Cabbage Fields Research Articles

The recovery of virulent nuclear-polyhedrosis virus of the cabbage looper, Trichoplusia ni, from the feces of birds

English sparrows have been observed methodically searching cabbage plants for insects. Cabbage loopers, Trichoplusia ni, in the advanced stages of nuclear polyhedrosis, lose their natural defense mechanisms and become easy prey for birds. Examination of individual aqueous suspensions of bird feces collected from a cabbage field in St. Louis County, Missouri, in July 1968, revealed high numbers of polyhedra inclusion bodies in 9 of the 12 samples. Per os inoculation of third instar T. ni larvae proved that all 12 suspensions contained virulent polyhedra (i.e., virus) capable of producing the polyhedrosis.

INTRODUCCIÓN Y EVALUACIÓN DEL PARASITOIDE <i>Diadegma semiclausum</i> (HELLEN) PARA EL CONTROL DE <i>Plutela xylostella</i> EN NICARAGUA

Con el propósito de evaluar el parasitoide Diadegmasemiclausum Hellen, como una alternativa biológica(parasitoide) en el manejo de Plutella xylostella (L) se introdujoa Nicaragua un pie de cría. Se realizaron estudios relacionado asaneamiento del pie de cría traído desde Taiwán (Cuarentena),comportamiento biológico del insecto en condiciones delaboratorio y establecimiento en campos de repollo. Losestudios se realizaron en el laboratorio de parasitoides de laUniversidad Nacional Agraria (Managua) y en condicionesde campo en el Departamento de Estelí. Las condiciones quese mantuvieron en el estudio fueron de 21°C de temperatura ypromedio de 65 % de humedad relativa. La fase de saneamientoconsistió en evaluar la idoneidad de los parasitoides enviadosdesde Taiwán. Se identificó cada uno de los insectos (adultos)proveniente del pie de cría y de las tres primeras generacionesen etapa de cuarentena. Durante este período no se encontraroninsectos atípicos a D. semiclausum. Otra variable evaluada fuela relación hembra: macho, la que comenzó con 1:7 del pie decría mejorándose hasta 1:2 al final de la etapa de cuarentena. Labiología se separó en periodos de huevo, larva; pupa y adultoobteniendo valores promedio de 10.2 días; 5.7 días y 14.8 díasrespectivamente, para un ciclo total de 31.4 días. El porcentajede parasitismo registrado durante las dos primeras fases alcanzóun promedio de 90 % en condiciones de laboratorio. Se colocouna parcela de repollo (Brassica oleoreacea var. Capitata)en el campo para conocer la incidencia de D. semiclausum, alfinal se encontró que en el periodo de cosecha del cultivo, elporcentaje de parasitismo fue de 70 % asociando la incidenciadel parasitoide nativo de la región D. insulare (Cresson) con un59 % y un 11 % de parasitismo del parasitoide introducido D.semiclausum.Palabras clave: Parasitoide, Diadegma semiclausum, Plutellaxylostella.DOI: 10.5377/calera.v9i12.5

Effect of ph on tYlenchorhynchus Dubius (Nematoda, Tylenchidae)

A survey of cabbage fields in Poland shows that the frequency of occurrence of T. dubius increases as soil pH decreases. The population increase of this nematode in pot experiments was greater as pH decreased. The optimal pH for hatching of eggs was found to be 7.0.

キャベツ株内でのモンシロチョウ,ヨトウガおよびタマナギンウワバの幼虫と蛹の葉位別分布

In the vicinity of the North Eastern end of Honshu, three crops of cabbages are produced each year: early summer, late summer and fall crops. To investigate the seasonal trends in population dynamics of the caterpillars in cabbage fields, egg, larvae and pupae of Pieris rapae crucivora BOISD., Plusia nigrisigna WALKER and Mamestra brassicae L. on cabbage plants were counted in fields of respective crops, during May to September, 1959.The seasonal changes in the average number of eggs, each instar larvae and pupae of the three species per plant in respective fields are given in Figs. 1, 2 and 3. Among these species, Mamestra brassicae was the most abundant during June to early July, and Pieris rapae crucivora during the late July, August and September. Plusia nigrisigna did not attain a significant proportion of the total population at all. As to the total number of the insects observed throughout the overall season, Pieris rapae crucivora was the most numerous, Mamestra brassicae came next, and Plusia nigrisigna showed no significant proportion. The caterpillar population reached its highest level in early September. In general, 50 per cent or more of the initial population in each generation of respective species was destroyed during the egg and the first larval instar. Moreover, 80 per cent or more of the survivors failed to pupate. The rate of reduction in number of early summer population of Pieris rapae crucivora was particularly high when the population density of Mamestra brassicae was the highest.

2.3. Control of Cabbage Root Fly in Turnips and Field Cabbage

2.3. Control of Cabbage Root Fly in Turnips and Field Cabbage

The Effect of Root Aeration on Plant Growth

AbstractRates of oxygen diffusion were measured in soil contained in 3‐foot‐cube lysimeters in field installations. Water tables were maintained by subsurface watering at 6‐ to 30‐inch depths below the soil surface. Some lysimeters were sheltered from rain. Soybeans, cabbage, grain sorghum, sweet corn, and dwarf field corn were grown in these lysimeters.The highest yields were obtained at oxygen diffusion rates of approximately 15 g. X 10‐8 per cm.2 per minute. The maximum yields were high in comparison with yields obtained in most field experiments. Oxygen diffusion rates at 6‐inch water table depths were below 5 g. X 10‐8 per cm.2 per minute. Under these conditions of extremely poor aeration, yields of grain sorghum, soybeans, cabbage, sweet corn, and dwarf field corn were reduced 25, 35, 40, 65, and 75%, respectively.

Factors influencing the occurrence of clubroot in semi-resistant populations of Brassica oleracea L.

1. In breeding for resistanceto clubroot the plants have to be exposed to infection as long as possible. The clubbing of a susceptible variety forms an unreliable measure of the efficiency of the clubroot test. 2. Semi-resistant populations may show variability in clubbing by differences in infection conditions. 3. A direct effect of temperature, pH and soil moisture on resistance has not been ascertained. 4. Between origins of Plasmodiophora brassicae there may be differences caused by unequal spore loads and by physiological specialisation. 5. To test sub-species of Brassica oleracea for clubroot resistance use must be made of a physiological race from infested cabbage fields. The plants that are most resistant to it are equally resistant to other origins of the fungus.

キャベツ畑における主要りんし目害虫の個体群動態の比較研究

In the vicinity of the North Eastern end of Honshu, three crops of cabbages are produced each year: early summer, late summer and fall crops. To investigate the seasonal trends in population dynamics of the caterpillars in cabbage fields, egg, larvae and pupae of Pieris rapae crucivora BOISD., Plusia nigrisigna WALKER and Mamestra brassicae L. on cabbage plants were counted in fields of respective crops, during May to September, 1959.The seasonal changes in the average number of eggs, each instar larvae and pupae of the three species per plant in respective fields are given in Figs. 1, 2 and 3. Among these species, Mamestra brassicae was the most abundant during June to early July, and Pieris rapae crucivora during the late July, August and September. Plusia nigrisigna did not attain a significant proportion of the total population at all. As to the total number of the insects observed throughout the overall season, Pieris rapae crucivora was the most numerous, Mamestra brassicae came next, and Plusia nigrisigna showed no significant proportion. The caterpillar population reached its highest level in early September. In general, 50 per cent or more of the initial population in each generation of respective species was destroyed during the egg and the first larval instar. Moreover, 80 per cent or more of the survivors failed to pupate. The rate of reduction in number of early summer population of Pieris rapae crucivora was particularly high when the population density of Mamestra brassicae was the highest.

Male sterility in some cole crops

Some male sterile plants were found in seed fields of cauliflower, Brussels sprouts and white cabbage. In all 3 crops the male sterile flowers were characterized by shorter stamens and shrivelled anthers. Male sterility did not seem to be greatly influenced by the environment.

Abundance of Aphids and Caterpillars in Commercial Cabbage Fields in the Vicinity of Sanford, Florida

During a study of host preference of insects that attack cole crops, Harrison and Brubaker (1943) found that in the vicinity of Baton Rouge, Louisiana, the imported cabbage worm, Pieris rapae (L.), the cabbage looper, Trichopulsia ni (Hbn.), and the larvae of the diamondback moth, Plutella maculipennis (Curt.), in the order named, were the more important caterpillars on cole crops. From the Charleston, South Carolina area, Reid and Bare (1952) reported that on the fall crop the cabbage looper, several species of agrotinae, and the cabbage webworm, Hellula rogatalis (Hulst) were the most abundant. On the spring crop the diamondback moth, the cabbage looper, and the imported cabbage worm were the most numerous. In eastern Ontario, Harcourt et. al. (1955) found that the imported cabbage worm, the diamondback moth, and the cabbage looper were the most abundant on the early crop, while the diamondback moth, the imported cabbage worm, and the cabbage looper were the most abundant on the late crop. The cabbage looper at no time formed a significant portion of the species complex in eastern Ontario, although this species had been generally believed to be the most abundant of the three. Since the use of the hydrocarbon and phosphatic insecticides has become widespread, cabbage growers in the vicinity of Sanford, Florida, have practiced what they call preventive insect control. In many cases this means that an application of toxaphene or toxaphene combined with parathion is applied once or twice a week regardless of the presence of insect pests. In some instances the toxaphene is applied alone during the early part of the week, to be followed by an application of TEPP dust later in the same week. During the past two years many growers in this area have complained that toxaphene is no longer as effective as when it was first used. Observations in the untreated plots in experimental plantings at the Experiment Station and in commercial fields gave the author the impression that growers in the Sanford area were wasting tremendous amounts of insecticides and encouraging the development of insecticide-resistant crop pests. The need to confirm these observations led to a survey of insects attacking commercial cabbage fields. This survey has been conducted during the past four growing seasons in the vicinity of Sanford, Florida.