Tag: toxic wastes and their effects

Allethrin is a synthetic pyrenoid used as an insecticide. These were made in 1949 and their chemical structure bears similarity to the natural pyrenoids obtained from the chrysanthemum plants. These are used to kill the flying and crawling insects in homes and workplaces.

Auxins are toxic to plants in large concentrations; they are most toxic to dicots and less so to monocots. Because of this property, synthetic auxin herbicides, including 2,4-D and 2,4,5-T, have been developed and used for weed control. Dioxins are environmental pollutants. They belong to the so-called dirty dozen - a group of dangerous chemicals known as persistent organic pollutants (POPs). Dioxins are of concern because of their highly toxic potential. Experiments have shown they affect a number of organs and systems.
Once dioxins enter the body, they last a long time because of their chemical stability and their ability to be absorbed by fat tissue, where they are then stored in the body. Their half-life in the body is estimated to be 7 to 11 years. In the environment, dioxins tend to accumulate in the food chain. The higher an animal is in the food chain, the higher the concentration of dioxins.
The chemical name for dioxin is: 2, 3, 7, 8 - tetrachlorodibenzo para dioxin (TCDD). The name "dioxins" is often used for the family of structurally and chemically related polychlorinated dibenzo para dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). Dioxins are mainly by-products of industrial processes but can also result from natural processes, such as volcanic eruptions and forest fires. Dioxins are unwanted by products of a wide range of manufacturing processes including smelting, chlorine bleaching of paper pulp and the manufacturing of some herbicides and pesticides.

Pesticides are applied to the soil to manage the weeds. The length of the time that the pesticide remains active in soil is referred to as "soil persistence". Though desirable in the season of application, its persistence in the soils may affect the crop growth and yield. Benzene Hexachloride(BHC) is a chemical compound with several stereoisomers of which one is an insecticide called Lindane and the by-product is β-hexachlorocyclohexane- the pesticide. This pesticide which was used widely to protect cotton plants during 1960 and 1970's is banned as it has high levels of soil persistence and is neurotoxic for the animals. 

Pesticides have had some of their most striking effects on birds, particularly those in the higher trophic levels of food chains, such as bald eagles, hawks and owls. These birds are often rare, endangered and susceptible to pesticide residues, such as those occurring from the bioconcentration of organochlorine insecticides through terrestrial food chains. Pesticides may kill grain and plant-feeding birds and the elimination of many rare species of ducks and geese has been reported. Populations of insect-eating birds, such as partridges, grouse and pheasants have decreased due to the loss of their insect food in agricultural fields through the use of insecticides. Thus, the correct answer is option D.

In 1972, the 'Environmental Protection Agency' banned the use of DDT in the United States as well as the use of pesticides, such as endrin and dieldrin. As a result, the levels of these persistent compounds in the environment have decreased in most areas, thus, the reproductive success of brown pelicans has increased.

Minor pests are the species that feed or oviposit on the crop plants but usually do not inflict damage of economic importance and often their effect on the plant is indiscernible.
A pest is "a plant or animal detrimental to humans or human concerns (as agriculture or livestock production)"; alternative meanings include organisms that cause nuisance and epidemic disease associated with high mortality.

Phytophthora palmivora has been used as an post emergent mycoherbicide to control milkweed or strangler vine, a major problem on citrus in south Florida. It controls the weed by a root and stem rot and girdling the stems of infested plant near the soil surface, resulting in the death of seedlings and the older plants.