Pesticides are substances that are meant to control pests. This includes herbicide, insecticide, nematicide, molluscicide, piscicide, avicide, rodenticide, bactericide, insect repellent, animal repellent, microbicide, fungicide, and lampricide. The most common of these are herbicides which account for approximately 80% of all pesticide use. Most pesticides are intended to serve as plant protection products, which in general, protect plants from weeds, fungi, or insects. As an example, the fungus Alternaria solani is used to combat the aquatic weed Salvinia.
Herbicides, also commonly known as weedkillers, are substances used to control undesired plants, also known as weeds. Selective herbicides control specific weed species, while leaving the desired crop relatively unharmed, while non-selective herbicides can be used to clear waste ground, industrial and construction sites, railways and railway embankments as they kill all plant material with which they come into contact. Apart from selective/non-selective, other important distinctions include persistence, means of uptake, and mechanism of action. Historically, products such as common salt and other metal salts were used as herbicides, however these have gradually fallen out of favor and in some countries a number of these are banned due to their persistence in soil, and toxicity and groundwater contamination concerns. Herbicides have also been used in warfare and conflict.
Weed control is a type of pest control, which attempts to stop or reduce growth of weeds, especially noxious weeds, with the aim of reducing their competition with desired flora and fauna including domesticated plants and livestock, and in natural settings preventing non native species competing with native species.
Plant hormone are signal molecules, produced within plants, that occur in extremely low concentrations. Plant hormones control all aspects of plant growth and development, from embryogenesis, the regulation of organ size, pathogen defense, stress tolerance and through to reproductive development. Unlike in animals each plant cell is capable of producing hormones. Went and Thimann coined the term "phytohormone" and used it in the title of their 1937 book.
Allelopathy is a biological phenomenon by which an organism produces one or more biochemicals that influence the germination, growth, survival, and reproduction of other organisms. These biochemicals are known as allelochemicals and can have beneficial or detrimental effects on the target organisms and the community. Allelopathy is often used narrowly to describe chemically-mediated competition between plants, however, it is sometimes defined more broadly as chemically-mediated competition between any type of organisms. Allelochemicals are a subset of secondary metabolites, which are not directly required for metabolism of the allelopathic organism.
MCPA is a powerful, selective, widely used phenoxy herbicide. The pure compound is a brown-colored powder. MCPA has been extensively used in agriculture to control broad-leaf weeds as a growth regulator primarily in pasture and cereal crops field since 1945. The mode of action of MCPA is as an auxin, which are growth hormones that naturally exist in plants. Overdose application of MCPA acts as an herbicide and results in abnormal growth.
Phytotoxicity describes any adverse effects on plant growth, physiology, or metabolism caused by a chemical substance, such as high levels of fertilizers, herbicides, heavy metals, or nanoparticles. General phytotoxic effects include altered plant metabolism, growth inhibition, or plant death. Changes to plant metabolism and growth are the result of disrupted physiological functioning, including inhibition of photosynthesis, water and nutrient uptake, cell division, or seed germination.
Crotalaria juncea, known as brown hemp, Indian hemp, Madras hemp, or sunn hemp, is a tropical Asian plant of the legume family (Fabaceae). It is generally considered to have originated in India.
Dithiopyr is a preemergent herbicide for crabgrass control in turf and ornamental grasses. It is effective on 45 grassy and broadleaf weeds. Dithiopyr inhibits root growth of susceptible weeds as well as turf grass and thus should be used only on established turf with a well-developed root system. Its duration of efficacy is approximately 4 months, so lawns should not be reseeded during this time frame following application of the chemical. Dithiopyr acts primarily as a preemergent herbicide but can also be used in early postemergent control of crabgrass.
Pesticide application refers to the practical way in which pesticides are delivered to their biological targets. Public concern about the use of pesticides has highlighted the need to make this process as efficient as possible, in order to minimise their release into the environment and human exposure. The practice of pest management by the rational application of pesticides is supremely multi-disciplinary, combining many aspects of biology and chemistry with: agronomy, engineering, meteorology, socio-economics and public health, together with newer disciplines such as biotechnology and information science.
Imazapyr is a non-selective herbicide used for the control of a broad range of weeds including terrestrial annual and perennial grasses and broadleaved herbs, woody species, and riparian and emergent aquatic species. It is used to eliminate Lithocarpus densiflorus and Arbutus menziesii. Additionally, imazapyr is used to control annual and perennial grass and broadleaved weeds, brush, vines and many deciduous trees. Imazapyr is absorbed by the leaves and roots, and moves rapidly through the plant. It accumulates in the meristem region of the plant. In plants, imazapyr disrupts protein synthesis and interferes with cell growth and DNA synthesis.
Propanil is a widely used contact herbicide. With an estimated use of about 8 million pounds in 2001, it is one of the more widely used herbicides in the United States. Propanil is said to be in use in approximately 400,000 acres of rice production each year.
A weed is a plant considered undesirable in a particular situation, "a plant in the wrong place", or a plant growing where it is not wanted. This introduces the concept of humans and their goals in a particular setting. The concept of weeds is particularly significant in agriculture, where the aim is growing crops or pastures of a single species, or a mixture of a few desired species. In such environments, other plant species are considered undesirable and therefore a weed. Besides, some weeds have undesirable characteristics making them a plant pest in most human settings.
Betaenone B, like other betaenones, is a secondary metabolite isolated from the fungus Pleospora betae, a plant pathogen. Its phytotoxic properties have been shown to cause sugar beet leaf spots, which is characterized by black, pycnidia containing, concentric circles eventually leading to necrosis of the leaf tissue. Of the seven phytotoxins isolated in fungal leaf spots from sugar beet, betaenone B showed the least amount of phytotoxicity showing only 8% inhibition of growth while betaenone A and C showed 73% and 89% growth inhibition, respectively. Betaenone B is therefore not considered toxic to the plant, but will produce leaf spots when present in high concentrations (0.33 μg/μL). While the mechanism of action of betaenone B has yet to be elucidated, betaenone C has been shown to inhibit RNA and protein synthesis. Most of the major work on betaenone B, including the initial structure elucidation of betaenone A, B and C as well as the partial elucidation mechanism of biosynthesis, was presented in three short papers published between 1983–88. The compounds were found to inhibit a variety of protein kinases signifying a possible role in cancer treatment.
2,4-Dichlorophenoxyacetic acid is an organic compound with the chemical formula C8H6Cl2O3 which is usually referred to by its ISO common name 2,4-D. It is a systemic herbicide which kills most broadleaf weeds by causing uncontrolled growth in them but most grasses such as cereals, lawn turf, and grassland are relatively unaffected.
4-Hydroxyphenylpyruvate dioxygenase (HPPD) inhibitors are a class of herbicides that prevent growth in plants by blocking 4-Hydroxyphenylpyruvate dioxygenase, an enzyme in plants that breaks down the amino acid tyrosine into molecules that are then used by plants to create other molecules that plants need. This process of breakdown, or catabolism, and making new molecules from the results, or biosynthesis, is something all living things do. HPPD inhibitors were first brought to market in 1980, although their mechanism of action was not understood until the late 1990s. They were originally used primarily in Japan in rice production, but since the late 1990s have been used in Europe and North America for corn, soybeans, and cereals, and since the 2000s have become more important as weeds have become resistant to glyphosate and other herbicides. Genetically modified crops are under development that include resistance to HPPD inhibitors. There is a pharmaceutical drug on the market, nitisinone, that was originally under development as an herbicide as a member of this class, and is used to treat an orphan disease, type I tyrosinemia.
The Celebrity tomato cultivar is a hybrid (biology) that produces long fruit-bearing stems holding 20 or more very plump, robust tomatoes. Fruits weigh approximately 8 oz., and are 4 inches across. Plants need caging or staking, and produce fruit throughout the growing season. The celebrity tomato is a cultivar of the species Solanum lycopersicum. It is a crossbreed of the common tomato that is widely used for various culinary purposes. This tomato is of great size and is known to be resistant to most tomato diseases such as Fusarium wilt, Verticillium wilt, Tobacco mosaic virus and Root-knot nematode due to its hybrid nature. Celebrity tomatoes are highly adaptive to harsh environments and can grow in a wide range of places including dry, humid and wet regions. They are resistant to cracking and splitting which usually occurs when there is an excess of water and sugar movement in the fruits. Therefore, causing the tomato skin to grow at a slower rate compared to the expansion of the fruit. They can survive in harsh uneven rainfall. However, they are highly susceptible to colder environments and are at a higher risk of dying in regions with short growing seasons. The plants can grow up to 5 feet in height with bright red medium-sized fruits. The plants are generally very thick and grow in clusters. The tomato fruits are mostly used in the making of various salsas, salads, juices and canned food.
Myrcia guianensis (pedra-ume-caá) is a species of the flowering plant family Myrtaceae. It is found in South America.
Linuron is a phenylurea herbicide that is used to control the growth of grass and weeds for the purpose of supporting the growth of crops like soybeans.
Aclonifen is a diphenyl ether herbicide which has been used in agriculture since the 1980s. Its mode of action has been uncertain, with evidence suggesting it might interfere with carotenoid biosynthesis or inhibit the enzyme protoporphyrinogen oxidase (PPO). Both mechanisms could result in the observed whole-plant effect of bleaching and the compound includes chemical features that are known to result in PPO effects, as seen with acifluorfen, for example. In 2020, further research revealed that aclonifen has a different and novel mode of action, targeting solanesyl diphosphate synthase which would also cause bleaching.
