates

Standard 14‐cm plastic‐petri dishes were used as root substrate chambers allowing controlled inoculation, regular inspection under the dissecting microscope, and manipulation of root infections with pathogens and mycorrhizal fungi under nonsterile conditions. Roots of young pine seedlings were placed on the root substrate and, especially those growing on the substrate surface under the lid, were very easy to manipulate. Mycorrhizal species and inoculation methods were compared and the infection process followed continuously under various conditions. The air pockets formed between the lid and the substrate favoured mycorrhiza formation. Brief, periodic flooding prevented formation of mycorrhizas in two mycorrhizal species having hydrophobic hyphae but did not prevent it in less hydrophobic species. IAA treatment of roots led to heavy production of mycorrhizas. Fruiting body formation in Lacearia laccata was induced and followed in the dish cultures. Pure mycorrhizal stock cultures were able to be revitalized in the dish cultures and reisolated in pure culture. The infection strategy of a weak root pathogen, Cylindrocarpon destructans, was studied with the same technique, which was also used for investigating treatments predisposing seedlings to pathogen infection.     

Wood-inhabiting fungi in stems of Fraxinus excelsior in declining ash stands of northern Lithuania,with particular reference to Armillaria cepistipes

Abstract

Stem bases of 210 Fraxinus excelsior trees of three different health categories were sampled by the means of an increment borer in declining ash stands in northern Lithuania. From this number, 15 sound-looking, 132 declining and 63 dead trees from three discrete plots yielded 352 isolates, representing 75 fungal species. In addition, mycelial fans and rhizomorphs typical of Armillaria spp. from 205 and 20 trees, respectively, were sampled and subjected to fungal isolations. Species richness was similar in trees from each health category, but community structures differed, indicating that species composition of wood-inhabiting fungi in stems changes along with the changes in tree health condition. Armillaria cepistipes was the most common species (86 isolates from 210 wood samples, or 41.0%), isolated more frequently and consistently than any other potential tree pathogen. It also showed abundant occurrence on a majority of trees in the form of mycelial fans and rhizomorphs, from which 64 and 14 isolates of the fungus were obtained, respectively. The population structure of A. cepistipes revealed the presence of 53–93 genets per hectare, some of which extended up to 30–55?m.     

果蔬采后致腐病菌检测及防治

引起果蔬采后腐烂的病原菌主要分属于葡萄孢属（Botrytis）、曲霉属（Aspergillus）、青霉属（Penicillium）、根霉属（Rhizopus）和链格孢属（Alternaria）.其中A.sp.和R.sp.是果蔬常温运输过程中的主要致腐菌,B.sp.、A.sp.和P.sp.是果蔬低温贮运条件下的主要致腐菌.采用仲丁胺和二氧化氯2种药剂对采后蔬菜进行熏蒸和浸泡保鲜处理.结果表明：低温与保鲜剂处理相结合,可明显提高果蔬采后运输及货架期9～11d.     

The potential for using cyanobacteria (blue-green algae) and algae in the biological control of plant pathogenic bacteria and fungi

Cyanobacteria (blue-green algae) and eukaryote algae occur in freshwater, marine, and terrestrial (soil) habitats. In fact, these microorganisms comprise most of the world's biomass. Although the cyanobacteria are mostly photoautotrophic, some are facultative heterotrophs, capable of growing on certain substrates in darkness. Also, some are non-phototrophic and hence, are obligate heterotrophs. A number of cyanobacteria and eukaryote algae, particularly macroalgae, produce various, biologically active compounds. These include antibiotics which in laboratory tests inhibited bacteria and fungi that incite diseases of humans. In addition, the following fungi which are of interest to plant pathologists, were inhibitedin vitro by substances produced by various cyanobacteria: The saprophytesChaetomium globosum, Cunninghamella blakesleeana, andAspergillus oryzae and the plant pathogensRhizoctonia solani andSclerotinia sclerotiorum. Extracts from seaweeds (macroalgae) sprayed on plants have been reported to reduce the incidence ofBotrytis cinerea (gray mold) on strawberries,Erysiphe polygoni (powdery mildew) on turnips, and damping-off of tomato seedlings. Because many cyanobacteria and algae produce a large number of antibacterial and antifungal materials, are almost never a threat to the environment, and many can be grown in quantity in mass culture, they are suitable candidates for exploitation as biocontrol agents of plant pathogenic bacteria and fungi. Much additional work remains to be done however, to thoroughly evaluate cyanobacteria and algae and their products for this role.     

A solar collector for soil disinfestation

A solar collector to be used for disinfestation of substrates for plant propagation is described. At a high solar radiation intensity (more than 1 cal cm^–2 min^–1), one day of treatment was sufficient for disinfestation of soil infested withSclerotium rolfsii, Sclerotinia sclerotiorum, Fusarium solani f.sp.phaseoli orPythium aphanidermatum.Treatment of soil in the solar collector strongly reduced the total numbers of fungi, bacteria and actinomycetes. The nutrient status of the soil was only slightly changed and did not result in an effect on plant growth.     

Ceratocystis species infecting stem wounds on Eucalyptus grandis in South Africa

Reports of Ceratocystis spp. causing disease of exotic plantation hardwood species have increased in recent years. Ceratocystis fimbriata causes wilt and canker on Eucalyptus spp. in Africa and South America, and C. albofundus results in wilt and death of Acacia mearnsii in Africa. Ceratocystis spp. generally infect wounds on trees, and artificial stem wounding can thus be used to determine the presence of these fungi. The aim of this study was to identify Ceratocystis spp. infecting wounds on Eucalyptus grandis in South Africa. Isolated Ceratocystis spp. were identified using morphological characteristics and comparisons of DNA sequence data for the ITS and 5·8S regions of the rRNA operon. Pathogenicity trials were conducted in the greenhouse to determine the possible role that these Ceratocystis spp. could have in disease development. These trials were also conducted under field conditions. Three Ceratocystis spp. were collected: C. fimbriata , C. moniliformis and C. pirilliformis . This is the first report of C. fimbriata and C. pirilliformis from Eucalyptus spp. in South Africa, and the first report of the latter fungus outside Australia. Both C. fimbriata and C. pirilliformis caused significant lesions on inoculated E. grandis trees. This is the first evidence that C. pirilliformis is a pathogen of Eucalyptus spp. From the results of both greenhouse and field trials, it has the potential to cause serious disease problems in Eucalyptus plantations.     

Airborne ascospores ofDidymella rabiei as a major primary inoculum for Ascochyta blight epidemics in chickpea crops in southern Spain

The incidence and severity of Ascochyta blight in potted chickpea trap plants exposed for 1-wk periods near infested chickpea debris in Córdoba, Spain, or in chickpea trap crops at least 100 m from infested chickpea debris in several locations in southern Spain were correlated with pseudothecial maturity and ascospore production ofDidymella rabiei from nearby chickpea debris. The period of ascospore availability varied from January to May and depended on rain and maturity of pseudothecia. The airborne concentration of ascospores ofD. rabiei was also monitored in 1988. Ascospores were trapped mostly from the beginning of January to late February; this period coincided with that of maturity of pseudothecia on the chickpea debris. Most ascospores were trapped on rainy days during daylight and 70% were trapped between 12.00 and 18.00 h. Autumn-winter sowings of chickpea were exposed longer to ascospore inoculum than the more traditional spring sowings because the autumn-winter sowings were exposed to the entire period of ascospore production on infested chickpea debris lying on the soil surface.     

Towards the management of field bindweed (Convolvulus arvensis) and hedge bindweed (Calystegia sepium) with fungal pathogens and cover crops

The bindweeds Calystegia sepium and Convolvulus arvensis aredifficult to control chemically. Calystegia sepium is often aproblem in maize or in vineyards, while C. arvensis is animportant weed of cereals. The biological control of these weedswith insects or fungal pathogens has been investigated since1970. More than 600 fungi collected in countries throughoutEurope have been isolated in our laboratories. The isolates withthe highest and most stable pathogenicity against bindweed belongto the genus Stagonospora. In a field trial in maize in 1995, oneof these Stagonospora isolates stopped the increase of groundcoverage by the bindweeds. In response to public concern aboutenvironmental problems caused by modern agriculture, new croppingsystems are being developed. Underseeding maize with a livinggreen cover achieves good control of a large spectrum of the weedflora typical of conventional tillage systems. However, C. sepiumand C. arvensis remain as problems. The research reported showsthat C. sepium is partly suppressed by the green cover, butescapes control by climbing the stems of the maize plants.Therefore, the application of spores of Stagonospora sp. in amaize field underseeded with a living green cover may allow alarge or a complete reduction of the herbicide input and promotea more sustainable agriculture     

Biological control of weeds in crops: a coordinated European research programme (COST-816)

For dominant weed species that are difficult to control by traditional means, the development of new, selective, control methods that can be implemented in integrated pest management (IPM) is essential. Here, biological control can be the appropriate means of control due to its high degree of selectivity and environmental safety (direct control value). The biocontrol strategy is based on a detailed analysis of the crop environment and, thus, provides a fundamental tool for developing sustainable agroecosystems (indirect, heuristic value). The successful application of biological weed control will lead to substantial reductions in pesticide use and, thus, will also contribute to the conservation, augmentation and utilization of biodiversity in agroecosystems, an explicit objective of IPM. Only cooperative and concerted efforts, such as those envisaged by COST, will allow the effective completion of weed biocontrol projects within a reasonable period of time. At present, over 25 institutions from 14 countries are participating in this COST action. The following six objectives have been defined for COST-816: to bring together European institutions, to promote a programme for scientific research and exchange, to draw up a general protocol for biological weed control in Europe, to integrate biological control into general weed management strategies, to establish a protocol to resolve potential conflicts of interest and to establish a list of agricultural weed species in Europe for biological control. Three principal methods of biological weed control are used in COST-816: the inoculative or classical approach, the system management approach and the inundative or microbial herbicide approach. Initially, Amaranthus spp., Convolvulus arvensis/Calystegia sepium, Chenopodium album and Senecio vulgaris were chosen as target weeds, each being the subject of a working group. A fifth working group on the control of Orobanche spp. control is in preparation. This concentration on a few target weed species has greatly stimulated cooperation and facilitated technology transfer between the research groups