Introductions of non-native plant pathogens into Great Britain, 1970–2004

An analysis of records of plant pathogens first identified in Great Britain from 1970 to 2004 (inclusive) was undertaken to determine the numbers of new species that have become established over time. Results show that the numbers of newly recorded pathogens have not varied significantly. Of the 234 pathogens recorded for the first time between 1970 and 2004, 157 were fungi, 27 were oomycetes, 26 were viruses, 23 were bacteria, and one was a phytoplasma. Approximately 53% of pathogens were found on ornamental crops, 16% on horticultural crops, 15% on wild native species, 12% on agricultural crops, 2% on pasture plants and 2% on exotic forestry tree species. Where the origin of introductions was known or strongly suspected, 47% came from the Netherlands. About 38% of newly recorded pathogens with information on the location of first record were discovered in the South East region of England. Plant Pathologists regarded 19% of all new pathogens as important because of actual or potential economic/environmental losses. The results indicate that the numbers of new or important pathogens establishing in recent years are not increasing and that most new findings are associated with ornamental plants.     

Survival of plant pathogens under structural solarization

Structural solarization of greenhouses is a nonchemical sanitation procedure. The method involves dry heating, since maximal temperatures may exceed 60°C and consequent relative humidity (r.h.) is low (ca 15%), under fluctuating temperature and r.h. regimes. Thirty-five structural solarization experiments were performed over 7 years, testing one bacterial and five fungal plant pathogens. Various aspects of pathogen thermal inactivation under this method were studied. Thermal inactivation of the various pathogens differed according to the organism and inoculum form. Sensitivity to heat was highest withClavibacter michiganensis subsp.michiganensis and lowest withFusarium oxysporum f.sp.radicislycopersici inoculum in dry infected tomato stems, with ED₈₀ values of 7 and 47 days, respectively; intermediate values were obtained forPythium sp.,F. oxysporum f.sp.melonis, F. oxysporum f.sp.basilici andSclerotium rolfsii. The maximal ambient temperatures were in the range of 28.2° to 33.1°C. Structural solarization for sanitation can be a useful component of integrated pest management in greenhouses. http://www.phytoparasitica.org posting Sept. 28, 2004.     

CEP peptide induces susceptibility of Arabidopsis thaliana to non-adapted pathogens

CEP peptide was synthesized and tested for induction of disease susceptibility using Arabidopsis Col-0. When Colletotrichum tropicale was used as a non-adapted fungal pathogen, the conidia germinated to form hyphal-like structures, which successfully penetrated epidermis, eventually causing disease symptoms. In such case, PEN2-, but not PEN3-dependent resistance was likely suppressed by CEP peptide. Similarly, the CEP peptide-mediated disease susceptibility was also effective to a non-adapted bacterial pathogen. Notably, such induced susceptibility was also evident on Arabidopsis mutants lacking the previously identified receptors, suggesting that the CEP peptide modulates Arabidopsis immunity through an unidentified receptor(s).

     

Survival of plant pathogens in static piles of ground green waste

Ground green waste is used as mulch in ornamental landscapes and for tree crops such as avocados. Survival of Armillaria mellea, Phytophthora cinnamomi, Sclerotinia sclerotiorum, and Tylenchulus semipenetrans was assessed for 8 weeks within unturned piles of either recently ground or partially composted green waste. S. sclerotiorum survived at the pile surface and at 10, 30, and 100 cm within the pile for the entire 8 weeks in both fresh green waste (FGW) and aged green waste (AGW). A. mellea and T. semipenetrans did not survive more than 2 days in FGW, while P. cinnamomi persisted for over 21 days in FGW. AGW was less effective in reducing pathogen viability than FGW, most likely because temperatures in AGW peaked at 45 degrees C compared with 70 degrees C in FGW. Survival modeling curves based on pile temperatures indicate the time to inactivate 10 propagules of pathogens was 11, 30, 363, and 50 days for A. mellea, P. cinnamomi, S. sclerotiorum, and T. semipenetrans, respectively. Sclerotia-forming pathogens pose the greatest risk for escape; to ensure eradication of persistent fungi, green waste stockpiles should be turned intermittently to mix pile contents and move pathogen propagules to a location within the pile where they are more likely to be killed by heat, microbial attack, or chemical degradation.     

长白山沿脉参类锈腐病菌比较生物学研究

 长白山沿脉是我国人参和西洋参的主要栽培区,长期以来,参根锈腐病一直是该地区参类栽培中最为严重的病害之一。有关参类锈腐病菌具体种类的报道不尽相同,为此,作者分离了长白山沿脉不同地区的12个人参和西洋参锈腐病菌株,在病原形态学研究的基础上,测试比较了各菌株对温度、pH、光照等不同培养条件下的异同,以了解其生物学特性,并辅助形态分类。     

Effect of the endophyte <Emphasis Type="Italic">Neotyphodium lolii</Emphasis> on susceptibility and host physiological response of perennial ryegrass to fungal pathogens

The effect of the endophyte Neotyphodium lolii on susceptibility of perennial ryegrass (Lolium perenne) to ten fungal pathogens in detached leaves was studied. The pathogens were Alternaria alternata, Ascochyta leptospora, Bipolaris sorokiniana, Curvularia lunata, Fusarium acuminatum, F. avenaceum, F. chlamydosporum, F. solani, F. oxysporum, and Gliocladium roseum. In addition, the effect of the endophyte on four pathogens (A. alternata, B. sorokiniana, Curvularia lunata and F. avenaceum) in living plants was studied, and changes in host superoxide dismutase (SOD) or peroxidases (POD) activity were examined. The total lengths of lesions on detached leaves were greater (P < 0.05) on E- plants than on E+ plants except for A. leptospora although differences between E+ and E- were not consistently significant at all sample times (days after inoculation).The numbers of lesions were greater (P < 0.05) and the lesions were larger (P < 0.05) on intact E- plants than on intact E+ plants for all of the four pathogens. SOD enzyme activity was significantly greater (P < 0.05) in E+ plants than in E- plants only for A. alternata, C. lunata, and F. avenaceum. POD enzyme activity was significantly greater (P < 0.05) in E+ plants than in E- plants only for C. lunata, B. sorokiniana and the uninoculated control.     

Survival of pathogens of Brussels sprouts (Brassica oleracea Gemmifera Group) in crop residues

Mycosphaerella brassicicola (ringspot), Alternaria brassicicola and A. brassicae (dark leaf spot) and Xanthomonas campestris pv. campestris (black spot) can infect leaves of Brussels sprouts resulting in yield losses. Infections of outer leaves of sprouts cause severe losses in quality. Crop residues can be a major primary inoculum source of the pathogens. Their population dynamics were followed in residues of leaves and stalks of crops of Brussels sprouts during 24 months using real‐time PCR assays. Leaf residues on the soil surface or buried in soil decomposed within 4 months. However, residues of stalks were present in the field after 24 months. In such residues, M. brassicicola populations increased during the first 2 months, but decreased thereafter and the pathogen was found only occasionally in the second year. Alternaria brassicicola multiplied on stalks exposed on the surface of field soil and was present on such residues after 24 months. Survival was less on residues buried in soil. Alternaria brassicae population increased in stalks exposed on the soil surface during the first months but decreased thereafter under the detection limit. Xanthomonas campestris cv. campestris populations fluctuated in time but 1 × 10⁴ cells mg^?1 stalk residue were still found after 24 months. Additionally, the four pathogens were present in residues of 11 commercial rapeseed crops that were analysed. The observed variation in population sizes of the pathogens between individual pieces of crop residues indicates a stochastic spread of pathogens. Unravelling the underlying processes will support the development of novel methods for sustainable disease prevention.     

Interception of Colorado beetle in England and Wales, 1983–1987

The policy of the British Government continues to be to maintain total freedom from Colorado beetle by preventing its introduction and eradicating any breeding colonies which are found. During the years 1983–1987, no breeding colonies have been found and there is no evidence that the Colorado beetle is established anywhere in the UK. Interceptions on imports during this period are analysed by country of origin and also by means of introduction. Total confirmed reports of live beetles are compared with those in previous reports; 250 were found in 1983–1987, 286 for the previous 5-year period and 563 of known origin for the 20-year period previous to 1978.     

Effect of phenology on susceptibility of Norway spruce (Picea abies) to fungal pathogens

Ceratocystis polonica and Heterobasidion parviporum are important fungal pathogens in Norway spruce (Picea abies). Tree susceptibility to these pathogens with respect to phenology was studied using artificial fungal inoculations at six stages of bud development, and assessed by measuring phloem necroses in the stems of 2‐ and 8‐year‐old trees. Tree capacity for resistance was assessed by measuring phloem nonstructural carbohydrates at each stage. Phloem necroses were significantly larger in trees with fungal versus control inoculations and increased significantly over time. Changes in nonstructural carbohydrates occurred in the trees; a significant decline in starch and a slight but significant increase in total sugars occurred over time. These results suggest that susceptibility to fungal pathogens and carbohydrate levels in the stems of the trees were related to fine‐scale changes in bud development. A trade‐off may occur between allocation of starch (the major fraction of the stem carbohydrate pool) to bud development/shoot growth versus defence of the stem. Previous tests of plant defence hypotheses have focused on herbivory on plants growing under different environmental conditions, but the role of phenology and the effect of pathogens are also important to consider in understanding plant resource allocation patterns.