G. D. Easton

Potato production and incidence ofVerticillium dahliae following rotation to nonhost crops and soil fumigation in the state of Washington

For three years, potato yields, tuber quality, and incidence ofVerticillium dahliae were measured in field plots previously cropped for one year to the following nonhosts: sudan grass, green peas followed by sudan grass (same year), spring wheat, spring wheat followed by sudan grass (same year), sweet corn and field corn. One year rotation to nonhosts did not reduce the population ofV. dahliae propagules in the soil and in only one of the three years wereV. dahliae propagule numbers in potato stems significantly reduced in plots following nonhost crops, compared with plots following potatoes. Verticillium wilt symptoms in potatoes were not reduced by one year rotation to any of these crops and only in one year in three was yield significantly increased. In two of three years, percent U.S. No. 1 tubers was increased following one-year rotation with green peas plus sudan grass, and in one of the two years, specific gravity was increased by rotation.Rotational cropping to nonhosts for two years between potatoes significantly reduced preplant soil populations ofV. dahliae propagules in the soil and in potato stems the following fall. However, soil populations in these two year rotational plots the spring following potato were not reduced compared to plots previously cropped to potatoes two consecutive years. Cropping to nonhosts for two years had no consistent effect on incidence of Verticillium wilt in subsequent potato crops. Two years’ rotation to nonhosts increased plant height and yield compared to continuous cropping to potato but not percent U.S. No. 1 tubers. The various nonhost crops all had about the same non-significant effect on yield.In two out of three years’ trials, fumigation significantly reduced both the incidence of Verticillium wilt and number ofV. dahliae propagules in stems in plots compared to plots non-fumigated. In only one trial, fumigation significantly increased tuber yields and percent U.S. No. 1 tubers.CompendioPor tres años, se midieron los rendimientos de la papa, la calidad de tubérculo y la incidencia delVerticillium dahliae en parcelas de campo previamente cultivadas por un año con los siguientes cultivos no hospedantes: pasto sudán, vainitas seguidas a continuación por pasto sudán (el mismo año), trigo de primavera, trigo de primavera seguido por pasto sudán (el mismo año), maíz dulce y maíz amarillo. Un año de rotación con no hospedantes no redujo la población de propágulos deV. dahliae en el suelo y sólo en uno de los tres años el número de propágulos deV. dahliae en los tallos de papa se redujo significativamente en las parcelas donde se cultivaron a continuación cultivos no hospedantes, en comparación con las parcelas donde se sembro nuevamente papa. Los síntomas de la marchitez porVerticillium en la papa no disminuyeron por la rotación de un año con cualesquier de los cultivos no hospedantes y sólo en un año el rendimiento fue significativamente incrementado. En dos de los trés años, el porcentaje de tubérculos U.S. No. 1 se incrementó después de una rotación de un año con vainitas además de pasto sudán, y en uno de los dos años, la gravedad específíca se incremento con la rotacion.El cultivo en rotación con no hospedantes, con dos afios entre cultivos de papa, redujo significativamente antes de la siembra las poblaciones de propágulos deV. dahliae en el suelo y en los tallos de papa en el otoño siguiente. Sin embargo, las poblaciones del suelo en las parcelas con rotacion de dos años, en la primavera que siguió al cultivo de papa, no fueron reducidas, en comparación con las parcelas cultivadas previamente con papa en dos años consecutivos. El cultivar en rotación con no hospedantes por dos años no tuvo efecto consistente sobre la incidencia de la marchitez porVerticillium en los cultivos posteriores de papa. La rotación con no hospedantes por dos años incrementó la altura y el rendimiento de las plantas en comparación con las del cultivo continuado de papa, pero no así el porcentaje de tubérculos U.S. No. 1. Todos los diversos cultivos no hospedantes tuvieron aproximadamente el mismo efecto no significativo sobre el rendimiento.En dos de los tres años de ensayos, la fumigación redujo significativamente tanto la incidencia de la marchitez porVerticillium como el numéro de propágulos deV. dahliae en los tallos en comparación con las parcelas no fumigadas. En sólo un ensayo, la fumigación incremento significativamente los rendimientos en tubérculos y el porcentaje de tubérculos U.S. No. 1.

Verticillium albo-atrum carried by certified seed potatoes into Washington and control by chemicals.

Fifty-one percent of 110 lots of certified seed potatoes from 10 states and Canada sampled in 1968 and 30% of 134 lots from nine states and Canada sampled in 1969 were infected withVerticillium albo-atrum. Fortyone percent of the 1968 lots and 13% of the 1969 lots carried soil infested with the fungus on tuber surfaces. The dark mycelial type ofV. albo-atrum was found infecting tubers more often than the microsclerotial type, however, high propapgule populations of the microsclerotial type were present on tuber surfaces in the soil of infested lots. Over 24% of the isolates ofV. albo-atrum infecting and infesting tubers from lots of seed potatoes were pathogenic to eggplant var. Black Beauty. Captan®, household bleach (5.25% sodium hypochlorite), Polyram®, Orthocide®, and Semesan Bel®, were effective in preventing germination of the fungus in small amounts of soil such as might be carried by infested tubers. Liquid treatments were more effective than dusts.

The incidence of decay and factors affecting bacterial soft rot of potatoes

The incidence of tuber decay in rail car shipments of potatoes from the State of Washington was determined from 1965 to 1969 inclusive. Reinspection certificates revealed that 7.9% of the rail cars of potatoes shipped during this period were rejected due to tuber defects; tuber decay accounted for 63% of these rejected cars. Percentage of rejections due to tuber decay was greater for Russet Burbank than for Norgold Russet potatoes.Temperature, moisture, and oxygen levels influenced development of bacterial soft rot in freshly harvested potatoes and in potatoes stored for 3 months at 35 F (2 C) previous to treatment. When tuber surfaces were kept dry, no soft rot developed in 11 days over ranges of 50–70 F (10–21 C) and 2–20.5% oxygen levels. Freshly harvested tubers partially immersed in water did not rot when cooled to 40 F (4.4 C) in < 24 hours and held for 8 days under either 20.5 or 4% oxygen levels; however, tubers, rotted when stored similarly but at 50 F or higher temperatures. Partially immersed tubers incubated for 1 day or longer at 70 F developed soft rot in a low oxygen (4%) when later stored for, 8 days at 40 F. When rot occurred, the amount was always greater under lower oxygen levels irrespective of storage temperature.Of various cooling methods tested in rail cars loaded with 100 lb (45.4 kg) sacks of potatoes, prechilling of tubers and icing of cars prior to loading lowered floor temperatures most rapidly. Icing cars after loading lowered floor temperatures the slowest. In a carton shipment, the temperature remained above 68 F (20 C) in cartons after 8 days in transit, even though the wall and floor temperatures had cooled to near 55 F (12.8 C) by the second day.Oxygen level surrounding, tubers in the center of car loads of 100 lb sacks of potatoes was approximately 20.5% after 8 days transit.

Systemic insecticides, soil fumigation and nitrogen fertilization for Vertîcillium wilt control.

Fumigation of Verticillium infested soils with Telone®+chloropicrin in 1966 increased yields of Russet Burbank potatoes 178 and 147 cwt/a (200 and 165 q/ha) over yields in unfumigated plots near Othello and Prosser, Washington, respectively. Systemic insecticides disulfoton and aldicarb banded at planting, sidedressed after planting, or applied in combination treatments did not increase yield at either location. Plots fumigated with Telone®+chloropicrin and fertilized with ammonium nitrate (150 and 350 lb N/a−168 and 392 kg N/ha) in 1967 significantly increased yields over that of the unfumigated, fertilized plots. Application of disulfoton and aldicarb to plots fertilized with ammonium nitrate (150 and 350 lb N/a−168 and 392 kg N/ha) did not increase yields over that of fertilized plots receiving no systemic insecticide.ResumenEn 1966, la fumagión con Telone®+Cloropicrina en suelosi nfestados conVerticillium sp., aumentó los rendimientos de la variedad de papa Russet Burbank (178 y 145 cwt/acre ó 200 y 165 q/ha), en comparación con la producción de las parcelas sin fumigar, en lotes localizados cerca a Othelo y Prosser, en el éstado de Washington, respectivamente. Los insecticidas sistémicos “disulfoton” y “aldicarb” que se aplicaron en bandas al moento de la siembra, al lado del cubrimiento (sidedressed) después de la siembra, o aplicados en forma combinada, noa umentaron los rendimientos en ninguna de las dos localidades.En 1967, las parcelas fumigadas con Telone®+Cloropicrina y fertilizadas con nitrato de amonio (150 y 350 lbs de N/acre ó 168 y 392 Kg de N/ha), aumentaron significativamente los rendimiéntos sobre las parcelas que no recibieron fumigación ni fertilización. Las aplicaciones de “disulfoton” y “aldicarb” a las parcelas fertilizadas con nitrato de amonio (150 y 350 lbs de N/acre o 168 y 392 Kg de N/ha) no aumentaron los rendimientos en comparación con lasf ertilizadas pero que no habían recibido los insecticidas sistémicos.

Potato seed piece treatment in Washington

Although a slight amount of seed piece decay occurred, blackleg did not develop, and yield was not reduced in trials with untreated seed pieces of Norgold Russet and Russet Burbank in 1968 and 1969. Chemical seed piece treatments reduced seed piece decay, but did not increase yield. Storing untreated cut seed of these two varieties up to 5 days at 50–90 F (10–32C) and 35–86% relative humidities with adequate ventilation did not affect seed piece decay, blackleg, or yield.ResumenAunque se encontraron varias semillas con daños, la “pata negra” (blackleg) no se presentó, y el rendimiento no se redujo en los ensayos con semilla sin tratar de Norgold Russet y Russet Burbank en 1968 y 1969. Los tratamientos con sustancias químicas redujeron el daño pero no se logró incrementar el rendimiento. Cuando se alma cenó la semilla cortada y sin tratar por 5 días a 50–90 F (10–32 C) y 35–86% de humedad relativa con adecuada ventilación, no varió el daño en la semilla, como tampoco la incidencia de la “pata negra” o el rendimiento.

Fumigants, rates, and application methods affecting Verticillium wilt incidence and potato yields

A three year comparison was made among fumigants, rates and placement for control ofVerticillium albo-atrum (microsclerotial type). Fumigants were placed in the soil by (i) row method [one shank with duck-foot tool attached to give two bands of fumigant 9 inches (22.8 cm) deep and 9 inches apart (4.5 inches = 11.4 cm from center of a 36-inch row = 91.44 cm)], (ii) deep shank method [one shank in center of a 36-inch row, 18–20 inches (45.7–50.8 cm) deep], (iii) and by the standard broadcast method (four shanks spaced 9 inches deep and 9 inches apart per 36-inch row). The row and deep shank methods were no more effective than the broadcast method when the fumigant rate was equal (calculated on an acre basis and not on the actual portion of the row treated by the method of application).Fewer wilted plants and increased yields (120–160 hundredweight per acre = 134–179 quintals per hectare) were found in plots treated with (i) DD + Picfume (4:1), (ii) Telone + Picfume (4:1), (iii) Telone C, (iv) Terr-o-cide 30, (v) Terr-o-cide 30D and (vi) Vorlex at 25 gal per acre (233.8 liters per hectare) for all years tested.Yield was increased in plots treated at 12.5 gal per acre (116.9 liters per hectare) in 1968 and 1970, but not in 1969. Rates below 12.5 gal per acre were not effective in increasing yield and there was no advantage to applying fumigants above 25 gal per acre. All the six fumigants were equally effective in their control.

Metalaxyl and other fungicides for control ofPhytophthora infestans on potato in northwest Washington State

In northwest Washington State, fungicidal control of late blight caused byPhytophthora infestons was evaluated for three years. During 1977, a high rainfall year with supplemental sprinkler irrigations, all metalaxyl and chlorothalonil treatments reduced tuber rot at harvest, but only metalaxyl extended control of tuber rot after 4 months’ storage. During 1978, a high rainfall year, one application of metalaxyl sprayed over or dusted on potato seed pieces at planting or applied five times to foliage at 2 or 4 wk intervals gave excellent blight control equal to that with chlorothalonil applied to foliage every 2 wk.In 1979, a low rainfall year,P. infestons did not kill plants in untreated plots until October. Five applications of metalaxyl sprayed every 2 wk on foliage did not control foliage blight. However, metalaxyl reduced foliage blight when dusted on cut potato seed pieces. Mancozeb sprayed every 2 wk also gave excellent control. The possibility that metalaxyl applied to foliage is effective in late blight control only when washed into the soil by rainfall or irrigation for uptake by roots is discussed.Yields and percent U.S. No. 1 grade tubers were not significantly affected by any treatment in these 3-year trials.ResumenEn el Estado de Washington en el noroeste de los EE.UU., se evaluó durante tres años el control por fungicidas del tizón tardio causado porPhytophthora infestons. Durante 1977, un año con un alto nivel de precipitaciones y con riego suplementario por aspersión, todos los tratamientos de metalaxil y clorotalonil redujeron la pudrición del tubérculo al momento de la cosecha. Pero sólo el metalaxil prolongó su control de la pudrición del tubérculo hasta después de 4 meses de almacenamiento.Durante 1978, un año con un alto nivel de precipitaciones, una aplicación de matalaxil rociado o espolvoreado sobre los tubérculos-semillas en la siembra o aplicado cinco veces en el follaje a intervalos de 2 a 4 semanas, dio un excelente control del tizón tardío, igual que el control por clorotalonil aplicado al follaje cada 2 semanas.En 1979, un año con un nivel bajo de precipitaciones,P. infestans no causó la muerte de las plantas en parcelas sin tratar hasta octubre. Cinco aplicaciones del metalaxil rociado en el follaje cada dos semanas no controlaron el tizón tardío. Sin embargo, el metalaxil redujo el tizón en el follaje al ser espolvoreado sobre los tubérculos-semillas cortados. El Mancoceb rociado cada dos semanas también dio un excelente control. Se discute la posibilidad de que el metalaxil aplicado en el follaje sea efectivo en el control del tizón tardio sólo al penetrar en el suelo con el agua de la lluvia o del riego y así ser asimilado por las raices.Los rendimientos y el porcentaje del primer tamaño según escala estadounidense no resultaron significativamente afectados por ningún tratamiento en los ensayos de esos tres años.

Terraclor (PCNB) for control ofRhizoctonia solani. II. PCNB residues in tubers

Terraclor (PCNB) applied to soils by broadcast and row slightly reduced the incidence ofRhizoctonia solani but did not increase yield or per cent of U. S. No. 1 tubers either by weight or numbers. Residues of PCNB in tubers grown in treated soils increased as the rate per acre of PCNB increased. Almost all of the residues were in the tuber peel.ResumenTerraclor (PCNB) aplicado al suelo en forma esparcida y en surcos, redujo levemente la incidencia deRhizoctonia solani, pero no encrementó el rendimiento o el porcentaje de tubérculos U. S. No. 1, bien sea por peso o número.Los residuos de PCNB, en tubérculos que se desarrollaron en suelos tratados, se aumentaron cuando el porcentaje de PCNB por acre se aumentó. La mayoría de los residuos se encontraron en la cáscara del tubérculo.

Effect of fertilizer, fumigants, and fungicides on leafroll-net necrosis in Russet Burbank potatoes

A total of 112 combinations of 13 fumigants, fertilizers, and a fungicide was tested in replicated plots in eastern Washington in 1963 and 1964 to determine their effects on the net necrosis produced in Russet Burbank potatoes by the leafroll virus. Plots treated with Telone® (dichloropropenes) or Telone+chloropicrin had significantly fewer tubers discolored with leafroll net necrosis than untreated plots; plots treated with lower rates of various chlorinated propenes and propanes or ethylene dibromide had fewer discolored tubers than plots treated with higher rates of these chemicals; and plots treated with higher rates of various combinations of dichloropropenes with methyl isothiocyanate or 3-bromo-1-propyne had fewer discolored tubers than plots treated with lower rates of these chemicals. An interaction took place between the chemicals and the leafroll virus that either increased or decreased the amount of net necrosis in the tubers. Other types of internal discoloration (OID) in the tubers were significantly increased by Telone treatments in some tests. Telone treatments showed no effects on OID in other tests compared to untreated tubers. Also, nitrogen, at 100 lb/acre and over, significantly increased the other types of discoloration over no nitrogen, but potassium at 0 to 150 lb/acre and pentachloronitrobenzene (PCNB) at 0 to 30 gal/acre showed no significant effect.