BIOLOGICAL CONTROL
The chemical control of plant pests became necessary as a result of human intervention and manipulation of the natural world. By selectively producing masses of desired plants and reducing or …
The Role of Adjuvants
Weather, the severity of host infection, and the stage of development of the irritant pest are all factors in the effectiveness of a pesticide. To waste time and/or product on …
. Pesticide Safety
The safe use of chemical pesticides requires a respect for their toxicity. All manufacturers and distributors of pesticides are required by federal law to provide explicit information about their products’ …
Product Packaging
When homeowners go to their local garden center to purchase a pesticide, they usually select from an assortment of liquid products contained in glass or plastic bottles, dusts packaged in …
Pesticide Product Formulations
Whether the pesticide is a fungicide, nematicide, insecticide, or herbicide, it is usually available in several different formulations. The choice of formulation is based on: • the size of the …
PESTICIDES
Understanding chemical pesticides requires knowing what they are and what they are not. What they are is poisonous. What they are not is medicinal. The belief that pesticides are medicines …
Principles of Control
The control of insects, pathogens, and weeds depends on how successfully the horticulturist applies one or more of the four basic principles of control. Exclusion Exclusion is the first principle …
THE CONTROL OF BIOTIC PESTS
In a text such as this, where insects, diseases, and weeds are treated in terms of their general effect on plants, a discussion of their control must be equally general. …
OTHER CAUSES OF INJURY
Insects, diseases, and weeds are collectively the major causes of injury to plants. However, there are other causes of injury, some biological and others nonbiological (see Table 6-1). Many home …
Classification of Weeds
Being plants, weeds share the binomial nomenclature of botanical classification. All are classified into families, genera, species, and varieties. Also, like other plants, weeds are classified in other ways. Their …
WEEDS
No discussion of the pests affecting ornamental plants is complete without considering the weeds. A weed may be defined as a plant having no positive economic value and/or growing in …
Color Changes
Resulting from the destruction of chlorophyll, color changes may be localized (spots, rings, lesions) or widespread through the plant. Lack of light turns a plant yellow in a condition termed …
SYMPTOMS OF INJURED PLANTS
Responses to pathogenic irritants and insects are termed symptoms. Some symptoms are common to numerous insects and diseases. Other symptoms are almost unique to certain irritant-host relationships. The sum of …
Relationships Between Plants and Pathogens
Plant diseases do not arise spontaneously. There must be a causal agent (the pathogen) in the vicinity of a susceptible plant (the host). The pathogen must be in a form …
Plant Pathogens
While many plant pathologists include the injuries induced by abiotic causes in their broadest consideration of plant disease, what will be explained here are the biotic, parasitic causal agents. Each …
PLANT DISEASES
Despite our best efforts at control, the United States loses an estimated 15 to 20 percent of crop productivity each year due to plant diseases. History is laden with accounts …
Growth and Change of Insects
No members of the animal kingdom transform more dramatically during their development than insects. The homely caterpillar becomes the graceful butterfly; the grub worm in last summer’s lawn becomes the …
The Classification of Insects
In the animal kingdom, the major divisions are known as phyla (singular phylum). The phylum Arthropoda contains the class Insecta, or the insects. Other classes of Arthropoda include the crayfish, …
PLANT INJURIES AND THEIR CONTROL
OBJECTIVES Upon completion of this chapter, you should be able to • state the major causes of injury to plants. • characterize insects and groups of pathogens as plant pests. …
MUTATIONS
Mutations are spontaneous changes in the genetic structure of a plant. They occur in nature as accidents, resulting from something that prevents the DNA of a chromosome from replicating exactly …
THE CONTRIBUTION OF GREGOR MENDEL
A look at the work of Gregor Mendel provides an appreciation of his contribution to learning along with a basic introduction to the study of plant improvement. Gregor Mendel was …
PLANT IMPROVEMENT
No study of plant reproduction is complete without some discussion of how plants change and improve through the years. The essence of vegetative reproduction is that there is no change; …
Asexual Propagation
Asexual propagation utilizes the vegetative parts of a plant to grow new plants. Stems or roots are more commonly used, but leaves can be used as well. Each vegetative cell …
HOW PLANTS ARE PROPAGATED
In the natural world, plants reproduce both sexually and asexually. For example, new plants may arise vegetatively from the root system of a plant while the same plant is producing …
SEXUAL AND ASEXUAL REPRODUCTION
The reproduction of plants through the formation of seeds is called sexual reproduction. It requires the fusion of two sex cells or gametes, each having one set of chromosomes (haploidal), …
PLANT REPRODUCTION
У OBJECTIVES Upon completion of this chapter, you should be able to • describe the characteristics of sexual and asexual reproduction in plants. • describe the processes of mitosis …
COMMERCIAL GROWTH REGULATORS
Even without fully understanding the way growth regulators work, scientists have been able to synthesize products that influence the growth of plants in a similar manner. Many products of commercial …
Gibberellins
Gibberellins are a group of thirty or more closely related plant hormones that promote cell enlargement, often causing dramatic increases in plant height. One of the common forms is gibberellic …
. PLANT GROWTH REGULATORS
Organic Fertilizers
Organic fertilizers tend to be low in nutrient content, especially nitrogen. Although they enjoy some popularity with organic gardeners and hobbyists, they have limited application to commercial ornamental horticulture. Not …
FERTILIZERS
Fertilizers are nutrient additives applied to the soil periodically to maintain optimum crop productivity. The need for fertilization may result from a deficiency of one or more mineral elements in …
Role in Mineral Absorption
It seems logical to assume that minerals are absorbed into plant roots as water is absorbed. It is a logical assumption but an incorrect one. The uptake of water and …
CATION EXCHANGE
To understand how colloidal clay particles and humus contribute to the chemical reactions of the soil, how the soil’s pH can be modified, and how the application of chemical fertilizer …
SOIL ACIDITY AND ALKALINITY
The soil’s water, held between the particles and granules of the soil, contains dissolved mineral salts. This liquid is known as the soil solution. The way the soil solution reacts …
SOIL STRUCTURE AND ORGANIC MATERIAL
In good loam soils, small soil particles adhere together to form larger particles or aggregates. This arrangement of soil particles into aggregates is termed the soil structure. Structure resulting from …
