Nursery Pots Research Articles

Hot Water Drench Treatments for the Control of Radopholus similis in Rhapis and Fishtail Palms

Exporters of potted nursery stock face strict quarantine regulations against the burrowing nematode, Radopholus similis. Currently, there are no treatments approved by quarantine authorities to disinfest plants of R. similis. Interceptions of the nematode lead to significant economic loss and curtailment of trade, therefore hot-water drench treatments were investigated for quarantine utility. Drenches with 50 °C water were applied for 10 to 16 minutes to two economically important palm species, rhapis (Rhapis excelsa) and fishtail (Caryota mitis). Plants were inoculated with 5,000 mixed life stages of R. similis and allowed to establish for 14 weeks before drench treatments. In rhapis, a moderately good host to R. similis, a 16-minute hot water drench had high efficacy, achieving 99.6% mortality. In fishtail, a poor host, all treatments longer than 10 minutes at 50 °C eliminated R. similis from the plants. Probit regression estimates of the LT99, were 16.9 and 10.3 minutes respectively. However χ2 goodness-of-fit tests were significant (χ2 = 21.136, df = 3, p < 0.0001) for rhapis. Since most observed values were between the 95% fiducial limits, this suggests that the large χ2 value was caused by variability in response or insufficient repetitions rather than an inappropriate model. A χ2 statistic could not be computed for fishtail because poor host status led to variances that were nearly equal to zero. The high efficacy of hot water drenches for the control of R. similis is approaching the Probit 9 standard of 99.9968% mortality required for approval as a quarantine treatment.

First Report of Powdery Mildew Caused by Erysiphe viburni on Viburnum tinus in California.

In June 2003, landscape and potted nursery plants of laurustinus (Viburnum tinus) in Monterey County, California, were found to be infected with a powdery mildew. White, ectophytic mycelial and conidial growth were present primarily on adaxial leaf sides with only sparse growth on abaxial surfaces. Severely infected leaves were buckled and slightly twisted. Affected leaf tissue exhibited slight purple-to-brown discoloration. Appressoria were opposite and lobed. Conidia were produced singly, cylindrical in shape, and measured 31 to 42 × 14 to 19 μm. No fibrosin bodies were observed in the conidia, and the conidia germinated at the ends. Ascomata were not observed. The fungus was identified as Erysiphe (section Microsphaera) viburni Duby (= Microsphaera sparsa Howe = Microsphaera penicillata [M. sparsa is not completely synonymous with M. penicillata because M. sparsa is defined as only those mildews that attack viburnum, whereas M. penicillata was defined as attacking dogwood, alder, etc.]) (1,2). Pathogenicity was demonstrated by gently pressing infected leaves with abundant sporulation onto recently expanded leaves of four, large, potted laurustinus in standard 5-gallon nursery containers (19 liters). Twelve leaves per plant were inoculated. The plants were incubated in a greenhouse (23 to 25°C). After 9 to 10 days, powdery mildew colonies developed on approximately 50% of the inoculated leaves. Such colonies were morphologically similar to the original fungus. Uninoculated control plants did not develop powdery mildew. Using the same technique, inoculating fully mature leaves of the same plants did not result in disease. To our knowledge, this is the first report of Erysiphe viburni infecting V. tinus in California. At some landscaped areas the powdery mildew was extremely severe, causing plants to take on a whitish appearance and resulting in all new foliage being misshapen. E. viburni has also been reported to infect V. japonicum in California.

Rediscovery and redescription of the centipede Paracryptops inexpectus Chamberlin, 1914, with an account of the genus (Scolopendromorpha: Cryptopidae: Cryptopinae)

Paracryptops inexpectus Chamberlin, 1914, known only from the holotype that was discovered in a potted plant from Guyana during quarantine inspection in Washington, DC, USA, is redescribed and illustrated based in part on two newly discovered specimens from Dominica, Lesser Antilles. A generic account is also presented along with a brief literature review. The species is the only generic representative in the Western Hemisphere; the other four species occur in southern/southeast Asia and the East Indies, as depicted in a distribution map. This pattern suggests that the New World occurrences of P. inexpectus result from human introductions, and that it is really an Asian species. As representatives of Paracryptops Pocock, 1891, have twice been intercepted in quarantines, another was discovered under flower pots in a plant nursery, and five others were taken in urban environments where allochthonous species typically predominate, these centipedes seem particularly amenable to transport and introduction through human agency. With few anatomical distinctions between them, P. inexpectus may be a junior synonym of P. weberi Pocock, 1891.

Fruit Yield and Quality of Greenhouse-grown Bell Pepper as Influenced by Density, Container, and Trellis System

Production and quality of bell pepper (Capsicum annuum) fruit were evaluated in a passively ventilated greenhouse, in soilless media trellised to a “V” system (two-stempruned plants) or the “Spanish” system (nonpruned plants) in flat bags or nursery pot containers; and densities of 1.5, 1.9, 3.0, and 3.8 plants/m2 (0.14, 0.18, 0.28, and 0.35 plants/ft2), in a winter-to-summer-crop in Gainesville, Fla. The trellis systems did not affect total marketable fruit yields but production of extra-large fruit was higher (38%) in non-pruned than in pruned plants. Marketable fruit yields were similar in plants grown in bags and pots, and had positive linear responses to increased plant density. Not pruning reduced by half the percentage of fruit with blossom-end rot. Pruned plants produced 50% fewer flower bud supporting nodes than non-pruned plants but had a greater percentage of fruit set. Regardless of trellis systems, fruit set per plant decreased linearly as plant density increased. Overall, the “Spanish” trellis system at a density of 3.8 plants/m2 resulted in greater yields of extra-large fruit and required 75% less labor than the “V” system to prune and support the plant canopy.

First Report of Sirococcus conigenus on Deodar Cedar in Oregon.

Cedrus deodara is a highly valued conifer widely grown as an ornamental in the Pacific Northwest and southern United States. C. deodara in the Pacific Northwest is normally problem free but occasionally is damaged by dieback of shoot tips, which has been associated with a fungus resembling Sirococcus conigenus. In February 2002, bleeding cankers were observed on 2- to 4-year-old stems of potted nursery stock of C. deodara cv. Karl Fuchs from Clackamas County, OR. Cankers were dark with indistinct margins, shallow, and up to 30 cm long. Infection appeared to have originated with small twigs that had died. Cultures isolated from discolored bark on streptomycin-amended potato dextrose agar (PDA) produced conidiomata with hyaline, fusiform, two-celled conidia typical of S. conigenus (1,3). Inter-simple sequence repeat-polymerase chain reaction fingerprints of an isolate from one of these trees were consistent with the P group of S. conigenus (mostly from hosts in Picea and Pinus spp.) (2). This isolate (02-04, ATCC MYA-2969) was used to inoculate two shoots on each of 12 3-year-old potted deodar cedars in each of two trials. Removing a needle wounded each shoot, and an agar plug colonized with mycelium was placed over the wound and held in place for 2 weeks with Parafilm. Sterile agar plugs were applied to two wounded control shoots on each tree in each trial. After 10 weeks, 25 of 48 inoculated shoots were blighted and drooped with yellow to brown needles that eventually dropped. The pathogen was reisolated from 24 of 25 symptomatic shoots but not from asymptomatic or control shoots. To our knowledge, this is the first confirmed report of S. conigenus as a pathogen of C. deodara.

Polygala myrtifolia as a New Natural Host of Cucumber mosaic virus.

Cucumber mosaic virus (CMV), Tomato spotted wilt virus (TSWV), and Impatiens necrotic spot virus (INSV) are among the most important viral pathogens of ornamental plants (1). Polygala myrtifolia L. (myrtle-leaf milkwort), originating from South Africa, and a member of the Polygalaceae, was recently introduced in Italy as a cultivated ornamental shrub for its fast and attractive free-flowering growth and drought-resistant characteristics. It can become an invasive plant and is now considered a serious problem in coastal areas of Australia where it was introduced as a garden plant. In Italy, P. myrtifolia is propagated by cuttings in commercial nurseries during the summer. In the winter of 2002, plants of P. myrtifolia growing in pots in an ornamental nursery in Sicily showed virus-like mosaic and malformation of leaves that appeared lanceolate with a lack of flowering. Leaf tissue was analyzed by double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) with polyclonal antisera to CMV, TSWV (Lettuce type), and INSV. Positive ELISA results were obtained only with the CMV polyclonal antisera. Complete remission of symptoms was observed on new flushes after pruning and incubation of infected plants at warm temperatures (30 and 20°C, day and night, respectively). This evidence led to the hypothesis that the disease or virus was disseminated by transportation and propagation of plants without visible symptoms during the hot season. A survey was also performed in two historical gardens of Catania (Sicily) where a group of apparently healthy P. myrtifolia plants, from the previously mentioned ornamental nursery in Sicily, were introduced as a single specimen or to form a hedge. These plants showed the same leaf malformations and mosaic symptoms observed in the nursery. DAS-ELISA confirmed the presence of CMV but not TSWV and INSV. To our knowledge, this is the first report of CMV on P. myrtifolia and it adds a new host to over 1,000 species (85 plant families) infected by this virus. Reference: (1) M. L. Daughtrey et al. Plant Dis. 81:1220, 1997.

Comparative evaluation of juvenoids for control of cat fleas (Siphonaptera: Pulicidae) in topsoil.

The efficacy of a photostable formulation of methoprene and two photostable juvenoids, fenoxycarb and pyriproxyfen, and their residual activity in inhibiting the emergence of adult cat fleas, Ctenocephalides felis (Bouché), was studied in topsoil. Nursery pots composed of clay, peat, and plastic, and wooden flats were used to hold soil samples. Treated soil samples were exposed to sunlight during the 63-d study period. Methoprene was as effective as fenoxycarb and pyriproxyfen against cat fleas for up to 42 d in clay, peat, and plastic pots at a concentration of 64.56 mg (AI)/m2 (6 mg [AI]/ft2), but its activity declined significantly thereafter. In contrast, fenoxycarb and pyriproxyfen showed strong residual activity for the entire 63 d. The activity of methoprene declined even more rapidly over time in wooden flats, while at the same concentrations the other two juvenoids showed significant residual activity for 63 d. Clay, peat, and plastic pots were therefore considered to be equally effective for evaluating the outdoor efficacy of juvenoids in comparison to the wooden flats. However, results obtained with wooden flats may be more realistic when testing residual activity of volatile chemicals such as methoprene. Fenoxycarb and pyriproxyfen showed strong efficacy and residual activity at concentrations of 8.07, 16.14, and 32.28 mg (AI)/m2, whereas methoprene did not cause a significant reduction of adult emergence at levels below 64.56 mg (AI)/m2. LC50 values for methoprene, fenoxycarb, and pyriproxyfen needed for preventing flea emergence when applied to topsoil were estimated to be 0.643, 0.031, and 0.028 ppm, respectively.

Global Status of the Production of Biobased Packaging Materials

Bioplastics from renewable origin are a new generation of plastics able to significantly reduce the environmental impact in terms of energy consumption and green-house ef-fect in specific applications. Bioplastics perform as traditional plastics when in use and are completely biodegradable within a composting cycle. Today bioplastics and partic-ularly starch-based plastics are used in specific industrial applications where bio-degradability is required. Examples are composting bags and sacks, fast food service-ware (cups, cutlery, plates, straws, etc.), packaging (soluble foams for industrial pack-aging, film wrapping, laminated paper, food containers), agriculture (much films, nur-sery pots, plant labels), hygiene (diaper back sheet, cotton swabs).Moreover new sec-tors are growing outside biodegradability, driven by improved technical performances of bioplastics versus traditional materials, as in the case of biofillers for tires. The market of starch-based bioplastics in 1999 has been estimated at about 20,000 t/a, with a strong incidence of soluble foams for packaging and films. Bioplas-tics from renewable origin, either biodegradable or non-biodegradable, still constitute a niche market which requires high efforts in the areas of material and application devel-opment; the technical and economical breakthroughs achieved in the last three years, however, open new possibilities for such products in the mass markets and specifical-ly in food packaging. This paper will review the recent industrial achievements of bioplastics in the sector of packaging, taking in consideration their in-use performances, biodegradation behav-iour and environmental impact.

A Single Basal Application of Total Nitrogen in Nursery Pot with Controlled Availability Fertilizer in Strawberry Culture

A Single Basal Application of Total Nitrogen in Nursery Pot with Controlled Availability Fertilizer in Strawberry Culture

Efficacy of Acetamiprid Tablet against Cotton Aphid on Cucumber by Various Application Methods

Efficacy of acetamiprid tablet against the cotton aphid on cucumber by various soil application methods was investigated compared to that of its granule applied under the same conditions. Acetamiprid tablet weighed 0.15 g including 20 mg active ingredient at 1 tablet/plant and controlled-release 2% granule at the dosage of 1 g/plant showed excellent efficacy when they were applied at the center of planting hole, similarly to the granule applied uniformly. The comparison between the efficacy in row application of tablet and soil surface application of granule suggested the efficacy of both applications became insufficient as the distance between the foot of seedling and application site became longer. Such a tendency was more remarkable with row application of the tablet than with soil surface application of granule. The tablet exhibited excellent efficacy at the dosage of 1 tablet/plant by being applied both at the foot of plant in nursery pot before transplanting to the field and at the center of the planting hole. Besides, efficacy of different sizes of tablet including same amount of acetamiprid was investigated by planting hole application. There was a tendency that tablet exhibited longer lasting activity as it became larger as far as the weight of 0.15, 0.3 and 0.6 g. With soil surface application the tendency of efficacy was reversed compared to that with planting hole application.

253 Influence of the Timing of Propagation and Cold Storage on the Growth and Development of Alstroemeria Pot Plants

Two butterfly-type cultivars of Alstroemeria were used to evaluate the effect of different dates of propagation and cold storage techniques on the growth and flowering of potted plants. The cultivars used were `Patricia Lynn' and FL-101. Plants were propagated during four different dates of 1997 (weeks 39, 41, 43, and 47) in large nursery pots (3.8 L) or in small nursery pots (1.4 L). Following division, all plants were grown for 4 weeks. After this period of establishment, plants in the large nursery pots were transferred directly to the final growing greenhouse (16 °C nights) and plants in the small pots were refrigerated at 4 °C for 8, 6, 4, or 0 weeks with either complete light or complete dark conditions. Once the cold treatment was accomplished, all plants were transferred on the same date to large nursery pots for finishing with those plants that had been initially propagated in large pots. All plants were cut back on week 3 of 1998. Plants were evaluated for date of harvest, visual evaluation, fresh aerial weight, number and length of flowering stems, and number of florets per flowering stem. Refrigerated treatments delayed the time of flowering when compared to plants that were grown with no refrigeration. Fresh weight and stem length values of plants that were not refrigerated were less than or equal to those of plants that were refrigerated, with the exception of plants that was propagated on week 47. In addition, the number of flowering stems that were produced from plants that were refrigerated was either greater than or the same as plants that were not refrigerated. The presence or absence of light during refrigeration had no effect on subsequent plant growth and development. There were no differences observed among treatments for visual evaluation and number of florets produced per inflorescence. This research demonstrated that potted Alstroemeria plants can be propagated early and stored under cold conditions without these procedures affecting final plant performance, but the process will affect the scheduling of the crop.

610 Evaluation of Sawmill Residue as a Component of Nursery Potting Mix

The standard mix used by most nurseries consist of a 9 pine bark: 1 sand. With the ever-increasing cost of bark, nurseries are looking for an alternative. Sawmill residue may hold potential utility as part of a potting mix. Although sawmill residue is highly variable, it can serve as soil bulk as well as an organic medium. The purpose of this study was to determine if old sawmill residue not treated by pathogen-free requirement procedures could be used “as is” as part of a nursery soil mix. For this study, a sample, a typical conglomerate of undetermined wood chips, bark, and soil particles, was obtained from an “old pile” (just how old is not known) of sawmill residue. To determine how this sample would function in a nursery bark/sand mix, tests were run on its physical properties of pore space and water-holding capacity. The sawmill residue had the following characteristics: a mean 44.2% porosity capacity, 23.4% air space, and 20.8% water holding capacity. A standard fertilizer and lime amendment package was added to the sawmill residue in the same rates as a regular nursery mix. The sawmill residue and the standard nursery mix were then blended according to the treatment percentages. The treatments were sawmill residue/standard nursery mix 0/100, 10/90, 30/70, 60/40, and 100/0. The Ilex crenata `Compacta' liners were planted into standard 1-gallon nursery pots filling to just below the rim. The pots were randomly placed on a well-drained rock surface in full sun. No additional fertilizer was used and watering was done as needed. Plants were grown for 1 year. Visual assessments were made throughout the growing period and at harvest. There was no visible difference in any of the treatments as far as overall growth was discerned. The plants were of uniform height and width showing consistent, even growth and good leaf color. Root system growth and development were evaluated visually and over all treatments were uniformly good. No root problems were noted. There was not any plant loss in any treatment over the entire study. Each plant was cut at the soil line and dried for 24 hours at 1150 °C. Dry weights were taken after the plant material had cooled for 4 hours. Results were based on four plants per treatment times four replications for a total of 16 plants per treatment. There was not any measurable growth difference in dry weight among treatments 1, 2, 3, and 4 [sawmill residue/standard nursery mix 0/100 (41.03 g dry weight), 10/90 (39.83 g dry weight), 30/70 (38.98 g dry weight), 60/40 (37.42 g dry weight)]. However, treatment 5 [100/0 (31.03 g dry weight)] was significantly lower when compared to the remaining four treatments. The lower dry weight may be attributed to the 100% sawmill residue being too heavy and not well-drained enough. However, the roots did not show any damage from being too wet. Further work is being done with the sawmill residue.

A plant growth promoting rhizobacterium and temperature effects on performance of 18 clones of potato

A survey of genotypic responses to beneficial bacterium (Pseudomonas sp. strain PsJN) was conductedin vitro andex vitro, under two temperature conditions, using eighteen clones of potato of different heat stress tolerance: temperate adapted cultivars Kennebec and Russet Burbank; heat tolerant DTO-2, DTO-28, DTO-33, LT-1, LT-2, LT-5, LT-6, LT-7, LT-8, LT-9, Y84-02, NDD277-2, Desiree, and Maine-47; and heat sensitive abscissic acid (ABA)-deficient mutants 11401-01 and 9120-05. Nodal explants taken from 6-week-old bacterized and non-bacterized control plantlets were culturedin vitro on a hormone-free potato nodal cutting medium, and placed at either 20/15 C or 33/25 C day/night temperature, 12h photoperiod and 250 µE m−2 s−1 mixture of fluorescent and incandescent light, for six weeks. The tuberization response was studiedex vitro after two weeks acclimation of 2-week old plantlets at 33/25C. The acclimated plantlets were transplanted to 3L plastic nursery pots containing peat-based Pro-Mix growing medium and placed in growth chambers at either 20/15 or 33/25 C day/night temperature, 12 h photoperiod, 475 μE m−2 s−1 light and ≈80% RH, for 12 weeks. Compared to the non-bacterized controls, bacterization significantly increased stem length of 12, shoot biomass of 9, and root biomass of 2 clones at 20/15C; and stem length of 14, shoot biomass of 15, and root biomass of 13 clones at 33/25C. High temperature increased length of internodes and had either no effect or slightly decreased node number. Temperature increase had the most dramatic effect on root development. An average shoot to root ratio decreased from 3.7 at 20/15 C to 1.7 at 33/25 C for non-bacterized plantlets and, respectively, from 4.3 to 1.5 for bacterized. The beneficial effect of bacterization on root biomass was the most pronounced in LT-1 and Maine-47 at 20/15 C and LT-8, Maine 47, DTO-2, Kennebec, NDD277-2 and 11401-01 at 33/25C. The temperature elevation did not significantly affect root biomass of LT-6, DTO-28 and Desiree. Temperature stress caused severe reduction in tuber number and tuber fresh weight. ABA-deficient mutants did not produce any tubers and LT-8, LT-9, Y84-027 and DTO-28 tuberized very poorly at 33/25C. DTO-33, Desiree, LT-1 and Kennebec gave the highest number of tubers per pot and Kennebec, LT-1, Desiree and LT-7 the highest yields at this temperature. There was no significant effect of bacterization on tuberization at 20/15 C but at 33/25 C bacterization significantly enhanced tuber number and weight in LT-7 and reduced tuber weight in DTO-2. Although there was no clear link between thein vitro response of particular clones to bacterization and their heat stress tolerance, improvement ofex vitro performance of heat tolerant LT-7 indicates that rhizosphere bacteria may play a role in clonal adaptation of potato to heat stress.

Real-Time Measurement of NO3− and NH4+ Leaching from Plant Nursery Pots

Concerns relating to pollution from nitrogen fertilizers leaching into ground water are increasing. This is especially important in southern Florida because the pollution threatens fragile ecosystems in Biscayne Bay, and the two National Parks that abut agricultural areas. The current research is focused on the development of an automatic system which can monitor and leaching from plant nursery pots. and electrodes and a load cell were used for real-time measurements of , , and leachate volume. The leachate was directed to pass the sensing areas of , reference, pH, and electrodes. It was collected and weighed in a container placed on a load cell. The analog signals from the electrodes and load cell were digitized through data acquisition technology using a 16-bit A/D converter and a self-developed software program. With this system the volume of the leachate and concentrations of and in the leachate were determined in situ. Based on this design, the dynamics of and leaching from pots can be observed. This system can be used to 1) determine soil (or media) holding capacity of and , 2) evaluate the effects of nitrogen fertilizer formulations on water quality, 3) develop best management practices of nitrogen application in containerized plant production, and 4) determine the soil-holding capacity to optimize the use of water. The advantages of the developed system are 1) low labor cost for sample collection and analysis and 2) high measurement resolution resulting from a minimization errors that occur during sampling and other manual operations.

Use of bacterial bioluminescence for monitoring the behavior of rhizobacteria introduced to plant rhizosphere

Bioluminescence (lux) genes from Vibrio harveyi were introduced into an artificial transposon vector pJFF350 as a constitutively expressing lux-genes set. The resultant recombinant plasmid pSOL2 was then transposed into the chromosome of fluorescent pseudomonad strains, in which the lux genes were stably integrated. Root colonization by the lux-marked strains was visually monitored by autophotography, and it was found that the bioluminescence intensities were highly correlated with the populations of the strains colonizing roots. A strain of Pseudomonas putida thus lux-marked was inoculated to spinach seedlings in nursery pots, and the root colonization was assayed. In sterile soil, the strain extensively colonized the entire part of the developing roots and the population densities at any sites were high. In non-sterile soil, only the inoculated site of the roots was weakly colonized. These results suggest that the presence of the indigenous microflora is an environmental constraint on root colonization of the introduced bacteria.

A Taste-test Comparison of Organic and Conventional Greenhouse Tomatoes

`Caruso' tomatoes were grown in a glass greenhouse in Winter and early Spring 1991. All plants were grown in 16-liter nursery pots. Half the plants were grown in a conventional peat-lite medium (Profi-mix) and were fertilized with synthetic water-soluble fertilizer containing micronutrients and (in ppm) 187 N, 46 P, 278 K, 177 Ca, and 48 Mg. The other plants were grown in a potting medium composed of 1 mature compost (chicken manure and leaves): 1 loam: 2 vermiculite (by volume); this medium was amended with 1.5 kg bone meal (2N–10P–0K) and 3 kg dolomitic lime/m3. The “organic” treatment was fertilized with a fish emulsion solution containing (in ppm) 150 N, 13 P, and 25 K. The experiment was repeated in 1992 with `Capello'. In both years, fruit were harvested around the half-ripe to three-quarters ripe stage. All insect control was with insecticidal soap and bio-control agents. A blind taste test was conducted on campus in both years. In 1991, of 70 participants, 73% preferred the “conventional” tomatoes, 20% preferred the organic tomatoes, and 7% expressed no preference. In 1992, of 105 participants, 67% preferred the “conventional” tomatoes, 24% preferred the organic tomatoes, and 10% expressed no preference.

Control of Spider Mites on Potted Viburnum, 1994

Abstract Trials were conducted on potted nursery stock in 5 gal containers that were heavily infested with spider mites. Individual plots consisted of single plants, arranged in a RCB design with five replications. Treatments were applied with a CO2 compressed air sprayer to point of run-off on 26 Jul. A second application was made 15 Aug, however plant vigor was declining rapidly at this point with many plants nearly killed. All evaluations were made by taking 8 leaves (2 from each cardinal point), washing the mites off with 70% EtOH and counting them under magnification (70X).

Forsythia: A New Host ofPhytophthora nicotianaein Italy

During the summer of 1990, seedlings of forsythia (Forsythia viridissima), grown in pots in a production nursery in Campania (Italy), showed symptoms of decline associated with root and crown rot. Phytophthora nicotianae of A 2 mating type was isolated from decayed tissues. Identification of the isolate was based on both morphological and physiological characters, and on the electrophoretic pattern of total native mycelial proteins. P. nicotianae was confirmed as the causal agent of this decline by fulfilling Koch's postulates. Seedlings of forsythia inoculated with the P. nicotianae isolate developed symptoms identical to those observed in natural infections

New Diseases and EpidemicsPhytophthora iranica,a New Root Pathogen of Myrtle from Italy

A homothallic Phyrophthora sp. producing persistent and markedly papillate sporangia was isolated, together with P. nicotianae, from the rotted roots of seedlings of myrtle (Myrtus communis), grown in pots in a commercial nursery in Sardinia, Italy. The homothallic species isolated from myrtle was identified as P. iranica on the basis of morphological and cultural characteristics; it differed from other known Phytophthora spp. belonging to Waterhouse's group I in its higher cardinal growth temperatures

Effect of Solarisation Using Single and Double Layers of Clear Plastic Mulch on Pythium, Phytophthora and Sclerotium Species in a Nursery Potting Mix.

In experiments conducted in Darwin, Australia, temperatures generated during November at 25 cm depth in nursery potting mix by solarisation reached maximum values of 51°C and 44.6°C under a double and single layer of clear plastic mulch, respectively. The lowest temperatures were 41.3° and 38.1°C in July under the double and single layer of clear plastic mulch, respectively. Acyclic pattern of temperatures occurs over a 12 month period, following closely the global radiation figures. Three soilborne plant pathogens, Pythium myriotylum, Phytophthora nicotianae var. nicotianae and Sclerotium rolfsii were eliminated under a double layer of plastic within 2–8 days during the spring, summer and autumn experiments while it took 4–20 days at the same time of the year to eliminate the same pathogens using a single layer of plastic.