RESUMEN

An unusual population of cyst nematode was found in soils collected from a Powell Butte, OR field with a cropping history including potato, wheat, other crops, and significant weed presence. These nematodes could not be placed with certainty into any known species and exhibited some unique morphological features in some specimens. Compared with Globodera pallida, the cyst body length was slightly longer and the second-stage juvenile stylet length was slightly shorter. In some individuals, the J2 stylet knob height was greater and the tail annules were more prominent than in G. pallida, and the tail abruptly narrowed, with a slight constriction near the posterior third of the hyaline terminus. Compared with G. rostochiensis, the hyaline tail terminus had a larger number of refractive bodies, and cysts of this population had a smaller Granek's ratio and fewer cuticular ridges between the anus and vulva. In some individuals, the tail termini of second-stage juveniles were more bluntly pointed, and the stylet knobs were more anteriorly directed with greater height. Unlike G. tabacum, the cyst wall often lacked a network-like pattern and, in some individuals, the juvenile tail terminus distinctly narrowed after a constriction. Molecularly, the population was distinct from G. pallida, G. rostochiensis, and G. tabacum. Multiplex polymerase chain reaction of the internal transcribed spacer (ITS) rDNA region gave results similar to G. tabacum; however, ITS restriction fragment length polymorphism patterns were observed to have individual bands in common with G. rostochiensis and G. pallida. Phylogenetic analysis based on ITS1 and -2 rDNA sequences showed greatest similarity to populations from Argentina and Chile; together, they form a moderately supported clade, distinct from G. rostochiensis, G. tabacum, G. "mexicana," European type G. pallida, and several G. pallida populations from South America.

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RESUMEN

Corky ringspot disease (CRS) of potato (Solanum tuberosum) is caused by the tobacco rattle virus (TRV), which is vectored by stubby-root nematodes, Paratrichodorus spp. and Trichodorus spp., and is a significant threat to potato quality and production in many areas of the western United States. Between 2002 and 2005, fields with a history of CRS were planted to potato and treated with various combinations of in-furrow (IF) and chemigated (water run, WR) oxamyl [Methyl N'N'-dimethyl-N-[(methyl carbamoyl)oxy]-1-thiooxamimidate] applications. Soil samples were collected to determine how Paratrichodorus allius populations responded to the various treatment regimes (2002-2004); potato tubers were evaluated for symptoms of CRS in 2004-2005. Applications of oxamyl to potato (1.1 kg a.i./ha) did not cause significant mortality of P. allius but did prevent the populations from increasing. Oxamyl applications that began at 55 days after planting (DAP) or later did not control CRS and were not different from the untreated control. However, application schedules that began early-season, either IF at planting, early WR (33 - 41 DAP), or both, significantly reduced CRS expression in cv. Yukon Gold. Therefore, oxamyl applications must be made early in the growing season to be effective in controlling CRS. Effects of oxamyl on CRS may be due to nematostatic action that suppresses feeding activity during early field season when most virus transmission probably occurs.

RESUMEN

Metam sodium (MS) is often applied to potato fields via sprinkler irrigation systems (water-run, WR) to reduce propagules of soil-borne pathogenic fungi, particularly Verticillium dahliae, to prevent yield loss from potato early dying disease. However, this procedure has not been effective for controlling quality defects in tubers caused by Columbia root-knot nematode (Meloidogyne chitwoodi). In five trials from 1996 to 2001, application of MS by soil shank injection (SH) provided better control and tuber quality than that generally obtained by WR MS, in three of five trials. Results were similar when SH MS was injected at one (41-45 cm), two (15 and 30 cm) or three (15, 30 and 45 cm) depths. In the two trials where SH metam potassium was tested, culls were reduced to 3% and 0% and were equivalent to those resulting from a similar rate in kg a.i./ha of SH MS. A shank-injected tank mix of MS plus ethoprop EC and SH MS plus in-season chemigation applications of oxamyl provided acceptable control in trials where SH MS alone was inadequate. In-furrow application of aldicarb at planting following SH MS did not appear to increase performance. Most consistent control (0-2% culled tubers in five trials) occurred when SH MS at 280 liters/ha was used together with 1,3- dichloropropene (140 liters/ha), applied simultaneously or sequentially. This was similar to combinations of 1,3-D and WR MS, but SH MS may be preferred under certain conditions.

RESUMEN

Corky ringspot disease (CRS) of potato produces necrotic areas in tubers that are considered quality defects that can lead to crop rejection. CRS is caused by tobacco rattle virus that is vectored by stubby-root nematodes (Paratrichodorus spp., Trichodorus spp.) at very low population densities, making disease management difficult and expensive. Fumigation with metam sodium (MS) is a common practice to control soil-borne fungi and increase potato yield. MS is generally applied in water via chemigation (water-run, WR) but is ineffective at controlling CRS when WR-applied, even at high rates. Therefore, WR MS is often used in combination with 1,3-dichloropropene (1,3-D), aldicarb or oxamyl to attain adequate CRS control. Between 1996 and 2000, fields with a history of CRS were treated with WR MS, shank-injected MS, and/or 1,3-D, and tubers were evaluated for symptoms of CRS. Shank injection of MS (SH MS) at depths of 41 cm, 15 and 30 cm, or 15, 30 and 45 cm controlled CRS over 3 years of testing. All rates of 280 liters/ha or greater were effective. Shank injection of metam potassium (MP) at rates of 448 liters/ha was also effective. 1,3-D controlled CRS alone or in combination with WR or SH MS. Proper shank application of MS or MP may adequately control CRS without the additional cost of other nematicides at low (<10 P. allius/250 g soil) to moderate (10 to 30 P. allius/250 g soil) populations of the nematode vector. Although SH MS was superior to WR MS, additional research is necessary to determine if this practice would be sufficient at higher CRS disease pressure or if addition of other nematicides would be necessary.

RESUMEN

The root-lesion nematode, Pratylenchus penetrans (de Man, 1880) Filipjev, 1936, is a common pathogen of potato in the United States east of the Rocky Mountains and frequently interacts with Verticillium dahliae to aggravate early dying disease (4). West of the Rocky Mountains, P. penetrans is associated with numerous crops including mint, tree, and small fruits but is rarely recovered from potato fields. Pratylenchus neglectus is a common plant-parasitic nematode on potato in the west, but causes little loss in yield and does not usually interact with V. dahliae (1). Management of P. neglectus is generally unnecessary; although a population of P. neglectus from Ontario, Canada appears to be more pathogenic and does interact with V. dahliae (1). During May 2003 (6 weeks after planting), large areas of stunted plants were observed in field inspections and in aerial photographs of two fields (50.6 ha) of cv. Ranger Russet in Benton County, Washington. Lower roots and stolons had numerous, dark lesions that are typical of P. penetrans damage and were severely stunted, while long, white roots had formed abnormally near the soil surface. In early May 2003, lesion nematodes (65 nematodes per 250 g of dry soil and 810 nematodes per g of fresh root weight) recovered from these potato fields were identified as P. penetrans on the basis of morphological characters (2,3). The crop responded to oxamyl (four applications at 1.1 kg of a.i. per ha between early May and mid-July), but the grower estimated that yields were 1.62 tons/ha (4 tons/acre) less than in comparable unaffected fields. To our knoweldge, this is the first report of severe damage to potato from P. penetrans in the Colombia Basin potato-production area. Soil fumigation with Telone II (1,3-dichloropropene) is commonly used in the Columbia Basin to control root-knot (Meloidogyne chitwoodi and M. hapla) and stubby-root (Paratrichodorus allius) nematodes, and metam sodium is used to control V. dahliae. However, since the only nematode recovered from preplant samples was assumed to be P. neglectus, and because cv. Ranger Russet is relatively tolerant to V. dahliae, no fumigant was used in these fields. An increase in mint production in this area may be responsible for introducing P. penetrans into previously uninfested fields since mint is propagated vegetatively and lesion nematodes are commonly associated with mint and could be easily spread in planting material and adhering soil. Identification of P. penetrans in stunted corn from two nearby fields during 2004 suggests that this nematode may be a new and emerging problem in this area. The Columbia Basin is one of the largest potato-producing regions in the United States, and widespread introduction of P. penetrans could add substantial cost to potato production in this area. References: (1) K. Mukerji. No. 458 in: Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, UK, 1975. (2) H. Scheck and S. Koike. Plant Dis. 83:877, 1999.

RESUMEN

Population growth of Pratylenchus penetrans on 13 fall and winter cover crops was studied in the greenhouse and field. All crops except oat cv. Saia supported population growth of P. penetrans in greenhouse experiments, although the response of P. penetrans to oat cv. Saia varied considerably between experiments. The mean ratio of the final population density/initial population density (Pf/Pi) after 16 weeks for P. penetrans added to a greenhouse soil mix was 0.09, whereas Pf/Pi values after 10 weeks for two experiments with naturally infested soil were 0.95 and 2.3. Although P. penetrans increased on sudangrass cv. Trudan 8 and sudangrass x sorghum hybrid cv. SS 222, subsequent incorporation of sudangrass vegetation into soil reduced P. penetrans populations to preplant levels. Field experiments were inconclusive but suggested that oat cv. Saia or rye cv. Wheeler may be better choices for winter cover than weed-contaminated fallow or other crops on P. penetrans-infested sites in the Pacific Northwest.

RESUMEN

During 1993-94, several fumigant and nonfumigant nematicides were tested alone and in combination at various rates for control of Columbia root-knot nematode (Meloidogyne chitwoodi) in potato. Ethoprop, oxamyl, or metam sodium alone did not adequately reduce tuber infection. Metam sodium plus ethoprop reduced culled tubers to 3%, and metam sodium plus 2 or 3 foliar applications of oxamyl reduced culls to

RESUMEN

Corky ringspot disease (CRS) of potato, caused by tobacco rattle virus that is vectored by stubby-root nematodes (Paratrichodorus spp.), is often controlled by aldicarb. When use of aldicarb on potato was suspended in 1989, an increase in crops rejected due to CRS in the Columbia Basin of the U.S. Pacific Northwest occurred. During 1992-94, several fumigant and nonfumigant nematicides were tested alone and in combination for control of P. allius and CRS. Aldicarb alone significantly reduced CRS but not to acceptable levels. Metam sodium or ethoprop alone did not control CRS, but metam sodium plus ethoprop provided adequate control under light disease pressure. Two or three postemergence applications of oxamyl, either with or without metham sodium, appeared to control CRS at low pressure. Fosthiazate reduced CRS incidence when used alone but not in combination with metam sodium. At low P. allius population densities, 1,3 dichloropropene (1,3-D) controlled CRS at 94 liters/ha, and rates of 140 liters/ha or greater were adequate at higher population densities. Treatment with 1,3-D plus chloropicrin was no better than 1,3-D alone and did not always control CRS. Combinations of 1,3-D at 94 liters/ha or greater plus metam sodium at 374 liters/ha or greater controlled CRS. Paratrichodorus allius numbers were higher and severity of CRS greater after wheat than after field corn, but P. allius declined rapidly after potato was planted and remained at low levels until harvest.

RESUMEN

A survey of vineyards in western Oregon was conducted in 1994 and 1995 to determine the association of plant-parasitic nematodes with vine health. Seventy vineyards in four regions of western Oregon (16 to 21 vineyards per region) were sampled. The regions were the northern, middle, and southern Willamette Valley, and southern Oregon. Vineyards were selected and partitioned into blocks by variety, age of planting, crop history, and soil characteristics. Mesocriconema xenoplax, Xiphinema americanum, Pratylenchus spp., and Paratylenchus spp. were recovered from more than 85% of the vineyards; only 10% of vineyards had detectable populations of Meloidogyne hapla. Mesocriconema xenoplax and X. americanum were found in 20% and 8% of vineyard blocks, respectively, at population densities reported to cause moderate yield loss in California. Mesocriconema xenoplax was found at greatest population densities in vineyards older than 10 years and on former Prunus orchard sites in the northern Willamette Valley. Populations of Mesocriconema xenoplax and X. americanum were associated with both healthy and stunted vines. The long-term impact of M. xenoplax, X. americanum, and other nematodes on Oregon vineyard production has not yet been determined.

RESUMEN

Production of storage and dehydration (dehy) onions is increasing rapidly in the northcentral Oregon region of the Columbia Basin. Roughly circular patches of stunted onions have been observed in many fields and are often numerous and (or) extensive in area. Onions in these patches often exhibit symptoms typical of stubby-root nematodes, and Paratrichodorus allius has been collected from several damaged areas. This study examined the relationship of P. allius densities to onion yield reduction and benefit from oxamyl application. Transect samples and onions harvested across areas with varying P. allius densities revealed that the total number of onions was not affected by P. allius but that onions were in smaller, less valuable size classes. Yield of the largest size class of storage onions (colossals) declined substantially (57-61%) even at low (5-16/250 g soil) nematode densities. Treatment with oxamyl at 1.1 kg a.i./ha mitigated most of the damage, and the value of both storage and dehy onions was increased by more than $1,200/ha. Early applications were superior to later applications, whereas treatment at both times was no better than the early treatment alone. Damage at low (<10/250 g soil) nematode densities, low treatment cost ($86-172/ha), and high crop values suggest an economic benefit from treatment at population densities of four or more P. allius/250 g soil. However, stunted patches of onions may occur for reasons other than nematodes, and the presence of P. allius should be confirmed before treating fields. This is the first report of stubby-root nematode damage to dehy onions and to storage onions in the Columbia Basin.

RESUMEN

Popcorn cultivars were evaluated in field and greenhouse tests for resistance to the Columbia root-knot nematode, Meloidogyne chitwoodi, as potential resistant crops in potato rotations. A nematode reproductive factor (Rf) was calculated for each cultivar. Reproductive factor values also were compared on a relative basis as percentages of the Rf on a susceptible field corn standard, Pioneer 3578. Popcorn cultivars W206 and Robust 33-77 consistently supported low population densities of M. chitwoodi in repeated tests. However, WOC 9508 had the greatest resistance in any of the field tests, with an Rf value of 0.04. Cultivars with a mean field and greenhouse Rf value less than 50% of the value for Pioneer 3578 were WOC 9508 (8%), WOC 9554 (13%), W206 (15%), WOX 9512 (23%), Robust 33-77 (30%), Robust 20-70 (38%), WOC 9510 (41%), and WOC 9504 (42%). If these cultivars were used in rotation, M. chitwoodi population densities at the end of the popcorn season would be between 58% and 92% less than if Pioneer 3578 were grown. In greenhouse tests, WOX 9511, WOX 9528, WOC 9556, and WOX 9531 also had low Rf values (7-46% that of Pioneer 3578), but field testing of these cultivars is needed.

RESUMEN

Endoparasitic nematode populations are usually measured separately for soil and roots without a determination of the quantitative relation between soil and root population components. In this study, Pratylenchus penetrans populations in peppermint soil, roots, and rhizomes were expressed as the density within a standardized core consisting of 500 g dry soil plus the roots and rhizomes contained therein. Populations of Paratylenchus sp. and Criconemella xenoplax in 500 g dry soil were also determined, thus measuring the total plant-parasitic nematode population associated with the plant. Mean wet root weight per standard core peaked in spring and again in late summer and was lowest early in the growing season and in early fall. Pratylenchus penetrans populations peaked 4 to 6 weeks after root weight peaks. The percentage of the total population in roots reached 70% to 90% in early April, decreased to 20% to 40% in August, and returned to higher percentages during the winter. Rhizomes never contained more than a minor proportion of the population. Mean Paratylenchus sp. populations increased through spring and peaked in late August. Mean C. xenoplax populations fluctuated, peaking in August or September. Populations of all parasitic species were lowest during winter. Evaluation using the standard core method permits assessment of the total P. penetrans population associated with the plant and of changes in root weight as well as the seasonal distribution of P. penetrans.

RESUMEN

Meloidogyne chitwoodi race 1 reproduced on Piper sudangrass (Sorghum bicolor (L.) Moench), 332 (sudangrass hybrid), and P855F and P877F (sorghum-sudangrass hybrids), but failed to reproduce efficiently on Trudan 8, Trudex 9 (sudangrass hybrids), and Sordan 79, SS-222, and Bravo II (sorghum-sudangrass hybrids). Meloidogyne chitwoodi race 2 behaved similarly and reproduced more efficiently on Piper, P855F, and P877F than on Trudan 8, Trudex 9, or Sordan 79. The mean reproductive factor for M. chitwoodi races on the poorer hosts ranged from <0.1 to 0.9 under greenhouse and field conditions. Meloidogyne hapla failed to reproduce on any of the cultivars tested. In the laboratory, leaves of each cultivar chopped and incorporated as green manure reduced the M. chitwoodi population in infested soil more than unamended or wheat green manure treatments. Trudan 8, although limited to the zone of incorporation, protected this zone from colonization of upward migrating second stage juveniles (J2) for up to 6 weeks. Leaves of Trudan 8 but not roots were effective against M. chitwoodi, and J2 appeared to be more sensitive than egg masses. Trudan 8 and Sordan 79 as green manure reduced M. chitwoodi in bucket microplots under field conditions.

RESUMEN

The efficacy of controlling Meloidogyne hapla on potato with water incorporation of ethoprop was compared to physical incorporation before planting. The standard practice of aldicarb application for insect control was also evaluated for M. hapla suppression with and without ethoprop. Physical incorporation before planting by rototilling or discing reduced (P

RESUMEN

Seasonal dynamics of soil nematodes and root biomass were examined from under western wheatgrass (Agropyron smithii) and little bluestem (Andropogon scoparius) from a heavily grazed prairie dog (Cynomys ludovicianus) colony occupied for 5 to 10 years and an adjacent lightly grazed, uncolonized area in Wind Cave National Park, South Dakota, USA. Nematodes were differentiated into classes of plant-parasitic Tylenchida and Dorylaimida and nonparasitic Dorylamida and Rhabditida. Root-feeding nematodes were generally more numerous from A. smithii than from A. scoparius, while nonparasitic populations were not different in soil from beneath the two plant species. Rhabditida, parasitic Dorylaimida and Tylenchida (from A. scoparius only) were more numerous on the prairie dog colony than from the uncolonized site, but nonparasitic Dorylaimida populations did not differ between the two areas. Mean total (live plus dead) root biomass beneath A. scoparius and A. smithii on the prairie dog colony averaged 71% and 81%, respectively, of values from the uncolonized area. Estimated consumption by root-feeding nematodes averaged 12.6% and 5.8% of annual net root production in the upper 10 cm from the prairie dog colony and uncolonized site, respectively. We conclude that, because of microhabitat modification or reductions in plant resistance to nematodes, heavy grazing by aboveground herbivores apparently facilitates grazing by belowground herbivores. Because heavily grazed plants have less roots than lightly grazed or ungrazed plants, the impact of root-feeding nematodes on primary producers is likely to be greatest in heavily grazed grasslands.

RESUMEN

Growth, biomass allocation and competition between blue grama plants were examined with and without application of carbofuran, a pesticide which has been used to study insect and nematode effects on primary production. Carbofuran had no apparent effect on total plant growth, biomass allocation, or competition between neighboring plants.

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RESUMEN

Thirteen patients with catheterization-proved idiopathic hypertrophic subaortic stenosis underwent intracardiac electrophysiologic study. There was a large incidence of arrhythmias and a strikingly large incidence of conduction system abnormalities among these patients. The P-A and A-H intervals were normal in all patients. Atrial pacing resulted in Mobitz type 1 block proximal to the His bundle at an abnormal rate (less than 140/min) in 2 of 12 patients (17 percent). H-V intervals were prolonged (greater than 50 msec) in 10 of 12 patients (83 percent) and were greater than 60 msec in 7 patients (58 percent). The atrial effective refractory period was prolonged in 3 of 12 patients and was markedly prolonged in 1 of them. Effective refractory period of the atrioventricular (A-V) node, determined in five patients, was prolonged in three. Dual responses of the A-V node to atrial extrastimuli were found in seven patients. Dual A-V nodal repsonses were evoked with propranolol in three patients and persisted in the other four patients with dual responses despite propranolol administration.

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RESUMEN

Six young women who had taken progestational agents for a period of time ranging from six months to five years developed symptoms and signs of pulmonary hypertension. Cardiac catheterization confirmed the presence of severe pulmonary hypertension without evidence of other cardiac or pulmonary abnormalities to explain this phenomenon. Three of the patients had potential predispositions to pulmonary hypertension, including a corrected patent ductus arteriosus with mild pulmonary hypertension in one, collagen vascular disease in a second, and family history of pulmonary hypertension in a third. Three patients had no known predisposing factors. Although the relationship between oral contraceptives and severe pulmonary hypertension is problematic, there have been isolated reports of cases of pulmonary hypertension secondary to oral contraceptive usage. These cases and the possible pathophysiologic mechanisms responsible are discussed.

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RESUMEN

Treadmill tests were performed in 19 patients with previously documented idiopathic hypertrophic subaortic stenosis (IHSS). Arrhythmias occurred in 79 percent (15) of the patients, and new arrhythmias not previously documented occurred in over 50 percent (10) of the patients. Paroxysmal supraventricular tachycardia (PSVT), ventricular premature beats (VPBs) (two or more per minute) or atrial premature beats (APBs) (three or more per minute) occurred in 10 of 19 patients. There was no association between treadmill arrhythmias and clinical symptoms, hemodynamic data, or electrocardiographic features. Propranolol administration resulted in failure of exercise to induce PSVT in one patient and had no effect on PSVT in two others, nor any effect on maximum frequency of APBs or VPBs. Treadmill testing is more productive than retrospective analysis of ECGs for characterizing arrhythmias in IHSS.

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