• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 421
  • 96
  • 51
  • 9
  • 4
  • 1
  • 1
  • 1
  • Tagged with
  • 715
  • 715
  • 178
  • 154
  • 119
  • 114
  • 112
  • 89
  • 82
  • 72
  • 72
  • 65
  • 63
  • 55
  • 51
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Combining Biorational Compounds to Optimize Control of Grape Powdery Mildew (Uncinula Necator)

Fiedler, Kathryn 01 January 2009 (has links)
In the Northeast, powdery mildew (PM), caused by Uncinula necator (Schewein.) Burrill is one of the most important grape diseases in terms of economic loss. It has been established that cultural practices, including proper sanitation, are the first step in preventing disease, and fungicide sprays are regularly applied to manage the disease. Currently, fungicides that successfully control PM have a strong potential to develop pathogen resistance, and alternatives with low risk of initiating resistance are not as effective in disease control. Our approach to this emerging resistance dilemma is to combine a systemic acquired resistance inducer (salicylic acid and potassium phosphate) with a topical fungicide, potassium bicarbonate. To determine each treatment’s level of efficacy, multiple aspects of infection and defense were quantified and qualified, including germination rate, lethality, lignin formation, callose formation, and vine and leaf growth. The first trial showed potassium bicarbonate and the standard fungicide (Pristine) inhibited the most germination and was most lethal against PM conidia. Potassium phosphate had little effect on germination and conidia death, and when combined with bicarbonate there was no different than the water control. In the second trial, the biorational mixture was able to reduce the level of powdery mildew infection significantly more than the other compounds, including the commercial standard. The salicylic acid and potassium bicarbonate mix may be successful enough to use in the vineyard to determine if the compound can tolerate field conditions with the same level of efficacy.

the Nature of Plant Resistance to Obligate Parasites.

Samborski, D.J. January 1955 (has links)
The nature of host susceptibility to phytopathogenic parasites, especially the obligates, remains one of the major problems in plant pathology even though it has been investigated extensively from the early part of the present century until the late thirties. Studies on the genetics of the pathogens and breeding for resistant varieties have predominated since that time. There is at present a revival of interest in the physiology of disease resistance. [...]

the Physiology of Verticillium Wilt of Tomato and Potato.

Campbell, J. Ewen. January 1961 (has links)
Verticillium wilt is often the cause of serious losses in potatoes in Eastern Canada and Northern United States. It is of minor importance in field tomatoes except in California and Utah. The disease is not uncommon in greenhouse tomatoes in North America and in Europe. [...]

Studies on verticillium wilt of forage legumes.

Aubé, Claude. January 1963 (has links)
Hay is the most important crop in Quebec. According to the annual report of the Quebec Bureau of Statistics for 1961, of a total cultivated area of 7,864,176 acres in Quebec, 3,458,000 acres were in hay. The value of the hay crop in 1961 was 55.8 percent of the value of all field crops in the province. Since alfalfa, birdsfoot trefoil, red, alsike, and ladino clovers are cominant in this hay crop, their agricultural importance is apparent. This, together with the fact that some of these forage legumes, mainly red clover and alfalfa, are the most common rotation crops, led to the choice of these plants for study.

Leucostoma canker of larch in Quebec.

Lavallée, André. January 1963 (has links)
The pathology of our native larch, Larix laricina (Du Roi) Koch, has never been carefully investigated in the province of Quebec. One of the explanations of this apparent lack of interest in diseases of this tree species is the very important infestation by the larch sawfly (Pristiphora Erichsonii Htg.), which, at the beginning of the present century, greatly reduced the best stands of larch in Northeast America. Usually the Eastern larch, commonly called tamarack, provides a hard, heavy and non-porous wood of high technical value. Its resistance to decay outweighs any other conifer of Eastern and Central Canada (2).

Studies of factors affecting certain nematopagous hyphomycetes.

Thomas, Garfield. B. January 1963 (has links)
A major objective of the Agricultural Sciences is the utilization of' natural resources in such a manner that the effects of factors which reduce the yields of products useful to man, will be minimized. Although nematodes, as parasites of vertebrates and plants, have been recognized as significant factors in reducing agricultural production, they are themselves victims of a number of parasitic organisms. Struggle for existence is universal among living organisms regardless of their biological level, and this competitive relationship between nematodes and other organisms in their environments is by no means unique. Fungi, that prey upon or parasitize microscopic animals, are usually referred to as predacious fungi.

A study on nematodes of the species Aphelenchus avenae Bastian, 1865.

Chin, Dudley. S. January 1964 (has links)
In recent years agricultural scientists have become aware of the fact that plant parasitic nematodes have been a serious world problem by depriving farmers of higher yields and greater returns from their crops. It is impossible to assess their economic importance even roughly, for in many parts of the world they have still to be sought, but it is probably safe to say that every country or every crop is troubled by nematodes. Nematodes of the species ‘Aphelenchus avenae’ Bastian, 1865 are of widespread occurrence in soil and in dead or dying plant parts that have been in or on the soil, yet their significance in relation to plant diseases and their role in the soil community remains uncertain.

Verticillium wilt of horticulture crops in Quebec.

Devaux, Alain. M-L. January 1964 (has links)
The production of horticultural crops, although it accounts for only 6.8 per cent of the total agricultural revenue of Quebec, is one of the most dynamic sections of the agricultural industry in this Province (39). The total area in vegetables grown for commercial purposes was estimated at 70,360 acres in 1962, compared to 66,690 in 1961 and 63,660 acres in 1960. Estimates of the farm value of production were 13.7 million dollars for 1962, compared with 13.2 million in 1961 and 12.6 million in 1960. Potatoes, as field crops, are grown on 90,200 acres in Quebec (29.1 per cent of the total acreage for potatoes in Canada), with an annual production of 8,833,000 bushels. Strawberries, as small fruit crops, were cultivated on 2,840 acres in 1962, with a production of 6,490,000 lbs. (Private communication with Dr. Jean David, Department of Horticulture, Macdonald College, McGill University).

On the use of histochemical tests for the demonstration of cytochrome oxidase in potato tubers infected by Phytophthora infestans (Mont.) De Bary.

Harwig, Joost. January 1964 (has links)
Among the physiological features of the infected plant, the pathological increase in respiration is a striking one. This altered rate of respiration, usually measured in terms of oxygen uptake, starts before symptoms of disease appear, rises gradually to a maximum as the disease develops, and declines rapidly as death is approached. These observations on abnormal rate of gas exchange indicate that the enzyme-catalysed processes resulting in oxygen absorption are accelerated in the host tissue as a result of infection. A natural question is then, what enzymes are involved in this acceleration. Among the great variety of enzymes that could possibly be involved, cytochrome oxidase can be regarded as an important one, as it functions as terminal oxidase in the phosphorylating electron transport system of the mitochondria.

The toxemia of halo blight of bean.

Hoitink, Henricus. A. January 1964 (has links)
The toxigenic theory of plant disease explains the occurrence of pathological disturbances in advance of the invading pathogen as the effect of a toxin produced in the course of host-pathogen interaction. A considerable amount of work has been done on such diseases, which are called toxemia; however much of it is still a matter of controversy. Much more research must be done on this subject before many of the concepts involved can be accepted. At present, there is need for studies to show that pathogens can produce the same toxins both in axenic culture and in infection, and that injection with toxins can reproduce the physiological disturbances and the symptoms characteristic of the disease.

Page generated in 0.0792 seconds