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2002 Potomac Division Meeting Abstracts

March 4-6, 2002 - Williamsburg, Virginia

Posted online April 25, 2003

Control of Phytophthora blight on annual vinca with phosphite foliar sprays. T. J. BANKO and C. Hong. Hampton Roads AREC, Virginia Tech, Virginia Beach, VA 23455. Publication no. P-2003-0001-PTA.

Phosphite, the salt of phosphorous acid, was evaluated for effectiveness in controlling Phytophthora blight of annual vinca (Catharanthus roseus) when applied as a foliar spray. Plants growing in a pine bark medium were fertilized by irrigating with a complete nutrient solution which provided P as phosphate at 0, 0.1, 0.3, or 0.5 mM. The plants were sprayed 5 times at 7-day intervals with P as phosphite at 0.5 mM, or they received no phosphite. Plants were then inoculated by misting with Phytophthora nicotianae zoospores. Inoculated plants sprayed with phosphite had significantly (P < 0.05) fewer diseased leaves and shoot tips than unsprayed plants, irrespective of the level of P provided in the nutrient solutions. In another experiment, vinca plants irrigated with a nutrient solution providing P as phosphate at 0.1 mM, were sprayed with a phosphite formulation providing P at 0.5 mM at 7-day intervals 4, 3, 2, or 1 times, then inoculated 1, 11, or 17 days after the last phosphite spray. Reduction in disease was obtained only if the last phosphite spray occurred 1 day prior to inoculation, regardless of the number of times sprayed.

Effects of preplant metam sodium and azoxystrobin applied in furrow on Cylindrocladium black rot of peanut in Georgia.
T. B. BRENNEMAN, R. C. Kemerait, Jr., and S. L. Rideout. Dept. Plant Pathology, University of Georgia, Tifton, GA 31794. Publication no. P-2003-0002-PTA.

Cylindrocladium black rot (CBR) of peanut is a disease of increasing importance in Georgia. Preplant metam sodium (94.6 l/ha) and azoxystrobin either in season alone (two sprays at 0.33 kg/ha) or in season plus azoxystrobin (0.11 kg/ha) in furrow were evaluated for their effects on CBR, stem rot, plant stand, and pod yield in 2000 and 2001. There were no fungicide by fumigant interactions either year. Metam sodium had little effect on plant stand or stem rot, but reduced CBR by 50-76% and increased yield by 574-1087 kg/ha. Azoxystrobin in season provided good control of stem rot and increased yield by 707-1466 kg/ha, but had no effect on CBR incidence. Azoxystrobin in furrow had no effect on plant stand, disease ratings, or pod yield, but these trials were established under ideal conditions. Planting weaker seed in adverse conditions may have given different results.

Puccinia lagenophorae
for biological control of common groundsel in the United States: Potential and concerns.
W. L. BRUCKART, III (1) and A. Senesac (2). (1) USDA-ARS-FDWSRU, Ft. Detrick, Maryland 21702; (2) Cornell Univ., Long Island Horticultural Res. Lab., Riverhead, NY 11901. Publication no. P-2003-0003-PTA.

Puccinia lagenophorae
(PL) is an exotic rust fungus candidate for biological control of common groundsel (Senecio vulgaris) in the U.S. In a containment greenhouse, PL caused a 30% reduction in plant dry weight compared with uninoculated controls. Bellis perennis (English daisy) also was susceptible to infection by PL in containment greenhouse studies. Not tested to date are any of nearly 100 species of Senecio native to North America. In 2001, PL was discovered on both S. vulgaris and B. perennis in the U.S. Issues with the discovery of PL in the U.S. include: 1) how much damage and control will the disease cause to common groundsel in the U.S., and 2) are North American species of Senecio and related plants at risk from PL? This is an appeal to document either the occurrence or lack of infection of S. vulgaris by PL in the Eastern U.S. Samples can be sent to the USDA-ARS in Frederick, MD, to confirm whether the infection is caused by PL.

A spinach isolate of Colletotrichum dematium from the United States and risk assessment of C. gloeosporioides from Russian thistle in Hungary.
C. A. CAVIN and W. L. Bruckart, III. USDA-ARS-FDWSRU, Ft. Detrick, MD 21702. Publication no. P-2003-0004-PTA.

An isolate of C. gloeosporioides (Cg) from Hungary is under evaluation for biological control of Russian thistle (Salsola tragus), a major weed pest of the U.S. This pathogen has been found to infect spinach in containment greenhouse studies. To clarify risk to spinach, studies have been initiated with a U.S. spinach isolate of C. dematium (Cd) as a standard for comparison with infections caused by Cg. Each pathogen has similar moisture and temperature requirements for infection, so comparative inoculations were made with 16-h dew at 25 DEG C. Cg damaged S. tragus Type A and not Type B, as expected from earlier studies, and Cg did not affect spinach biomass. Cd, the spinach pathogen, did not affect either type of S. tragus, and it did not reduce spinach biomass. Spinach plants bolted during the study, and it was difficult to assess the effect of either pathogen on spinach. In a current study with conditions favorable for spinach growth (no bolting), disease by Cd on spinach after 2 wk was significant (100% incidence, n = 10, and a mean rating of 1.6 [scale from 0 - 4]), compared to infections by Cg (30% incidence and a mean rating of 0.3).

Biocontrol potential of the fungi Hirsutella rhossiliensis and H. minnesotensis against Heterodera glycines.
S. Y. Chen. University of Minnesota Southern Research and Outreach Center, Waseca, MN 56093. Publication no. P-2003-0005-PTA.

Hirsutella rhossiliensis
and Hirsutella minnesotensis are spore-producing hyphomycetes that parasitize vermiform nematodes. The fungi were frequently encountered on the second-stage juveniles of the soybean cyst nematode, Heterodera glycines, in Minnesota, and they also have been observed on the nematode from Michigan and South Dakota. The effectiveness of biological control of H. glycines using the two fungi was evaluated in laboratory, greenhouse, and fields. Variation exists between the two species and among isolates. Hirsutella rhossiliensis is more effective than H. minnesotensis in lowering the H. glycines population density in greenhouse experiments. Field experiments during 1998-2001 showed that both fungi reduced SCN population density and increased soybean yield sometimes, but not always.

Efficacy of ultraviolet irradiance for disinfesting recycled irrigation water.
D. R. COHN and C. X. Hong. Virginia Tech, Hampton Roads Agricultural Research and Extension Center, Virginia Beach, VA 23455. Publication no. P-2003-0006-PTA.

Ultraviolet light can be used to treat recycled irrigation water and minimize its potential as a source of inoculum. We have evaluated the effectiveness of UV technology on pythiaceous species and other microbes in recycled irrigation water at different flow rates. Water samples at three flow rates and one untreated control were collected. Each sample was filtered through a membrane that was then rinsed in a water agar solution. Resultant suspension was spread onto plates containing one of three media (PARP-V8, PARPH-V8 or APDA). Isolation plates were incubated in the dark at 23°C. Microbial growth was examined daily and colonies were counted. There were significant differences among the pathogen recoveries with respect to flow rate. On an average PARP-V8 plate, 4.5 colonies of pythiaceous species were recovered from untreated water, while only 1.6, 0.7, or 0.06 colonies were recovered from treated water at 50, 30, or 10 gal/min, respectively. The results of this study will aid growers in the selection of UV units with appropriate capacities and use of UV technology in combination with other disinfestation systems.

QTL mapping of partial resistance in wheat to Stagonospora nodorum blotch.
P. C. CZEMBOR (1), E. Arseniuk (1), and P. Ueng (2). (1) Department of Plant Pathology, Plant Breeding & Acclimatization Institute, Radzików, 05-870 Blonie, Poland; (2) U.S. Department of Agriculture, ARS, Beltsville, MD 20705. Publication no. P-2003-0007-PTA.

A population of 111 doubled-haploid lines derived from a cross between a resistant wheat cultivar Liwilla and a susceptible cultivar Begra was screened for partial resistance toward Stagonospora nodorum under controlled conditions. Three resistance components, such as length of incubation period (INC), length of latent period (LAT) and disease severity (DIS), were evaluated. Bulk segregant analysis was used to detect the microsatellites and putative resistance gene analogs related to QTL resistance loci. Using the interval mapping method, four markers with LOD values higher than 3.0 on different chromosomes were detected: PtoKin(185,-) (2B), gwm499 (5B), gwm389 (3B) and gwm205 (5D). Of these molecular markers, gwm499 (5B) accounted for 19.3% of the variation in INC, 22.3% in DIS and 20.8% in LAT. There was another uncharacterized locus between Xgwm205 and Xgwm212 loci on chromosome 5D, which had a LOD value higher than 3.0 and accounted for 19-37% of the variation in three resistance components.

AFLP as a tool for identification and characterization of Pythium species.
C. D. GARZON, D. M. Geiser, and G. W. Moorman. Dept. Plant Pathology, The Pennsylvania State University, University Park, PA 16802. Publication no. P-2003-0008-PTA.

Identification of Pythium species is a difficult and time demanding process due to limited variation of morphological characters present in this organism. Molecular techniques are useful tools that facilitate this process. One of the newest molecular techniques is AFLP fingerprinting, developed by Vos et al. (1995). Although AFLP shares the versatility of other PCR fingerprinting procedures, it has a great advantage over them by using DNA restriction enzymes in the process of producing genomic DNA fragments. The specific activity of restriction enzymes produces a highly reproducible fingerprint, which makes the AFLP technique a very reliable procedure for diagnostics. We will present a general description of the AFLP technique and some insights of its use in diagnostics based on our experience. In general, to produce a species AFLP fingerprint it is necessary to invest a considerable amount of time reading gels, scoring bands, as well as choosing those characters that should be excluded, and those that are consistent and reliable. We’ll describe some of the obstacles and difficulties found during this process, information we consider very useful for first time users of this technique.

Single-strand conformation polymorphism analysis for rapid identification of plant pathogens.
C. X. HONG and P. Kong. Virginia Tech, Hampton Roads AREC, Virginia Beach, VA 23455. Publication no. P-2003-0009-PTA.

Single-strand conformation polymorphism (SSCP) analysis enables rapid detection of a single mutation of DNA fragments. This paper reviewed the examples of SSCP analyses for differentiation of plant pathogenic fungi, nematodes and viruses, illustrating the principles and procedures of this method, and its potential as a taxonomic and diagnostic tool. Strategies to ensure the reproducibility and increase the sensitivity of SSCP analysis were also examined, with special reference given to our recently developed species-specific SSCP markers for rapid identification of Phytophthora species that are common in recycled nursery irrigation water. SSCP analysis was also compared with other DNA polymorphism-based techniques such as restriction fragment length polymorphism (RFLP) for sensitivity, cost-effectiveness, and accessibility.

Ribosomal RNA interoperon sequence heterogeneity in new phytoplasma lineages infecting oak, campion, thistle, and dandelion.
R. JOMANTIENE (1,2), R. E. Davis (2), A. Alminaite (1), J. Staniulis (1), and D. Valiunas (1). (1) Institute of Botany, 2021 Vilnius, Lithuania; (2) Molecular Plant Pathology Laboratory, USDA-Agricultural Research Service, Beltsville, MD 20705. Publication no. P-2003-0010-PTA.

Oak trees (Quercus robur) with shoot proliferation on the main trunk (OakP), campion (Silene vulgaris) with yellowing of leaves and virescence of flowers (SilY), dandelion (Taraxacum officinale) with virescence of flowers (DanVir), and thistle (Cirsium arvense) with white leaf symptoms (CirWL) were observed in Lithuania. On the basis of collective restriction fragment length polymorphism (RFLP) patterns of 16S rDNA, OakP and SilY phytoplasmas were classified as members of group 16SrI (aster yellows group). CirWL and DanVir phytoplasmas were classified in group 16SrIII (X-disease group), new subgroups III-P and III-R, respectively. RFLP and nucleotide sequence analyses revealed 16S rRNA interoperon sequence heterogeneity in OakP, SilY, DanVir, and CirWL phytoplasmas. Results from phylogenetic analysis of 16S rDNA sequences were consistent with the concept that CirWL and DanVir represent distinct new lineages within the group 16SrIII phytoplasma subclade.

Simple, rapid PCR template preparations of pythiaceous species from mycelia, zoospore suspension and irrigation water samples.
P. KONG and C. X. Hong. Virginia Tech, Hampton Roads AREC, Virginia Beach, VA 23455. Publication no. P-2003-0011-PTA.

Preparation of DNA from a target source is an important step in polymerase chain reaction (PCR)-based research. In this study, we developed three simple and rapid protocols for PCR template DNA preparation. These protocols include (i) a one-step mycelium boiling method, (ii) direct addition of spore suspension into PCR mixes, and (iii) customization of a soil DNA kit for use in DNA purification from runoff and recycled irrigation water. These protocols have several advantages over current methods. None of these protocols requires lyophilizing, freezing, homogenizing or use of any hazardous chemicals. These protocols are also simpler, easier-to-use, less laborious and more cost-effective. Use of these protocols has greatly facilitated molecular characterization and detection of pythiaceous species in recycled irrigation water in our laboratory. These protocols are applicable to DNA extraction of other microbes and will promote the applications of PCR technology for molecular characterization and detection of other plant pathogens from recycled irrigation water and other inoculum sources.

Evaluation of selected fungicides for control of anthracnose on bell pepper.
J. MARVEL and S. A. Alexander. Dept. Plant Pathology, Physiology & Weed Science, Eastern Shore AREC, Virginia Polytechnic Institute & State University, Painter, VA 23420. Publication no. P-2003-0012-PTA.

Anthracnose disease has become an increasing problem on peppers grown on the Eastern Shore of Virginia. Previously pepper anthracnose was considered to be a minor problem easily controlled with maneb treatments, but in the past few years, growers have had significant yield reductions due to this disease. An experiment was established to evaluate the effectiveness of standard and newer fungicides. The fungicides were used singly and in a series of different alternations. The treatments were established in a randomized complete block design with four replications. Guard rows were inoculated with isolates of the pathogen taken from infected pepper fields to provide uniform disease pressure. There were three picks of pepper fruit during the experiment. The fruit was rated for number and weight of healthy fruit and diseased fruit. Treatments of azoxystrobin, trifloxystrobin, and kresoxim-methyl alone and in alternation with maneb provided the most effective control of pepper anthracnose.

Recent spread of rose rosette disease in the southeastern United States.
A. R. Peck (1), A. Baudoin (2), M. A. Hansen (2), and J. W. Amrine, Jr. (3). (1) Rt. 2 Box 198E, Blaine, TN 37709; (2) Dept. Plant Pathology, Physiology, and Weed Science, Virginia Tech, Blacksburg, VA 24061; (3) Division of Plant & Soil Science, West Virginia University, Morgantown, WV 26506. Publication no. P-2003-0013-PTA.

Rose rosette is a disease of unconfirmed but probably viral etiology, which is often lethal to wild as well as cultivated roses, and which has been proposed and used as a biological control for multiflora rose. In recent decades, the disease has become common in areas of the Midwestern USA, and has gradually spread eastward. By 1999, the known distribution of rose rosette disease included western Pennsylvania, Maryland, West Virginia, and Tennessee. Here we report that by 2001 rose rosette had spread to areas east of the Chesapeake Bay in Maryland, to several widely dispersed locations in northern as well as western and central Virginia (east of the Blue Ridge Mountains, including Henrico Co.), western North Carolina, western and one location in central South Carolina (Orangeburg Co.), and to northern Georgia. These records are based on characteristic symptoms. The disease was commonly found in wild (multiflora) as well as in cultivated roses.

Potential of common weed species to harbor Phytophthora nicotianae in nursery production.
P. A. RICHARDSON, J. F. Derr, and C. X. Hong. Virginia Tech, Hampton Roads AREC, Virginia Beach, VA 23455. Publication no. P-2003-0014-PTA.

Eight weed species were examined for susceptibility to Phytophthora nicotianae. Weeds included spurge (Euphorbia maculata), woodsorrel (Oxalis corniculata), chickweed (Stellaria media), groundsel (Senecio vulgaris), Eclipta alba, bluegrass (Poa annua), crabgrass (Digitaria sanguinalis), and sowthistle (Sonchus sp.). Tomato (Lycopersicon sp.) and annual vinca (Catharanthus roseus) were used as controls. In two separate experiments, weeds were either seeded in four replicate flats or young plants were transplanted to soil infested with 2% v:v vermiculite culture, averaging 5500 cfu/g soil. Disease symptoms were not observed on any weed species evaluated one month after seeding or transplanting. However, P. nicotianae was isolated from roots of all weeds except eclipta in the infested flats. Two to 35% of weed seedlings were infested, compared with >75% of tomato and >50% of vinca. Pathogen population in soil was 31-38% of the initial count. Transplants showed higher percent infestation in all weed species, ranging from 12% to 81%. These data, demonstrating that symptomless weeds are capable of harboring this pathogen, will aid in integrated weed and disease management decisions.

Development and evaluation of weather-based spray advisories for southern stem rot of peanuts.
S. L. RIDEOUT, T. B. Brenneman, and A. K. Culbreath. Dept. of Plant Pathology, Univ. of Georgia, Coastal Plain Exp. Station, Tifton, GA 31793. Publication no. P-2003-0015-PTA.

Temporal progression of southern stem rot (Sclerotium rolfsii) in peanut varies across seasons, reducing efficacy of calendar-based fungicide applications. Spray advisories based on soil temperature, precipitation, and host growth were tested in 1999, 2000, and 2001 in four locations each. Azoxystrobin was applied a maximum of twice at 0.34 kg a.i./ha on all treatments. In 1999, combined analyses could be performed on the four trials. Two advisories based on all three variables improved stem rot control (47.4 and 50.6% incidence) when compared to the calendar-based program (56.4%). However, no significant differences in yield were noted. Combined analyses were not performed in 2000 and 2001 due to significant trial-treatment interactions. In three of the eight trials, some advisories provided significantly better stem rot control than did the calendar-based program, but no significant differences in yield were observed. Calendar-based sprays were generally effective, but reduced disease in advisory plots indicates a potential for better stem rot control using environmental conditions.

Development of biological seed treatments to control soilborne pathogens of vegetables and wheat.
D. P. Roberts (1), E. L. Stromberg (2), G. H. Lacy (2), and J. S. Buyer (1). (1) Sustainable Ag Systems Lab, USDA-ARS, Beltsville, MD; (2) PPWS, Virginia Tech, Blacksburg. Publication no. P-2003-0016-PTA.

Biological agents are being developed to suppress take-all in wheat. A method was devised to screen hundreds of isolates of bacteria for take-all suppression in the field. Bacteria isolated from apparently healthy wheat roots from fields with take-all were identified using fatty acid methyl ester profiles. Meter row trials were conducted with diverse collections of bacteria applied as seed treatments in a gelatin formulation. Field screening identified diverse bacteria providing suppression of take-all in multiple years. Biocontrol agents are also being developed for suppression of damping-off of cucumber caused by Pythium ultimum and other soilborne pathogens of cucumber. Previous experiments show that ecological fitness in cucumber rhizosphere is not required for damping-off suppression. A diverse collection of bacteria and fungi from several sources was identified as potential agents for disease suppression. Potential biocontrol isolates are used to determine advantages of preparations containing multiple agents.

The use of GUS and GFP to investigate the interactions of pathogenic and non-pathogenic strains of Fusarium oxysporum on tomato roots.
J. C. RUPE (1), C. Olivain (2), C. Humbert (3), and C. Alabouvette (2). (1) University of Arkansas, Fayetteville, AR, USA; (2) UMR BBCE-IPM CMSE INRA Dijon, France; (3) Centre commun de Microscopie de L'Universite de Bourgogne, Dijon, France. Publication no. P-2003-0017-PTA.

Root colonization by the pathogen Fusarium oxysporum f. sp. lycopersici (Fol32) and the biological control agent F. oxysporum (Fo47) was observed on tomato roots grown in soil infested with one or both of the fungi. To distinguish the fungi, Fol32 was transformed with the GUS gene, incubated in X-Gluc and observed with transmitted light. Fo47 was transformed with the GFP gene and viewed with filtered light (excitation 395 nm; emission 510 nm.). Chlamydospores were added to pasteurized soil to give three treatments: Fol32 at 10(^3), Fol32 at 10(^3) + Fo47 at 10(^3), and Fol32 at 10(^3) + Fo47 at 10(^5). Five days after planting, root colonization by Fol32 was restricted in soil with Fo47 at 10(^5), but not at 10(^3). Root colonization by either strain was discontinuous, however Fo47 was observed growing down the root. The fungi were not observed together on the same area of the root.

Host genotype, plant tissue, and isolate effects on infection of peanut by Sclerotinia minor.
B. B. SHEW, J. E. Hollowell, and D. L. Smith. Dept. Plant Pathology, NC State Univ., Raleigh, NC 27695. Publication no. P-2003-0018-PTA.

Detached leaf inoculation is a rapid, simple and reliable method to identify resistance to Sclerotinia blight in peanut and characterize isolate aggressiveness in S. minor. The second leaf is detached from main stems of 8 wk old plants and leaflets are inoculated with agar plugs of S. minor. Inoculations consistently result in infections and data are taken within 3 da. Mean lesion lengths differed significantly on 12 peanut entries and several lines also exhibit resistance in the field. Detached leaves were inoculated with 48 isolates of S. minor, revealing significant differences in aggressiveness. Mean lesion lengths ranged from <3 to 24 mm. To evaluate isolate specificity, leaflets from five peanut lines were inoculated with two aggressive, one intermediate, two unaggressive, and a standard isolate. Isolate and peanut line effects were significant and no significant isolate by line effect was found. Pegs and leaflets were more susceptible than main and lateral stems of three peanut lines inoculated with this method. Results of detached leaf inoculation were consistent across different experiments and runs of the same experiment.

species isolated from within greenhouses: diversity and pathogenicity.
N. SHISHKOFF, J. Knoedler, and M. Daughtrey. Cornell Univ., LIHREC, Riverhead, NY 11901. Publication no. P-2003-0019-PTA.

Oomycetes from plants, greenhouse surfaces and soil were collected from greenhouses in New York and New England using a seed baiting technique. Isolates are being examined to determine their species and pathogenicity. Of 11 species identified so far, nine were found to be pathogens. In pathogenicity tests, 73 isolates that caused seedling death in geranium seedling assays caused stem lesions in geranium cutting tests, and one did not. There was less correlation, however, between a positive result in either of these tests and a positive result in a geranium stunting assay. Most isolates collected from symptomatic plants were pathogenic, but in addition, so were half the isolates collected from greenhouse surfaces. In four greenhouses sampled over time, an average of six species of Pythium were collected per greenhouse. When soil was collected from the pots of random, asymptomatic plants in these greenhouses, Pythium spp. were isolated from 12 of 48 pooled samples, but of isolates tested for pathogenicity so far, only one out of nine was positive.


Managing the wheat crown rot complex (Fusarium and Bipolaris spp.) in the Pacific Northwest. R. W. Smiley. Oregon State University, Columbia Basin Agric. Res. Center, Pendleton, OR. Publication no. P-2003-0020-PTA.

Winter and spring wheat in the Pacific Northwest are damaged by a crown rot complex (dryland foot rot, Fusarium foot rot) caused primarily by Fusarium pseudograminearum, F. culmorum and Bipolaris sorokiniana. Other pathogens include F. avenaceum and Microdochium nivale. F. pseudograminearum is most widespread and damaging. Surveys revealed that dominance among pathogens varied seasonally and spatially. High seasonal and locational variability occurred among rankings when wheat entries were rated for tolerance in breeding nurseries. Management strategies (fertilizer, planting date, seed treatment, tillage, rotation) are marginally effective and damage is increasing with adoption of annual crop and direct-drill systems. Wheat is now screened for tolerance and/or resistance in paired plots inoculated or not inoculated with multiple isolates of F. pseudograminearum. The pathogen reduced grain yield of 69 winter wheat lines by 2 to 28 percent during 1999-2000 and 0 to 22 percent during 2000-2001 (11 to 12 percent means). Selected entries had yield constraints less than 5 percent each year, more than 15 percent, or were highly variable.

Root lesion nematodes in non-irrigated field crops in the Pacific Northwest.
R. W. Smiley. Oregon State University, Columbia Basin Agric. Res. Center, Pendleton, OR. Publication no. P-2003-0021-PTA.

Annual no-till cropping is increasing in semiarid eastern Oregon and Washington where winter wheat-summer fallow rotation has been traditional. Samples from annual cereal, brassica and legume crops during 1999 revealed Pratylenchus neglectus and/or P. thornei populations (root lesion nematode, RLN) up to 4,369 per g root and 3,970 per kg soil. RLN was inversely correlated (R(^2) = 0.56; p = 0.002) with yield in a crop rotation experiment planted uniformly to winter wheat during the sixth year. RLN numbers in 109 fields from 10 OR and WA counties during 2000 ranged from zero to 2,449 per g root and zero to 35,960 per kg soil. Wheat rotated with fallow had fewer than 100 per g root. High numbers (above 300 per g root for dry environments) occurred in 44 percent of fields cropped more than 2 of 4 years. Tillage system had no influence. Numbers were lowest in flax and safflower, and lower in cereals following cereals than legumes or brassicas. Grain yield for 5 spring wheat varieties treated or not with aldicarb at planting during 2001 was inversely correlated with RLN in roots (R(^2) = 0.21, p = 0.01) and with RLN plus Hessian fly-infested plants (R(^2) = 0.50, p = 0.001).

“A Tree Grows In Virginia.”
R. J. Stipes. Dept. Plant Pathology, Physiology and Weed Science, Virginia Tech, Blacksburg, VA 24061. Publication no. P-2003-0022-PTA.

The title is borrowed from “A Tree Grows in Brooklyn,” the 1943 novel by Betty Smith, and the tree is Ailanthus altissima, an invasive exotic from China which has become a pervasive weed tree on many roadside and landscape sites in Virginia and throughout the USA. Ailanthus is strongly allelopathic, competes with higher quality native vegetation and has become an overall pest. We have surveyed roadsides for declining Ailanthus, and have isolated numerous fungi, including Fusarium oxysporum f. sp. perniciosum (Fop), the vascular pathogen that has essentially destroyed the beautiful mimosa tree (Albizia julibrissin). Fop isolates from Ailanthus or Albizia induce typical wilt syndromes on either host in greenhouse seedling root-dip inoculations using spore suspensions as inoculum. We propose to develop this Fusarium as a mycoherbicide for Ailanthus, and plan further surveys of declining Ailanthus.